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| versions
list | update_date
timestamp[s] | authors_parsed
sequence |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0708.2349 | Vadim Gorin | Vadim Gorin | Non-intersecting paths and Hahn orthogonal polynomial ensemble | 25 pages, 5 figures | Funct. Anal. Appl., 42 (2008), no. 3 , 180-197 | null | null | math.PR math-ph math.CO math.MP | null | We compute the bulk limit of the correlation functions for the uniform
measure on lozenge tilings of a hexagon. The limiting determinantal process is
a translation invariant extension of the discrete sine process, which also
describes the ergodic Gibbs measure of an appropriate slope.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 11:45:38 GMT"
}
] | 2011-08-19T00:00:00 | [
[
"Gorin",
"Vadim",
""
]
] |
0708.2350 | Raman Prinja | R. K. Prinja, S. E. Hodges, D. L. Massa, A. W. Fullerton, A. W.
Burnley | Structure and clumping in the fast wind of NGC6543 | 11 pages, 11 figures. Accepted for publication in MNRAS | null | 10.1111/j.1365-2966.2007.12360.x | null | astro-ph | null | Far-UV spectroscopy from the FUSE satellite is analysed to uniquely probe
spatial structure and clumping in the fast wind of the central star of the
H-rich planetary nebula NGC6543 (HD164963). Time-series data of the unsaturated
PV 1118, 1128 resonance line P Cygni profiles provide a very sensitive
diagnostic of variable wind conditions in the outflow. We report on the
discovery of episodic and recurrent optical depth enhancements in the PV
absorption troughs, with some evidence for a 0.17-day modulation time-scale.
SEI line-synthesis modelling is used to derive physical properties, including
the optical depth evolution of individual `events'. The characteristics of
these features are essentially identical to the `discrete absorption
components' (DACs) commonly seen in the UV lines of massive OB stars. We have
also employed the unified model atmosphere code CMFGEN to explore spectroscopic
signatures of clumping, and report in particular on the clear sensitivity of
the PV lines to the clump volume filling factor. The results presented here
have implications for the downward revision of mass-loss rates in PN central
stars. We conclude that the temporal structures seen in the PV lines of NGC6543
likely have a physical origin that is similar to that operating in massive,
luminous stars, and may be related to near-surface perturbations caused by
stellar pulsation and/or magnetic fields.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 11:50:39 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Prinja",
"R. K.",
""
],
[
"Hodges",
"S. E.",
""
],
[
"Massa",
"D. L.",
""
],
[
"Fullerton",
"A. W.",
""
],
[
"Burnley",
"A. W.",
""
]
] |
0708.2351 | Judit Nagy-Gy\"orgy | Judit Nagy-Gy\"orgy | Randomized algorithm for the k-server problem on decomposable spaces | 11 pages | null | null | null | cs.DS cs.DM | null | We study the randomized k-server problem on metric spaces consisting of
widely separated subspaces. We give a method which extends existing algorithms
to larger spaces with the growth rate of the competitive quotients being at
most O(log k). This method yields o(k)-competitive algorithms solving the
randomized k-server problem, for some special underlying metric spaces, e.g.
HSTs of "small" height (but unbounded degree). HSTs are important tools for
probabilistic approximation of metric spaces.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 11:54:44 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Nagy-György",
"Judit",
""
]
] |
0708.2352 | Irina Sagert | I. Sagert, J. Schaffner-Bielich | Pulsar kicks by anisotropic neutrino emission from quark matter in
strong magnetic fields | 14 pages, 10 figures | null | 10.1051/0004-6361:20078530 | null | astro-ph nucl-th | null | We discuss a pulsar acceleration mechanism based on asymmetric neutrino
emission from the direct quark Urca process in the interior of proto neutron
stars. The anisotropy is caused by a strong magnetic field which polarises the
spin of the electrons opposite to the field direction. Due to parity violation
the neutrinos and anti-neutrinos leave the star in one direction accelerating
the pulsar. We calculate for varying quark chemical potentials the kick
velocity in dependence of the quark phase temperature and its radius. Ignoring
neutrino quark scattering we find that within a quark phase radius of 10 km and
temperatures larger than 5 MeV kick velocities of 1000km s$^{-1}$ can be
reached very easily. On the other hand taking into account the small neutrino
mean free paths it seems impossible to reach velocities higher than 100km
s$^{-1}$ even when including effects from colour superconductivity where the
neutrino quark interactions are suppressed.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:28:10 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Sagert",
"I.",
""
],
[
"Schaffner-Bielich",
"J.",
""
]
] |
0708.2353 | Vladimir Vovk | Vladimir Vovk | Continuous and randomized defensive forecasting: unified view | 10 pages. The new version: (1) relaxes the assumption that the
outcome space is finite, and now it is only assumed to be compact; (2) shows
that in the case where the outcome space is finite of cardinality C, the
randomized forecasts can be chosen concentrated on a finite set of
cardinality at most C | null | null | null | cs.LG | null | Defensive forecasting is a method of transforming laws of probability (stated
in game-theoretic terms as strategies for Sceptic) into forecasting algorithms.
There are two known varieties of defensive forecasting: "continuous", in which
Sceptic's moves are assumed to depend on the forecasts in a (semi)continuous
manner and which produces deterministic forecasts, and "randomized", in which
the dependence of Sceptic's moves on the forecasts is arbitrary and
Forecaster's moves are allowed to be randomized. This note shows that the
randomized variety can be obtained from the continuous variety by smearing
Sceptic's moves to make them continuous.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:18:24 GMT"
},
{
"version": "v2",
"created": "Thu, 23 Aug 2007 12:44:34 GMT"
}
] | 2007-08-23T00:00:00 | [
[
"Vovk",
"Vladimir",
""
]
] |
0708.2354 | Hendrik Weimer | Hendrik Weimer, Markus J. Henrich, Florian Rempp, Heiko Schr\"oder,
G\"unter Mahler | Local effective dynamics of quantum systems: A generalized approach to
work and heat | 5 pages, 1 figure, published version | Europhys. Lett. 83, 30008 (2008) | 10.1209/0295-5075/83/30008 | null | quant-ph cond-mat.stat-mech | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | By computing the local energy expectation values with respect to some local
measurement basis we show that for any quantum system there are two
fundamentally different contributions: changes in energy that do not alter the
local von Neumann entropy and changes that do. We identify the former as work
and the latter as heat. Since our derivation makes no assumptions on the system
Hamiltonian or its state, the result is valid even for states arbitrarily far
from equilibrium. Examples are discussed ranging from the classical limit to
purely quantum mechanical scenarios, i.e. where the Hamiltonian and the density
operator do not commute.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:25:37 GMT"
},
{
"version": "v2",
"created": "Mon, 4 Aug 2008 12:16:16 GMT"
}
] | 2008-08-04T00:00:00 | [
[
"Weimer",
"Hendrik",
""
],
[
"Henrich",
"Markus J.",
""
],
[
"Rempp",
"Florian",
""
],
[
"Schröder",
"Heiko",
""
],
[
"Mahler",
"Günter",
""
]
] |
0708.2355 | Alexander Yakimenko | Yu. A. Zaliznyak and A. I. Yakimenko | Three-dimensional solitons and vortices in dipolar Bose-Einstein
condensates | 5 pages, 6 figures | null | 10.1016/j.physleta.2008.01.010 | null | nlin.PS | null | Three-dimensional solitary and vortex structures in Bose-Einstein condensates
are studied in the framework of Gross-Pitaevskii model including the
simultaneous action of local cubic-quintic nonlinearity and nonlocal
dipole-dipole interactions. Nonlocal interactions are shown to change
significantly the formation threshold and the numbers of atoms confined into
the coherent structures. An appearance of robust high-order ($m=2$)
three-dimensional vortices is revealed.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:25:40 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Zaliznyak",
"Yu. A.",
""
],
[
"Yakimenko",
"A. I.",
""
]
] |
0708.2356 | Elizabeth Winstanley | J. E. Baxter, Marc Helbling and Elizabeth Winstanley | Abundant stable gauge field hair for black holes in anti-de Sitter space | 4 pages, 3 figures, new introduction, additional minor changes,
published in Physical Review Letters | Phys.Rev.Lett.100:011301,2008 | 10.1103/PhysRevLett.100.011301 | null | gr-qc hep-th | null | We present new hairy black hole solutions of su(N) Einstein-Yang-Mills theory
(EYM) in asymptotically anti-de Sitter (adS) space. These black holes are
described by N+1 independent parameters, and have N-1 independent gauge field
degrees of freedom. Solutions in which all gauge field functions have no zeros
exist for all N, and for sufficiently large (and negative) cosmological
constant. At least some of these solutions are shown to be stable under
classical, linear, spherically symmetric perturbations. Therefore there is no
upper bound on the amount of stable gauge field hair with which a black hole in
adS can be endowed.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:40:08 GMT"
},
{
"version": "v2",
"created": "Tue, 8 Jan 2008 16:51:57 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Baxter",
"J. E.",
""
],
[
"Helbling",
"Marc",
""
],
[
"Winstanley",
"Elizabeth",
""
]
] |
0708.2357 | Elizabeth Winstanley | J. E. Baxter, Marc Helbling and Elizabeth Winstanley | Soliton and black hole solutions of su(N) Einstein-Yang-Mills theory in
anti-de Sitter space | 15 pages, 20 figures, minor changes, accepted for publication in
Physical Review D | Phys.Rev.D76:104017,2007 | 10.1103/PhysRevD.76.104017 | null | gr-qc hep-th | null | We present new soliton and hairy black hole solutions of su(N)
Einstein-Yang-Mills theory in asymptotically anti-de Sitter space. These
solutions are described by N+1 independent parameters, and have N-1 gauge field
degrees of freedom. We examine the space of solutions in detail for su(3) and
su(4) solitons and black holes. If the magnitude of the cosmological constant
is sufficiently large, we find solutions where all the gauge field functions
have no zeros. These solutions are of particular interest because we anticipate
that at least some of them will be linearly stable.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:53:06 GMT"
},
{
"version": "v2",
"created": "Thu, 1 Nov 2007 15:49:25 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Baxter",
"J. E.",
""
],
[
"Helbling",
"Marc",
""
],
[
"Winstanley",
"Elizabeth",
""
]
] |
0708.2358 | Michael Kinyon | Piroska Csorgo, Ales Drapal and Michael K. Kinyon | Buchsteiner loops | 33 pages | Internat. J. Algebra Comput. 19 (2009), no. 8, 1049-1088 | null | null | math.GR | null | Buchsteiner loops are those which satisfy the identity $x\backslash (xy \cdot
z) = (y \cdot zx)/ x$. We show that a Buchsteiner loop modulo its nucleus is an
abelian group of exponent four, and construct an example where the factor
achieves this exponent.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:48:29 GMT"
}
] | 2011-08-19T00:00:00 | [
[
"Csorgo",
"Piroska",
""
],
[
"Drapal",
"Ales",
""
],
[
"Kinyon",
"Michael K.",
""
]
] |
0708.2359 | Marc Wagner | Marc Wagner | Fermionic fields in the pseudoparticle approach | Talk presented at Lattice 2007 (Vacuum Structure and Confinement), 7
pages, 3 figures | PoSLAT2007:339,2007 | null | HU-EP-07/32 | hep-lat hep-ph hep-th | null | The pseudoparticle approach is a numerical method to compute path integrals
without discretizing spacetime. The basic idea is to consider only those field
configurations, which can be represented as a linear superposition of a small
number of localized building blocks (pseudoparticles), and to replace the
functional integration by an integration over the pseudoparticle degrees of
freedom. In previous papers we have successfully applied the pseudoparticle
approach to SU(2) Yang-Mills theory. In this work we discuss the inclusion of
fermionic fields in the pseudoparticle approach. To test our method, we compute
the phase diagram of the 1+1-dimensional Gross-Neveu model in the large-N limit
as well as the chiral condensate in the crystal phase.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:52:30 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Wagner",
"Marc",
""
]
] |
0708.2360 | Demosthenes Kazanas | Manasse R. Mbonye and Demosthenes Kazanas | Can gravitational collapse sustain singularity-free trapped surfaces? | 17 pages, 3 figures, accepted for publication in International
Journal of Modern Physics D | Int.J.Mod.Phys.D17:165-177,2008 | 10.1142/S0218271808011924 | null | gr-qc astro-ph hep-th | null | In singularity generating spacetimes both the out-going and in-going
expansions of null geodesic congruences $\theta ^{+}$ and $\theta ^{-}$ should
become increasingly negative without bound, inside the horizon. This behavior
leads to geodetic incompleteness which in turn predicts the existence of a
singularity. In this work we inquire on whether, in gravitational collapse,
spacetime can sustain singularity-free trapped surfaces, in the sense that such
a spacetime remains geodetically complete. As a test case, we consider a well
known solution of the Einstien Field Equations which is Schwarzschild-like at
large distances and consists of a fluid with a $p=-\rho $ equation of state
near $r=0$. By following both the expansion parameters $\theta ^{+}$ and
$\theta ^{-}$ across the horizon and into the black hole we find that both
$\theta ^{+}$ and $\theta ^{+}\theta ^{-}$ have turning points inside the
trapped region. Further, we find that deep inside the black hole there is a
region $0\leq r<r_{0}$ (that includes the black hole center) which is not
trapped. Thus the trapped region is bounded both from outside and inside. The
spacetime is geodetically complete, a result which violates a condition for
singularity formation. It is inferred that in general if gravitational collapse
were to proceed with a $p=-\rho $ fluid formation, the resulting black hole may
be singularity-free.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 12:59:31 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Mbonye",
"Manasse R.",
""
],
[
"Kazanas",
"Demosthenes",
""
]
] |
0708.2361 | Dmitri Gal'tsov | Adel Bouchareb, Chiang-Mei Chen, Gerard Clement, Dmitri V. Gal'tsov,
Nikolai G. Scherbluk and Thomas Wolf | $G_2$ generating technique for minimal D=5 supergravity and black rings | 21 pages revtex-4, 1 figure, typo corrected in Eq. (103) | Phys.Rev.D76:104032,2007; Erratum-ibid.D78:029901,2008 | 10.1103/PhysRevD.76.104032 10.1103/PhysRevD.78.029901 | DTP-MSU/07-19, LAPTH-1203/07 | hep-th gr-qc | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | A solution generating technique is developed for D=5 minimal supergravity
with two commuting Killing vectors based on the $G_2$ U-duality arising in the
reduction of the theory to three dimensions. The target space of the
corresponding 3-dimensional sigma-model is the coset $G_{2(2)}/(SL(2,R)\times
SL(2,R))$. Its isometries constitute the set of solution generating symmetries.
These include two electric and two magnetic Harrison transformations with the
corresponding two pairs of gauge transformations, three $SL(2,R) S$-duality
transformations, and the three gravitational scale, gauge and Ehlers
transformations (altogether 14). We construct a representation of the coset in
terms of $7\times 7$ matrices realizing the automorphisms of split octonions.
Generating a new solution amounts to transforming the coset matrices by
one-parametric subgroups of $G_{2(2)}$ and subsequently solving the dualization
equations. Using this formalism we derive a new charged black ring solution
with two independent parameters of rotation.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 13:09:18 GMT"
},
{
"version": "v2",
"created": "Sat, 18 Aug 2007 02:22:52 GMT"
},
{
"version": "v3",
"created": "Sat, 7 Jun 2008 14:49:36 GMT"
}
] | 2014-11-18T00:00:00 | [
[
"Bouchareb",
"Adel",
""
],
[
"Chen",
"Chiang-Mei",
""
],
[
"Clement",
"Gerard",
""
],
[
"Gal'tsov",
"Dmitri V.",
""
],
[
"Scherbluk",
"Nikolai G.",
""
],
[
"Wolf",
"Thomas",
""
]
] |
0708.2362 | Chris Kouvaris | Chris Kouvaris | WIMP Annihilation and Cooling of Neutron Stars | 20 pages, 2 figures | Phys.Rev.D77:023006,2008 | 10.1103/PhysRevD.77.023006 | null | astro-ph | null | We study the effect of WIMP annihilation on the temperature of a neutron
star. We shall argue that the released energy due to WIMP annihilation inside
the neutron stars, might affect the temperature of stars older than 10 million
years, flattening out the temperature at $\sim 10^4$ K for a typical neutron
star.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 13:19:23 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Kouvaris",
"Chris",
""
]
] |
0708.2363 | Vahan Mkrtchyan | R. R. Kamalian, V. V. Mkrtchyan | On a constructive characterization of a class of trees related to pairs
of disjoint matchings | 22 pages, 17 figures | null | null | null | cs.DM | null | For a graph consider the pairs of disjoint matchings which union contains as
many edges as possible, and define a parameter $\alpha$ which eqauls the
cardinality of the largest matching in those pairs. Also, define $\betta$ to be
the cardinality of a maximum matching of the graph.
We give a constructive characterization of trees which satisfy the
$\alpha$=$\betta$ equality. The proof of our main theorem is based on a new
decomposition algorithm obtained for trees.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 13:19:49 GMT"
}
] | 2009-09-29T00:00:00 | [
[
"Kamalian",
"R. R.",
""
],
[
"Mkrtchyan",
"V. V.",
""
]
] |
0708.2364 | Giovanni Catanzaro Dr. | R. Ventura, G. Catanzaro, J. Christensen-Dalsgaard, M. P. Di Mauro, L.
Paterno' | A spectroscopic search for non-radial pulsations in the delta Scuti star
gamma Bootis | 9 pages, 7 figures, to be published in MNRAS | null | 10.1111/j.1365-2966.2007.12334.x | null | astro-ph | null | High-resolution spectroscopic observations of the rapidly rotating delta
Scuti star gamma Bootis have been carried out on 2005, over 6 consecutive
nights, in order to search for line-profile variability. Time series,
consisting of flux measurements at each wavelength bin across the TiII 4571.917
A line profile as a function of time, have been Fourier analyzed. The results
confirm the early detection reported by Kennelly et al. (1992) of a dominant
periodic component at frequency 21.28 c/d in the observer's frame, probably due
to a high azimuthal order sectorial mode. Moreover, we found other
periodicities at 5.06 c/d, 12.09 c/d, probably present but not secure, and at
11.70 c/d and 18.09 c/d, uncertain. The latter frequency, if present, should be
identifiable as another high azimuthal order sectorial mode and three
additional terms, probably due to low-l modes, as proved by the analysis of the
first three moments of the line. Owing to the short time baseline and the
one-site temporal sampling we consider our results only preliminary but
encouraging for a more extensive multisite campaign. A refinement of the
atmospheric physical parameters of the star has been obtained from our
spectroscopic data and adopted for preliminary computations of evolutionary
models of gamma Bootis.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 13:24:57 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Ventura",
"R.",
""
],
[
"Catanzaro",
"G.",
""
],
[
"Christensen-Dalsgaard",
"J.",
""
],
[
"Di Mauro",
"M. P.",
""
],
[
"Paterno'",
"L.",
""
]
] |
0708.2365 | Petri Vaisanen | P. Vaisanen, S. Mattila, A. Kniazev, A. Adamo, A. Efstathiou, D.
Farrah, P. H. Johansson, G. Ostlin, D. A. H. Buckley, E. B. Burgh, L. Crause,
Y. Hashimoto, P. Lira, N. Loaring, K. Nordsieck, E. Romero-Colmenero, S.
Ryder, M. Still, A. Zijlstra | Adaptive optics imaging and optical spectroscopy of a multiple merger in
a luminous infrared galaxy | 24 pages, 16 figures. Accepted MNRAS version, minor corrections only,
references added. Higher resolution version (1.3MB) is available from
http://www.saao.ac.za/~petri/bird/ulirg_bird_highres_vaisanen_v2.pdf | MNRAS 384, 886 (2008) | 10.1111/j.1365-2966.2007.12703.x | null | astro-ph | null | (abridged) We present near-infrared (NIR) adaptive optics imaging obtained
with VLT/NACO and optical spectroscopy from the Southern African Large
Telescope (SALT) of a luminous infrared galaxy (LIRG) IRAS 19115-2124. These
data are combined with archival HST imaging and Spitzer imaging and
spectroscopy, allowing us to study this disturbed interacting/merging galaxy,
dubbed the Bird, in extraordinary detail. In particular, the data reveal a
triple system where the LIRG phenomenon is dominated by the smallest of the
components.
One nucleus is a regular barred spiral with significant rotation, while
another is highly disturbed with a surface brightness distribution intermediate
to that of disk and bulge systems, and hints of remaining arm/bar structure. We
derive dynamical masses in the range 3-7x10^10 M_solar for both. The third
component appears to be a 1-2x10^10 M_solar mass irregular galaxy. The total
system exhibits HII galaxy-like optical line ratios and strengths, and no
evidence for AGN activity is found from optical or mid-infrared data. The star
formation rate is estimated to be 190 M_solar/yr. We search for SNe, super star
clusters, and detect 100-300 km/s outflowing gas from the Bird. Overall, the
Bird shows kinematic, dynamical, and emission line properties typical for cool
ultra luminous IR galaxies. However, the interesting features setting it apart
for future studies are its triple merger nature, and the location of its star
formation peak - the strongest star formation does not come from the two major
K-band nuclei, but from the third irregular component. Aided by simulations, we
discuss scenarios where the irregular component is on its first high-speed
encounter with the more massive components.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:37:08 GMT"
},
{
"version": "v2",
"created": "Tue, 13 Nov 2007 13:33:06 GMT"
}
] | 2010-02-16T00:00:00 | [
[
"Vaisanen",
"P.",
""
],
[
"Mattila",
"S.",
""
],
[
"Kniazev",
"A.",
""
],
[
"Adamo",
"A.",
""
],
[
"Efstathiou",
"A.",
""
],
[
"Farrah",
"D.",
""
],
[
"Johansson",
"P. H.",
""
],
[
"Ostlin",
"G.",
""
],
[
"Buckley",
"D. A. H.",
""
],
[
"Burgh",
"E. B.",
""
],
[
"Crause",
"L.",
""
],
[
"Hashimoto",
"Y.",
""
],
[
"Lira",
"P.",
""
],
[
"Loaring",
"N.",
""
],
[
"Nordsieck",
"K.",
""
],
[
"Romero-Colmenero",
"E.",
""
],
[
"Ryder",
"S.",
""
],
[
"Still",
"M.",
""
],
[
"Zijlstra",
"A.",
""
]
] |
0708.2366 | Betul Tanbay | Charles A. Akemann, Betul Tanbay and Ali Ulger | A Note On The Kadison-Singer Problem | null | null | null | null | math.OA | null | Let H be a separable Hilbert space with a fixed orthonormal basis (e_n),
n>=1, and B(H) be the full von Neumann algebra of the bounded linear operators
T: H -> H. Identifying l^\infty = C(\beta N) with the diagonal operators, we
consider C(\beta N) as a subalgebra of B(H). For each t in \beta N, let
[\delta_t] be the set of the states of B(H) that extend the Dirac measure
\delta_t. Our main result shows that, for each t in \beta N, this set either
lies in a finite dimensional subspace of B(H)* or else it must contain a
homeomorphic copy of \beta N.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 13:42:55 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Akemann",
"Charles A.",
""
],
[
"Tanbay",
"Betul",
""
],
[
"Ulger",
"Ali",
""
]
] |
0708.2367 | Brandon Carter | Brandon Carter | Objective and subjective time in anthropic reasoning | 15 pages Latex, work prepared at SR21 meeting, Salonika, May, 2007
and 12th Peyresq Physics workshop, June 2007, new version with corrected
typos and some additional comments and references for presentation at SR21
meeting, Athens, September 2007 | null | null | null | hep-th | null | The original formulation of the (weak) anthropic principle was prompted by a
question about objective time at a macroscopic level, namely the age of the
universe when ``anthropic'' observers such as ourselves would be most likely to
emerge. Theoretical interpretation of what one observes requires the theory to
indicate what is expected, which will commonly depend on where, and
particularly when, the observation can be expected to occur. In response to the
question of where and when, the original version of the anthropic principle
proposed an {it a priori} probability weighting proportional to the number of
``anthropic'' observers present. The present discussion takes up the question
of the time unit characterising the biological clock controlling our subjective
internal time, using a revised alternative to a line of argument due to Press,
who postulated that animal size is limited by the brittleness of bone. On the
basis of a static support condition depending on the tensile strength of flesh
rather than bone, it is reasoned here that our size should be subject to a
limit inversely proportional to the terrestrial gravitation field g, which is
itself found to be proportional (with a factor given by the 5/2 power of the
fine structure constant) to the gravitational coupling constant.This provides
an animal size limit that will in all cases be of the order of a thousandth of
the maximum mountain height, which will itself be of the order of a thousandth
of the planetary radius. The upshot, via the (strong) anthropic principle, is
that the need for brains, and therefore planets, that are large in terms of
baryon number may be what explains the weakness of gravity relative to
electromagnetism.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:35:30 GMT"
},
{
"version": "v2",
"created": "Tue, 23 Oct 2007 09:44:44 GMT"
}
] | 2007-10-23T00:00:00 | [
[
"Carter",
"Brandon",
""
]
] |
0708.2368 | Martin Kober | Martin Kober, Benjamin Koch and Marcus Bleicher | First Order Calculation of the Inclusive Cross Section pp to ZZ by
Graviton Exchange in Large Extra Dimensions | 7 pages, 7 figures, accepted for publication in Phys. Rev. D | Phys.Rev.D76:125001,2007 | 10.1103/PhysRevD.76.125001 | null | hep-ph | null | We calculate the inclusive cross section of double Z-boson production within
large extra dimensions at the Large Hadron Collider (LHC). Using perturbatively
quantized gravity in the ADD model we perform a first order calculation of the
graviton mediated contribution to the pp to ZZ cross section. At low energies
(e.g. Tevatron) this additional contribution is very small, making it virtually
unobservable, for a fundamental mass scale above 2500 GeV. At LHC energies
however, the calculation indicates that the ZZ-production rate within the ADD
model should differ significantly from the Standard Model if the new
fundamental mass scale would be below 15000 GeV. A comparison with the observed
production rate at the LHC might therefore provide direct hints on the number
and structure of the extra dimensions.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 13:58:20 GMT"
},
{
"version": "v2",
"created": "Mon, 27 Aug 2007 12:56:55 GMT"
},
{
"version": "v3",
"created": "Thu, 30 Aug 2007 11:16:00 GMT"
},
{
"version": "v4",
"created": "Thu, 18 Oct 2007 16:17:06 GMT"
},
{
"version": "v5",
"created": "Tue, 27 Nov 2007 15:16:12 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Kober",
"Martin",
""
],
[
"Koch",
"Benjamin",
""
],
[
"Bleicher",
"Marcus",
""
]
] |
0708.2369 | Shiqing Ling | Shiqing Ling | Testing for change points in time series models and limiting theorems
for NED sequences | Published at http://dx.doi.org/10.1214/009053606000001514 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org) | Annals of Statistics 2007, Vol. 35, No. 3, 1213-1237 | 10.1214/009053606000001514 | IMS-AOS-AOS0202 | math.ST stat.TH | null | This paper first establishes a strong law of large numbers and a strong
invariance principle for forward and backward sums of near-epoch dependent
sequences. Using these limiting theorems, we develop a general asymptotic
theory on the Wald test for change points in a general class of time series
models under the no change-point hypothesis. As an application, we verify our
assumptions for the long-memory fractional ARIMA model.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:00:25 GMT"
}
] | 2007-08-22T00:00:00 | [
[
"Ling",
"Shiqing",
""
]
] |
0708.2370 | Denis Dujmic | D. Dujmic, H. Tomita, M. Lewandowska, S. Ahlen, P. Fisher, S.
Henderson, A. Kaboth, G. Kohse, R. Lanza, J. Monroe, A. Roccaro, G. Sciolla,
N. Skvorodnev, R. Vanderspek, H. Wellenstein, R. Yamamoto | Observation of the 'head-tail' effect in nuclear recoils of low-energy
neutrons | 14 pages, 8 figures, submitted to Nucl.Instr.Meth | Nucl.Instrum.Meth.A584:327-333,2008; Erratum-ibid.A592:123,2008 | 10.1016/j.nima.2007.10.037 10.1016/j.nima.2008.04.001 | null | physics.ins-det astro-ph hep-ex | null | Directional detection of dark matter can provide unambiguous observation of
dark matter interactions even in the presence of background. This article
presents an experimental method to measure the direction tag ("head-tail") of
the dark matter wind by detecting the scintillation light created by the
elastic nuclear recoils in the scattering of dark matter particles with the
detector material. The technique is demonstrated by tagging the direction of
the nuclear recoils created in the scattering of low-energy neutrons with CF4
in a low-pressure time-projection chamber that is developed by the DMTPC
collaboration. The measurement of the decreasing ionization rate along the
recoil trajectory provides the direction tag of the incoming neutrons, and
proves that the "head-tail" effect can be observed.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:07:01 GMT"
},
{
"version": "v2",
"created": "Tue, 9 Oct 2007 15:21:46 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Dujmic",
"D.",
""
],
[
"Tomita",
"H.",
""
],
[
"Lewandowska",
"M.",
""
],
[
"Ahlen",
"S.",
""
],
[
"Fisher",
"P.",
""
],
[
"Henderson",
"S.",
""
],
[
"Kaboth",
"A.",
""
],
[
"Kohse",
"G.",
""
],
[
"Lanza",
"R.",
""
],
[
"Monroe",
"J.",
""
],
[
"Roccaro",
"A.",
""
],
[
"Sciolla",
"G.",
""
],
[
"Skvorodnev",
"N.",
""
],
[
"Vanderspek",
"R.",
""
],
[
"Wellenstein",
"H.",
""
],
[
"Yamamoto",
"R.",
""
]
] |
0708.2371 | Chaohui Zhang | Chaohui Zhang | Singularities of quadratic differentials and extremal Teichm\"{u}ller
mappings defined by Dehn twists | 13 pages | null | null | null | math.CV math.GT | null | Let $S$ be a Riemann surface of type $(p,n)$ with $3p-3+n>0$. Let $\omega$ be
a pseudo-Anosov map of $S$ that is obtained from Dehn twists along two families
$\{A,B\}$ of simple closed geodesics that fill $S$. Then $\omega$ can be
realized as an extremal Teichm\"{u}ller mapping on a surface of type $(p,n)$
which is also denoted by $S$. Let $\phi$ be the corresponding holomorphic
quadratic differential on $S$. In this paper, we compare the locations of some
distinguished points on $S$ in the $\phi$-flat metric to their locations with
respect to the complete hyperbolic metric. More precisely, we show that all
possible non-puncture zeros of $\phi$ must stay away from all closures of once
punctured disk components of $S\backslash \{A, B\}$, and the closure of each
disk component of $S\backslash \{A, B\}$ contains at most one zero of $\phi$.
As a consequence of the result, we assert that the number of distinct zeros and
poles of $\phi$ is less than or equal to the number of components of
$S\backslash \{A, B\}$.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:19:37 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Zhang",
"Chaohui",
""
]
] |
0708.2372 | R. N. Manchester | R. N. Manchester | Searching for a Pulsar in SN1987A | 10 pages, 3 figures. To appear in "Supernova 1987A: Twenty Years
After: Supernovae and Gamma-Ray Bursters", edited by S. Immler, K. W. Weiler
and R. McCray, American Institute of Physics, New York, 2007, in press | AIPConf.Proc.937:134-143,2007 | 10.1063/1.2803553 | null | astro-ph | null | SN 1987A offered a unique opportunity to detect a pulsar at the very
beginning of its life and to study its early evolution. Despite many searches
at radio and optical wavelengths, no pulsar has yet been detected. Details of a
recent search using the Parkes radio telescope are given. Limits on the X-ray,
optical and radio luminosity of a point source at the centre of SN 1987A place
limits on the properties of a central neutron star. However, neither these nor
the pulsar limits preclude the presence of a relatively slowly rotating neutron
star (P >~ 100 ms) with a moderate surface dipole magnetic field in SN 1987A.
Galactic studies suggest that a significant fraction of pulsars are born with
parameters in this range. In view of this, continued searches for a pulsar in
SN 1987A are certainly justified.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:25:54 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Manchester",
"R. N.",
""
]
] |
0708.2373 | Ching-Kang Ing | Ching-Kang Ing | Accumulated prediction errors, information criteria and optimal
forecasting for autoregressive time series | Published at http://dx.doi.org/10.1214/009053606000001550 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org) | Annals of Statistics 2007, Vol. 35, No. 3, 1238-1277 | 10.1214/009053606000001550 | IMS-AOS-AOS0247 | math.ST stat.TH | null | The predictive capability of a modification of Rissanen's accumulated
prediction error (APE) criterion, APE$_{\delta_n}$, is investigated in
infinite-order autoregressive (AR($\infty$)) models. Instead of accumulating
squares of sequential prediction errors from the beginning, APE$_{\delta_n}$ is
obtained by summing these squared errors from stage $n\delta_n$, where $n$ is
the sample size and $1/n\leq \delta_n\leq 1-(1/n)$ may depend on $n$. Under
certain regularity conditions, an asymptotic expression is derived for the
mean-squared prediction error (MSPE) of an AR predictor with order determined
by APE$_{\delta_n}$. This expression shows that the prediction performance of
APE$_{\delta_n}$ can vary dramatically depending on the choice of $\delta_n$.
Another interesting finding is that when $\delta_n$ approaches 1 at a certain
rate, APE$_{\delta_n}$ can achieve asymptotic efficiency in most practical
situations. An asymptotic equivalence between APE$_{\delta_n}$ and an
information criterion with a suitable penalty term is also established from the
MSPE point of view. This offers new perspectives for understanding the
information and prediction-based model selection criteria. Finally, we provide
the first asymptotic efficiency result for the case when the underlying
AR($\infty$) model is allowed to degenerate to a finite autoregression.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:28:21 GMT"
}
] | 2007-08-22T00:00:00 | [
[
"Ing",
"Ching-Kang",
""
]
] |
0708.2374 | Rustem Khasanov | R. Khasanov, S. Str\"assle, D. Di Castro, T. Masui, S. Miyasaka, S.
Tajima, A. Bussmann-Holder and H. Keller | Universal observation of multiple order parameters in cuprate
superconductors | 5 pages, 3 figures | Phys. Rev. Lett. 99, 237601 (2007) | 10.1103/PhysRevLett.99.237601 | null | cond-mat.supr-con | null | The temperature dependence of the London penetration depth \lambda was
measured for an untwined single crystal of YBa_2Cu_3O_{7-\delta} along the
three principal crystallographic directions (a, b, and c). Both in-plane
components (\lambda_a and \lambda_b) show an inflection point in their
temperature dependence which is absent in the component along the c-direction
(\lambda_c). The data provide convincing evidence that the in-plane
superconducting order parameter is a mixture of s+d-wave symmetry whereas it is
exclusively s-wave along the c-direction. In conjunction with previous results
it is concluded that coupled s+d-order parameters are universal and intrinsic
to cuprate superconductors.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:34:09 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Khasanov",
"R.",
""
],
[
"Strässle",
"S.",
""
],
[
"Di Castro",
"D.",
""
],
[
"Masui",
"T.",
""
],
[
"Miyasaka",
"S.",
""
],
[
"Tajima",
"S.",
""
],
[
"Bussmann-Holder",
"A.",
""
],
[
"Keller",
"H.",
""
]
] |
0708.2375 | Sebastian M\"uller | Jonathan P. Keating and Sebastian M\"uller | Resummation and the semiclassical theory of spectral statistics | 10 pages, no figures | Proc. R. Soc. Lond. A 463, 3241 (2007) | 10.1098/rspa.2007.0178 | null | nlin.CD | null | We address the question as to why, in the semiclassical limit, classically
chaotic systems generically exhibit universal quantum spectral statistics
coincident with those of Random Matrix Theory. To do so, we use a semiclassical
resummation formalism that explicitly preserves the unitarity of the quantum
time evolution by incorporating duality relations between short and long
classical orbits. This allows us to obtain both the non-oscillatory and the
oscillatory contributions to spectral correlation functions within a unified
framework, thus overcoming a significant problem in previous approaches. In
addition, our results extend beyond the universal regime to describe the
system-specific approach to the semiclassical limit.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:35:37 GMT"
}
] | 2009-06-11T00:00:00 | [
[
"Keating",
"Jonathan P.",
""
],
[
"Müller",
"Sebastian",
""
]
] |
0708.2376 | Marcos Montenegro | Ezequiel R. Barbosa, Marcos Montenegro | On the geometric dependence of Riemannian Sobolev best constants | 19 pages | null | null | null | math.DG math.AP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We concerns here with the continuity on the geometry of the second Riemannian
L^p-Sobolev best constant B_0(p,g) associated to the AB program. Precisely, for
1 <= p <= 2, we prove that B_0(p,g) depends continuously on g in the
C^2-topology. Moreover, this topology is sharp for p = 2. From this discussion,
we deduce some existence and C^0-compactness results on extremal functions.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:40:09 GMT"
},
{
"version": "v2",
"created": "Sun, 10 Aug 2008 23:38:12 GMT"
}
] | 2008-08-11T00:00:00 | [
[
"Barbosa",
"Ezequiel R.",
""
],
[
"Montenegro",
"Marcos",
""
]
] |
0708.2377 | Roberto Alamino | Roberto C. Alamino, Nestor Caticha | Online Learning in Discrete Hidden Markov Models | 8 pages, 6 figures | null | 10.1063/1.2423274 | null | stat.ML | null | We present and analyse three online algorithms for learning in discrete
Hidden Markov Models (HMMs) and compare them with the Baldi-Chauvin Algorithm.
Using the Kullback-Leibler divergence as a measure of generalisation error we
draw learning curves in simplified situations. The performance for learning
drifting concepts of one of the presented algorithms is analysed and compared
with the Baldi-Chauvin algorithm in the same situations. A brief discussion
about learning and symmetry breaking based on our results is also presented.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 14:41:58 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Alamino",
"Roberto C.",
""
],
[
"Caticha",
"Nestor",
""
]
] |
0708.2378 | Glenn Barnich | Glenn Barnich and Geoffrey Compere | Surface charge algebra in gauge theories and thermodynamic integrability | 40 pages Latex file, published version | J.Math.Phys.49:042901,2008 | 10.1063/1.2889721 | ULB-TH/06-30 | gr-qc hep-th | null | Surface charges and their algebra in interacting Lagrangian gauge field
theories are investigated by using techniques from the variational calculus. In
the case of exact solutions and symmetries, the surface charges are interpreted
as a Pfaff system. Integrability is governed by Frobenius' theorem and the
charges associated with the derived symmetry algebra are shown to vanish. In
the asymptotic context, we provide a generalized covariant derivation of the
result that the representation of the asymptotic symmetry algebra through
charges may be centrally extended. Finally, we make contact with Hamiltonian
and with covariant phase space methods.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 15:40:13 GMT"
},
{
"version": "v2",
"created": "Sun, 18 May 2008 22:41:25 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Barnich",
"Glenn",
""
],
[
"Compere",
"Geoffrey",
""
]
] |
0708.2379 | Mark Westmoquette | M. S. Westmoquette, K. M. Exter, L. J. Smith and J. S. Gallagher III | Gemini GMOS/IFU spectroscopy of NGC 1569 - I: Mapping the properties of
a young star cluster and its environment | 22 pages, 14 figures, 4 tables, accepted to MNRAS | null | 10.1111/j.1365-2966.2007.12346.x | null | astro-ph | null | [Abridged] We present Gemini-North GMOS/IFU observations of a young star
cluster (cluster 10) and its environment near the centre of the dwarf irregular
starburst galaxy NGC 1569. This forms part of a larger and on-going study of
the formation and collimation mechanisms of galactic winds, including three
additional IFU pointings in NGC 1569 covering the base of the galactic wind
which are analysed in a companion paper. The good spatial- and
spectral-resolution of these GMOS/IFU observations, covering 4740-6860 A, allow
us to probe the interactions between clusters and their environments on small
scales. Combining our GMOS spectrum with HST imaging, we find that cluster 10
is composed of two very close components with ages of 5-7 Myr and <5 Myr, and a
combined mass of 7 +/- 5 x 10^3 Msun.
A detailed analysis of the H_alpha emission line profile shapes across the
whole field-of-view shows them to be composed of a bright narrow feature
(intrinsic FWHM ~ 50 km/s) superimposed on a fainter broad component (FWHM <
300 km/s). By mapping the properties of each individual component, we
investigate the small-scale structure and properties of the ionized ISM,
including reddening, excitation and electron densities, and for the first time
find spatial correlations between the line component properties. We discuss in
detail the possible mechanisms that could give rise to the two components and
these correlations, and conclude that the most likely explanation for the broad
emission is that it is produced in a turbulent mixing layer on the surface of
the cool gas clumps embedded within the hot, fast-flowing cluster winds. We
conclude we are sampling well within the outer bounding shocks of the expanding
superbubbles and within the outflow 'energy injection zone'.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 15:03:42 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Westmoquette",
"M. S.",
""
],
[
"Exter",
"K. M.",
""
],
[
"Smith",
"L. J.",
""
],
[
"Gallagher",
"J. S.",
"III"
]
] |
0708.2380 | H\'{e}l\`{e}ne Massam | G\'erard Letac, H\'el\`ene Massam | Wishart distributions for decomposable graphs | Published at http://dx.doi.org/10.1214/009053606000001235 in the
Annals of Statistics (http://www.imstat.org/aos/) by the Institute of
Mathematical Statistics (http://www.imstat.org) | Annals of Statistics 2007, Vol. 35, No. 3, 1278-1323 | 10.1214/009053606000001235 | IMS-AOS-AOS0243 | math.ST stat.TH | null | When considering a graphical Gaussian model ${\mathcal{N}}_G$ Markov with
respect to a decomposable graph $G$, the parameter space of interest for the
precision parameter is the cone $P_G$ of positive definite matrices with fixed
zeros corresponding to the missing edges of $G$. The parameter space for the
scale parameter of ${\mathcal{N}}_G$ is the cone $Q_G$, dual to $P_G$, of
incomplete matrices with submatrices corresponding to the cliques of $G$ being
positive definite. In this paper we construct on the cones $Q_G$ and $P_G$ two
families of Wishart distributions, namely the Type I and Type II Wisharts. They
can be viewed as generalizations of the hyper Wishart and the inverse of the
hyper inverse Wishart as defined by Dawid and Lauritzen [Ann. Statist. 21
(1993) 1272--1317]. We show that the Type I and II Wisharts have properties
similar to those of the hyper and hyper inverse Wishart. Indeed, the inverse of
the Type II Wishart forms a conjugate family of priors for the covariance
parameter of the graphical Gaussian model and is strong directed hyper Markov
for every direction given to the graph by a perfect order of its cliques, while
the Type I Wishart is weak hyper Markov. Moreover, the inverse Type II Wishart
as a conjugate family presents the advantage of having a multidimensional shape
parameter, thus offering flexibility for the choice of a prior.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 15:10:15 GMT"
}
] | 2009-09-29T00:00:00 | [
[
"Letac",
"Gérard",
""
],
[
"Massam",
"Hélène",
""
]
] |
0708.2381 | Rickard Jonsson | Rickard Jonsson | Embedding spacetime via a geodesically equivalent metric of Euclidean
signature | 28 pages, 17 figures. As compared to the published version there are
corrections to Eqs. 46-49 (no impact on the discussion) and minor cosmetical
updates in the figures. An addendum is also included, 5 pages, 2 figures | Gen.Rel.Grav.33:1207,2001 | 10.1023/A:1012037418513 | null | gr-qc | null | Starting from the equations of motion in a 1 + 1 static, diagonal, Lorentzian
spacetime, such as the Schwarzschild radial line element, I find another
metric, but with Euclidean signature, which produces the same geodesics x(t).
This geodesically equivalent, or dual, metric can be embedded in ordinary
Euclidean space. On the embedded surface freely falling particles move on the
shortest path. Thus one can visualize how acceleration in a gravitational field
is explained by particles moving freely in a curved spacetime. Freedom in the
dual metric allows us to display, with substantial curvature, even the weak
gravity of our Earth. This may provide a nice pedagogical tool for elementary
lectures on general relativity. I also study extensions of the dual metric
scheme to higher dimensions. In an addendum I extend the analysis concerning
the shape of an embedding of the dual spacetime of a line through a planet of
constant proper density.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 15:28:00 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Jonsson",
"Rickard",
""
]
] |
0708.2382 | Ingo Fr\"ohlich | I. Froehlich, L. Cazon Boado, T. Galatyuk, V. Hejny, R. Holzmann, M.
Kagarlis, W. Kuehn, J.G.Messchendorp, V. Metag, M.-A. Pleier, W. Przygoda, B.
Ramstein, J. Ritman, P. Salabura, J. Stroth and M. Sudol | Pluto: A Monte Carlo Simulation Tool for Hadronic Physics | XI International Workshop on Advanced Computing and Analysis
Techniques in Physics Research, April 23-27 2007, Amsterdam, the Netherlands | PoS ACAT2007:076,2007 | null | null | nucl-ex | null | Pluto is a Monte-Carlo event generator designed for hadronic interactions
from Pion production threshold to intermediate energies of a few GeV per
nucleon, as well as for studies of heavy ion reactions. This report gives an
overview of the design of the package, the included models and the user
interface.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 15:41:58 GMT"
},
{
"version": "v2",
"created": "Tue, 6 Nov 2007 16:23:11 GMT"
}
] | 2009-04-15T00:00:00 | [
[
"Froehlich",
"I.",
""
],
[
"Boado",
"L. Cazon",
""
],
[
"Galatyuk",
"T.",
""
],
[
"Hejny",
"V.",
""
],
[
"Holzmann",
"R.",
""
],
[
"Kagarlis",
"M.",
""
],
[
"Kuehn",
"W.",
""
],
[
"Messchendorp",
"J. G.",
""
],
[
"Metag",
"V.",
""
],
[
"Pleier",
"M. -A.",
""
],
[
"Przygoda",
"W.",
""
],
[
"Ramstein",
"B.",
""
],
[
"Ritman",
"J.",
""
],
[
"Salabura",
"P.",
""
],
[
"Stroth",
"J.",
""
],
[
"Sudol",
"M.",
""
]
] |
0708.2383 | Juan Carlos Pardo Millan | Loic Chaumont (LAREMA), Andreas Kyprianou (UB), Juan Carlos Pardo
Millan (PMA, UB) | Some explicit identities associated with positive self-similar Markov
processes | null | null | null | null | math.PR | null | We consider some special classes of L\'evy processes with no gaussian
component whose L\'evy measure is of the type $\pi(dx)=e^{\gamma x}\nu(e^x-1)
dx$, where $\nu$ is the density of the stable L\'evy measure and $\gamma$ is a
positive parameter which depends on its characteristics. These processes were
introduced in \cite{CC} as the underlying L\'evy processes in the Lamperti
representation of conditioned stable L\'evy processes. In this paper, we
compute explicitly the law of these L\'evy processes at their first exit time
from a finite or semi-finite interval, the law of their exponential functional
and the first hitting time probability of a pair of points.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 15:33:51 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Chaumont",
"Loic",
"",
"LAREMA"
],
[
"Kyprianou",
"Andreas",
"",
"UB"
],
[
"Millan",
"Juan Carlos Pardo",
"",
"PMA, UB"
]
] |
0708.2384 | Indranil Mitra Mr | Indranil Mitra, Sisir Roy, Gary Hastings | Co-operativity in neurons and the role of noise in brain | 12 Pages, Updated Version, SPIE 2007 Conference | null | null | null | q-bio.NC q-bio.QM | null | In view of some recent results in case of the dopaminergic neurons exhibiting
long range correlations in VTA of the limbic brain we are interested to find
out whether any stochastic nonlinear response may be reproducible in the nano
scales usimg the results of quantum mechanics. We have developed a scheme to
investigate this situation in this paper by taking into consideration the
Schrodinger equation (SE) in an arbitrary manifold with a metric, which is in
some sense a special case of the heat kernel equation. The special case of this
heat kernel equation is the diffusion equation, which may reproduce some key
phenomena of the neural activities. We make a dual equivalent circuit model of
SE and incorporate non commutativity and noise inside the circuit scheme. The
behaviour of the circuit elements with interesting limits are investigated. The
most bizarre part is the long range response of the model by dint of the
Central Limit Theorem, which is responsible for coherent behaviour of a large
assembly of neurons.
| [
{
"version": "v1",
"created": "Wed, 15 Aug 2007 14:47:57 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Mitra",
"Indranil",
""
],
[
"Roy",
"Sisir",
""
],
[
"Hastings",
"Gary",
""
]
] |
0708.2385 | Simon Casassus | S. Casassus (1), L.-A. Nyman (2,3), C. Dickinson (4,5), T. J. Pearson
(4) | A centimetre-wave excess over free-free emission in planetary nebulae | accepted for publication in MNRAS; corrected the title (the short
running title was copied in the first posting) | null | 10.1111/j.1365-2966.2007.12366.x | null | astro-ph | null | We report a centimetre-wave (cm-wave, 5-31GHz) excess over free-free emission
in PNe. Accurate 31 and 250GHz measurements show that the 31GHz flux densities
in our sample are systematically higher than the level of optically thin
free-free continuum extrapolated from 250GHz. The 31GHz excess is observed,
within one standard deviation, in all 18 PNe with reliable 31 and 250GHz data,
and is significant in 9 PNe. The only exception is the peculiar object M2-9,
whose radio spectrum is that of an optically thick stellar wind. On average the
fraction of non-free-free emission represents 51% of the total flux density at
31GHz, with a scatter of 11%. The average 31-250GHz spectral index of our
sample is <alpha_{31}^{250}> = -0.43+-0.03 (in flux density, with a scatter of
0.14). The 31--250 GHz drop is reminiscent of the anomalous foreground observed
in the diffuse ISM by CMB anisotropy experiments. The 5--31 GHz spectral
indices are consistent with both flat spectra and spinning dust emissivities,
given the 10% calibration uncertainty of the comparison 5GHz data. But a
detailed study of the objects with the largest cm-excess, including the low
frequency data available in the literature, shows that present spinning dust
models cannot alone explain the cm-excess in PNe. Although we have no
definitive interpretation of our data, the least implausible explanation
involves a synchrotron component absorbed by a cold nebular screen. We give
flux densities for 37 objects at 31GHz, and for 26 objects at 250GHz.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 15:43:36 GMT"
},
{
"version": "v2",
"created": "Wed, 21 Nov 2007 17:51:42 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Casassus",
"S.",
""
],
[
"Nyman",
"L. -A.",
""
],
[
"Dickinson",
"C.",
""
],
[
"Pearson",
"T. J.",
""
]
] |
0708.2386 | Diego Marques | G. S. Lozano, D. Marques, F. A. Schaposnik | Non-Abelian Vortices on the Torus | null | JHEP 0709:095,2007 | 10.1088/1126-6708/2007/09/095 | null | hep-th | null | We study periodic arrays of non-Abelian vortices in an $SU(N) \times U(1)$
gauge theory with $N_f$ flavors of fundamental matter multiplets. We carefully
discuss the corresponding twisted boundary conditions on the torus and propose
an ansatz to solve the first order Bogomolnyi equations which we find by
looking to a bound of the energy. We solve the equations numerically and
construct explicit vortex solutions.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 15:51:17 GMT"
}
] | 2009-06-11T00:00:00 | [
[
"Lozano",
"G. S.",
""
],
[
"Marques",
"D.",
""
],
[
"Schaposnik",
"F. A.",
""
]
] |
0708.2387 | Lo\"ic Duchayne | Lo\"ic Duchayne, Flavien Mercier and Peter Wolf | Orbit determination for next generation space clocks | 18 pages, 7 figures, submitted to Journal Of Geodesy | null | null | null | physics.space-ph physics.geo-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Over the last decade of the 20th century and the first few years of the 21st,
the uncertainty of atomic clocks has decreased by about two orders of
magnitude, passing from the low 10^-14 to below 10^-16, in relative frequency .
Space applications in fundamental physics, geodesy, time/frequency metrology,
navigation etc... are among the most promising for this new generation of
clocks. Onboard terrestrial or solar system satellites, their exceptional
frequency stability and accuracy makes them a prime tool to test the
fundamental laws of nature, and to study gravitational potentials and their
evolution.
In this paper, we study in more detail the requirements on orbitography
compatible with operation of next generation space clocks at the required
uncertainty based on a completely relativistic model. Using the ACES (Atomic
Clock Ensemble in Space) mission as an example, we show that the required
accuracy goal can be reached with relatively modest constraints on the
orbitography of the space clock, much less stringent than expected from "naive"
estimates. Our results are generic to all space clocks and represent a
significant step towards the generalised use of next generation space clocks in
fundamental physics, geodesy, and time/frequency metrology.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:03:32 GMT"
},
{
"version": "v2",
"created": "Mon, 29 Oct 2007 10:15:57 GMT"
},
{
"version": "v3",
"created": "Sun, 3 May 2009 21:04:13 GMT"
}
] | 2009-05-04T00:00:00 | [
[
"Duchayne",
"Loïc",
""
],
[
"Mercier",
"Flavien",
""
],
[
"Wolf",
"Peter",
""
]
] |
0708.2388 | Victor M. Villalba | A. Lopez, V. M. Villalba, E. Medina | Two electron entanglement enhancement by an inelastic scattering process | 8 pages, to appear in Phys. Rev B | null | 10.1103/PhysRevB.76.115107 | null | quant-ph | null | In order to assess inelastic effects on two fermion entanglement production,
we address an exactly solvable two-particle scattering problem where the target
is an excitable scatterer. Useful entanglement, as measured by the two particle
concurrence, is obtained from post-selection of oppositely scattered particle
states. The $S$ matrix formalism is generalized in order to address non-unitary
evolution in the propagating channels. We find the striking result that
inelasticity can actually increase concurrence as compared to the elastic case
by increasing the uncertainty of the single particle subspace. Concurrence
zeros are controlled by either single particle resonance energies or total
reflection conditions that ascertain precisely one of the electron states.
Concurrence minima also occur and are controlled by entangled resonance
situations were the electron becomes entangled with the scatterer, and thus
does not give up full information of its state. In this model, exciting the
scatterer can never fully destroy phase coherence due to an intrinsic limit to
the probability of inelastic events.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:08:47 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Lopez",
"A.",
""
],
[
"Villalba",
"V. M.",
""
],
[
"Medina",
"E.",
""
]
] |
0708.2389 | Stefan Str\"uber | Stefan Str\"uber, Dirk H. Rischke | Vector and axialvector mesons at nonzero temperature within a gauged
linear sigma model | 20 pages, 6 figures | Phys.Rev.D77:085004,2008 | 10.1103/PhysRevD.77.085004 | null | hep-th hep-ph nucl-th | null | We consider vector and axialvector mesons in the framework of a gauged linear
sigma model with chiral $U(N_f)_R \times U(N_f)_L$ symmetry. For $N_f=2$, we
investigate the behavior of the chiral condensate and the meson masses as a
function of temperature by solving a system of coupled Dyson-Schwinger
equations derived via the 2PI formalism in double-bubble approximation. We find
that the inclusion of vector and axialvector mesons tends to sharpen the chiral
transition. Within our approximation scheme, the mass of the $\rho$ meson
increases by about 100 MeV towards the chiral transition.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:10:29 GMT"
},
{
"version": "v2",
"created": "Fri, 9 Nov 2007 16:29:34 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Strüber",
"Stefan",
""
],
[
"Rischke",
"Dirk H.",
""
]
] |
0708.2390 | Rachel Akeson | R. L. Akeson, W. K. M. Rice, A. F. Boden, A. I. Sargent, J. M.
Carpenter, G. Bryden | The circumbinary disk of HD 98800 B: Evidence for disk warping | 19 pages, 3 figures, to appear in the Astrophysical Journal | Astrophys.J.670:1240-1246,2007 | 10.1086/522579 | null | astro-ph | null | The quadruple young stellar system HD 98800 consists of two spectroscopic
binary pairs with a circumbinary disk around the B component. Recent work by
Boden and collaborators using infrared interferometry and radial velocity data
resulted in a determination of the physical orbit for HD 98800 B. We use the
resulting inclination of the binary and the measured extinction toward the B
component stars to constrain the distribution of circumbinary material.
Although a standard optically and geometrically thick disk model can reproduce
the spectral energy distribution, it can not account for the observed
extinction if the binary and the disk are co-planar. We next constructed a
dynamical model to investigate the influence of the A component, which is not
in the Ba-Bb orbital plane, on the B disk. We find that these interactions have
a substantial impact on the inclination of the B circumbinary disk with respect
to the Ba-Bb orbital plane. The resulting warp would be sufficient to place
material into the line of sight and the non-coplanar disk orientation may also
cause the upper layers of the disk to intersect the line of sight if the disk
is geometrically thick. These simulations also support that the dynamics of the
Ba-Bb orbit clear the inner region to a radius of ~3 AU. We then discuss
whether the somewhat unusual properties of the HD 98800 B disk are consistent
with material remnant from the star formation process or with more recent
creation by collisions from larger bodies.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:14:44 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Akeson",
"R. L.",
""
],
[
"Rice",
"W. K. M.",
""
],
[
"Boden",
"A. F.",
""
],
[
"Sargent",
"A. I.",
""
],
[
"Carpenter",
"J. M.",
""
],
[
"Bryden",
"G.",
""
]
] |
0708.2391 | Arturo Magidin | Arturo Magidin | On the capability of finite groups of class two and prime exponent | 43 pp; incorporates results from older paper; fix amsrefs/hyperref
incompatibility and a typo | null | null | null | math.GR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the capability of $p$-groups of class two and odd prime exponent.
The question of capability is shown to be equivalent to a statement about
vector spaces and linear transformations, and using the equivalence we give
proofs of some old results and several new ones. In particular, we establish a
number of new necessary and new sufficient conditions for capability, including
a sufficient condition based only on the ranks of $G/Z(G)$ and $[G,G]$.
Finally, we characterise the capable groups among the 5-generated groups in
this class.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:18:46 GMT"
},
{
"version": "v2",
"created": "Mon, 19 Jan 2009 20:17:27 GMT"
}
] | 2009-01-19T00:00:00 | [
[
"Magidin",
"Arturo",
""
]
] |
0708.2392 | Pascal Grange | Pascal Grange, Sakura Schafer-Nameki | Towards mirror symmetry \`a la SYZ for generalized Calabi-Yau manifolds | 30 pages, 3 figures, LaTeX; v2: references added | JHEP 0710:052,2007 | 10.1088/1126-6708/2007/10/052 | null | hep-th | null | Fibrations of flux backgrounds by supersymmetric cycles are investigated. For
an internal six-manifold M with static SU(2) structure and mirror \hat{M}, it
is argued that the product M x \hat{M} is doubly fibered by supersymmetric
three-tori, with both sets of fibers transverse to M and \hat{M}. The mirror
map is then realized by T-dualizing the fibers. Mirror-symmetric properties of
the fluxes, both geometric and non-geometric, are shown to agree with previous
conjectures based on the requirement of mirror symmetry for Killing
prepotentials. The fibers are conjectured to be destabilized by fluxes on
generic SU(3)xSU(3) backgrounds, though they may survive at type-jumping
points. T-dualizing the surviving fibers ensures the exchange of pure spinors
under mirror symmetry.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:38:15 GMT"
},
{
"version": "v2",
"created": "Tue, 28 Aug 2007 17:37:47 GMT"
}
] | 2009-06-11T00:00:00 | [
[
"Grange",
"Pascal",
""
],
[
"Schafer-Nameki",
"Sakura",
""
]
] |
0708.2393 | Nikolai Kivel | Nikolai Kivel | QCD factorization approach for rare $\bar B^0\to D^*\gamma$ decay | null | null | null | RUB-TPII-03/07 | hep-ph | null | We present the estimate of the branching ratio for the rare decay $\bar
B^0\to D^*\gamma$. We use QCD factorization approach in order to compute the
amplitude of the process. The calculation is carried out with the leading order
accuracy. % Our consideration is based on the % factorization for the amplitude
of the process which % has been derived with the leading order accuracy. The
appearing non-perturbative matrix elements have been estimated using the
large$-N_c$ limit and QCD sum rule approach. We obtained that $\mathcal{B}(\bar
B^0\to D^*\gamma)\simeq 1.52\times 10^{-7}$. Such value of the branching
fraction is too small in order to be measured at present experiments.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:36:16 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Kivel",
"Nikolai",
""
]
] |
0708.2394 | Shunsuke Takagi | Craig Huneke, Mircea Mustata, Shunsuke Takagi and Kei-ichi Watanabe | F-thresholds, tight closure, integral closure, and multiplicity bounds | 22 pages; v.2: minor changes, to appear in Michigan Math. J | null | null | null | math.AC math.AG | null | The F-threshold $c^J(\a)$ of an ideal $\a$ with respect to the ideal $J$ is a
positive characteristic invariant obtained by comparing the powers of $\a$ with
the Frobenius powers of $J$. We show that under mild assumptions, we can detect
the containment in the integral closure or the tight closure of a parameter
ideal using F-thresholds. We formulate a conjecture bounding $c^J(\a)$ in terms
of the multiplicities $e(\a)$ and $e(J)$, when $\a$ and $J$ are
zero-dimensional ideals, and $J$ is generated by a system of parameters. We
prove the conjecture when $J$ is a monomial ideal in a polynomial ring, and
also when $\a$ and $J$ are generated by homogeneous systems of parameters in a
Cohen-Macaulay graded $k$-algebra.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:28:41 GMT"
},
{
"version": "v2",
"created": "Mon, 26 Nov 2007 02:33:03 GMT"
}
] | 2007-11-26T00:00:00 | [
[
"Huneke",
"Craig",
""
],
[
"Mustata",
"Mircea",
""
],
[
"Takagi",
"Shunsuke",
""
],
[
"Watanabe",
"Kei-ichi",
""
]
] |
0708.2395 | Milton Chowdhury | M. M. Chowdhury | Key Agreement and Authentication Schemes Using Non-Commutative
Semigroups | null | null | null | null | cs.CR | null | We give a new two-pass authentication scheme, whichis a generalisation of an
authentication scheme of Sibert-Dehornoy-Girault based on the Diffie-Hellman
conjugacy problem. Compared to the above scheme, for some parameters it is more
efficient with respect to multiplications. We sketch a proof that our
authentication scheme is secure. We give a new key agreement protocols.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:38:43 GMT"
},
{
"version": "v2",
"created": "Mon, 20 Aug 2007 00:15:01 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Chowdhury",
"M. M.",
""
]
] |
0708.2396 | Scott M. Cohen | Scott M. Cohen | Understanding entanglement as resource: locally distinguishing
unextendible product bases | Final, published version. Many revisions following very useful
suggestions of the referee have been added. In particular, Appendix A has
been completely rewritten | PHYSICAL REVIEW A 77, 012304 (2008) | 10.1103/PhysRevA.77.012304 | null | quant-ph | null | It is known that the states in an unextendible product basis (UPB) cannot be
distinguished perfectly when the parties are restricted to local operations and
classical communication (LOCC). Previous discussions of such bases have left
open the following question: What entanglement resources are necessary and/or
sufficient for this task to be possible with LOCC? In this paper, I present
protocols which use entanglement more efficiently than teleportation to
distinguish certain classes of UPB's. The ideas underlying my approach to this
problem offer rather general insight into why entanglement is useful for such
tasks.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:43:46 GMT"
},
{
"version": "v2",
"created": "Tue, 8 Jan 2008 23:33:45 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Cohen",
"Scott M.",
""
]
] |
0708.2397 | Milton Chowdhury | M. M. Chowdhury | On the AAGL Protocol | This version differs from the first version because a new attack is
given | null | null | null | cs.CR | null | Recently the AAGL (Anshel-Anshel-Goldfeld-Lemieux) has been proposed which
can be used for RFID tags. We give algorithms for the problem (we call the
MSCSPv) on which the security of the AAGL protocol is based upon. Hence we give
various attacks for general parameters on the recent AAGL protocol proposed.
One of our attacks is a deterministic algorithm which has space complexity and
time complexity both atleast exponentialin the worst case. In a better case
using a probabilistic algorithm the time complexity canbe
O(|XSS(ui')^L5*(n^(1+e)) and the space complexity can be O(|XSS(ui')|^L6),
where the element ui' is part of a public key, n is the index of braid group,
XSS is a summit type set and e is a constant in a limit. The above shows the
AAGL protocol is potentially not significantly more secure as using key
agreement protocols based on the conjugacy problem such as the AAG
(Anshel-Anshel-Goldfeld) protocol because both protocols can be broken with
complexity which do not significantly differ. We think our attacks can be
improved.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:48:13 GMT"
},
{
"version": "v2",
"created": "Tue, 21 Aug 2007 00:44:02 GMT"
},
{
"version": "v3",
"created": "Mon, 1 Oct 2007 10:26:48 GMT"
},
{
"version": "v4",
"created": "Mon, 19 Nov 2007 16:11:45 GMT"
},
{
"version": "v5",
"created": "Thu, 22 Nov 2007 22:27:48 GMT"
}
] | 2007-11-23T00:00:00 | [
[
"Chowdhury",
"M. M.",
""
]
] |
0708.2398 | Richard Keith Ellis | R. K. Ellis, W. T. Giele and Z. Kunszt | A Numerical Unitarity Formalism for Evaluating One-Loop Amplitudes | 29 pages with 8 figures; references updated in rsponse to readers'
suggestions | JHEP 0803:003,2008 | 10.1088/1126-6708/2008/03/003 | Fermilab-PUB-07-419-T | hep-ph | null | Recent progress in unitarity techniques for one-loop scattering amplitudes
makes a numerical implementation of this method possible. We present a
4-dimensional unitarity method for calculating the cut-constructible part of
amplitudes and implement the method in a numerical procedure. Our technique can
be applied to any one-loop scattering amplitude and offers the possibility that
one-loop calculations can be performed in an automatic fashion, as tree-level
amplitudes are currently done. Instead of individual Feynman diagrams, the
ingredients for our one-loop evaluation are tree-level amplitudes, which are
often already known. To study the practicality of this method we evaluate the
cut-constructible part of the 4, 5 and 6 gluon one-loop amplitudes numerically,
using the analytically known 4, 5 and 6 gluon tree-level amplitudes.
Comparisons with analytic answers are performed to ascertain the numerical
accuracy of the method.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 17:02:21 GMT"
},
{
"version": "v2",
"created": "Fri, 24 Aug 2007 22:08:37 GMT"
}
] | 2009-09-17T00:00:00 | [
[
"Ellis",
"R. K.",
""
],
[
"Giele",
"W. T.",
""
],
[
"Kunszt",
"Z.",
""
]
] |
0708.2399 | Juan Facundo Albacete Colombo | J. F. Albacete Colombo, M. Caramazza, E. Flaccomio, G. Micela and S.
Sciortino | X-ray flaring from the young stars in CygnusOB2 | Accepted for publication in A&A, 11 pages, 9 figures | null | 10.1051/0004-6361:20078064 | null | astro-ph | null | Aims: We characterize individual and ensemble properties of X-ray flares from
stars in the CygOB2 and ONC star-forming regions. Method: We analyzed X-ray
lightcurves of 1003 CygOB2 sources observed with Chandra for 100 ksec and of
1616 ONC sources detected in the ``Chandra Orion Ultra-deep Project'' 850 ksec
observation. We employed a binning-free maximum likelihood method to segment
the light-curves into intervals of constants signal and identified flares on
the basis of both the amplitude and the time-derivative of the source
luminosity. We then derived and compared the flare frequency and energy
distribution of CygOB2 and ONC sources. The effect of the length of the
observation on these results was investigated by repeating the statistical
analysis on five 100 ksec-long segments extracted from the ONC data. Results:
We detected 147 and 954 flares from the CygOB2 and ONC sources, respectively.
The flares in CygOB2 have decay times ranging from ~0.5 to about 10 hours. The
flare energy distributions of all considered flare samples are described at
high energies well by a power law with index alpha=-(2.1+-0.1). At low
energies, the distributions flatten, probably because of detection
incompleteness. We derived average flare frequencies as a function of flare
energy. The flare frequency is seen to depend on the source's intrinsic X-ray
luminosity, but its determination is affected by the length of the observation.
The slope of the high-energy tail of the energy distribution is, however,
affected little. A comparison of CygOB2 and ONC sources, accounting for
observational biases, shows that the two populations, known to have similar
X-ray emission levels, have very similar flare activity.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 16:58:56 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Colombo",
"J. F. Albacete",
""
],
[
"Caramazza",
"M.",
""
],
[
"Flaccomio",
"E.",
""
],
[
"Micela",
"G.",
""
],
[
"Sciortino",
"S.",
""
]
] |
0708.2400 | Lei Hao | J. R. Houck, D. W. Weedman (Cornell University), E. Le Floc'h
(University of Hawaii) and Lei Hao (Cornell University) | Spitzer Spectra of a 10 mJy Galaxy Sample and the Star Formation Rate in
the Local Universe | accepted to publish in ApJ | null | 10.1086/522689 | null | astro-ph | null | A complete flux-limited sample of 50 galaxies is presented having
f_{\nu}(24um) > 10mJy, chosen from a survey with the Multiband Imaging
Photometer on Spitzer (MIPS) of 8.2 deg^{2} within the NOAO Deep Wide-Field
Survey region in Bootes (NDWFS). Spectra obtained with the low-resolution
modules of the Infrared Spectrograph on Spitzer (IRS) are described for 36
galaxies within this sample; 25 show strong PAH emission features
characteristic of starbursts, and 11 show silicate absorption or emission,
emission lines, or featureless spectra characteristic of AGN. Infrared or
optical spectral classifications are available for 48 of the entire sample of
50; 33 galaxies are classified as starbursts and 15 as AGN. (There are an
additional 19 Galactic stars with f_{\nu}(24um) > 10mJy in the survey area.)
Using a relation between 7.7um PAH luminosity and star formation rate derived
from previous IRS observations of starbursts, the star formation rate per unit
volume of the local universe (SFRD) is determined from the complete sample and
is found to be 0.008 \mdot Mpc^{-3}. Individual sources in the sample have star
formation rates from 0.14 to 160 \mdot. The derived value for the local SFRD is
about half that of the local SFRD deduced from bolometric luminosities of the
IRAS 60um Bright Galaxy Sample, with the deficiency being at lower luminosities
and arising primarily from the small number of low luminosity sources in the 10
mJy sample. The agreement for higher luminosities confirms the validity of
using the 7.7um PAH feature as a measure of SFRD in the high redshift universe,
where this is often the only indicator available for faint sources.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 17:02:19 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Houck",
"J. R.",
"",
"Cornell University"
],
[
"Weedman",
"D. W.",
"",
"Cornell University"
],
[
"Floc'h",
"E. Le",
"",
"University of Hawaii"
],
[
"Hao",
"Lei",
"",
"Cornell University"
]
] |
0708.2401 | Aparna Baskaran | Aparna Baskaran and M. Cristina Marchetti | Hydrodynamics of self-propelled hard rods | 10 pages, 3 figures. Submitted to PRE | Phys. Rev. E Vol. 77, 031311 (2008) | 10.1103/PhysRevE.77.011920 | null | cond-mat.soft cond-mat.stat-mech | null | Motivated by recent simulations and by experiments on aggregation of gliding
bacteria, we study a model of the collective dynamics of self-propelled hard
rods on a substrate in two dimensions. The rods have finite size, interact via
excluded volume and their dynamics is overdamped by the interaction with the
substrate. Starting from a microscopic model with non-thermal noise sources, a
continuum description of the system is derived. The hydrodynamic equations are
then used to characterize the possible steady states of the systems and their
stability as a function of the particles packing fraction and the speed of self
propulsion.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 17:48:35 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Baskaran",
"Aparna",
""
],
[
"Marchetti",
"M. Cristina",
""
]
] |
0708.2402 | Marco Caldarelli | Alice Bernamonti, Marco M. Caldarelli, Dietmar Klemm, Rodrigo Olea,
Christoph Sieg and Emanuele Zorzan | Black strings in AdS_5 | 40 pages, 7 figures, JHEP3. v2: minor corrections, 2 references
added. v3: typos in holographic stress tensor corrected, 3 references added | JHEP 0801:061,2008 | 10.1088/1126-6708/2008/01/061 | IFUM-898-FT | hep-th gr-qc | null | We present non-extremal magnetic black string solutions in five-dimensional
gauged supergravity. The conformal infinity is the product of time and S^1xS_h,
where S_h denotes a compact Riemann surface of genus h. The construction is
based on both analytical and numerical techniques. We compute the holographic
stress tensor, the Euclidean action and the conserved charges of the solutions
and show that the latter satisfy a Smarr-type formula. The phase structure is
determined in the canonical ensemble, and it is shown that there is a first
order phase transition from small to large black strings, which disappears
above a certain critical magnetic charge that is obtained numerically. For
another particular value of the magnetic charge, that corresponds to a twisting
of the dual super Yang-Mills theory, the conformal anomalies coming from the
background curvature and those arising from the coupling to external gauge
fields exactly cancel. We also obtain supersymmetric solutions describing waves
propagating on extremal BPS magnetic black strings, and show that they possess
a Siklos-Virasoro reparametrization invariance.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 17:30:53 GMT"
},
{
"version": "v2",
"created": "Mon, 15 Oct 2007 14:52:39 GMT"
},
{
"version": "v3",
"created": "Thu, 10 Jan 2008 15:41:41 GMT"
}
] | 2009-06-11T00:00:00 | [
[
"Bernamonti",
"Alice",
""
],
[
"Caldarelli",
"Marco M.",
""
],
[
"Klemm",
"Dietmar",
""
],
[
"Olea",
"Rodrigo",
""
],
[
"Sieg",
"Christoph",
""
],
[
"Zorzan",
"Emanuele",
""
]
] |
0708.2403 | Andreas Fring | Paulo E. G. Assis and Andreas Fring | Metrics and isospectral partners for the most generic cubic PT-symmetric
non-Hermitian Hamiltonian | 21 pages | Journal of Physics A: Math. Theor. 41 (2008) 244001 | 10.1088/1751-8113/41/24/244001 | null | quant-ph hep-th | null | We investigate properties of the most general PT-symmetric non-Hermitian
Hamiltonian of cubic order in the annihilation and creation operators as a ten
parameter family. For various choices of the parameters we systematically
construct an exact expression for a metric operator and an isospectral
Hermitian counterpart in the same similarity class by exploiting the
isomorphism between operator and Moyal products. We elaborate on the subtleties
of this approach. For special choices of the ten parameters the Hamiltonian
reduces to various models previously studied, such as to the complex cubic
potential, the so-called Swanson Hamiltonian or the transformed version of the
from below unbounded quartic -x^4-potential. In addition, it also reduces to
various models not considered in the present context, namely the single site
lattice Reggeon model and a transformed version of the massive sextic
x^6-potential, which plays an important role as a toy modelto identify theories
with vanishing cosmological constant.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 17:34:04 GMT"
}
] | 2008-11-21T00:00:00 | [
[
"Assis",
"Paulo E. G.",
""
],
[
"Fring",
"Andreas",
""
]
] |
0708.2404 | Georg von Hippel | Zh. Hao, G. M. von Hippel, R. R. Horgan, Q. J. Mason, H. D. Trottier | Unquenching Effects on the Coefficients of the L\"uscher-Weisz Action | 7 pages, 5 eps figures, uses PoS.cls; talk presented at XXV
International Symposium on Lattice Field Theory, July 30 - August 4 2007,
Regensburg, Germany | PoSLAT2007:258,2007 | null | null | hep-lat | null | The effects of unquenching on the perturbative improvement coefficients in
the Symanzik action are computed within the framework of L\"uscher-Weisz
on-shell improvement. We find that the effects of quark loops are surprisingly
large, and their omission may well explain the scaling violations observed in
some unquenched studies.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 17:35:47 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Hao",
"Zh.",
""
],
[
"von Hippel",
"G. M.",
""
],
[
"Horgan",
"R. R.",
""
],
[
"Mason",
"Q. J.",
""
],
[
"Trottier",
"H. D.",
""
]
] |
0708.2405 | Andreas Fring | Andreas Fring | PT-symmetry and Integrability | Proceeding of the Micro conference Analytic and algebraic methods II,
Doppler Institute, Prague, April 2007 | Acta Polytechnica 47 (2007) 44-49 | null | null | quant-ph hep-th | null | We briefly explain some simple arguments based on pseudo Hermiticity,
supersymmetry and PT-symmetry which explain the reality of the spectrum of some
non-Hermitian Hamiltonians. Subsequently we employ PT-symmetry as a guiding
principle to construct deformations of some integrable systems, the
Calogero-Moser-Sutherland model and the Korteweg deVries equation. Some
properties of these models are discussed.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 17:40:08 GMT"
}
] | 2008-04-17T00:00:00 | [
[
"Fring",
"Andreas",
""
]
] |
0708.2406 | William W. Menasco | Hiroshi Matsuda and William W. Menasco | On rectangular diagrams, Legendrian knots and transverse knots | 15 pages, 11 figures | null | null | null | math.GT math.AT | null | A correspondence is studied by H. Matsuda between front projections of
Legendrian links in the standard contact structure for 3-space and rectangular
diagrams. In this paper, we introduce braided rectangular diagrams, and study a
relationship with Legendrian links in the standard contact structure for
3-space. We show Alexander and Markov Theorems for Legendrian links in 3-space.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 17:43:54 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Matsuda",
"Hiroshi",
""
],
[
"Menasco",
"William W.",
""
]
] |
0708.2407 | Jose Francisco Gomes | J. F. Gomes, L. H. Ymai and A. H. Zimerman | Classical Integrable N=1 and $N= 2$ Super Sinh-Gordon Models with Jump
Defects | talk presented at the V International Symposium on Quantum Theory and
Symmetries, Valladolid, Spain, July 22-28,2007 | J.Phys.Conf.Ser.128:012004,2008 | 10.1088/1742-6596/128/1/012004 | null | nlin.SI hep-th | null | The structure of integrable field theories in the presence of jump defects is
discussed in terms of boundary functions under the Lagrangian formalism.
Explicit examples of bosonic and fermionic theories are considered. In
particular, the boundary functions for the N=1 and N=2 super sinh-Gordon models
are constructed and shown to generate the Backlund transformations for its
soliton solutions. As a new and interesting example, a solution with an
incoming boson and an outgoing fermion for the N=1 case is presented. The
resulting integrable models are shown to be invariant under supersymmetric
transformation.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 18:05:31 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Gomes",
"J. F.",
""
],
[
"Ymai",
"L. H.",
""
],
[
"Zimerman",
"A. H.",
""
]
] |
0708.2408 | Masa Ishigami | J. H. Chen, C. Jang, M. S. Fuhrer, E. D. Williams and M. Ishigami | Charged Impurity Scattering in Graphene | 19 pages, 5 figures, Manuscript and figures completely updated | Nature Physics 4, 377 (2008) | 10.1038/nphys935 | null | cond-mat.other | null | Since the experimental realization of graphene1, extensive theoretical work
has focused on short-range disorder2-5, ''ripples''6, 7, or charged
impurities2, 3, 8-13 to explain the conductivity as a function of carrier
density sigma_(n)[1,14-18], and its minimum value sigma_min near twice the
conductance quantum 4e2/h[14, 15, 19, 20]. Here we vary the density of charged
impurities nimp on clean graphene21 by deposition of potassium in ultra high
vacuum. At non-zero carrier density, charged impurity scattering produces the
ubiquitously observed1, 14-18 linear sigma_(n) with the theoretically-predicted
magnitude. The predicted asymmetry11 for attractive vs. repulsive scattering of
Dirac fermions is observed. Sigma_min occurs not at the carrier density which
neutralizes nimp, but rather the carrier density at which the average impurity
potential is zero10. Sigma_min decreases initially with nimp, reaching a
minimum near 4e2/h at non-zero nimp, indicating that Sigma_min in present
experimental samples does not probe Dirac-point physics14, 15, 19, 20 but
rather carrier density inhomogeneity due to the impurity potential3, 9, 10.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 18:06:26 GMT"
},
{
"version": "v2",
"created": "Fri, 9 Nov 2007 14:34:21 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Chen",
"J. H.",
""
],
[
"Jang",
"C.",
""
],
[
"Fuhrer",
"M. S.",
""
],
[
"Williams",
"E. D.",
""
],
[
"Ishigami",
"M.",
""
]
] |
0708.2409 | Thais Idiart TI | T. P. Idiart, J. Silk, J. A. de Freitas Pacheco | Ages of Elliptical Galaxies: Single versus Multi Population
Interpretation | 10 pages and 6 figures. Accepted for publication in Monthly Notices
of the Royal Astronomical Society Main Journal | null | 10.1111/j.1365-2966.2007.12355.x | null | astro-ph | null | New calibrations of spectrophotometric indices of elliptical galaxies as
functions of spectrophotometric indices are presented, permitting estimates of
mean stellar population ages and metallicities. These calibrations are based on
evolutionary models including a two-phase interstellar medium, infall and a
galactic wind.Free parameters were fixed by requiring that models reproduce the
mean trend of data in the color-magnitude diagram as well as in the plane of
indices Hbeta-Mg2 and Mg2-<Fe>. To improve the location of faint ellipticals(MB
> -20) in the Hbeta-Mg2 diagram, down-sizing was introduced. An application of
our calibrations to a sample of ellipticals and a comparison with results
derived from single stellar population models is given. Our models indicate
that mean population ages span an interval of 7-12 Gyr and are correlated with
metallicities, which range from approximately half up to three times solar.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 18:16:22 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Idiart",
"T. P.",
""
],
[
"Silk",
"J.",
""
],
[
"Pacheco",
"J. A. de Freitas",
""
]
] |
0708.2410 | Pablo M. Gleiser | P. M. Gleiser | How to become a superhero | null | J. Stat. Mech. (2007) P09020 | 10.1088/1742-5468/2007/09/P09020 | null | physics.soc-ph physics.data-an | null | We analyze a collaboration network based on the Marvel Universe comic books.
First, we consider the system as a binary network, where two characters are
connected if they appear in the same publication. The analysis of degree
correlations reveals that, in contrast to most real social networks, the Marvel
Universe presents a disassortative mixing on the degree. Then, we use a weight
measure to study the system as a weighted network. This allows us to find and
characterize well defined communities. Through the analysis of the community
structure and the clustering as a function of the degree we show that the
network presents a hierarchical structure. Finally, we comment on possible
mechanisms responsible for the particular motifs observed.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 18:20:56 GMT"
}
] | 2007-09-27T00:00:00 | [
[
"Gleiser",
"P. M.",
""
]
] |
0708.2411 | Jacques Tempere | J. Tempere | Flow and critical velocity of an imbalanced Fermi gas through an optical
potential | 8 pages, 1 figure, contribution for the QFS 2007 conference | Journal of Low Temp. Physics 150 3/4, 636-642 (2008). | 10.1007/s10909-007-9593-5 | null | cond-mat.supr-con | null | Optical lattices offer the possibility to investigate the superfluid
properties of both Bose condensates and Fermionic superfluid gases. When a
population imbalance is present in a Fermi mixture, this leads to frustration
of the pairing, and the superfluid properties will be affected. In this
contribution, the influence of imbalance on the flow of a Fermi superfluid
through an optical lattice is investigated. The flow through the lattice is
analysed by taking into account coupling between neighbouring layers of the
optical lattice up to second order in the interlayer tunneling amplitude for
single atoms. The critical velocity of flow through the lattice is shown to
decrease monotonically to zero as the imbalance is increased to 100%.
Closed-form analytical expressions are given for the tunneling contribution to
the action and for the critical velocity as a function of the binding energy of
pairs in the (quasi) two-dimensional Fermi superfluid and as a function of the
imbalance.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 18:31:19 GMT"
}
] | 2008-03-06T00:00:00 | [
[
"Tempere",
"J.",
""
]
] |
0708.2412 | A. Rebei | M. Benakli, J. Hohlfeld, A. Rebei | Current-Induced Motion of Narrow Domain Walls and Dissipation in
Ferromagnetic Metals | null | null | 10.1063/1.2829775 | null | cond-mat.mes-hall cond-mat.mtrl-sci | null | Spin transport equations in a non-homogeneous ferromagnet are derived in the
limit where the sd exchange coupling between the electrons in the conduction
band and those in the d band is dominant. It is shown that spin diffusion in
ferromagnets assumes a tensor form. The diagonal terms are renormalized with
respect to that in normal metals and enhances the dissipation in the magnetic
system while the off-diagonal terms renormalize the precessional frequency of
the conduction electrons and enhances the non-adiabatic spin torque. To
demonstrate the new physics in our theory, we show that self-consistent
solutions of the spin diffusion equations and the Landau-Lifshitz equations in
the presence of a current lead to a an increase in the terminal velocity of a
domain wall which becomes strongly dependent on its width. We also provide a
simplified equation that predicts damping due to the conduction electrons.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 18:57:51 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Benakli",
"M.",
""
],
[
"Hohlfeld",
"J.",
""
],
[
"Rebei",
"A.",
""
]
] |
0708.2413 | Jan Martin Pawlowski | Jens Braun, Holger Gies, Jan M. Pawlowski | Quark Confinement from Color Confinement | 5 pages, 1 figure | Phys.Lett.B684:262-267,2010 | 10.1016/j.physletb.2010.01.009 | HD-THEP-07-22 | hep-th hep-lat hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We relate quark confinement, as measured by the Polyakov-loop order
parameter, to color confinement, as described by the
Kugo-Ojima/Gribov-Zwanziger scenario. We identify a simple criterion for quark
confinement based on the IR behaviour of ghost and gluon propagators, and
compute the order-parameter potential from the knowledge of Landau-gauge
correlation functions with the aid of the functional RG. Our approach predicts
the deconfinement transition in quenched QCD to be of first order for SU(3) and
second order for SU(2) -- in agreement with general expectations. As an
estimate for the critical temperature, we obtain T_c=284MeV for SU(3).
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 19:55:32 GMT"
},
{
"version": "v2",
"created": "Fri, 27 Nov 2009 15:15:06 GMT"
}
] | 2010-02-17T00:00:00 | [
[
"Braun",
"Jens",
""
],
[
"Gies",
"Holger",
""
],
[
"Pawlowski",
"Jan M.",
""
]
] |
0708.2414 | Kristina Lerman | Kristina Lerman | User Participation in Social Media: Digg Study | Workshops of 2007 IEEE/WIC/ACM International Conference on Web
Intelligence and Intelligent Agent Technology (WI-IAT 07) | null | 10.1109/WI-IATW.2007.68 | null | cs.CY | null | The social news aggregator Digg allows users to submit and moderate stories
by voting on (digging) them. As is true of most social sites, user
participation on Digg is non-uniformly distributed, with few users contributing
a disproportionate fraction of content. We studied user participation on Digg,
to see whether it is motivated by competition, fueled by user ranking, or
social factors, such as community acceptance.
For our study we collected activity data of the top users weekly over the
course of a year. We computed the number of stories users submitted, dugg or
commented on weekly. We report a spike in user activity in September 2006,
followed by a gradual decline, which seems unaffected by the elimination of
user ranking. The spike can be explained by a controversy that broke out at the
beginning of September 2006. We believe that the lasting acrimony that this
incident has created led to a decline of top user participation on Digg.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 18:46:55 GMT"
}
] | 2016-11-18T00:00:00 | [
[
"Lerman",
"Kristina",
""
]
] |
0708.2415 | Dragana Popovic | J. Jaroszynski and Dragana Popovic | Aging Effects Across the Metal-Insulator Transition in Two Dimensions | 4+ pages, 5 figures; minor changes, accepted for publication in PRL | Phys. Rev. Lett. 99, 216401 (2007) | 10.1103/PhysRevLett.99.216401 | null | cond-mat.str-el cond-mat.dis-nn | null | Aging effects in the relaxations of conductivity of a two-dimensional
electron system in Si have been studied as a function of carrier density. They
reveal an abrupt change in the nature of the glassy phase at the
metal-insulator transition (MIT): (a) while full aging is observed in the
insulating regime, there are significant departures from full aging on the
metallic side of the MIT, before the glassy phase disappears completely at a
higher density $n_g$; (b) the amplitude of the relaxations peaks just below the
MIT, and it is strongly suppressed in the insulating phase. Other aspects of
aging, including large non-Gaussian noise and similarities to spin glasses,
also have been discussed.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 18:49:19 GMT"
},
{
"version": "v2",
"created": "Fri, 19 Oct 2007 15:54:29 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Jaroszynski",
"J.",
""
],
[
"Popovic",
"Dragana",
""
]
] |
0708.2416 | Brant M. Johnson | PHENIX Collaboration: S.S. Adler, et al | Centrality dependence of charged hadron production in deuteron+gold and
nucleon+gold collisions at sqrt(s_NN)=200 GeV | 330 authors, 15 pages text, 16 figures, 3 tables. Submitted to Phys.
Rev. Lett. v2 has minor changes to reflect revisions during review process.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.html | Phys.Rev.C77:014905,2008 | 10.1103/PhysRevC.77.014905 | null | nucl-ex | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We present transverse momentum (p_T) spectra of charged hadrons measured in
deuteron-gold and nucleon-gold collisions at \sqrts = 200 GeV for four
centrality classes. Nucleon-gold collisions were selected by tagging events in
which a spectator nucleon was observed in one of two forward rapidity
detectors. The spectra and yields were investigated as a function of the number
of binary nucleon-nucleon collisions, \nu, suffered by deuteron nucleons. A
comparison of charged particle yields to those in p+p collisions show that the
yield per nucleon-nucleon collision saturates with \nu for high momentum
particles. We also present the charged hadron to neutral pion ratios as a
function of p_T.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 19:00:03 GMT"
},
{
"version": "v2",
"created": "Wed, 11 Jun 2008 19:29:36 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"PHENIX Collaboration",
"",
""
],
[
"Adler",
"S. S.",
""
]
] |
0708.2417 | Sumit Gangwal | Sumit Gangwal, Olivier J. Cayre, Martin Z. Bazant, Orlin D. Velev | Induced-charge Electrophoresis of Metallo-dielectric Particles | 11 pages, 4 figures; Supplementary Info: Last 2 pages, 2 figures | null | 10.1103/PhysRevLett.100.058302 | null | physics.flu-dyn | null | The application of AC electric fields in aqueous suspensions of anisotropic
particles leads to unbalanced liquid flows and nonlinear, induced-charge
electrophoretic (ICEP) motion. We report experimental observations of the
motion of "Janus" microparticles with one dielectric and one metal-coated
hemisphere induced by uniform fields of frequency 100 Hz - 10 kHz in NaCl
solutions. The motion is perpendicular to the field axis and persists after
particles are attracted to a glass wall. This phenomenon may find applications
in microactuators, microsensors, and microfluidic devices.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 19:00:34 GMT"
},
{
"version": "v2",
"created": "Wed, 2 Jan 2008 20:59:35 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Gangwal",
"Sumit",
""
],
[
"Cayre",
"Olivier J.",
""
],
[
"Bazant",
"Martin Z.",
""
],
[
"Velev",
"Orlin D.",
""
]
] |
0708.2418 | Michel Pleimling | Florian Baumann and Michel Pleimling | Local aging phenomena close to magnetic surfaces | 16 pages, 3 figures, accepted for publication in Physical Review B | Phys. Rev. B 76, 104422 (2007) | 10.1103/PhysRevB.76.104422 | null | cond-mat.stat-mech | null | Surface aging phenomena are discussed for semi-infinite systems prepared in a
fully disordered initial state and then quenched to or below the critical
point. Besides solving exactly the semi-infinite Ising model in the limit of
large dimensions, we also present results of an extensive numerical study of
the nonequilibrium dynamical behavior of the two-dimensional semi-infinite
Ising model undergoing coarsening. The studied models reveal a simple aging
behavior where some of the nonequilibrium surface exponents take on values that
differ from their bulk counterparts. For the two-dimensional semi-infinite
Ising model we find that the exponent $b_1$, that describes the scaling
behavior of the surface autocorrelation, vanishes. These simulations also
reveal the existence of strong finite-time corrections that to some extent mask
the leading scaling behavior of the studied two-time quantities.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 19:07:54 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Baumann",
"Florian",
""
],
[
"Pleimling",
"Michel",
""
]
] |
0708.2419 | Tobias Schaefer | Tobias Schaefer Richard O. Moore | A Path Integral Method for Coarse-Graining Noise in Stochastic
Differential Equations with Multiple Time Scales | null | null | null | null | nlin.PS nlin.SI | null | We present a new path integral method to analyze stochastically perturbed
ordinary differential equations with multiple time scales. The objective of
this method is to derive from the original system a new stochastic differential
equation describing the system's evolution on slow time scales. For this
purpose, we start from the corresponding path integral representation of the
stochastic system and apply a multi-scale expansion to the associated path
integral kernel of the corresponding Lagrangian. As a concrete example, we
apply this expansion to a system that arises in the study of random dispersion
fluctuations in dispersion-managed fiber optic communications. Moreover, we
show that, for this particular example, the new path integration method yields
the same result at leading order as an asymptotic expansion of the associated
Fokker-Planck equation.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 19:13:26 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Moore",
"Tobias Schaefer Richard O.",
""
]
] |
0708.2420 | Laurent Loinard | Laurent Loinard (CRyA-UNAM), Claire J. Chandler (NRAO), Luis F.
Rodriguez (CRyA-UNAM), Paola D'Alessio (CRyA-UNAM), Crystal L. Brogan (NRAO),
David J. Wilner (CfA) and Paul T. P. Ho (CfA and ASIAA) | New Radio Sources and the Composite Structure of Component B in the Very
Young Protostellar System IRAS 16293-2422 | 21 pages, 6 figures, accepted by ApJ | null | 10.1086/522568 | null | astro-ph | null | In this article, we report high-resolution (~ 0.1" -- 0.3"), high-sensitivity
(~ 50 -100 uJy beam-1) Very Large Array 0.7 and 1.3 cm observations of the
young stellar system IRAS 16293-2422 in rho-Ophiuchus. In the 0.7 cm image,
component A to the south-east of the system looks like its usual binary self.
In the new 1.3 cm image, however, component A2 appears to have split into two
sub-components located roughly symmetrically around the original position of
A2. This change of morphology is likely the result of a recent bipolar
ejection, one of the very first such events observed in a low-mass source. Also
in component A, a marginal detection of 0.7 cm emission associated with the
submillimeter component Ab is reported. If confirmed, this detection would
imply that Ab is a relatively extended dusty structure, where grain coagulation
may already have taken place. With an angular size increasing with frequency,
and an overall spectra index of 2, the emission from component B to the
north-west of the system is confirmed to be dominated by optically thick
thermal dust emission associated with a fairly massive, nearly face-on,
circumstellar disk. In the central region, however, we find evidence for a
modest free-free contribution that originates in a structure elongated roughly
in the east-west direction. We argue that this free-free component traces the
base of the jet driving the large-scale bipolar flow at a position angle of
about 110 degrees that has long been known to be powered by IRAS 16293-2422.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 19:28:38 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Loinard",
"Laurent",
"",
"CRyA-UNAM"
],
[
"Chandler",
"Claire J.",
"",
"NRAO"
],
[
"Rodriguez",
"Luis F.",
"",
"CRyA-UNAM"
],
[
"D'Alessio",
"Paola",
"",
"CRyA-UNAM"
],
[
"Brogan",
"Crystal L.",
"",
"NRAO"
],
[
"Wilner",
"David J.",
"",
"CfA"
],
[
"Ho",
"Paul T. P.",
"",
"CfA and ASIAA"
]
] |
0708.2421 | Sergei Maslov | Sergei Maslov, I. Ispolatov | Propagation of large concentration changes in reversible protein binding
networks | 5 pages, 7 figures | Proc Nat Acad Sci U S A 104(34): 13655-13660 (2007) | 10.1073/pnas.0702905104 | null | q-bio.MN q-bio.BM | null | We study how the dynamic equilibrium of the reversible protein-protein
binding network in yeast Saccharomyces cerevisiae responds to large changes in
abundances of individual proteins. The magnitude of shifts between free and
bound concentrations of their immediate and more distant neighbors in the
network is influenced by such factors as the network topology, the distribution
of protein concentrations among its nodes, and the average binding strength.
Our primary conclusion is that, on average, the effects of a perturbation are
strongly localized and exponentially decay with the network distance away from
the perturbed node, which explains why, despite globally connected topology,
individual functional modules in such networks are able to operate fairly
independently. We also found that under specific favorable conditions, realized
in a significant number of paths in the yeast network, concentration
perturbations can selectively propagate over considerable network distances (up
to four steps). Such "action-at-a-distance" requires high concentrations of
heterodimers along the path as well as low free (unbound) concentration of
intermediate proteins.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 19:42:27 GMT"
}
] | 2007-08-20T00:00:00 | [
[
"Maslov",
"Sergei",
""
],
[
"Ispolatov",
"I.",
""
]
] |
0708.2422 | Rudolph E. Schild | Rudolph E. Schild, Darryl J. Leiter and Stanley L. Robertson | Direct Microlensing-Reverberation Observations of the Intrinsic magnetic
Structure of AGN in Different Spectral States: A Tale of Two Quasars | 26 page manuscript with 2 tables and 2 figures, submitted to
Astronomical Journal | null | 10.1088/0004-6256/135/3/947 | null | astro-ph | null | We show how direct microlensing-reverberation analysis performed on two
well-known Quasars (Q2237 - The Einstein Cross and Q0957 - The Twin) can be
used to observe the inner structure of two quasars which are in significantly
different spectral states. These observations allow us to measure the detailed
internal structure of quasar Q2237 in a radio quiet high-soft state, and
compare it to quasar Q0957 in a radio loud low-hard state. We find that the
observed differences in the spectral states of these two quasars can be
understood as being due to the location of the inner radii of their accretion
disks relative to the co-rotation radii of rotating intrinsically magnetic
supermassive compact objects in the centers of these quasars.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 19:56:38 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Schild",
"Rudolph E.",
""
],
[
"Leiter",
"Darryl J.",
""
],
[
"Robertson",
"Stanley L.",
""
]
] |
0708.2423 | Nidal Chamoun | E. I. Lashin and N. Chamoun | Zero minors of the neutrino mass matrix | latex, 22 pages, 7 figures, 2 tables, accepted version to appear in
PRD | Phys.Rev.D78:073002,2008 | 10.1103/PhysRevD.78.073002 | null | hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We examine the possibility that a certain class of neutrino mass matrices,
namely those with two independent vanishing minors in the flavor basis,
regardless of being invertible or not, is sufficient to describe current data.
We compute generic formulae for the ratios of the neutrino masses and for the
Majorana phases. We find that seven textures with two vanishing minors can
accommodate the experimental data. We present an estimate of the mass matrix
for these patterns. All the possible textures can be dynamically generated
through the seesaw mechanism augmented with a discrete Abelian symmetry.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 20:10:14 GMT"
},
{
"version": "v2",
"created": "Sat, 9 Aug 2008 11:11:10 GMT"
},
{
"version": "v3",
"created": "Mon, 22 Sep 2008 15:01:22 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Lashin",
"E. I.",
""
],
[
"Chamoun",
"N.",
""
]
] |
0708.2424 | Mario G. Santos | Mario G. Santos (1), Alexandre Amblard (2), Jonathan Pritchard (3,4),
Hy Trac (4,5), Renyue Cen (5), Asantha Cooray (2) ((1) CENTRA - IST, (2) UC
Irvine, (3) Caltech, (4) CfA, (5) Princeton) | Cosmic Reionization and the 21-cm signal: Comparison between an
analytical model and a simulation | Major paper revision to match version accepted for publication in
ApJ. Simulation now fully includes fluctuations in the X-ray heating and the
Lya radiation field. 18 pages, 13 figures | Astrophys.J.689:1-16, 2008 | 10.1086/592487 | null | astro-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We measure several properties of the reionization process and the
corresponding low-frequency 21-cm signal associated with the neutral hydrogen
distribution, using a large volume, high resolution simulation of cosmic
reionization. The brightness temperature of the 21-cm signal is derived by
post-processing this numerical simulation with a semi-analytical prescription.
Our study extends to high redshifts (z ~ 25) where, in addition to collisional
coupling, our post-processed simulations take into account the inhomogeneities
in the heating of the neutral gas by X-rays and the effect of an inhomogeneous
Lya radiation field. Unlike the well-studied case where spin temperature is
assumed to be significantly greater than the temperature of the cosmic
microwave background due to uniform heating of the gas by X-rays, spatial
fluctuations in both the Lya radiation field and X-ray intensity impact
predictions related to the brightness temperature at z > 10, during the early
stages of reionization and gas heating. The statistics of the 21-cm signal from
our simulation are then compared to existing analytical models in the
literature and we find that these analytical models provide a reasonably
accurate description of the 21-cm power spectrum at z < 10. Such an agreement
is useful since analytical models are better suited to quickly explore the full
astrophysical and cosmological parameter space relevant for future 21-cm
surveys. We find, nevertheless, non-negligible differences that can be
attributed to differences in the inhomogeneous X-ray heating and Lya coupling
at z > 10 and, with upcoming interferometric data, these differences in return
can provide a way to better understand the astrophysical processes during
reionization.
| [
{
"version": "v1",
"created": "Mon, 20 Aug 2007 16:09:41 GMT"
},
{
"version": "v2",
"created": "Thu, 28 Aug 2008 23:10:11 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Santos",
"Mario G.",
""
],
[
"Amblard",
"Alexandre",
""
],
[
"Pritchard",
"Jonathan",
""
],
[
"Trac",
"Hy",
""
],
[
"Cen",
"Renyue",
""
],
[
"Cooray",
"Asantha",
""
]
] |
0708.2425 | Min-Su Shin | Min-Su Shin, Hy Trac and Renyue Cen (Princeton) | Cosmological HII Bubble Growth During Reionization | 10 pages, 14 figures; accepted version; higher resolution figures and
supplementary material can be found at
http://www.astro.princeton.edu/~msshin/reionization/web.htm | null | 10.1086/588247 | null | astro-ph | null | We present general properties of ionized hydrogen (HII) bubbles and their
growth based on a state-of-the-art large-scale (100 Mpc/h) cosmological
radiative transfer simulation. The simulation resolves all halos with atomic
cooling at the relevant redshifts and simultaneously performs radiative
transfer and dynamical evolution of structure formation. Our major conclusions
include: (1) for significant HII bubbles, the number distribution is peaked at
a volume of $\sim 0.6 {\rm Mpc^{3}/h^{3}}$ at all redshifts. But, at $z\le 10$,
one large, connected network of bubbles dominates the entire HII volume. (2)
HII bubbles are highly non-spherical. (3) The HII regions are highly biased
with respect to the underlying matter distribution with the bias decreasing
with time. (4) The non-gaussianity of the HII region is small when the universe
becomes 50% ionized. The non-gaussianity reaches its maximal near the end of
the reionization epoch $z\sim 6$. But at all redshifts of interest there is a
significant non-gaussianity in the HII field. (5) Population III galaxies may
play a significant role in the reionization process. Small bubbles are
initially largely produced by Pop III stars. At $z\ge 10$ even the largest HII
bubbles have a balanced ionizing photon contribution from Pop II and Pop III
stars, while at $z\le 8$ Pop II stars start to dominate the overall ionizing
photon production for large bubbles, although Pop III stars continue to make a
non-negligible contribution. (6) The relationship between halo number density
and bubble size is complicated but a strong correlation is found between halo
number density and bubble size for large bubbles.
| [
{
"version": "v1",
"created": "Mon, 20 Aug 2007 19:12:36 GMT"
},
{
"version": "v2",
"created": "Thu, 13 Mar 2008 15:54:52 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Shin",
"Min-Su",
"",
"Princeton"
],
[
"Trac",
"Hy",
"",
"Princeton"
],
[
"Cen",
"Renyue",
"",
"Princeton"
]
] |
0708.2426 | Harold Steinacker | Harold Steinacker | Emergent Gravity from Noncommutative Gauge Theory | 28 pages + 11 pages appendix. V2: references and discussion added.
V3: minor correction | JHEP 0712:049,2007 | 10.1088/1126-6708/2007/12/049 | UWTHPh-2007-17 | hep-th gr-qc | null | We show that the matrix-model action for noncommutative U(n) gauge theory
actually describes SU(n) gauge theory coupled to gravity. This is elaborated in
the 4-dimensional case. The SU(n) gauge fields as well as additional scalar
fields couple to an effective metric G_{ab}, which is determined by a dynamical
Poisson structure. The emergent gravity is intimately related to
noncommutativity, encoding those degrees of freedom which are usually
interpreted as U(1) gauge fields. This leads to a class of metrics which
contains the physical degrees of freedom of gravitational waves, and allows to
recover e.g. the Newtonian limit with arbitrary mass distribution. It also
suggests a consistent picture of UV/IR mixing in terms of an induced gravity
action. This should provide a suitable framework for quantizing gravity.
| [
{
"version": "v1",
"created": "Mon, 20 Aug 2007 16:24:51 GMT"
},
{
"version": "v2",
"created": "Tue, 13 Nov 2007 21:31:28 GMT"
},
{
"version": "v3",
"created": "Wed, 19 Dec 2007 14:16:46 GMT"
}
] | 2009-11-18T00:00:00 | [
[
"Steinacker",
"Harold",
""
]
] |
0708.2427 | Aseshkrishna Datta | Subhaditya Bhattacharya, AseshKrishna Datta, Biswarup Mukhopadhyaya | Non-universal gaugino masses: a signal-based analysis for the Large
Hadron Collider | 54 pages, 18 figures | JHEP0710:080,2007 | 10.1088/1126-6708/2007/10/080 | null | hep-ph | null | We discuss the signals at the Large Hadron Collider (LHC) for scenarios with
non-universal gaugino masses in supersymmetric (SUSY) theories. We perform a
multichannel analysis, and consider the ratios of event rates in different
channels such as $jets + {E}_T/ $, $same$ - and $opposite$-$sign dileptons$
$+jets+ {E}_T/ $, as well as $single-lepton$ and $trilepton$ final states
together with $jets + {E}_T/ $ . Low-energy SUSY spectra corresponding to
high-scale gaugino non-universality arising from different breaking schemes of
SU(5) as well as SO(10) Grand Unified (GUT) SUSY models are considered, with
both degenerate low-energy sfermion masses and those arising from a
supergravity scenario. We present the numerical predictions over a wide range
of the parameter space using the event generator {\tt Pythia}, specifying the
event selection criteria and pointing out regions where signals are likely to
be beset with backgrounds. Certain broad features emerge from the study, which
may be useful in identifying the signatures of different GUT breaking schemes
and distinguishing them from a situation with a universal gaugino mass at high
scale. The absolute values of the predicted event rates for different scenarios
are presented together with the various event ratios, so that these can also be
used whenever necessary.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 20:37:22 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Bhattacharya",
"Subhaditya",
""
],
[
"Datta",
"AseshKrishna",
""
],
[
"Mukhopadhyaya",
"Biswarup",
""
]
] |
0708.2428 | Hermanus Batelaan | Adam Caprez, Brett Barwick and Herman Batelaan | A macroscopic test of the Aharonov-Bohm effect | 13 pages, 4 figures | null | 10.1103/PhysRevLett.99.210401 | null | quant-ph | null | The Aharonov-Bohm (AB) effect is a purely quantum mechanical effect. The
original (classified as Type-I) AB-phase shift exists in experimental
conditions where the electromagnetic fields and forces are zero. It is the
absence of forces that makes the AB-effect entirely quantum mechanical.
Although the AB-phase shift has been demonstrated unambiguously, the absence of
forces in Type-I AB-effects has never been shown. Here, we report the
observation of the absence of time delays associated with forces of the
magnitude needed to explain the AB-phase shift for a macroscopic system.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 20:49:47 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Caprez",
"Adam",
""
],
[
"Barwick",
"Brett",
""
],
[
"Batelaan",
"Herman",
""
]
] |
0708.2429 | Jean Berney | M.T. Portella-Oberli, J. Berney, L. Kappei, F. Morier-Genoud, J.
Szczytko, B. Deveaud | Dynamics of trion formation in GaAs quantum wells | null | null | null | null | cond-mat.mtrl-sci | null | We propose a double channel mechanism for the formation of charged excitons
(trions); they are formed through bi- and tri-molecular processes. This
directly implies that both negatively and positively charged excitons coexist
in a quantum well, even in the absence of excess carriers. The model is applied
to a time-resolved photoluminescence experiment performed on a very high
quality InGaAs quantum well sample, in which the photoluminescence
contributions at the energy of the trion, exciton and at the band edge can be
clearly separated and traced over a broad range of times and densities. The
unresolved discrepancy between the theoretical and experimental radiative decay
time of the exciton in a doped semiconductor is explained.
| [
{
"version": "v1",
"created": "Mon, 20 Aug 2007 12:34:04 GMT"
}
] | 2009-09-29T00:00:00 | [
[
"Portella-Oberli",
"M. T.",
""
],
[
"Berney",
"J.",
""
],
[
"Kappei",
"L.",
""
],
[
"Morier-Genoud",
"F.",
""
],
[
"Szczytko",
"J.",
""
],
[
"Deveaud",
"B.",
""
]
] |
0708.2430 | Gouranga Nayak | Gouranga C. Nayak (SUNY, Stony Brook) | Schwinger Mechanism for Gluon Pair Production in the Presence of
Arbitrary Time Dependent Chromo-Electric Field | 13 pages latex, Published in European Physical Journal C | Eur.Phys.J.C59:715-722,2009 | 10.1140/epjc/s10052-008-0819-8 | YITP-SB-07-28 | hep-ph | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We study Schwinger mechanism for gluon pair production in the presence of
arbitrary time-dependent chromo-electric background field $E^a(t)$ with
arbitrary color index $a$=1,2,...8 in SU(3) by directly evaluating the path
integral. We obtain an exact expression for the probability of non-perturbative
gluon pair production per unit time per unit volume and per unit transverse
momentum $\frac{dW}{d^4x d^2p_T}$ from arbitrary $E^a(t)$. We show that the
tadpole (or single gluon) effective action does not contribute to the
non-perturbative gluon pair production rate $\frac{dW}{d^4x d^2p_T}$. We find
that the exact result for non-perturbative gluon pair production is independent
of all the time derivatives $\frac{d^nE^a(t)}{dt^n}$ where $n=1,2,....\infty$
and has the same functional dependence on two casimir invariants
$[E^a(t)E^a(t)]$ and $[d_{abc}E^a(t)E^b(t)E^c(t)]^2$ as the constant
chromo-electric field $E^a$ result with the replacement: $E^a \to E^a(t)$. This
result may be relevant to study the production of a non-perturbative
quark-gluon plasma at RHIC and LHC.
| [
{
"version": "v1",
"created": "Mon, 20 Aug 2007 18:25:02 GMT"
},
{
"version": "v2",
"created": "Thu, 8 Jan 2009 23:26:39 GMT"
}
] | 2010-10-27T00:00:00 | [
[
"Nayak",
"Gouranga C.",
"",
"SUNY, Stony Brook"
]
] |
0708.2431 | Khee-Gan Lee | Khee-Gan Lee, Renyue Cen, J. Richard Gott III and Hy Trac (Princeton) | The Topology of Cosmological Reionization | 9 pages, 6 figures, accepted by ApJ | 2008ApJ...675....8L | 10.1086/525520 | null | astro-ph | null | Using the largest cosmological reionization simulation to-date (~24 billion
particles), we use the genus curve to quantify the topology of neutral hydrogen
distribution on scales > 1 Mpc as it evolves during cosmological reionization.
We find that the reionization process proceeds primarily in an inside-out
fashion, where higher density regions become ionized earlier than lower density
regions. There are four distinct topological phases: (1) Pre-reionization at z
~ 15, when the genus curve is consistent with a Gaussian density distribution.
(2) Pre-overlap at 10 < z < 15, during which the number of HII bubbles
increases gradually with time, until percolation of HII bubbles starts to take
effect, characterized by a very flat genus curve at high volume fractions. (3)
Overlap at 8 < z < 10, when large HII bubbles rapidly merge, manifested by a
precipitous drop in the amplitude of the genus curve. (4) Post-overlap at 6 < z
< 8, when HII bubbles have mostly overlapped and the genus curve is consistent
with a diminishing number of isolated neutral islands. After the end of
reionization (z < 6), the genus of neutral hydrogen is consistent with Gaussian
random phase, in agreement with observations.
| [
{
"version": "v1",
"created": "Mon, 20 Aug 2007 19:48:05 GMT"
},
{
"version": "v2",
"created": "Wed, 7 Nov 2007 18:36:57 GMT"
}
] | 2009-03-02T00:00:00 | [
[
"Lee",
"Khee-Gan",
"",
"Princeton"
],
[
"Cen",
"Renyue",
"",
"Princeton"
],
[
"Gott",
"J. Richard",
"III",
"Princeton"
],
[
"Trac",
"Hy",
"",
"Princeton"
]
] |
0708.2432 | Oliver Knill | Oliver Knill and Jose Ramirez-Herran | A structure from motion inequality | 15 pages, 22 figures | null | null | null | cs.CV cs.AI | null | We state an elementary inequality for the structure from motion problem for m
cameras and n points. This structure from motion inequality relates space
dimension, camera parameter dimension, the number of cameras and number points
and global symmetry properties and provides a rigorous criterion for which
reconstruction is not possible with probability 1. Mathematically the
inequality is based on Frobenius theorem which is a geometric incarnation of
the fundamental theorem of linear algebra. The paper also provides a general
mathematical formalism for the structure from motion problem. It includes the
situation the points can move while the camera takes the pictures.
| [
{
"version": "v1",
"created": "Sat, 18 Aug 2007 14:36:28 GMT"
}
] | 2007-08-21T00:00:00 | [
[
"Knill",
"Oliver",
""
],
[
"Ramirez-Herran",
"Jose",
""
]
] |
0708.2433 | Jean-Yves Ollitrault | Jean-Yves Ollitrault | Relativistic hydrodynamics for heavy-ion collisions | Lectures given at the Advanced School on Quark-Gluon Plasma, Indian
Institute of Technology, Bombay, 3-13 July, 2007 | Eur.J.Phys.29:275-302,2008 | 10.1088/0143-0807/29/2/010 | Saclay T07/124 | nucl-th | null | Relativistic hydrodynamics is essential to our current understanding of
nucleus-nucleus collisions at ultrarelativistic energies (current experiments
at the Relativistic Heavy Ion Collider, forthcoming experiments at the CERN
Large Hadron Collider). This is an introduction to relativistic hydrodynamics
for graduate students. It includes a detailed derivation of the equations, and
a description of the hydrodynamical evolution of a heavy-ion collisions. Some
knowledge of thermodynamics and special relativity is assumed.
| [
{
"version": "v1",
"created": "Mon, 20 Aug 2007 13:15:34 GMT"
},
{
"version": "v2",
"created": "Mon, 7 Jan 2008 12:23:11 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Ollitrault",
"Jean-Yves",
""
]
] |
0708.2434 | Gennadi Sardanashvily | G. Sardanashvily | Graded infinite order jet manifolds | 30 pages | Int. J. Geom. Methods Mod. Phys. v.4 (2007) 1335-1362 | 10.1142/S0219887807002582 | null | math-ph math.MP | null | The relevant material on differential calculus on graded infinite order jet
manifolds and its cohomology is summarized. This mathematics provides the
adequate formulation of Lagrangian theories of even and odd variables on smooth
manifolds in terms of the Grassmann-graded variational bicomplex.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 21:14:10 GMT"
}
] | 2015-05-13T00:00:00 | [
[
"Sardanashvily",
"G.",
""
]
] |
0708.2435 | Justin Malecki | Justin Malecki | The Two Dimensional Kondo Model with Rashba Spin-Orbit Coupling | 22 pages, 1 figure; reference updated | J. Stat. Phys. 129, 741 (2007) | 10.1007/s10955-007-9414-x | null | cond-mat.str-el cond-mat.mes-hall | null | We investigate the effect that Rashba spin-orbit coupling has on the low
energy behaviour of a two dimensional magnetic impurity system. It is shown
that the Kondo effect, the screening of the magnetic impurity at temperatures T
< T_K, is robust against such spin-orbit coupling, despite the fact that the
spin of the conduction electrons is no longer a conserved quantity. A proposal
is made for how the spin-orbit coupling may change the value of the Kondo
temperature T_K in such systems and the prospects of measuring this change are
discussed. We conclude that many of the assumptions made in our analysis
invalidate our results as applied to recent experiments in semi-conductor
quantum dots but may apply to measurements made with magnetic atoms placed on
metallic surfaces.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 21:21:15 GMT"
},
{
"version": "v2",
"created": "Tue, 11 Sep 2007 18:28:10 GMT"
}
] | 2007-11-01T00:00:00 | [
[
"Malecki",
"Justin",
""
]
] |
0708.2436 | Joshua Faber | Joshua A. Faber, Thomas W. Baumgarte, Zachariah B. Etienne, Stuart L.
Shapiro, Keisuke Taniguchi | Relativistic hydrodynamics in the presence of puncture black holes | 21 pages, 21 figures, RevTex, accepted by PRD; minor updates | Phys.Rev.D76:104021,2007 | 10.1103/PhysRevD.76.104021 | null | gr-qc astro-ph | null | Many of the recent numerical simulations of binary black holes in vacuum
adopt the moving puncture approach. This successful approach avoids the need to
impose numerical excision of the black hole interior and is easy to implement.
Here we wish to explore how well the same approach can be applied to moving
black hole punctures in the presence of relativistic hydrodynamic matter.
First, we evolve single black hole punctures in vacuum to calibrate our BSSN
(Baumgarte-Shapiro-Shibata-Nakamura) implementation and to confirm that the
numerical solution for the exterior spacetime is invariant to any ``junk''
(i.e., constraint-violating) initial data employed in the black hole interior.
Then we focus on relativistic Bondi accretion onto a moving puncture
Schwarzschild black hole as a numerical testbed for our high-resolution
shock-capturing relativistic hydrodynamics scheme. We find that the
hydrodynamical equations can be evolved successfully in the interior without
imposing numerical excision. These results help motivate the adoption of the
moving puncture approach to treat the binary black hole-neutron star problem
using conformal thin-sandwich initial data.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 21:30:26 GMT"
},
{
"version": "v2",
"created": "Tue, 11 Sep 2007 22:00:55 GMT"
},
{
"version": "v3",
"created": "Mon, 15 Oct 2007 18:38:03 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Faber",
"Joshua A.",
""
],
[
"Baumgarte",
"Thomas W.",
""
],
[
"Etienne",
"Zachariah B.",
""
],
[
"Shapiro",
"Stuart L.",
""
],
[
"Taniguchi",
"Keisuke",
""
]
] |
0708.2437 | Saar Rahav | Saar Rahav, Christopher Jarzynski | Fluctuation relations and coarse-graining | 19 pages, 6 figures, very minor changes | J. Stat. Mech. (2007) P09012 | 10.1088/1742-5468/2007/09/P09012 | null | cond-mat.stat-mech | null | We consider the application of fluctuation relations to the dynamics of
coarse-grained systems, as might arise in a hypothetical experiment in which a
system is monitored with a low-resolution measuring apparatus. We analyze a
stochastic, Markovian jump process with a specific structure that lends itself
naturally to coarse-graining. A perturbative analysis yields a reduced
stochastic jump process that approximates the coarse-grained dynamics of the
original system. This leads to a non-trivial fluctuation relation that is
approximately satisfied by the coarse-grained dynamics. We illustrate our
results by computing the large deviations of a particular stochastic jump
process. Our results highlight the possibility that observed deviations from
fluctuation relations might be due to the presence of unobserved degrees of
freedom.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 21:31:24 GMT"
},
{
"version": "v2",
"created": "Wed, 19 Sep 2007 14:08:01 GMT"
}
] | 2007-09-19T00:00:00 | [
[
"Rahav",
"Saar",
""
],
[
"Jarzynski",
"Christopher",
""
]
] |
0708.2438 | Oliver Knill | Oliver Knill and Jose Ramirez-Herran | On Ullman's theorem in computer vision | 16 pages, 13 figures | null | null | null | cs.CV cs.AI | null | Both in the plane and in space, we invert the nonlinear Ullman transformation
for 3 points and 3 orthographic cameras. While Ullman's theorem assures a
unique reconstruction modulo a reflection for 3 cameras and 4 points, we find a
locally unique reconstruction for 3 cameras and 3 points. Explicit
reconstruction formulas allow to decide whether picture data of three cameras
seeing three points can be realized as a point-camera configuration.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 21:36:08 GMT"
}
] | 2007-08-21T00:00:00 | [
[
"Knill",
"Oliver",
""
],
[
"Ramirez-Herran",
"Jose",
""
]
] |
0708.2439 | Mathew Rogers | Mathew D. Rogers | An extension of Boyd's $p$-adic algorithm for the harmonic series | 17 pages, 2 tables | null | null | null | math.NT | null | In this paper we will extend a $p$-adic algorithm of Boyd in order to study
the size of the set: \[J_p(y)=\left\{n :\sum_{j=1}^{n}\frac{y^j}{j}\equiv
0(\mod p)\right\}.\] Suppose that $p$ is one of the first 100 odd primes and
$y\in\{1,2,...,p-1\}$, then our calculations prove that $|J_p(y)|<\infty$ in
24240 out of 24578 possible cases. Among other results we show that
$|J_{13}(9)|=18763$. The paper concludes by discussing some possible
applications of our method to sums involving Fibonacci numbers.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 21:38:26 GMT"
}
] | 2007-08-21T00:00:00 | [
[
"Rogers",
"Mathew D.",
""
]
] |
0708.2440 | Ranga-Ram Chary | Ranga-Ram Chary, Edo Berger, Len Cowie | Spitzer Observations of Gamma-Ray Burst Host Galaxies: A Unique Window
into High Redshift Chemical Evolution and Star-formation | ApJ, in press | null | 10.1086/522692 | null | astro-ph | null | We present deep Spitzer 3.6 micron observations of three z~5 GRB host
galaxies. Our observations reveal that z~5 GRB hosts are a factor of 3 less
luminous than the median rest-frame V-band luminosity of spectroscopically
confirmed z~5 galaxies in the GOODS fields and the UDF. The strong connection
between GRBs and massive star formation implies that not all star-forming
galaxies at these redshifts are currently being accounted for in deep surveys
and GRBs provide a unique way to measure the contribution to the star-formation
rate density from galaxies at the faint end of the galaxy luminosity function.
By correlating the co-moving star-formation rate density with co-moving GRB
rates at lower redshifts, we estimate a lower limit to the star-formation rate
density of 0.12+/-0.09 and 0.09+/-0.05 M_sun/yr/Mpc^3 at z~4.5 and z~6,
respectively. Finally, we provide evidence that the average metallicity of
star-forming galaxies evolves as (stellar mass density)^(0.69+/-0.17) between
$z\sim5$ and $z\sim0$, probably indicative of the loss of a significant
fraction of metals to the intergalactic medium, particularly in low-mass
galaxies.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 21:38:49 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Chary",
"Ranga-Ram",
""
],
[
"Berger",
"Edo",
""
],
[
"Cowie",
"Len",
""
]
] |
0708.2441 | Javier Z\'u\~niga | Javier Z\'u\~niga | Compactifications of Moduli Spaces and Cellular Decompositions | 31 pages, 21 figures. Added references, corrected typos, and improved
content | Algebr. Geom. Topol. 15 (2015) 1-41 | 10.2140/agt.2015.15.1 | null | math.GT math.AT | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This paper studies compactifications of moduli spaces involving closed
Riemann surfaces. The first main result identifies the homeomorphism types of
these compactifications. The second main result introduces orbicell
decompositions on these spaces using semistable ribbon graphs extending the
earlier work of Looijenga.
| [
{
"version": "v1",
"created": "Mon, 20 Aug 2007 00:36:29 GMT"
},
{
"version": "v2",
"created": "Wed, 7 Jan 2009 18:31:16 GMT"
},
{
"version": "v3",
"created": "Sat, 26 Jan 2013 08:01:22 GMT"
}
] | 2015-05-27T00:00:00 | [
[
"Zúñiga",
"Javier",
""
]
] |
0708.2442 | Oliver Knill | Oliver Knill and Jose Ramirez-Herran | Space and camera path reconstruction for omni-directional vision | null | null | null | null | cs.CV cs.AI | null | In this paper, we address the inverse problem of reconstructing a scene as
well as the camera motion from the image sequence taken by an omni-directional
camera. Our structure from motion results give sharp conditions under which the
reconstruction is unique. For example, if there are three points in general
position and three omni-directional cameras in general position, a unique
reconstruction is possible up to a similarity. We then look at the
reconstruction problem with m cameras and n points, where n and m can be large
and the over-determined system is solved by least square methods. The
reconstruction is robust and generalizes to the case of a dynamic environment
where landmarks can move during the movie capture. Possible applications of the
result are computer assisted scene reconstruction, 3D scanning, autonomous
robot navigation, medical tomography and city reconstructions.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 21:53:41 GMT"
}
] | 2007-08-21T00:00:00 | [
[
"Knill",
"Oliver",
""
],
[
"Ramirez-Herran",
"Jose",
""
]
] |
0708.2443 | Daniel Ma\^itre | T. Huber, D. Ma\^itre | HypExp 2, Expanding Hypergeometric Functions about Half-Integer
Parameters | 38 pages, 7 figures. Minor changes. Version to appear in CPC. The
package can be downloaded from http://krone.physik.unizh.ch/~maitreda/HypExp/ | Comput.Phys.Commun.178:755-776,2008 | 10.1016/j.cpc.2007.12.008 | SLAC-PUB-12748, PITHA-07/06 | hep-ph | null | In this article, we describe a new algorithm for the expansion of
hypergeometric functions about half-integer parameters. The implementation of
this algorithm for certain classes of hypergeometric functions in the already
existing Mathematica package HypExp is described. Examples of applications in
Feynman diagrams with up to four loops are given.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 22:13:31 GMT"
},
{
"version": "v2",
"created": "Fri, 11 Jan 2008 16:16:06 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Huber",
"T.",
""
],
[
"Maître",
"D.",
""
]
] |
0708.2444 | Daniel Whalen | Daniel Whalen, Michael L. Norman | Ionization Front Instabilities in Primordial H II Regions | 13 pages, 11 figures, accepted by ApJ with minor revisions | null | 10.1086/524400 | LA-UR 07-2307 | astro-ph | null | Radiative cooling by metals in shocked gas mediates the formation of
ionization front instabilities in the galaxy today that are responsible for a
variety of phenomena in the interstellar medium, from the morphologies of
nebulae to triggered star formation in molecular clouds. An important question
in early reionization and chemical enrichment of the intergalactic medium is
whether such instabilities arose in the H II regions of the first stars and
primeval galaxies, which were devoid of metals. We present three-dimensional
numerical simulations that reveal both shadow and thin-shell instabilities
readily formed in primordial gas. We find that the hard UV spectra of
Population III stars broadened primordial ionization fronts, causing H2
formation capable of inciting violent thin- shell instabilities in D-type
fronts, even in the presence of intense Lyman-Werner flux. The high post- front
gas temperatures associated with He ionization sustained and exacerbated shadow
instabilities, unaided by molecular hydrogen cooling. Our models indicate that
metals eclipsed H2 cooling in I-front instabilities at modest concentrations,
from 0.001- 0.01 solar. We conclude that ionization front instabilities were
prominent in the H II regions of the first stars and galaxies, influencing the
escape of ionizing radiation and metals into the early universe.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 22:07:44 GMT"
},
{
"version": "v2",
"created": "Thu, 6 Dec 2007 08:33:24 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Whalen",
"Daniel",
""
],
[
"Norman",
"Michael L.",
""
]
] |
0708.2445 | Marcio Catelan | M. Catelan (PUC-Chile) | Horizontal Branch Stars and the Ultraviolet Universe | 14 pages, four figures. Invited review, to appear in New Quests in
Stellar Astrophysics II: The Ultraviolet Properties of Evolved Stellar
Populations (proceedings of the Puerto Vallarta conference) | null | 10.1007/978-0-387-87621-4_27 | null | astro-ph | null | Extremely hot horizontal branch (HB) stars and their progeny are widely
considered to be responsible for the "ultraviolet upturn" (or UVX) phenomenon
observed in elliptical galaxies and the bulges of spirals. Yet, the precise
evolutionary channels that lead to the production of these stars remain the
source of much debate. In this review, we discuss two key physical ingredients
that are required in order for reliable quantitative models of the UV output of
stellar populations to be computed, namely, the mass loss rates of red giant
branch stars and the helium enrichment "law" at high metallicities. In
particular, the recent evidence pointing towards a strong enhancement in the
abundances of the alpha-elements in the Galactic bulge (compared to the disk),
and also the available indications of a similar overabundance in (massive)
elliptical galaxies, strongly suggest that the helium abundance Y may be higher
in ellipticals and bulges than it is in spiral disks by an amount that may
reach up to 0.15 at [Fe/H] ~ +0.5. If so, this would strongly favor the
production of hot HB stars at high metallicity in galactic spheroids. We also
discuss the existence of mass loss recipes beyond the commonly adopted Reimers
"law" that are not only more consistent with the available empirical data, but
also much more favorable to the production of extended HB stars at high
metallicity. Finally, we discuss new empirical evidence that suggests that
different evolutionary channels may be responsible for the production of EHB
stars in the field and in clusters.
| [
{
"version": "v1",
"created": "Sat, 18 Aug 2007 00:49:00 GMT"
}
] | 2020-08-05T00:00:00 | [
[
"Catelan",
"M.",
"",
"PUC-Chile"
]
] |
0708.2446 | Janet Conrad | J.M. Conrad | Neutrino Experiments | 65 pages | null | null | null | hep-ex | null | This article is a summary of four introductory lectures on ``Neutrino
Experiments,'' given at the 2006 TASI summer school. The purposes were to
sketch out the present questions in neutrino physics and to discuss the
experimental challenges in addressing them. This article concentrates on
specific, illustrative examples rather than providing a complete overview of
the field of neutrino physics. These lectures were meant to lay the ground-work
for the talks which followed on specific, selected topics in neutrino physics.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 22:27:54 GMT"
}
] | 2007-08-21T00:00:00 | [
[
"Conrad",
"J. M.",
""
]
] |
0708.2447 | Stepan Bulanov | S. S. Bulanov, A. Macchi, A. Maksimchuk, T. Matsuoka, J. Nees and F.
Pegoraro | Electromagnetic pulse reflection at self-generated plasma mirrors: laser
pulse shaping and high order harmonic generation | 12 pages, 6 figures; to appear in Physics of Plasmas | null | 10.1063/1.2776906 | null | physics.plasm-ph | null | A thin layer of overdense plasma is created when an electromagnetic pulse
interacts with a rapidly ionizing thin foil. This layer will reflect the
incoming pulse, forming a so-called plasma mirror. A simple realistic model
based on paired kinetic and wave equations is used to describe analytically the
process of mirror formation and the reflection and transmission of the incident
pulse. The model incorporates the exact description of the ionization process
in the foil and the polarization and conduction currents that follow. The
analytical description of the reflected and transmitted pulses as well as their
dependence on foil parameters, and initial pulse amplitude and form are
presented. Possible application and effectiveness of this process to improve
laser pulse contrast are discussed. In the case of the linearly polarized
incident pulse, there harmonic generation occurs, that is absent in the case of
the circular polarization. The spectra of the reflected pulses for different
initial forms and amplitudes are studied.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 22:44:03 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Bulanov",
"S. S.",
""
],
[
"Macchi",
"A.",
""
],
[
"Maksimchuk",
"A.",
""
],
[
"Matsuoka",
"T.",
""
],
[
"Nees",
"J.",
""
],
[
"Pegoraro",
"F.",
""
]
] |
0708.2448 | Woowon Kang | M. D. Godfrey, P. Jiang, W. Kang, S. H. Simon, K. W. Baldwin, L. N.
Pfeiffer and K. W. West | Aharonov-Bohm-Like Oscillations in Quantum Hall Corrals | null | null | null | null | cond-mat.mes-hall | null | Experimental study of quantum Hall corrals reveals Aharonov-Bohm-Like (ABL)
oscillations. Unlike the Aharonov-Bohm effect which has a period of one flux
quantum, $\Phi_{0}$, the ABL oscillations possess a flux period of
$\Phi_{0}/f$, where $f$ is the integer number of fully filled Landau levels in
the constrictions. Detection of the ABL oscillations is limited to the low
magnetic field side of the $\nu_{c}$ = 1, 2, 4, 6... integer quantum Hall
plateaus. These oscillations can be understood within the Coulomb blockade
model of quantum Hall interferometers as forward tunneling and backscattering,
respectively, through the center island of the corral from the bulk and the
edge states. The evidence for quantum interference is weak and circumstantial.
| [
{
"version": "v1",
"created": "Fri, 17 Aug 2007 22:29:18 GMT"
}
] | 2007-08-21T00:00:00 | [
[
"Godfrey",
"M. D.",
""
],
[
"Jiang",
"P.",
""
],
[
"Kang",
"W.",
""
],
[
"Simon",
"S. H.",
""
],
[
"Baldwin",
"K. W.",
""
],
[
"Pfeiffer",
"L. N.",
""
],
[
"West",
"K. W.",
""
]
] |
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