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|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0704.3001 | Hans-Thomas Janka | L. Scheck (1), H.-Th. Janka (1), T. Foglizzo (2), and K. Kifonidis (1)
((1) MPI for Astrophysics, Garching; (2) Service d'Astrophysique, CEA-Saclay) | Multidimensional supernova simulations with approximative neutrino
transport. II. Convection and the advective-acoustic cycle in the supernova
core | 23 pages, 20 figures; revised version with extended Sect.5, accepted
by Astronomy & Astrophysics; high-resolution images can be obtained upon
request | Astron.Astrophys.477:931,2008 | 10.1051/0004-6361:20077701 | J-MPA2103e | astro-ph | null | By 2D hydrodynamic simulations including a detailed equation of state and
neutrino transport, we investigate the interplay between different non-radial
hydrodynamic instabilities that play a role during the postbounce accretion
phase of collapsing stellar cores. The convective mode of instability, which is
driven by negative entropy gradients caused by neutrino heating or by time
variations of the shock strength, can be identified clearly by the development
of typical Rayleigh-Taylor mushrooms. However, in cases where the gas in the
postshock region is rapidly advected towards the gain radius, the growth of
such a buoyancy instability can be suppressed. In such a situation the shocked
flow nevertheless can develop non-radial asymmetry with an oscillatory growth
of the amplitude. This phenomenon has been termed ``standing accretion shock
instability'' (SASI). It is shown here that the SASI oscillations can trigger
convective instability and like the latter they lead to an increase of the
average shock radius and of the mass in the gain layer. Both hydrodynamic
instabilities in combination stretch the advection time of matter through the
neutrino-heating layer and thus enhance the neutrino energy deposition in
support of the neutrino-driven explosion mechanism. A rapidly contracting and
more compact nascent NS turns out to be favorable for explosions, because the
accretion luminosity and neutrino heating are larger and the growth rate of the
SASI is higher. Moreover, we show that the oscillation period of the SASI and a
variety of other features in our simulations agree with estimates for the
advective-acoustic cycle (AAC), in which perturbations are carried by the
accretion flow from the shock to the neutron star and pressure waves close an
amplifying global feedback loop. (abridged)
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:29:28 GMT"
},
{
"version": "v2",
"created": "Tue, 20 Nov 2007 08:30:21 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Scheck",
"L.",
"",
"MPI for Astrophysics, Garching;"
],
[
"Janka",
"H. -Th.",
"",
"MPI for Astrophysics, Garching;"
],
[
"Foglizzo",
"T.",
"",
"Service d'Astrophysique, CEA-Saclay"
],
[
"Kifonidis",
"K.",
"",
"MPI for Astrophysics, Garching;"
]
] |
0704.3002 | Vladimir Vershinin | Vladimir V. Vershinin | On the inverse braid monoid | 18 pages, 5 figures | Topology Appl. 156 (2009) 1153--1166 | null | null | math.GR math.GT | null | Inverse braid monoid describes a structure on braids where the number of
strings is not fixed. So, some strings of initial $n$ may be deleted. In the
paper we show that many properties and objects based on braid groups may be
extended to the inverse braid monoids. Namely we prove an inclusion into a
monoid of partial monomorphisms of a free group. This gives a solution of the
word problem. Another solution is obtained by an approach similar to that of
Garside. We give also the analogues of Artin presentation with two generators
and Sergiescu graph-presentations.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 13:30:12 GMT"
}
] | 2012-02-20T00:00:00 | [
[
"Vershinin",
"Vladimir V.",
""
]
] |
0704.3003 | Yuri A. Rylov | Yuri A. Rylov | Deformation principle and further geometrization of physics | 18 page, 0 figures | null | null | null | physics.gen-ph | null | The space-time geometry is considered to be a physical geometry, i.e. a
geometry described completely by the world function. All geometrical concepts
and geometric objects are taken from the proper Euclidean geometry. They are
expressed via the Euclidean world function \sigma_E and declared to be concepts
and objects of any physical geometry, provided the Euclidean world function
\sigma_E is replaced by the world function \sigma of the physical geometry in
question. The set of physical geometries is more powerful, than the set of
Riemannian geometries, and one needs to choose a true space-time geometry. In
general, the physical geometry is multivariant (there are many vectors which
are equivalent to a given vector, but are not equivalent between themselves).
The multivariance admits one to describe quantum effects as geometric effects
and to consider existence of elementary particles as a geometrical problem,
when the possibility of the physical existence of an elementary geometric
object in the form of a physical body is determined by the space-time geometry.
Multivariance admits one to describe discrete and continuous geometries, using
the same technique. A use of physical geometry admits one to realize the
geometrical approach to the quantum theory and to the theory of elementary
particles.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 13:31:12 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Rylov",
"Yuri A.",
""
]
] |
0704.3004 | Ronny Thomas | R. Thomas, T. Hilger, B. Kampfer | Four-Quark Condensates in Nucleon QCD Sum Rules | Version accepted for publication: corrected typos, minor changes
based on referee comments included, reference added | Nucl.Phys.A795:19-46,2007 | 10.1016/j.nuclphysa.2007.08.012 | null | hep-ph nucl-th | null | The in-medium behavior of the nucleon spectral density including
self-energies is revisited within the framework of QCD sum rules. Special
emphasis is given to the density dependence of four-quark condensates. A
complete catalog of four-quark condensates is presented and relations among
them are derived. Generic differences of such four-quark condensates occurring
in QCD sum rules for light baryons and light vector mesons are discussed.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 13:33:50 GMT"
},
{
"version": "v2",
"created": "Fri, 7 Sep 2007 14:40:06 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Thomas",
"R.",
""
],
[
"Hilger",
"T.",
""
],
[
"Kampfer",
"B.",
""
]
] |
0704.3005 | Yasser Roudi | Yasser Roudi, Peter E. Latham | A balanced memory network | Accepted for publications in PLoS Comp. Biol | null | 10.1371/journal.pcbi.0030141 | null | q-bio.NC cond-mat.dis-nn | null | A fundamental problem in neuroscience is understanding how working memory --
the ability to store information at intermediate timescales, like 10s of
seconds -- is implemented in realistic neuronal networks. The most likely
candidate mechanism is the attractor network, and a great deal of effort has
gone toward investigating it theoretically. Yet, despite almost a quarter
century of intense work, attractor networks are not fully understood. In
particular, there are still two unanswered questions. First, how is it that
attractor networks exhibit irregular firing, as is observed experimentally
during working memory tasks? And second, how many memories can be stored under
biologically realistic conditions? Here we answer both questions by studying an
attractor neural network in which inhibition and excitation balance each other.
Using mean field analysis, we derive a three-variable description of attractor
networks. From this description it follows that irregular firing can exist only
if the number of neurons involved in a memory is large. The same mean field
analysis also shows that the number of memories that can be stored in a network
scales with the number of excitatory connections, a result that has been
suggested for simple models but never shown for realistic ones. Both of these
predictions are verified using simulations with large networks of spiking
neurons.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 13:45:38 GMT"
}
] | 2015-05-13T00:00:00 | [
[
"Roudi",
"Yasser",
""
],
[
"Latham",
"Peter E.",
""
]
] |
0704.3006 | Przemyslaw Repetowicz | Kieran Kelly, Przemys{\l}aw Repetowicz, and Seosamh macR\'eamoinn | On the Equilibrium Fluctuations of an Isolated System | 30 pages, 7 figures, work has been presented at COST workshop
``Networks, Topology, dynamics and Risk'' and submitted to Physica A. Text
has been edited, figures have been cleaned up and a new section, a new
Appendix, new references and one additional figure have been added | null | null | 0704.0023 | math-ph math.MP | null | Traditionally, it is understood that fluctuations in the equilibrium
distribution are not evident in thermodynamic systems of large $N$ (the number
of particles in the system) \cite{Huang1}. In this paper we examine the
validity of this perception by investigating whether such fluctuations can in
reality depend on temperature.
Firstly, we describe fluctuations in the occupation numbers of the energy
levels for an isolated system, using previously unknown identities that we have
derived for the purpose, which allow us to calculate the moments of the
occupation numbers. Then we compute analytically the probability distribution
of these fluctuations. We show that, for every system of fixed and finite $N$,
fluctuations about the equilibrium distribution do, in fact, depend on the
temperature. Indeed, at higher temperatures the fluctuations can be so large
that the system does not fully converge on the Maxwell-Boltzmann distribution
but actually fluctuates around it. We term this state, where not one macrostate
but a region of macrostates closely fit the underlying distribution, a ``{\it
fluctuating equilibrium}''. Finally, we speculate on how this finding is
applicable to networks, financial markets, and other thermodynamic-like
systems.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 13:46:27 GMT"
},
{
"version": "v2",
"created": "Tue, 1 May 2007 19:34:04 GMT"
},
{
"version": "v3",
"created": "Tue, 15 May 2007 18:28:19 GMT"
},
{
"version": "v4",
"created": "Wed, 3 Oct 2007 10:00:34 GMT"
}
] | 2007-10-03T00:00:00 | [
[
"Kelly",
"Kieran",
""
],
[
"Repetowicz",
"Przemysław",
""
],
[
"macRéamoinn",
"Seosamh",
""
]
] |
0704.3007 | Pierre Schapira | Pierre Schapira | Deformation quantization modules on complex symplectic manifolds | To appear in the Proceedings of the Poisson 2006 (Tokyo), AMS
Contemporary Mathematics | null | null | null | math.QA math.AG | null | We study modules over the algebroid stack $\W[\stx]$ of deformation
quantization on a complex symplectic manifold $\stx$ and recall some results:
construction of an algebra for $\star$-products, existence of (twisted) simple
modules along smooth Lagrangian submanifolds, perversity of the complex of
solutions for regular holonomic $\W[\stx]$-modules, finiteness and duality for
the composition of ``good'' kernels. As a corollary, we get that the derived
category of good $\W[\stx]$-modules with compact support is a Calabi-Yau
category. We also give a conjectural Riemann-Roch type formula in this
framework.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 13:47:24 GMT"
},
{
"version": "v2",
"created": "Wed, 20 Jun 2007 11:02:28 GMT"
}
] | 2007-06-20T00:00:00 | [
[
"Schapira",
"Pierre",
""
]
] |
0704.3008 | Izaskun Jimenez-Serra | I. Jimenez-Serra (1), J. Martin-Pintado (1), A. Rodriguez-Franco (1),
C. Chandler (2), C. Comito (3) and P. Schilke (3) ((1) DAMIR-IEM-CSIC, Spain,
(2) NRAO, USA, (3) MPIfR, Germany) | A Photoevaporating Rotating Disk in the Cepheus A HW2 Star Cluster | 4 pages, 2 figures, accepted for publication in ApJL | null | 10.1086/519005 | null | astro-ph | null | We present VLA and PdBI subarcsecond images (0.15"-0.6") of the
radiocontinuum emission at 7 mm and of the SO2 J=19_{2,18}-18_{3,15} and
J=27_{8,20}-28_{7,21} lines toward the Cepheus A HW2 region. The SO2 images
reveal the presence of a hot core internally heated by an intermediate mass
protostar, and a circumstellar rotating disk around the HW2 radio jet with size
600AUx100AU and mass of 1M_sun. Keplerian rotation for the disk velocity
gradient of 5 kms-1 requires a 9 M_sun central star, which cannot explain the
total luminosity observed in the region. This may indicate that the disk does
not rotate with a Keplerian law due to the extreme youth of this object. Our
high sensitivity radiocontinuum image at 7 mm shows in addition to the ionized
jet, an extended emission to the west (and marginally to the south) of the HW2
jet, filling the south-west cavity of the HW2 disk. From the morphology and
location of this free-free continuum emission at centimeter and millimeter
wavelengths (spectral index of 0.4-1.5), we propose that the disk is
photoevaporating due to the UV radiation from the central star. All this
indicates that the Cepheus A HW2 region harbors a cluster of massive stars.
Disk accretion seems to be the most plausible way to form massive stars in
moderate density/luminosity clusters.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:01:54 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Jimenez-Serra",
"I.",
""
],
[
"Martin-Pintado",
"J.",
""
],
[
"Rodriguez-Franco",
"A.",
""
],
[
"Chandler",
"C.",
""
],
[
"Comito",
"C.",
""
],
[
"Schilke",
"P.",
""
]
] |
0704.3009 | Vicent Quilis | V. Quilis, A.C. Gonz\'alez-Garc\'ia, D. S\'aez and J. A. Font | Gravitational waves from galaxy encounters | 9 pages with revtex style, 3 ps figures; to be published in Physical
Review D | Phys.Rev.D75:104008,2007; Erratum-ibid.D75:109901,2007 | 10.1103/PhysRevD.75.104008 10.1103/PhysRevD.75.109901 | null | astro-ph | null | We discuss the emission of gravitational radiation produced in encounters of
dark matter galactic halos. To this aim we perform a number of numerical
simulations of typical galaxy mergers, computing the associated gravitational
radiation waveforms as well as the energy released in the processes. Our
simulations yield dimensionless gravitational wave amplitudes of the order of
$10^{-13}$ and gravitational wave frequencies of the order of $10^{-16}$ Hz,
when the galaxies are located at a distance of 10 Mpc. These values are of the
same order as those arising in the gravitational radiation originated by strong
variations of the gravitational field in the early Universe, and therefore,
such gravitational waves cannot be directly observed by ground-based detectors.
We discuss the feasibility of an indirect detection by means of the B-mode
polarization of the Cosmic Microwave Background (CMB) induced by such waves.
Our results show that the gravitational waves from encounters of dark matter
galactic halos leave much too small an imprint on the CMB polarization to be
actually observed with ongoing and future missions.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:03:21 GMT"
}
] | 2019-08-19T00:00:00 | [
[
"Quilis",
"V.",
""
],
[
"González-García",
"A. C.",
""
],
[
"Sáez",
"D.",
""
],
[
"Font",
"J. A.",
""
]
] |
0704.3010 | Aigars Atvars | C. Andreeva, A. Atvars, M. Auzinsh, K.Bluss, S. Cartaleva, L. Petrov,
and D. Slavov | Ground-state magneto-optical resonances in Cesium vapour confined in an
extremely thin cell | null | null | 10.1103/PhysRevA.76.063804 | null | physics.atom-ph | null | Experimental and theoretical studies are presented related to the
ground-state magneto-optical resonance prepared in Cesium vapour confined in an
Extremely Thin Cell (ETC, with thickness equal to the wavelength of the
irradiating light). It is shown that the utilization of the ETC allows one to
examine the formation of a magneto-optical resonance on the individual
hyperfine transitions, thus distinguishing processes resulting in dark (reduced
absorption) or bright (enhanced absorption) resonance formation. We report on
an experimental evidence of the bright magneto-optical resonance sign reversal
in Cs atoms confined in the ETC. A theoretical model is proposed based on the
optical Bloch equations that involves the elastic interaction processes of
atoms in the ETC with its walls resulting in depolarization of the Cs excited
state which is polarized by the exciting radiation. This depolarization leads
to the sign reversal of the bright resonance. Using the proposed model, the
magneto-optical resonance amplitude and width as a function of laser power are
calculated and compared with the experimental ones. The numerical results are
in good agreement with the experiment.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:05:19 GMT"
}
] | 2009-11-23T00:00:00 | [
[
"Andreeva",
"C.",
""
],
[
"Atvars",
"A.",
""
],
[
"Auzinsh",
"M.",
""
],
[
"Bluss",
"K.",
""
],
[
"Cartaleva",
"S.",
""
],
[
"Petrov",
"L.",
""
],
[
"Slavov",
"D.",
""
]
] |
0704.3011 | Immanuel Bloch | Immanuel Bloch, Jean Dalibard, Wilhelm Zwerger | Many-Body Physics with Ultracold Gases | revised version, accepted for publication in Rev. Mod. Phys | Rev. Mod. Phys. 80, 885 (2008) | 10.1103/RevModPhys.80.885 | null | cond-mat.other | null | This article reviews recent experimental and theoretical progress on
many-body phenomena in dilute, ultracold gases. Its focus are effects beyond
standard weak-coupling descriptions, like the Mott-Hubbard-transition in
optical lattices, strongly interacting gases in one and two dimensions or
lowest Landau level physics in quasi two-dimensional gases in fast rotation.
Strong correlations in fermionic gases are discussed in optical lattices or
near Feshbach resonances in the BCS-BEC crossover.
| [
{
"version": "v1",
"created": "Sun, 22 Apr 2007 23:06:35 GMT"
},
{
"version": "v2",
"created": "Wed, 17 Oct 2007 20:46:06 GMT"
}
] | 2008-07-21T00:00:00 | [
[
"Bloch",
"Immanuel",
""
],
[
"Dalibard",
"Jean",
""
],
[
"Zwerger",
"Wilhelm",
""
]
] |
0704.3012 | Jos\'e A. de Diego | T. Verdugo, J.A. de Diego, M. Limousin | MS 2053.7-0449: Confirmation of a bimodal mass distribution from strong
gravitational lensing | To be published in ApJ (accepted) | Astrophys.J.664:702-712,2007 | 10.1086/519153 | null | astro-ph | null | We present the first strong lensing study of the mass distribution in the
cluster MS 2053-04 based on HST archive data. This massive, X-ray luminous
cluster has a redshift z=0.583, and it is composed of two structures that are
gravitationally bound to each other. The cluster has one multiply imaged system
constituted by a double gravitational arc.
We have performed a parametric strong lensing mass reconstruction using NFW
density profiles to model the cluster potential. We also included perturbations
from 23 galaxies, modeled like elliptical singular isothermal sphere, that are
approximately within 1'x1' around the cluster center. These galaxies were
constrained in both the geometric and dynamical parameters with observational
data. Our analysis predicts a third image which is slightly demagnified. We
found a candidate for this counter-image near the expected position and with
the same F702W-F814W colors as the gravitational arcs in the cluster. The
results from the strong lensing model shows the complex structure in this
cluster, the asymmetry and the elongation in the mass distribution, and are
consistent with previous spectrophotometric results that indicate that the
cluster has a bimodal mass distribution. Finally, the derived mass profile was
used to estimate the mass within the arcs and for comparison with X-ray
estimates.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 17:57:15 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Verdugo",
"T.",
""
],
[
"de Diego",
"J. A.",
""
],
[
"Limousin",
"M.",
""
]
] |
0704.3013 | Kamal Lochan Panigrahi | J. Kluson, Kamal L. Panigrahi | On the Universal Tachyon and Geometrical Tachyon | 24 pages, minor changes | JHEP 0706:015,2007 | 10.1088/1126-6708/2007/06/015 | null | hep-th | null | We study properties of non-BPS D(p+1)-brane in the background of k
NS5-branes, with one transverse direction compactified on a circle, from the
point of view of Dirac-Born-Infeld action. We present the analysis of two
different embedding of non-BPS D(p+1)-brane in given background and study the
classical solutions of given world-volume theory. We argue for the
configuration of a non-BPS D(p+1)-brane which allows us to find solutions of
the equations of motion that give unified descriptions of G and U-type branes.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:20:13 GMT"
},
{
"version": "v2",
"created": "Mon, 4 Jun 2007 06:55:49 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Kluson",
"J.",
""
],
[
"Panigrahi",
"Kamal L.",
""
]
] |
0704.3014 | Alessandro Silva | Avraham Schiller, Alessandro Silva | Adiabatic pumping through a quantum dot in the Kondo regime: Exact
results at the Toulouse limit | 14 pages, 3 figures, revised version | Phys. Rev. B 77, 045330 (2008) | 10.1103/PhysRevB.77.045330 | null | cond-mat.mes-hall cond-mat.str-el | null | Transport properties of ultrasmall quantum dots with a single unpaired
electron are commonly modeled by the nonequilibrium Kondo model, describing the
exchange interaction of a spin-1/2 local moment with two leads of
noninteracting electrons. Remarkably, the model possesses an exact solution
when tuned to a special manifold in its parameter space known as the Toulouse
limit. We use the Toulouse limit to exactly calculate the adiabatically pumped
spin current in the Kondo regime. In the absence of both potential scattering
and a voltage bias, the instantaneous charge current is strictly zero for a
generic Kondo model. However, a nonzero spin current can be pumped through the
system in the presence of a finite magnetic field, provided the spin couples
asymmetrically to the two leads. Tunneling through a Kondo impurity thus offers
a natural mechanism for generating a pure spin current. We show, in particular,
that one can devise pumping cycles along which the average spin pumped per
cycle is closely equal to $\hbar$. By analogy with Brouwer's formula for
noninteracting systems with two driven parameters, the pumped spin current is
expressed as a geometrical property of a scattering matrix. However, the
relevant %Alex: I replaced topological with geometrical in the sentence above
scattering matrix that enters the formulation pertains to the Majorana fermions
that appear at the Toulouse limit rather than the physical electrons that carry
the current. These results are obtained by combining the nonequilibrium Keldysh
Green function technique with a systematic gradient expansion, explicitly
exposing the small parameter controlling the adiabatic limit.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:21:07 GMT"
},
{
"version": "v2",
"created": "Tue, 13 Nov 2007 09:22:14 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Schiller",
"Avraham",
""
],
[
"Silva",
"Alessandro",
""
]
] |
0704.3015 | Lionel Bureau | Lionel Bureau (INSP) | A surface force apparatus for nanorheology under large shear strain | null | Review of Scientific Instruments 78 (2007) 065110 | 10.1063/1.2748362 | null | cond-mat.soft | null | We describe a surface force apparatus designed to probe the rheology of a
nanoconfined medium under large shear amplitudes (up to 500 $\mu$m). The
instrument can be operated in closed-loop, controlling either the applied
normal load or the thickness of the medium during shear experiments. Feedback
control allows to greatly extend the range of confinement/shear strain
attainable with the surface force apparatus. The performances of the instrument
are illustrated using hexadecane as the confined medium.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:23:17 GMT"
},
{
"version": "v2",
"created": "Tue, 24 Apr 2007 11:13:23 GMT"
}
] | 2011-11-09T00:00:00 | [
[
"Bureau",
"Lionel",
"",
"INSP"
]
] |
0704.3016 | Kevin Kr\"oninger | I. Abt, A. Caldwell, K. Kr\"oninger, J. Liu, X. Liu, B. Majorovits | Pulse shapes from electron and photon induced events in segmented
high-purity germanium detectors | 18 pages, 7 figures, to be submitted to Nucl. Instrum. Meth. A | Eur.Phys.J.C52:19-27,2007 | 10.1140/epjc/s10052-007-0390-8 | MPP-2007-47 | nucl-ex | null | Experiments built to search for neutrinoless double beta-decay are limited in
their sensitivity not only by the exposure but also by the amount of background
encountered. Radioactive isotopes in the surrounding of the detectors which
emit gamma-radiation are expected to be a significant source of background in
the GERmanium Detector Array, GERDA.
Methods to select electron induced events and discriminate against photon
induced events inside a germanium detector are presented in this paper. The
methods are based on the analysis of the time structure of the detector
response. Data were taken with a segmented GERDA prototype detector. It is
shown that the analysis of the time response of the detector can be used to
distinguish multiply scattered photons from electrons.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:23:53 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Abt",
"I.",
""
],
[
"Caldwell",
"A.",
""
],
[
"Kröninger",
"K.",
""
],
[
"Liu",
"J.",
""
],
[
"Liu",
"X.",
""
],
[
"Majorovits",
"B.",
""
]
] |
0704.3017 | Thomas Schaepers | I. E. Batov, Th. Schapers, N. M. Chtchelkatchev, H. Hardtdegen, and A.
V. Ustinov | Andreev reflection and strongly enhanced magnetoresistance oscillations
in GaInAs/InP heterostructures with superconducting contacts | 5 pages, 5 figures | null | 10.1103/PhysRevB.76.115313 | null | cond-mat.mes-hall | null | We study the magnetotransport in small hybrid junctions formed by
high-mobility GaInAs/InP heterostructures coupled to superconducting (S) and
normal metal (N) terminals. Highly transmissive superconducting contacts to a
two-dimensional electron gas (2DEG) located in a GaInAs/InP heterostructure are
realized by using a Au/NbN layer system. The magnetoresistance of the S/2DEG/N
structures is studied as a function of dc bias current and temperature. At bias
currents below a critical value, the resistance of the S/2DEG/N structures
develops a strong oscillatory dependence on the magnetic field, with an
amplitude of the oscillations considerably larger than that of the reference
N/2DEG/N structures. The experimental results are qualitatively explained by
taking Andreev reflection in high magnetic fields into account.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:25:32 GMT"
},
{
"version": "v2",
"created": "Tue, 24 Apr 2007 10:39:53 GMT"
},
{
"version": "v3",
"created": "Wed, 1 Aug 2007 06:25:41 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Batov",
"I. E.",
""
],
[
"Schapers",
"Th.",
""
],
[
"Chtchelkatchev",
"N. M.",
""
],
[
"Hardtdegen",
"H.",
""
],
[
"Ustinov",
"A. V.",
""
]
] |
0704.3018 | Bing Wang | Bing Wang | On the Conditions to Extend Ricci Flow | null | null | null | null | math.DG | null | Along a Ricci flow solution on a closed manifold, we show that if Ricci
curvature is uniformly bounded from below, then a scalar curvature integral
bound is enough to extend flow. Moreover, this integral bound condition is
optimal in some sense.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:52:15 GMT"
},
{
"version": "v2",
"created": "Mon, 23 Apr 2007 20:28:14 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Wang",
"Bing",
""
]
] |
0704.3019 | Oliver Henkel | Oliver Henkel | Arbitrary Rate Permutation Modulation for the Gaussian Channel | to appear in the Proceedings of the International Symposium of
Information Theory (ISIT 2007) | null | null | null | cs.IT math.IT | null | In this paper non-group permutation modulated sequences for the Gaussian
channel are considered. Without the restriction to group codes rather than
subsets of group codes, arbitrary rates are achievable. The code construction
utilizes the known optimal group constellations to ensure at least the same
performance but exploit the Gray code ordering structure of multiset
permutations as a selection criterion at the decoder. The decoder achieves near
maximum likelihood performance at low computational cost and low additional
memory requirements at the receiver.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:31:17 GMT"
}
] | 2007-07-13T00:00:00 | [
[
"Henkel",
"Oliver",
""
]
] |
0704.3020 | Alessandra Faggionato | A. Faggionato | Random walks and exclusion processes among random conductances on random
infinite clusters: homogenization and hydrodynamic limit | 24 pages. extensions and corrections. new title | null | null | null | math.PR math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider a stationary and ergodic random field {\omega(b)} parameterized
by the family of bonds b in Z^d, d>1. The random variable \omega(b) is thought
of as the conductance of bond b and it ranges in a finite interval [0,c_0].
Assuming that the set of bonds with positive conductance has a unique infinite
cluster C, we prove homogenization results for the random walk among random
conductances on C. As a byproduct, applying the general criterion of \cite{F}
leading to the hydrodynamic limit of exclusion processes with bond-dependent
transition rates, for almost all realizations of the environment we prove the
hydrodynamic limit of simple exclusion processes among random conductances on
C. The hydrodynamic equation is given by a heat equation whose diffusion matrix
does not depend on the environment. We do not require any ellipticity
condition. As special case, C can be the infinite cluster of supercritical
Bernoulli bond percolation.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:51:07 GMT"
},
{
"version": "v2",
"created": "Thu, 10 May 2007 07:38:00 GMT"
},
{
"version": "v3",
"created": "Tue, 16 Sep 2008 09:04:51 GMT"
}
] | 2008-09-16T00:00:00 | [
[
"Faggionato",
"A.",
""
]
] |
0704.3021 | Gerrit Verschuur Ph.D. | Gerrit L. Verschuur | On the Critical Ionization Velocity Effect in Interstellar Space and
Possible Detection of Related Continuum Emission | To be published in IEEE Trans. Plasma Sci. Aug 2007 | null | 10.1109/TPS.2007.898037 | null | astro-ph | null | Interstellar neutral hydrogen (HI) emission spectra manifest several families
of linewidths whose numerical values (34, 13 & 6 km/s) appear to be related to
the critical ionization velocities (CIVs) of the most abundant interstellar
atomic species. Extended new analysis of HI emission profiles shows that the 34
km/s wide component, probably corresponding to the CIV for helium, is
pervasive. The 34 km/s wide linewidth family is found in low-velocity (local)
neutral hydrogen (HI) profiles as well as in the so-called high-velocity
clouds. In addition, published studies of HI linewidths found in the Magellanic
Stream, Very-High-Velocity Clouds, and Compact High-Velocity Clouds, all of
which are believed to be intergalactic, have noted that typical values are of
the same order. If the critical ionization velocity effect does play a role in
interstellar space it may be expected to produce locally enhanced electron
densities where rapidly moving neutral gas masses interact with surrounding
plasma. Evidence is presented that suggests that this phenomenon is occurring
in interstellar space. It manifests as a spatial association between peaks in
HI structure offset with respect to peaks in high-frequency radio continuum
data obtained with the Wilkinson Microwave Anisotropy Probe.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 14:59:46 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Verschuur",
"Gerrit L.",
""
]
] |
0704.3022 | Mark Pankov | Mark Pankov | Order preserving transformations of the Hilbert grassmannian: complex
case | null | null | null | null | math.FA math.OA | null | Let $H$ be a separable complex Hilbert space. Denote by ${\mathcal
G}_{\infty}(H)$ the Grassmannian consisting of closed linear subspaces with
infinite dimension and codimension. This Grassmannian is partially ordered by
the inclusion relation. We show that every continuous order preserving
bijective transformation of ${\mathcal G}_{\infty}(H)$ is induced by an
invertible bounded semi-linear operator.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:03:44 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Pankov",
"Mark",
""
]
] |
0704.3023 | Marc Wagner | Marc Wagner | Fermions in the pseudoparticle approach | 11 pages, 10 figures | Phys.Rev.D76:076002,2007 | 10.1103/PhysRevD.76.076002 | null | hep-lat hep-ph physics.comp-ph | null | The pseudoparticle approach is a numerical technique to compute path
integrals without discretizing spacetime. The basic idea is to integrate over
those field configurations, which can be represented by a sum of a fixed number
of localized building blocks (pseudoparticles). In a couple of previous papers
we have successfully applied the pseudoparticle approach to pure SU(2)
Yang-Mills theory. In this work we discuss how to incorporate 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.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:03:48 GMT"
}
] | 2007-10-04T00:00:00 | [
[
"Wagner",
"Marc",
""
]
] |
0704.3024 | David Ehrenreich | David Ehrenreich (IAP), Arnaud Cassan (ARI) | Are extrasolar oceans common throughout the Galaxy? | Accepted in Astronomische Nachrichten (Astronomical Notes) | null | 10.1002/asna.200710798 | null | astro-ph | null | Light and cold extrasolar planets such as OGLE 2005-BLG-390Lb, a 5.5
Earth-mass planet detected via microlensing, could be frequent in the Galaxy
according to some preliminary results from microlensing experiments. These
planets can be frozen rocky- or ocean-planets, situated beyond the snow line
and, therefore, beyond the habitable zone of their system. They can nonetheless
host a layer of liquid water, heated by radiogenic energy, underneath an ice
shell surface for billions of years, before freezing completely. These results
suggest that oceans under ice, like those suspected to be present on icy moons
in the Solar system, could be a common feature of cold low-mass extrasolar
planets.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:19:39 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Ehrenreich",
"David",
"",
"IAP"
],
[
"Cassan",
"Arnaud",
"",
"ARI"
]
] |
0704.3025 | Shintaro Ishiwata | S. Ishiwata, I. Terasaki, F. Ishii, N. Nagaosa, H. Mukuda, Y. Kitaoka,
T. Saito, and M. Takano | Two-Staged Magnetoresistance Driven by Ising-like Spin Sublattice in
SrCo6O11 | 14 pages, 4 figures, accepted for publication in Phys. Rev. Lett | null | 10.1103/PhysRevLett.98.217201 | null | cond-mat.str-el | null | A two-staged, uniaxial magnetoresistive effect has been discovered in
SrCo6O11 having a layered hexagonal structure. Conduction electrons and
localized Ising spins are in different sublattices but their interpenetration
makes the conduction electrons sensitively pick up the stepwise
field-dependence of magnetization. The stepwise field-dependence suggests two
competitive interlayer interactions between ferromagnetic Ising-spin layers,
i.e., a ferromagnetic nearest-layer interaction and an antiferromagnetic
next-nearest-layer interaction. This oxide offers a unique opportunity to study
nontrivial interplay between conduction electrons and Ising spins, the coupling
of which can be finely controlled by a magnetic field of a few Tesla.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:16:54 GMT"
},
{
"version": "v2",
"created": "Tue, 24 Apr 2007 05:03:36 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Ishiwata",
"S.",
""
],
[
"Terasaki",
"I.",
""
],
[
"Ishii",
"F.",
""
],
[
"Nagaosa",
"N.",
""
],
[
"Mukuda",
"H.",
""
],
[
"Kitaoka",
"Y.",
""
],
[
"Saito",
"T.",
""
],
[
"Takano",
"M.",
""
]
] |
0704.3026 | Kristen McQuinn | K. B. W. McQuinn, Charles E. Woodward, S. P. Willner, E. F. Polomski,
R. D. Gehrz, Roberta M. Humphreys, Jacco Th. van Loon, M. L. N. Ashby, K.
Eicher, and G. G. Fazio | The M33 Variable Star Population Revealed by Spitzer | Accepted for publication in ApJ. See published article for full
resolution figures and electronic tables | Astrophys.J.664:850-861,2007 | 10.1086/519068 | null | astro-ph | null | We analyze five epochs of Spitzer Space Telescope/Infrared Array Camera
(IRAC) observations of the nearby spiral galaxy M33. Each epoch covered nearly
a square degree at 3.6, 4.5, and 8.0 microns. The point source catalog from the
full dataset contains 37,650 stars. The stars have luminosities characteristic
of the asymptotic giant branch and can be separated into oxygen-rich and
carbon-rich populations by their [3.6] - [4.5] colors. The [3.6] - [8.0] colors
indicate that over 80% of the stars detected at 8.0 microns have dust shells.
Photometric comparison of epochs using conservative criteria yields a catalog
of 2,923 variable stars. These variables are most likely long-period variables
amidst an evolved stellar population. At least one-third of the identified
carbon stars are variable.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:12:33 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"McQuinn",
"K. B. W.",
""
],
[
"Woodward",
"Charles E.",
""
],
[
"Willner",
"S. P.",
""
],
[
"Polomski",
"E. F.",
""
],
[
"Gehrz",
"R. D.",
""
],
[
"Humphreys",
"Roberta M.",
""
],
[
"van Loon",
"Jacco Th.",
""
],
[
"Ashby",
"M. L. N.",
""
],
[
"Eicher",
"K.",
""
],
[
"Fazio",
"G. G.",
""
]
] |
0704.3027 | Daniel Burgarth | Daniel Burgarth and Vittorio Giovannetti | Full control by locally induced relaxation | 4 pages, 2 figures | Phys. Rev. Lett. 99, 100501 (2007) | 10.1103/PhysRevLett.99.100501 | null | quant-ph | null | We demonstrate a scheme for controlling a large quantum system by acting on a
small subsystem only. The local control is mediated to the larger system by
some fixed coupling Hamiltonian. The scheme allows to transfer arbitrary and
unknown quantum states from a memory on the large system (``upload access'') as
well as the inverse (``download access''). We study sufficient conditions of
the coupling Hamiltonian and give lower bounds on the fidelities for
downloading and uploading.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:17:25 GMT"
}
] | 2007-09-05T00:00:00 | [
[
"Burgarth",
"Daniel",
""
],
[
"Giovannetti",
"Vittorio",
""
]
] |
0704.3028 | Mario Bessa | Mario Bessa and Joao Lopes Dias | Generic dynamics of 4-dimensional C2 Hamiltonian systems | null | Communications in Mathematical Physics, Vol 281, n{\deg} 1,
597-619, 2008 | 10.1007/s00220-008-0500-y | null | math.DS | null | We study the dynamical behaviour of Hamiltonian flows defined on
4-dimensional compact symplectic manifolds. We find the existence of a
C2-residual set of Hamiltonians for which every regular energy surface is
either Anosov or it is in the closure of energy surfaces with zero Lyapunov
exponents a.e. This is in the spirit of the Bochi-Mane dichotomy for
area-preserving diffeomorphisms on compact surfaces and its continuous-time
version for 3-dimensional volume-preserving flows.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:19:49 GMT"
},
{
"version": "v2",
"created": "Mon, 21 Jan 2008 19:25:08 GMT"
}
] | 2010-10-05T00:00:00 | [
[
"Bessa",
"Mario",
""
],
[
"Dias",
"Joao Lopes",
""
]
] |
0704.3029 | Mikhail Voloshin | M.B. Voloshin | Isospin properties of the X state near the D {\bar D}^{*} threshold | 10 pages, 1 figure | Phys.Rev.D76:014007,2007 | 10.1103/PhysRevD.76.014007 | FTPI-MINN-07/14, UMN-TH-2601/07 | hep-ph | null | The $D {\bar D}^*$ scattering amplitude and the production of the final
states $\pi^+ \pi^- J/\psi$ and $\pi^+ \pi^- \pi^0 J/\psi$ near the $D^0 {\bar
D}^{*0}$ threshold are discussed following the recent suggestion that the
observed peaks X(3872) and X(3875) in the decays $B \to X K$ are due to a
virtual state $X$ in the $D^0 {\bar D}^{*0}$ channel. The strong interaction is
treated using the small interaction radius approximation. It is shown that the
mass difference between the charged and neutral $D^{(*)}$ mesons results in a
distinctive behavior of the relevant isotopic amplitudes. In particular, the
shape of the peak in the $\pi^+ \pi^- J/\psi$ channel should be significantly
narrower than in the $\pi^+ \pi^- \pi^0 J/\psi$ channel, which property can be
used for an experimental test of the virtual state hypothesis.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:51:41 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Voloshin",
"M. B.",
""
]
] |
0704.3030 | James L. Clem | Arlo U. Landolt, Alan K. Uomoto | Optical Multicolor Photometry of Spectrophotometric Standard Stars | 76 pages, 48 figures - published version available here:
http://www.journals.uchicago.edu/AJ/journal/issues/v133n3/205588/205588.html
. Also see ERRATUM at:
http://www.journals.uchicago.edu/AJ/journal/issues/v133n5/205838/205838.html | Astron.J.133:768-790,2007 | 10.1086/510485 10.1086/518002 | null | astro-ph | null | Photoelectric data on the Johnson-Kron-Cousins UBVRI broadband photometric
system are provided for a set of stars which have been used as
spectrophotometric standard stars at the Hubble Space Telescope.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:26:43 GMT"
}
] | 2010-11-05T00:00:00 | [
[
"Landolt",
"Arlo U.",
""
],
[
"Uomoto",
"Alan K.",
""
]
] |
0704.3031 | Simon Radford | Simon J. E. Radford, Riccardo Giovanelli, Thomas A. Sebring, Jonas
Zmuidzinas | The Cornell Caltech Atacama Telescope | 18th International Symposium on Space Terahertz Technology | null | null | null | astro-ph | null | Cornell University, the California Institute for Technology, and the Jet
Propulsion Laboratory are jointly studying the construction of a 25 m diameter
telescope for submillimeter astronomy on a high mountain in northern Chile.
This Cornell Caltech Atacama Telescope (CCAT) will combine high sensitivity, a
wide field of view, and a broad wavelength range to provide an unprecedented
capability for deep, large area, multi-color submillimeter surveys to
complement narrow field, high resolution studies with ALMA. CCAT observations
will address fundamental themes in contemporary astronomy, notably the
formation and evolution of galaxies, the nature of the dark matter and dark
energy that comprise most of the content of the universe, the formation of
stars and planets, the conditions in circumstellar disks, and the conditions
during the early history of the Solar system. The candidate CCAT site, at 5600
m in northern Chile, enjoys superb observing conditions. To accommodate large
format bolometer cameras, CCAT is designed with a 20 arcmin field of view. CCAT
will incorporate closed loop active control of its segmented primary mirror to
maintain a half wavefront error of 10 mum rms or less. Instrumentation under
consideration includes both short (650 mum-200 mum) and long (2 mm-750 mum)
wavelength bolometer cameras, direct detection spectrometers, and heterodyne
receiver arrays. The University of Colorado, a Canadian university consortium,
and the UK Astronomy Technology Centre on behalf of the UK community are
pursuing participation in the CCAT consortium. When complete early in the next
decade, CCAT will be the largest and most sensitive facility of its class as
well as the highest altitude astronomical facility on Earth.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:48:03 GMT"
},
{
"version": "v2",
"created": "Wed, 25 Apr 2007 23:40:02 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Radford",
"Simon J. E.",
""
],
[
"Giovanelli",
"Riccardo",
""
],
[
"Sebring",
"Thomas A.",
""
],
[
"Zmuidzinas",
"Jonas",
""
]
] |
0704.3032 | Zolt\'an Nagy | Nenad Manojlovic and Zoltan Nagy | Algebraic Bethe ansatz for the elliptic quantum group
$E_{\tau,\eta}(A_2^{(2)})$ | 15 pages; v2: minor corrections. A reference is added, a more precise
abstract is written, a section title is changed and typos are corrected | Journal of Mathematical Physics 48, 123515 (2007) | 10.1063/1.2823974 | null | math.QA math-ph math.MP nlin.SI | null | We implement the Bethe anstaz method for the elliptic quantum group
$E_{\tau,\eta}(A_2^{(2)})$. The Bethe creation operators are constructed as
polynomials of the Lax matrix elements expressed through a recurrence relation.
We also give the eigenvalues of the family of commuting transfer matrices
defined in the tensor product of fundamental representations.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:51:15 GMT"
},
{
"version": "v2",
"created": "Fri, 27 Apr 2007 15:28:01 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Manojlovic",
"Nenad",
""
],
[
"Nagy",
"Zoltan",
""
]
] |
0704.3033 | Satoshi Miyashita | Satoshi Miyashita and Kenji Yonemitsu | Charge ordering in \theta-(BEDT-TTF)2RbZn(SCN)4: Cooperative effects of
electron correlations and lattice distortions | 7 peges, 7 figures, accepted for publication in Phys. Rev. B | null | 10.1103/PhysRevB.75.245112 | null | cond-mat.str-el | null | Combined effects of electron correlations and lattice distortions are
investigated on the charge ordering in \theta-(BEDT-TTF)2RbZn(SCN)4
theoretically in a two-dimensional 3/4-filled extended Hubbard model with
electron-lattice couplings. It is known that this material undergoes a phase
transition from a high-symmetry metallic state to a low-symmetry insulating
state with a horizontal-stripe charge order (CO) by lowering temperature. By
means of the exact-diagonalization method, we show that electron-phonon
interactions are crucial to stabilize the horizontal-stripe CO and to realize
the low-symmetry crystal structure.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:45:21 GMT"
},
{
"version": "v2",
"created": "Mon, 23 Apr 2007 20:11:09 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Miyashita",
"Satoshi",
""
],
[
"Yonemitsu",
"Kenji",
""
]
] |
0704.3034 | James L. Clem | Arlo U. Landolt | UBVRI Photometric Standard Stars Around the Sky at -50 Degrees
Declination | 80 pages, 57 figures - published version available here:
http://www.journals.uchicago.edu/AJ/journal/issues/v133n6/205795/205795.html | Astron.J.133:2502-2523,2007 | 10.1086/518000 | null | astro-ph | null | UBVRI photoelectric observations have been made of 109 stars around the sky,
centered more or less at -50 degrees declination. The majority of the stars
fall in the magnitude range 10.4 < V < 15.5 and in the color index range -0.33
< (B - V) < +1.66. These new broadband photometric standard stars average 16.4
measurements each from data taken on 116 different nights over a period of 4
yr. Similar data are tabulated for 19 stars of interest that were not observed
often enough to make them well-defined standard stars.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:50:15 GMT"
}
] | 2010-11-05T00:00:00 | [
[
"Landolt",
"Arlo U.",
""
]
] |
0704.3035 | Ender Tekin | Ender Tekin, Aylin Yener | Achievable Rates for Two-Way Wire-Tap Channels | International Symposium on Information Theory (ISIT) 2007, June 24-29 | null | null | null | cs.IT cs.CR math.IT | null | We consider two-way wire-tap channels, where two users are communicating with
each other in the presence of an eavesdropper, who has access to the
communications through a multiple-access channel. We find achievable rates for
two different scenarios, the Gaussian two-way wire-tap channel, (GTW-WT), and
the binary additive two-way wire-tap channel, (BATW-WT). It is shown that the
two-way channels inherently provide a unique advantage for wire-tapped
scenarios, as the users know their own transmitted signals and in effect help
encrypt the other user's messages, similar to a one-time pad. We compare the
achievable rates to that of the Gaussian multiple-access wire-tap channel
(GMAC-WT) to illustrate this advantage.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:26:59 GMT"
}
] | 2007-07-13T00:00:00 | [
[
"Tekin",
"Ender",
""
],
[
"Yener",
"Aylin",
""
]
] |
0704.3036 | Stefaan Caenepeel | D. Bulacu, S. Caenepeel, B. Torrecillas | Involutory quasi-Hopf algebras | 26 pages | null | null | null | math.QA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We introduce and investigate the basic properties of an involutory (dual)
quasi-Hopf algebra. We also study the representations of an involutory
quasi-Hopf algebra and prove that an involutory dual quasi-Hopf algebra with
non-zero integral is cosemisimple.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:51:32 GMT"
},
{
"version": "v2",
"created": "Tue, 9 Dec 2008 13:52:26 GMT"
}
] | 2008-12-09T00:00:00 | [
[
"Bulacu",
"D.",
""
],
[
"Caenepeel",
"S.",
""
],
[
"Torrecillas",
"B.",
""
]
] |
0704.3037 | Cristobal Lopez | Stefano Berti, Cristobal Lopez, Davide Vergni and Angelo Vulpiani | Discreteness effects in a reacting system of particles with finite
interaction radius | 23 pages, 13 figures | null | 10.1103/PhysRevE.76.031139 | null | cond-mat.stat-mech | null | An autocatalytic reacting system with particles interacting at a finite
distance is studied. We investigate the effects of the discrete-particle
character of the model on properties like reaction rate, quenching phenomenon
and front propagation, focusing on differences with respect to the continuous
case. We introduce a renormalized reaction rate depending both on the
interaction radius and the particle density, and we relate it to macroscopic
observables (e.g., front speed and front thickness) of the system.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:52:15 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Berti",
"Stefano",
""
],
[
"Lopez",
"Cristobal",
""
],
[
"Vergni",
"Davide",
""
],
[
"Vulpiani",
"Angelo",
""
]
] |
0704.3038 | Claudia Wigger | C. Wigger, W. Hajdas, A. Zehnder, K. Hurley, E. Bellm, S. Boggs, M.
Bandstra, D.M. Smith | Spectral Analysis of GRBs Measured by RHESSI | 4 pages, 4 figures, conference proceedings, 'Swift and GRBs:
Unveiling the Relativistic Universe', San Servolo, Venice, 5-9 June 2006, to
appear in Il Nouvo Cimento | Nuovo Cim.B121:1117-1121,2006 | 10.1393/ncb/i2007-10072-9 | null | astro-ph | null | The Ge spectrometer of the RHESSI satellite is sensitive to Gamma Ray Bursts
(GRBs) from about 40 keV up to 17 MeV, thus ideally complementing the Swift/BAT
instrument whose sensitivity decreases above 150 keV. We present preliminary
results of spectral fits of RHESSI GRB data. After describing our method, the
RHESSI results are discussed and compared with Swift and Konus.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 15:53:53 GMT"
}
] | 2010-11-11T00:00:00 | [
[
"Wigger",
"C.",
""
],
[
"Hajdas",
"W.",
""
],
[
"Zehnder",
"A.",
""
],
[
"Hurley",
"K.",
""
],
[
"Bellm",
"E.",
""
],
[
"Boggs",
"S.",
""
],
[
"Bandstra",
"M.",
""
],
[
"Smith",
"D. M.",
""
]
] |
0704.3039 | Alain Corfdir | Alain Corfdir (ENPC-Cermes) | Yield design for porous media subjected to unconfined flow: construction
of approximate pressure fields | null | Comptes Rendus M\'ecanique 334, 3 (2006) 183-189 | 10.116/j.crme.2006.011 | null | physics.class-ph | null | We consider the stability of a porous medium submitted to a steady-state flow
with free-boundary. Assuming some hypotheses, it is possible to implement the
kinematic method by using an approximate pressure field bounding the true
pressure field from below. We are interested in finding such approximate
pressure fields and in proving that they bound the true pressure field from
below without knowing the true pressure field. We use fields which are
solutions of a problem with relaxed conditions with regard to the real problem.
Under a uniqueness condition of the solution of a weak formulation of the
problem, such fields are lower bounds for the true pressure field. Finally, we
give the example of a vertical dam.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 16:01:28 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Corfdir",
"Alain",
"",
"ENPC-Cermes"
]
] |
0704.3040 | Ari Pakman | Ari Pakman and Amit Sever | Exact N=4 correlators of AdS(3)/CFT(2) | 3 pages. v2:minor changes | Phys.Lett.B652:60-62,2007 | 10.1016/j.physletb.2007.06.041 | YITP-SB-07-15, BRX-TH-587 | hep-th | null | We extend to chiral N=4 operators the holographic agreement recently found
between correlators of the symmetric orbifold of M^4 at large N and type IIB
strings propagating in AdS(3) x S^3 x M^4, where M^4=T^4 or K3. We also present
expressions for some bulk correlators not yet computed in the boundary.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:24:11 GMT"
},
{
"version": "v2",
"created": "Tue, 24 Apr 2007 19:50:29 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Pakman",
"Ari",
""
],
[
"Sever",
"Amit",
""
]
] |
0704.3041 | Natalia Tristan | E.A. Popova, D.V. Volkov, A.N. Vasiliev, A.A. Demidov, N.P. Kolmakova,
I.A. Gudim, L.N. Bezmaternykh, N. Tristan, Yu. Skourski, B. B\"uchner, C.
Hess, R. Klingeler | Magnetization and specific heat of TbFe3(BO3)4: Experiment and crystal
field calculations | 10 pages, 10 figures, 20 references, accepted by Phys. Rev. B | null | 10.1103/PhysRevB.75.224413 | null | cond-mat.other | null | We have studied the thermodynamic properties of single-crystalline
TbFe3(BO3)4. Magnetization measurements have been carried out as a function of
magnetic field (up to 50 T) and temperature up to 350K with the magnetic field
both parallel and perpendicular to the trigonal c-axis of the crystal. The
specific heat has been measured in the temperature range 2-300K with a magnetic
field up to 9 T applied parallel to the c-axis. The data indicate a structural
phase transition at 192 K and antiferromagnetic spin ordering at 40 K. A
Schottky anomaly is present in the specific heat data around 20 K, arising due
to two low-lying energy levels of the Tb3+ ions being split by f-d coupling.
Below TN magnetic fields parallel to the c-axis drive a spin-flop phase
transition, which is associated with a large magnetization jump. The highly
anisotropic character of the magnetic susceptibility is ascribed mainly to the
Ising-like behavior of the Tb3+ ions in the trigonal crystal field. We describe
our results in the framework of an unified approach which is based on
mean-field approximation and crystal-field calculations.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 16:05:27 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Popova",
"E. A.",
""
],
[
"Volkov",
"D. V.",
""
],
[
"Vasiliev",
"A. N.",
""
],
[
"Demidov",
"A. A.",
""
],
[
"Kolmakova",
"N. P.",
""
],
[
"Gudim",
"I. A.",
""
],
[
"Bezmaternykh",
"L. N.",
""
],
[
"Tristan",
"N.",
""
],
[
"Skourski",
"Yu.",
""
],
[
"Büchner",
"B.",
""
],
[
"Hess",
"C.",
""
],
[
"Klingeler",
"R.",
""
]
] |
0704.3042 | Yeongduk Kim | W.G. Kang, Y.D. Kim, J.I. Lee, I.S. Hahn, A.R. Kim, H.J. Kim | Measurement on the thermal neutron capture cross section of w-180 | 10 pages, 4 figures | Phys.Rev.C76:067602,2007 | 10.1103/PhysRevC.76.067602 | null | nucl-ex | null | We have measured the thermal neutron capture cross section for w-180 nucleus.
There is only one previous data on this cross section with a value of 30
$^{+300%}_{-100%}$ barn. To consider w-181 as a low energy neutrino source, the
thermal neutron capture cross section should be measured more precisely to
estimate the production rate of w-181 inside a nuclear reactor. We measured the
cross section of w-180 with a natural tungsten foil and obtained a new value of
21.9 $\pm$ 2.5 barn
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 16:14:50 GMT"
},
{
"version": "v2",
"created": "Tue, 24 Apr 2007 03:40:35 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Kang",
"W. G.",
""
],
[
"Kim",
"Y. D.",
""
],
[
"Lee",
"J. I.",
""
],
[
"Hahn",
"I. S.",
""
],
[
"Kim",
"A. R.",
""
],
[
"Kim",
"H. J.",
""
]
] |
0704.3043 | Jailson Alcaniz | F.C. Carvalho (on), J.S. Alcaniz (on), J.A.S. Lima (USP), R. Silva
(UERN) | CMB and LSS constraints on a single-field model of inflation | 5 pages, 4 figures, LaTeX | Europhys.Lett.83:29001,2008 | 10.1209/0295-5075/83/29001 | null | astro-ph gr-qc hep-th | null | A new inflationary scenario whose exponential potential $V(\Phi)$ has a
quadratic dependence on the field $\Phi$ in addition to the standard linear
term is confronted with the tree-year observations of the Wilkinson-Microwave
Anisotropy Probe and the Sloan Digital Sky Survey data. The number of e-folds
($N$), the ratio of tensor-to-scalar perturbations ($r$), the spectral scalar
index of the primordial power spectrum ($n_s$) and its running ($dn_s/d\ln k$)
depend on the dimensionless parameter $\alpha$ multiplying the quadratic term
in the potential. In the limit $\alpha \to 0$ all the results of the standard
exponential potential are fully recovered. For values of $\alpha \neq 0$, we
find that the model predictions are in good agreement with the current
observations of the Cosmic Microwave Background (CMB) anisotropies and
Large-Scale Structure (LSS) in the Universe.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 16:15:21 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Carvalho",
"F. C.",
"",
"on"
],
[
"Alcaniz",
"J. S.",
"",
"on"
],
[
"Lima",
"J. A. S.",
"",
"USP"
],
[
"Silva",
"R.",
"",
"UERN"
]
] |
0704.3044 | Pasquale Dario Serpico | Alessandro Mirizzi, Georg G. Raffelt, and Pasquale D. Serpico | Signatures of axion-like particles in the spectra of TeV gamma-ray
sources | 8 pages, 1 eps figure; typos corrected, matches published version | Phys.Rev.D76:023001,2007 | 10.1103/PhysRevD.76.023001 | FERMILAB-PUB-07-082-A, MPP-2007-44 | astro-ph hep-ph | null | One interpretation of the unexplained signature observed in the PVLAS
experiment invokes a new axion-like particle (ALP) with a two-photon vertex,
allowing for photon-ALP oscillations in the presence of magnetic fields. In the
range of masses and couplings suggested by PVLAS, the same effect would lead to
a peculiar dimming of high-energy photon sources. For typical parameters of the
turbulent magnetic field in the galaxy, the effect sets in at E_gamma >~ 10
TeV, providing an ALP signature in the spectra of TeV gamma sources that can be
probed with Cherenkov telescopes. A dedicated search will be strongly motivated
if the ongoing photon regeneration experiments confirm the PVLAS particle
interpretation.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 16:16:28 GMT"
},
{
"version": "v2",
"created": "Fri, 13 Jul 2007 15:32:04 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Mirizzi",
"Alessandro",
""
],
[
"Raffelt",
"Georg G.",
""
],
[
"Serpico",
"Pasquale D.",
""
]
] |
0704.3045 | Igor Strakovsky | Ya. Azimov (PNPI), K. Goeke (Ruhr-Universitaet), I. Strakovsky (GWU) | A possible explanation why the Theta+ is seen in some experiments and
not in others | 18 pages. Some changes in the text; experimental suggestions
collected in a special subsection, references added and refreshed | null | 10.1103/PhysRevD.76.074013 | null | hep-ph hep-ex nucl-ex nucl-th | null | To understand the whole set of positive and null data on the
Theta+(1530)-production, we suggest the hypothesis that multiquark hadrons are
mainly generated from many-quark states, which emerge either as short-term
hadron fluctuations, or as hadron remnants in hard processes. This approach
allows us to describe both non-observation of the Theta+ in current null
experiments and peculiar features of its production in positive experiments.
Further, we are able to propose new experiments that might be decisive for the
problem of the Theta+ existence. Distributions of the Theta+ in such
experiments can give important information both on higher Fock components of
conventional hadrons and about structure and hadronization properties of hadron
remnants produced in hard processes. We also explain that description of
multiquark hadrons may require a modified form of the constituent quark model,
with quark masses and couplings being intermediate between their values for the
familiar constituent quarks and the current ones.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:27:42 GMT"
},
{
"version": "v2",
"created": "Fri, 15 Jun 2007 20:25:34 GMT"
}
] | 2013-05-29T00:00:00 | [
[
"Azimov",
"Ya.",
"",
"PNPI"
],
[
"Goeke",
"K.",
"",
"Ruhr-Universitaet"
],
[
"Strakovsky",
"I.",
"",
"GWU"
]
] |
0704.3046 | Artemio Gonzalez-Lopez | A. Enciso, F. Finkel, A. Gonzalez-Lopez, M.A. Rodriguez | A novel quasi-exactly solvable spin chain with nearest-neighbors
interactions | 38 pages, 8 figures | Nucl.Phys.B789:452-482,2008 | 10.1016/j.nuclphysb.2007.07.001 | null | hep-th cond-mat.other math-ph math.MP | null | In this paper we study a novel spin chain with nearest-neighbors interactions
depending on the sites coordinates, which in some sense is intermediate between
the Heisenberg chain and the spin chains of Haldane-Shastry type. We show that
when the number of spins is sufficiently large both the density of sites and
the strength of the interaction between consecutive spins follow the Gaussian
law. We develop an extension of the standard freezing trick argument that
enables us to exactly compute a certain number of eigenvalues and their
corresponding eigenfunctions. The eigenvalues thus computed are all integers,
and in fact our numerical studies evidence that these are the only integer
eigenvalues of the chain under consideration. This fact suggests that this
chain can be regarded as a finite-dimensional analog of the class of
quasi-exactly solvable Schroedinger operators, which has been extensively
studied in the last two decades. We have applied the method of moments to study
some statistical properties of the chain's spectrum, showing in particular that
the density of eigenvalues follows a Wigner-like law. Finally, we emphasize
that, unlike the original freezing trick, the extension thereof developed in
this paper can be applied to spin chains whose associated dynamical spin model
is only quasi-exactly solvable.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 16:37:14 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Enciso",
"A.",
""
],
[
"Finkel",
"F.",
""
],
[
"Gonzalez-Lopez",
"A.",
""
],
[
"Rodriguez",
"M. A.",
""
]
] |
0704.3047 | Aurelien Perrin | A. Perrin (LCFIO), H. Chang (LCFIO), V. Krachmalnicoff (LCFIO), M.
Schellekens (LCFIO), D. Boiron (LCFIO), A. Aspect (LCFIO), C. I. Westbrook
(LCFIO) | Observation of atom pairs in spontaneous four wave mixing of two
colliding Bose-Einstein Condensates | A few typos have been corrected | Physical Review Letters 99, 15 (2007) 150405 | 10.1103/PhysRevLett.99.150405 | null | quant-ph cond-mat.other | null | We study atom scattering from two colliding Bose-Einstein condensates using a
position sensitive, time resolved, single atom detector. In analogy to quantum
optics, the process can also be thought of as spontaneous, degenerate four wave
mixing of de Broglie waves. We find a clear correlation between atoms with
opposite momenta, demonstrating pair production in the scattering process. We
also observe a Hanbury Brown and Twiss correlation for collinear momenta, which
permits an independent measurement of the size of the pair production source
and thus the size of the spatial mode. The back to back pairs occupy very
nearly two oppositely directed spatial modes, a promising feature for future
quantum optics experiments.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:31:05 GMT"
},
{
"version": "v2",
"created": "Mon, 1 Oct 2007 12:56:36 GMT"
},
{
"version": "v3",
"created": "Thu, 11 Oct 2007 08:28:37 GMT"
},
{
"version": "v4",
"created": "Mon, 12 May 2008 19:39:59 GMT"
}
] | 2008-05-12T00:00:00 | [
[
"Perrin",
"A.",
"",
"LCFIO"
],
[
"Chang",
"H.",
"",
"LCFIO"
],
[
"Krachmalnicoff",
"V.",
"",
"LCFIO"
],
[
"Schellekens",
"M.",
"",
"LCFIO"
],
[
"Boiron",
"D.",
"",
"LCFIO"
],
[
"Aspect",
"A.",
"",
"LCFIO"
],
[
"Westbrook",
"C. I.",
"",
"LCFIO"
]
] |
0704.3048 | V. Nefer \c{S}eno\u{g}uz | V. Nefer Senoguz | Non-thermal leptogenesis with strongly hierarchical right handed
neutrinos | 7 pages, 5 figures. v2: added some comments and references, v3: minor
corrections and additions, v4: a typo corrected, published version | Phys.Rev.D76:013005,2007 | 10.1103/PhysRevD.76.013005 | null | hep-ph | null | Assuming the Dirac-type neutrino masses m_D are related to quark or charged
lepton masses, neutrino oscillation data indicate that right handed neutrino
masses are in general strongly hierarchical. In particular, if m_D is similar
to the up-type quark masses, the mass of the lightest right handed neutrino
M_1<~10^6 GeV. We show that non-thermal leptogenesis by inflaton decay can
yield sufficient baryon asymmetry despite this constraint, and discuss how the
asymmetry is correlated with the low energy neutrino masses and CP-violating
phases.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 16:47:04 GMT"
},
{
"version": "v2",
"created": "Fri, 27 Apr 2007 20:33:20 GMT"
},
{
"version": "v3",
"created": "Tue, 19 Jun 2007 21:44:03 GMT"
},
{
"version": "v4",
"created": "Wed, 25 Jul 2007 15:57:31 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Senoguz",
"V. Nefer",
""
]
] |
0704.3049 | Ryan Gutenkunst | Ryan N. Gutenkunst, Fergal P. Casey, Joshua J. Waterfall, Christopher
R. Myers, James P. Sethna | Extracting falsifiable predictions from sloppy models | 4 pages, 2 figures. Submitted to the Annals of the New York Academy
of Sciences for publication in "Reverse Engineering Biological Networks:
Opportunities and Challenges in Computational Methods for Pathway Inference" | Annals of the New York Academy of Sciences 1115:203-211 (2007) | 10.1196/annals.1407.003 | null | q-bio.QM | null | Successful predictions are among the most compelling validations of any
model. Extracting falsifiable predictions from nonlinear multiparameter models
is complicated by the fact that such models are commonly sloppy, possessing
sensitivities to different parameter combinations that range over many decades.
Here we discuss how sloppiness affects the sorts of data that best constrain
model predictions, makes linear uncertainty approximations dangerous, and
introduces computational difficulties in Monte-Carlo uncertainty analysis. We
also present a useful test problem and suggest refinements to the standards by
which models are communicated.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 17:00:09 GMT"
}
] | 2007-11-24T00:00:00 | [
[
"Gutenkunst",
"Ryan N.",
""
],
[
"Casey",
"Fergal P.",
""
],
[
"Waterfall",
"Joshua J.",
""
],
[
"Myers",
"Christopher R.",
""
],
[
"Sethna",
"James P.",
""
]
] |
0704.3050 | M. B. N. Kouwenhoven | M.B.N. Kouwenhoven (1,2,3), M. Bureau (4), S. Kim (5), P.T. de Zeeuw
(2) ((1) University of Sheffield (2) Leiden University (3) University of
Amsterdam (4) University of Oxford (5) Sejong University) | Optical BVI Imaging and HI Synthesis Observations of the Dwarf Irregular
Galaxy ESO 364-G 029 | 10 pages, 11 figures, accepted by A&A | null | 10.1051/0004-6361:20077531 | null | astro-ph | null | As part of an effort to enlarge the number of well-studied Magellanic-type
galaxies, we obtained broadband optical imaging and neutral hydrogen radio
synthesis observations of the dwarf irregular galaxy ESO 364-G 029. The optical
morphology characteristically shows a bar-like main body with a one-sided
spiral arm, an approximately exponential light distribution, and offset
photometric and kinematic centers. The HI distribution is mildly asymmetric
and, although slightly offset from the photometric center, roughly follows the
optical brightness distribution, extending to over 1.2 Holmberg radii (where
mu_B = 26.5 mag/arcsec^2). In particular, the highest HI column densities
closely follow the bar, one-arm spiral, and a third optical extension. The
rotation is solid-body in the inner parts but flattens outside of the optical
extent. The total HI flux F_HI = 23.1 pm 1.2 Jy km/s, yielding a total HI mass
M_HI= (6.4 pm 1.7) x 10^8 Msun (for a distance D = 10.8 pm 1.4 Mpc) and a total
HI mass-to-blue-luminosity ratio M_HI/L_B = (0.96 pm 0.14) Msun / Lsun,B
(distance independent). The HI data suggest a very complex small-scale HI
structure, with evidence of large shells and/or holes, but deeper observations
are required for a detailed study. Follow-up observations are also desirable
for a proper comparison with the Large Magellanic Cloud, where despite an
optical morphology very similar to ESO 364-G 029 the HI bears little
resemblance to the optical.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 17:36:57 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Kouwenhoven",
"M. B. N.",
""
],
[
"Bureau",
"M.",
""
],
[
"Kim",
"S.",
""
],
[
"de Zeeuw",
"P. T.",
""
]
] |
0704.3051 | Stephane Toulin | Jalil Ouazzani (ICMCB), Yves Garrabos (ICMCB) | A new numerical algorithm for Low Mach number supercritical fluids | null | null | null | null | physics.class-ph | null | A new algorithm has been developed to compute low Mach Numbers supercritical
fluid flows. The algorithm is applied using a finite volume method based on the
SIMPLER algorithm. Its main advantages are to decrease significantly the CPU
time, and the possibility for supercritical fluid flow modelisation to use
other discretisation methods (such as spectral methods and/or finite
differences) and other algorithms such as PISO or projection. It makes it
possible to solve 3D problems within reasonable CPU time even when considering
complex equations of state. The algorithm is given after first a brief
description of the previously existing algorithm to solve for supercritical
fluids. The side and bottom heated near critical carbon dioxide filled cavity
problems are respectively solved and compared to the previously obtained
results.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:14:40 GMT"
}
] | 2007-08-21T00:00:00 | [
[
"Ouazzani",
"Jalil",
"",
"ICMCB"
],
[
"Garrabos",
"Yves",
"",
"ICMCB"
]
] |
0704.3052 | Kerry Soileau | Kerry M. Soileau | Representation Of Level Paths Of An Analytic Function | null | null | null | null | math.GM | null | We find an arc-parameterization of the contour on which an given analytic
function has constant modulus. This contour is seen to satisfy a differential
equation which we explicitly give.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:15:07 GMT"
},
{
"version": "v2",
"created": "Fri, 27 Apr 2007 15:52:34 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Soileau",
"Kerry M.",
""
]
] |
0704.3053 | Braito Valentina | R. M. Sambruna (1), J. N. Reeves (1, 2), V. Braito (1,3) ((1) NASA
GSFC, (2) Astrophysics Group, School of Physical and Geographical Sciences,
Keele University, (3) JHU) | The remarkable X-ray spectrum of the Broad-Line Radio Galaxy 3C 445 | 32 pages, 3 figures, 2 tables, accepted for publication in ApJ | Astrophys.J.665:1030-1037,2007 | 10.1086/519306 | null | astro-ph | null | We present the results of the analysis of an archival 15 ks XMM-Newton
observation of the nearby (z=0.057) radio-loud source 3C445, optically
classified as a Broad-Line Radio Galaxy. While the RGS data are of insufficient
quality to allow a meaningful analysis, the EPIC data show a remarkable X-ray
spectrum. The 2-10 keV continuum is described by a heavily absorbed (Nh~ 1e22 -
1e23 cm-2) power law with photon index Gamma ~1.4, and strong (R~2) cold
reflection. A narrow, unresolved Fe Kalpha emission line is detected,
confirming previous findings, with EW 120eV. A soft excess is present below 2
keV over the extrapolation of the hard X-ray power law, which we model with a
power law with the same photon index as the hard power law, absorbed by a
column density Nh=6e20 cm-2 in excess to Galactic. A host of emission lines are
present below 2 keV, confirming previous indications from ASCA, due to H- and
He-like O, Mg, and Si. We attribute the origin of the lines to a photoionized
gas, with properties very similar to radio-quiet obscured AGN. Two different
ionized media, or a single stratified medium, are required to fit the soft
X-ray data satisfactorily. The similarity of the X-ray spectrum of 3C445 to
Seyferts underscores that the central engines of radio-loud and radio-quiet AGN
similarly host both cold and warm gas.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:17:56 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Sambruna",
"R. M.",
""
],
[
"Reeves",
"J. N.",
""
],
[
"Braito",
"V.",
""
]
] |
0704.3054 | Peter Parker | Peter A. Parker, Patrick Mitran, Daniel W. Bliss, and Vahid Tarokh | On bounds and algorithms for frequency synchronization for collaborative
communication systems | Submitted to IEEE Transaction on Signal Processing | null | 10.1109/TSP.2008.924799 | null | stat.AP math.ST stat.TH | null | Cooperative diversity systems are wireless communication systems designed to
exploit cooperation among users to mitigate the effects of multipath fading. In
fairly general conditions, it has been shown that these systems can achieve the
diversity order of an equivalent MISO channel and, if the node geometry
permits, virtually the same outage probability can be achieved as that of the
equivalent MISO channel for a wide range of applicable SNR. However, much of
the prior analysis has been performed under the assumption of perfect timing
and frequency offset synchronization. In this paper, we derive the estimation
bounds and associated maximum likelihood estimators for frequency offset
estimation in a cooperative communication system. We show the benefit of
adaptively tuning the frequency of the relay node in order to reduce estimation
error at the destination. We also derive an efficient estimation algorithm,
based on the correlation sequence of the data, which has mean squared error
close to the Cramer-Rao Bound.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:08:46 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Parker",
"Peter A.",
""
],
[
"Mitran",
"Patrick",
""
],
[
"Bliss",
"Daniel W.",
""
],
[
"Tarokh",
"Vahid",
""
]
] |
0704.3055 | Maurice Kleman | Maurice Kleman, Jacques Friedel | Disclinations, dislocations and continuous defects: a reappraisal | 72 pages, 36 figures | Rev. Mod. Phys. January-March 2008, 80, 61-115 | 10.1103/RevModPhys.80.61 | null | cond-mat.soft | null | Disclinations, first observed in mesomorphic phases, are relevant to a number
of ill-ordered condensed matter media, with continuous symmetries or frustrated
order. They also appear in polycrystals at the edges of grain boundaries. They
are of limited interest in solid single crystals, where, owing to their large
elastic stresses, they mostly appear in close pairs of opposite signs. The
relaxation mechanisms associated with a disclination in its creation, motion,
change of shape, involve an interplay with continuous or quantized dislocations
and/or continuous disclinations. These are attached to the disclinations or are
akin to Nye's dislocation densities, well suited here. The notion of 'extended
Volterra process' takes these relaxation processes into account and covers
different situations where this interplay takes place. These concepts are
illustrated by applications in amorphous solids, mesomorphic phases and
frustrated media in their curved habit space. The powerful topological theory
of line defects only considers defects stable against relaxation processes
compatible with the structure considered. It can be seen as a simplified case
of the approach considered here, well suited for media of high plasticity
or/and complex structures. Topological stability cannot guarantee energetic
stability and sometimes cannot distinguish finer details of structure of
defects.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:30:04 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Kleman",
"Maurice",
""
],
[
"Friedel",
"Jacques",
""
]
] |
0704.3056 | Michael Hartmann Mr | Michael J. Hartmann, Fernando G.S.L. Brandao and Martin B. Plenio | Effective spin systems in coupled micro-cavities | 5 pages, 4 figures | Phys. Rev. Lett. 99, 160501 (2007) | 10.1103/PhysRevLett.99.160501 | null | quant-ph cond-mat.other | null | We show that atoms trapped in micro-cavities that interact via exchange of
virtual photons can model an anisotropic Heisenberg spin-1/2 chain in an
external magnetic field. All parameters of the effective Hamiltonian can
individually be tuned via external lasers. Since the occupation of excited
atomic levels and photonic states are strongly suppressed, the effective model
is robust against decoherence mechanisms, has a long lifetime and its
implementation is feasible with current experimental technology. The model
provides a feasible way to create cluster states in these devices.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:31:42 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Hartmann",
"Michael J.",
""
],
[
"Brandao",
"Fernando G. S. L.",
""
],
[
"Plenio",
"Martin B.",
""
]
] |
0704.3057 | Benjamin Safdi | Benjamin R. Safdi and Harvey Segur | Explosive instability due to 4-wave mixing | null | null | 10.1103/PhysRevLett.99.245004 | null | nlin.SI | null | It is known that an explosive instability can occur when nonlinear waves
propagate in certain media that admit 3-wave mixing. The purpose of this paper
is to show that explosive instabilities can occur even in media that admit no
3-wave mixing. Instead, the instability is caused by 4-wave mixing: four
resonantly interacting wavetrains gain energy from a background, and all blow
up in a finite time. Unlike singularities associated with self-focussing, these
singularities can occur with no spatial structure - the waves blow up
everywhere in space, simultaneously.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:36:48 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Safdi",
"Benjamin R.",
""
],
[
"Segur",
"Harvey",
""
]
] |
0704.3058 | Milan Janjic | Milan Janji\'c | Some integer sequences based on derangements | null | null | null | null | math.CO | null | Sequences whose terms are equal to the number of functions with specified
properties are considered. Properties are based on the notion of derangements
in a more general sense. Several sequences which generalize the standard notion
of derangements are thus obtained. These sequences generate a number of integer
sequences from the well-known Sloane's encyclopedia.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:58:43 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Janjić",
"Milan",
""
]
] |
0704.3059 | Rob P. Olling | Rob P. Olling | Finding Solar System Analogs With SIM and HIPPARCOS: A White Paper for
the ExoPlanet Task Force | A White Paper for the ExoPlanet Task Force: 7 pages | null | null | null | astro-ph | null | The astrometric signature imposed by a planet on its primary increases
substantially towards longer periods (proportinal to P^2/3), so that
long-period planets can be more easily detected, in principle. For example, a
one Solar-mass (M_Sun) star would be pulled by roughly 1 mas by a one
Jupiter-mass (M_J) planet with a period of one-hundred years at a distance of
20 pc. Such position accuracies can now be obtained with both ground-based and
space-based telescopes. The difficulty was that it often takes many decades
before a detectable position shift will occur. However, by the time the next
generation of astrometric missions such as SIM will be taking data, several
decades will have past since the first astrometric mission, HIPPARCOS. Here we
propose to use a new astrometric method that employs a future, highly accurate
SIM Quick-Look survey and HIPPARCOS data taken twenty years prior. Using
position errors for SIM of 4 muas, this method enables the detection and
characterization of Solar-system analogs (SOSAs) with periods up to 240 (500)
years for 1 (10) M_J companions. Because many tens of thousands nearby stars
can be surveyed this way for a modest expenditure of SIM time and SOSAs may be
quite abundant, we expect to find many hundreds of extra-solar planets with
long-period orbits. Such a data set would nicely complement the short-period
systems found by the radial-velocity method. Brown dwarfs and low-mass stellar
companions can be found and characterized if their periods are shorter than
about 500 years. This data set will provide invaluable constraints on models of
planet formation, as well as a database for systems where the location of the
giant planets allow for the formation of low-mass planets in the habitable
zone. [Abridged]
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:42:10 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Olling",
"Rob P.",
""
]
] |
0704.3060 | Klaus Hornberger | Klaus Hornberger | Open quantum dynamics via environmental monitoring | 11 pages, 3 figures. Talk at DICE 2006; to appear in J. Phys.: Conf.
Ser. (2007) | null | 10.1088/1742-6596/67/1/012002 | null | quant-ph | null | A general method is discussed to obtain Markovian master equations which
describe the interaction with the environment in a microscopic and
non-perturbative fashion. It is based on combining time-dependent scattering
theory with the concept of continuous quantum measurements. The applications to
the case of a Brownian point particle and to the case of a complex molecule,
both in the presence of a gaseous environment, are outlined.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:45:11 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Hornberger",
"Klaus",
""
]
] |
0704.3061 | Evgeny Smirnov | Evgeny Smirnov | Bruhat order for two subspaces and a flag | 30 pages, with figures | null | null | null | math.RT math.AG math.CO | null | The classical Ehresmann-Bruhat order describes the possible degenerations of
a pair of flags in a finite-dimensional vector space V; or, equivalently, the
closure of an orbit of the group GL(V) acting on the direct product of two full
flag varieties.
We obtain a similar result for triples consisting of two subspaces and a
partial flag in V; this is equivalent to describing the closure of a
GL(V)-orbit in the product of two Grassmannians and one flag variety. We give a
rank criterion to check whether such a triple can be degenerated to another
one, and we classify the minimal degenerations. Our methods involve only
elementary linear algebra and combinatorics of graphs (originating in
Auslander-Reiten quivers).
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:59:56 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Smirnov",
"Evgeny",
""
]
] |
0704.3062 | Dmitry Klochkov | D. Klochkov, R. Staubert, S. Tsygankov, A. Lutovinov, K. P. Postnov,
N. I. Shakura, S. A. Potanin, C. Ferrigno, I. Kreykenbohm, and J.Wilms | INTEGRAL observations of HER X-1 | To be published in the proceedings of the 6th INTEGRAL Workshop "The
Obscured Universe" (3-7 July 2006, Moscow) | null | null | null | astro-ph | null | First results of observations of the low mass X-ray binary Her X-1/HZ Her
performed by the INTEGRAL satellite in July-August 2005 are presented. A
significant part of one 35 day main-on state was covered. The cyclotron line in
the X-ray spectrum is well observed and its position and shape, as well as its
variability with time and phase of the 1.24 s pulsation are explored. X-ray
pulse profiles for different energy bands are studied throughout the
observation. The pulse period is found to vary on short time scales revealing a
dynamical spin-up/spin-down behavior. Results of simultaneous optical
observations of HZ Her are also discussed.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 18:58:24 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Klochkov",
"D.",
""
],
[
"Staubert",
"R.",
""
],
[
"Tsygankov",
"S.",
""
],
[
"Lutovinov",
"A.",
""
],
[
"Postnov",
"K. P.",
""
],
[
"Shakura",
"N. I.",
""
],
[
"Potanin",
"S. A.",
""
],
[
"Ferrigno",
"C.",
""
],
[
"Kreykenbohm",
"I.",
""
],
[
"Wilms",
"J.",
""
]
] |
0704.3063 | Pamela Morehouse | S. B. Athar, et al, CLEO Collaboration | Search for Radiative Decays of Upsilon(1S) into eta and eta' | 14 pages postscript,also available through
http://www.lns.cornell.edu/public/CLNS/2007/, Submitted to PRD | Phys.Rev.D76:072003,2007 | 10.1103/PhysRevD.76.072003 | CLNS 07/1995, CLEO 07-5 | hep-ex | null | We report on a search for the radiative decay of Upsilon(1S) to the
pseudoscalar mesons eta and etaprime in 21.2 +/- 0.2 times 10^6 Upsilon(1S)
decays collected with the CLEO III detector at the Cornell Electron Storage
Ring (CESR). The eta meson was reconstructed in the three modes eta to
gamma-gamma, eta to pi+pi-pi0 and eta to 3pi0. The etaprime meson was
reconstructed in the mode etaprime to pi+ pi- eta with eta decaying through any
of the above three modes, and also etaprime to gamma rho, where rho decays to
pi^+ pi^-.
Five out of the seven sub-modes are found to be virtually background-free. In
four of them we find no signal candidates and in one Upsilon(1S) to
gamma-etaprime, etaprime to pi+ pi- eta, eta to pi+pi-pi0 there are two good
signal candidates, which is insufficient evidence to claim a signal. The other
two sub-modes eta to gamma-gamma and etaprime to gamma rho are background
limited, and show no excess of events in their signal regions. We combine the
results from different channels and obtain upper limits at the 90% C.L. which
are B(Upsilon(1S) to gamma eta) < 1.0 times 10^-6 and B(Upsilon(1S) to gamma
etaprime) < 1.9 times 10^-6. Our limits are an order of magnitude tighter than
the previous ones and below the predictions made by some theoretical models.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 19:04:42 GMT"
}
] | 2010-04-08T00:00:00 | [
[
"Athar",
"S. B.",
""
],
[
"Collaboration",
"CLEO",
""
]
] |
0704.3064 | Kyle Lawson | Kyle Lawson and Ariel R.Zhitnitsky | Diffuse cosmic gamma-rays at 1-20 MeV: A trace of the dark matter? | 13 pages, 1 figure | JCAP 0801:022,2008 | 10.1088/1475-7516/2008/01/022 | null | astro-ph hep-ph | null | Several independent observations of the galactic core suggest hitherto
unexplained sources of energy. The most well known case is the 511 keV line
which has proven very difficult to explain with conventional astrophysical
positron sources. A similar, but less well known mystery is the excess of
gamma-ray photons detected by COMPTEL across a broad energy range 1-20 MeV.
Such photons are found to be very difficult to produce via known astrophysical
sources. We show in this work that dark matter in the form of dense antimatter
droplets provides a natural explanations for the observed flux of gamma-rays in
the 1-20 MeV range. We argue thatsuch photons must always accompany the 511 keV
line as they produced by the same mechanism within our framework. We calculate
the spectrum and intensity of the 1-20 MeV gamma-rays, and find it to be
consistent with the COMPTEL data.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 21:37:41 GMT"
},
{
"version": "v2",
"created": "Thu, 2 Aug 2007 16:19:48 GMT"
},
{
"version": "v3",
"created": "Mon, 26 Nov 2007 16:35:05 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Lawson",
"Kyle",
""
],
[
"Zhitnitsky",
"Ariel R.",
""
]
] |
0704.3065 | Elena Jimenez-Bailon | E. Jimenez-Bailon, N. Loiseau, M. Guainazzi, G. Matt, D.
Rosa-Gonzalez, E. Piconcelli, and M. Santos-Lleo | XMM-Newton view of galaxy pairs: activation of quiescent black holes? | Accepted for publication in A&A | null | 10.1051/0004-6361:20066761 | null | astro-ph | null | We report on XMM-Newton observations of three nearby galaxy pairs,
AM0707-273, AM1211-465, and AM2040-674. All six galaxies were previously
classified as HII galaxies based on optical and IR spectroscopic analysis. All
galaxies were detected with XMM-Newton and each member was isolated and
analyzed independently. The X-ray spectra reveal strong evidence of AGN
activity in the NE member of AM1211-465 pair. We measured a luminosity of
1.94(+0.11/-0.15)x10^42 erg/s in the 2-10 keV band and the presence of a
neutral FeK_alpha line with a confidence level of 98.8%. The high nH value,
2.2+/-0.2x10^22 cm^-2, would explain the misclassification of the source.
Marginal evidence of AGN nature was found in the X-ray spectra of AM1211-465SW
and AM0707-273E. The X-ray emission of the three remaining galaxies can be
explained by starburst activity.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 22:06:19 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Jimenez-Bailon",
"E.",
""
],
[
"Loiseau",
"N.",
""
],
[
"Guainazzi",
"M.",
""
],
[
"Matt",
"G.",
""
],
[
"Rosa-Gonzalez",
"D.",
""
],
[
"Piconcelli",
"E.",
""
],
[
"Santos-Lleo",
"M.",
""
]
] |
0704.3066 | Mark Lindeman | Mark. A. Lindeman, Kathleen A. Barger, Donald E. Brandl, S. Gwynne
Crowder, Lindsay Rocks, and Dan McCammon | Complex impedance measurements of calorimeters and bolometers:
correction for stray impedances | 5 pages, 6 figures | Rev.Sci.Instrum.78:043105,2007 | 10.1063/1.2723066 | null | astro-ph | null | Impedance measurements provide a useful probe of the physics of bolometers
and calorimeters. We describe a method for measuring the complex impedance of
these devices. In previous work, stray impedances and readout electronics of
the measurement apparatus have resulted in artifacts in the impedance data. The
new technique allows experimenters to find an independent Thevenin or Norton
equivalent circuit for each frequency. This method allows experimenters to
easily isolate the device impedance from the effects of parasitic impedances
and frequency dependent gains in amplifiers.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 22:00:10 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Lindeman",
"Mark. A.",
""
],
[
"Barger",
"Kathleen A.",
""
],
[
"Brandl",
"Donald E.",
""
],
[
"Crowder",
"S. Gwynne",
""
],
[
"Rocks",
"Lindsay",
""
],
[
"McCammon",
"Dan",
""
]
] |
0704.3067 | Brant Jones | Brant C. Jones | Kazhdan--Lusztig polynomials for maximally-clustered hexagon-avoiding
permutations | 18 pages | null | null | null | math.CO math.RT | null | We provide a non-recursive description for the bounded admissible sets of
masks used by Deodhar's algorithm to calculate the Kazhdan--Lusztig polynomials
$P_{x,w}(q)$ of type $A$, in the case when $w$ is hexagon avoiding and
maximally clustered. This yields a combinatorial description of the
Kazhdan--Lusztig basis elements of the Hecke algebra associated to such
permutations $w$. The maximally-clustered hexagon-avoiding elements are
characterized by avoiding the seven classical permutation patterns $\{3421,
4312, 4321, 46718235, 46781235, 56718234, 56781234\}$. We also briefly discuss
the application of heaps to permutation pattern characterization.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 22:06:24 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Jones",
"Brant C.",
""
]
] |
0704.3068 | Sydney A. Barnes | Sydney A. Barnes | Ages for illustrative field stars using gyrochronology: viability,
limitations and errors | 58 pages, 18 color figures, accepted for publication in The
Astrophysical Journal; Age uncertainties slightly modified upon correcting an
algebraic error in Section 4 | Astrophys.J.669:1167-1189,2007 | 10.1086/519295 | null | astro-ph | null | We here develop an improved way of using a rotating star as a clock, set it
using the Sun, and demonstrate that it keeps time well. This technique, called
gyrochronology, permits the derivation of ages for solar- and late-type main
sequence stars using only their rotation periods and colors. The technique is
clarified and developed here, and used to derive ages for illustrative groups
of nearby, late-type field stars with measured rotation periods. We first
demonstrate the reality of the interface sequence, the unifying feature of the
rotational observations of cluster and field stars that makes the technique
possible, and extends it beyond the proposal of Skumanich by specifying the
mass dependence of rotation for these stars. We delineate which stars it cannot
currently be used on. We then calibrate the age dependence using the Sun. The
errors are propagated to understand their dependence on color and period.
Representative age errors associated with the technique are estimated at ~15%
(plus possible systematic errors) for late-F, G, K, & early-M stars. Ages
derived via gyrochronology for the Mt. Wilson stars are shown to be in good
agreement with chromospheric ages for all but the bluest stars, and probably
superior. Gyro ages are then calculated for each of the active main sequence
field stars studied by Strassmeier and collaborators where other ages are not
available. These are shown to be mostly younger than 1Gyr, with a median age of
365Myr. The sample of single, late-type main sequence field stars assembled by
Pizzolato and collaborators is then assessed, and shown to have gyro ages
ranging from under 100Myr to several Gyr, and a median age of 1.2Gyr. Finally,
we demonstrate that the individual components of the three wide binaries
XiBooAB, 61CygAB, & AlphaCenAB yield substantially the same gyro ages.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 23:57:30 GMT"
},
{
"version": "v2",
"created": "Thu, 17 May 2007 22:17:18 GMT"
}
] | 2011-03-28T00:00:00 | [
[
"Barnes",
"Sydney A.",
""
]
] |
0704.3069 | Nestor Mirabal | N. Mirabal, J. P. Halpern, P. T. O'Brien | GRB 050826: A Subluminous Event at z = 0.296 Finds its Place in the
Luminosity Distribution of Gamma-Ray Burst Afterglows | Accepted for publication in ApJ | null | 10.1086/519006 | null | astro-ph | null | We present the optical identification and spectroscopy of the host galaxy of
GRB 050826 at a redshift z = 0.296 +/- 0.001. Image subtraction among
observations obtained on three consecutive nights, reveals a fading object 5
hours after the burst, confirming its identification as the optical afterglow
of this event. Deep imaging shows that the optical afterglow is offset by 0.4
arcseconds (~1.76 kpc) from the center of its irregular host galaxy, which is
typical for long-duration gamma-ray bursts. Combining these results with X-ray
measurements acquired by the Swift XRT instrument, we find that GRB 050826
falls entirely within the subluminous, subenergetic group of long gamma-ray
bursts at low redshift (z < 0.3). The results are discussed in the context of
models that possibly account for this trend, including the nature of the
central engine, the evolution of progenitor properties as a function of
redshift, and incompleteness in current gamma-ray burst samples.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 22:15:00 GMT"
},
{
"version": "v2",
"created": "Fri, 11 May 2007 15:11:35 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Mirabal",
"N.",
""
],
[
"Halpern",
"J. P.",
""
],
[
"O'Brien",
"P. T.",
""
]
] |
0704.3070 | Ward Struyve | S. Goldstein, W. Struyve | On the Uniqueness of Quantum Equilibrium in Bohmian Mechanics | 15 pages, no figures, LaTex | J. Stat. Phys. 128, 1197-1209 (2007) | 10.1007/s10955-007-9354-5 | null | quant-ph cond-mat.other | null | In Bohmian mechanics the distribution $|\psi|^2$ is regarded as the
equilibrium distribution. We consider its uniqueness, finding that it is the
unique equivariant distribution that is also a local functional of the wave
function $\psi$.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 22:17:14 GMT"
}
] | 2011-11-09T00:00:00 | [
[
"Goldstein",
"S.",
""
],
[
"Struyve",
"W.",
""
]
] |
0704.3071 | Karina Mazzitello | K. I. Mazzitello, C. M. Arizmendi, and H. G. E. Hentschel | Converting genetic network oscillations into somite spatial pattern | 7 pages, 7 figures | null | 10.1103/PhysRevE.78.021906 | null | q-bio.QM | null | In most vertebrate species, the body axis is generated by the formation of
repeated transient structures called somites. This spatial periodicity in
somitogenesis has been related to the temporally sustained oscillations in
certain mRNAs and their associated gene products in the cells forming the
presomatic mesoderm. The mechanism underlying these oscillations have been
identified as due to the delays involved in the synthesis of mRNA and
translation into protein molecules [J. Lewis, Current Biol. {\bf 13}, 1398
(2003)]. In addition, in the zebrafish embryo intercellular Notch signalling
couples these oscillators and a longitudinal positional information signal in
the form of an Fgf8 gradient exists that could be used to transform these
coupled temporal oscillations into the observed spatial periodicity of somites.
Here we consider a simple model based on this known biology and study its
consequences for somitogenesis. Comparison is made with the known properties of
somite formation in the zebrafish embryo . We also study the effects of
localized Fgf8 perturbations on somite patterning.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 22:20:53 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Mazzitello",
"K. I.",
""
],
[
"Arizmendi",
"C. M.",
""
],
[
"Hentschel",
"H. G. E.",
""
]
] |
0704.3072 | Rob P. Olling | Rob P. Olling | LEAVITT: A MIDEX-class Mission for Finding & Characterizing 10,000
Transiting Planets in the Solar Neighborhood | A White Paper for the ExoPlanet Task Force, 7 pages | null | null | null | astro-ph | null | We propose a MIDEX-class space mission with the goal to find and characterize
roughly 10,000 transiting planets. When transits occur, a much more detailed
characterization of the planet is possible and so a large data base of
transiting planets will provide planets with a large range in periods and radii
for follow-up studies. Our survey will be all-sky and focused on stars brighter
than V=14.8. Down to V=12, LEAVITT will be able to detect Neptune-sized
objects. Because of it's high cadence, LEAVITT is about 100 times more
sensitive at detecting transits than GAIA, while it will find more than 20
times as many transits as KEPLER. LEAVITT has multi-band photometric capability
implemented via a low-resolution dispersive element which can obtain 0.2% (2
mmag) photometry down to V=14.8. LEAVITT's high multi-band photometric accuracy
reduces the number of false-positives significantly.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 23:10:48 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Olling",
"Rob P.",
""
]
] |
0704.3073 | Roland Kothes | R. Kothes, S.M. Dougherty | The distance and neutral environment of the massive stellar cluster
Westerlund 1 | 8 pages, accepted for publication in A&A | Astron.Astrophys.468:993-1000,2007 | 10.1051/0004-6361:20077309 | null | astro-ph | null | The goal of this study is to determine a distance to Westerlund 1 independent
of the characteristics of the stellar population and to study its neutral
environment, using observations of atomic hydrogen. The HI observations are
taken from the Southern Galactic Plane Survey to study HI absorption in the
direction of the HII region created by the members of Westerlund 1 and to
investigate its environment as observed in the HI line emission. A Galactic
rotation curve was derived using the recently revised values for the Galactic
centre distance of $R_\odot = 7.6$ kpc, and the velocity of the Sun around the
Galactic centre of $\Theta_\odot = 214$ km s$^{-1}$. The newly determined
rotation model leads us to derive a distance of $3.9\pm 0.7$ kpc to Westerlund
1, consistent with a location in the Scutum-Crux Arm. Included in this estimate
is a very careful investigation of possible sources of error for the Galactic
rotation curve. We also report on small expanding HI features around the
cluster with a maximum dynamic age of 600,000 years and a larger bubble which
has a minimum dynamic age of 2.5 million years. Additionally we re-calculated
the kinematic distances to nearby HII regions and supernova remnants based on
our new Galaxic rotation curve. We propose that in the early stages of the
development of Wd 1 a large interstellar bubble of diameter about 50 pc was
created by the cluster members. This bubble has a dynamic age similar to the
age of the cluster. Small expanding bubbles, with dynamical ages $\sim 0.6$ Myr
are found around Wd 1, which we suggest consist of recombined material lost by
cluster members through their winds.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 23:33:33 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Kothes",
"R.",
""
],
[
"Dougherty",
"S. M.",
""
]
] |
0704.3074 | Florin Moldoveanu | Florin Moldoveanu | Quantum Mechanics and Closed Timelike Curves | 8 pages, 1 figure (removed LaTex command) | Quant. Biosys. 1, 66 (2007) | null | null | physics.gen-ph | null | General relativity allows solutions exhibiting closed timelike curves. Time
travel generates paradoxes and quantum mechanics generalizations were proposed
to solve those paradoxes. The implications of self-consistent interactions on
acausal region of space-time are investigated. If the correspondence principle
is true, then all generalizations of quantum mechanics on acausal manifolds are
not renormalizable. Therefore quantum mechanics can only be defined on global
hyperbolic manifolds and all general relativity solutions exhibiting time
travel are unphysical.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 23:50:55 GMT"
}
] | 2009-01-05T00:00:00 | [
[
"Moldoveanu",
"Florin",
""
]
] |
0704.3075 | James P. Crutchfield | Karoline Wiesner and James P. Crutchfield | Computation in Sofic Quantum Dynamical Systems | 10 pages, 4 figures;
http://cse.ucdavis.edu/~cmg/compmech/pubs.htm#StochasticComputation | null | null | null | quant-ph | null | We analyze how measured quantum dynamical systems store and process
information, introducing sofic quantum dynamical systems. Using recently
introduced information-theoretic measures for quantum processes, we quantify
their information storage and processing in terms of entropy rate and excess
entropy, giving closed-form expressions where possible. To illustrate the
impact of measurement on information storage in quantum processes, we analyze
two spin-1 sofic quantum systems that differ only in how they are measured.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:49:54 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Wiesner",
"Karoline",
""
],
[
"Crutchfield",
"James P.",
""
]
] |
0704.3076 | Martin Kunz | M. Kunz, N. Aghanim, A. Riazuelo and O. Forni | On the detectability of non-trivial topologies | 11 pages, 9 figures | Phys.Rev.D77:023525,2008 | 10.1103/PhysRevD.77.023525 | null | astro-ph | null | We explore the main physical processes which potentially affect the
topological signal in the Cosmic Microwave Background (CMB) for a range of
toroidal universes. We consider specifically reionisation, the integrated
Sachs-Wolfe (ISW) effect, the size of the causal horizon, topological defects
and primordial gravitational waves. We use three estimators: the information
content, the S/N statistic and the Bayesian evidence. While reionisation has
nearly no effect on the estimators, we show that taking into account the ISW
strongly decreases our ability to detect the topological signal. We also study
the impact of varying the relevant cosmological parameters within the 2 sigma
ranges allowed by present data. We find that only Omega_Lambda, which
influences both ISW and the size of the causal horizon, significantly alters
the detection for all three estimators considered here.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:00:12 GMT"
}
] | 2008-12-18T00:00:00 | [
[
"Kunz",
"M.",
""
],
[
"Aghanim",
"N.",
""
],
[
"Riazuelo",
"A.",
""
],
[
"Forni",
"O.",
""
]
] |
0704.3077 | Eric F. Bell | Eric F. Bell (1), Xian Zhong Zheng (1,2), Casey Papovich (3), Andrea
Borch (4), Christian Wolf (5), and Klaus Meisenheimer (1) ((1) MPIA,
Heidelberg, (2) Purple Mountain Observatory, (3) Steward Observatory, (4)
ARI, Heidelberg, (5) Oxford) | Star Formation and the Growth of Stellar Mass | 9 Pages; ApJ in press | Astrophys.J.663:834-843,2007 | 10.1086/518594 | null | astro-ph | null | Recent observations have demonstrated a significant growth in the integrated
stellar mass of the red sequence since z=1, dominated by a steadily increasing
number of galaxies with stellar masses M* < 10^11 M_sun. In this paper, we use
the COMBO-17 photometric redshift survey in conjunction with deep Spitzer 24
micron data to explore the relationship between star formation and the growth
of stellar mass. We calculate `star formation rate functions' in four different
redshift slices, splitting also into contributions from the red sequence and
blue cloud for the first time. We find that the growth of stellar mass since
z=1 is consistent with the integrated star formation rate. Yet, most of the
stars formed are in blue cloud galaxies. If the stellar mass already in, and
formed in, z<1 blue cloud galaxies were to stay in the blue cloud the total
stellar mass in blue galaxies would be dramatically overproduced. We explore
the expected evolution of stellar mass functions, finding that in this picture
the number of massive M* > 3x10^10 M_sun blue galaxies would also be
overproduced; i.e., most of the new stars formed in blue cloud galaxies are in
the massive galaxies. We explore a simple truncation scenario in which these
`extra' blue galaxies have their star formation suppressed by an unspecified
mechanism or mechanisms; simple cessation of star formation in these extra blue
galaxies is approximately sufficient to build up the red sequence at M*<10^11
M_sun.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:00:13 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Bell",
"Eric F.",
""
],
[
"Zheng",
"Xian Zhong",
""
],
[
"Papovich",
"Casey",
""
],
[
"Borch",
"Andrea",
""
],
[
"Wolf",
"Christian",
""
],
[
"Meisenheimer",
"Klaus",
""
]
] |
0704.3078 | A. V. Maccio' | Andrea V. Maccio'(MPIA), Ioannis Sideris (Zurich), Marco Miranda
(Zurich), Ben Moore (Zurich), Roland Jesseit (Munich Obs.) | Influence of Orbital Behaviour and Chaos on the Shape of Dark Matter
Halos | 14 pages, 8 figures, MNRAS submitted, a preprint with high-resolution
figures is available at http://www-theorie.physik.unizh.ch/~andrea/Orbits/ | null | null | null | astro-ph | null | It has been shown that the dissipative gas infall during galaxy formation has
the capability to modify the shape of dark matter halos. In this paper we
perform the first detailed analysis of particle orbits in a cosmological dark
matter halos to understand {\it how} and {\it why} baryons alter its shape. We
perform a series of numerical experiments where we grow a baryonic core inside
a live dark matter halo extracted from a cosmological simulation. We follow the
orbits of more than 300 particles with more that 50000 timesteps. Our results
clearly show that the dissipational component is responsible for repeatedly
deflecting orbits which visit often the center of the system. Moreover the
gravitational potential time dependence associated with the growth of the
baryonic mass, shifts the frequencies of the orbits, making them extremely
chaotic. This randomization makes the orbits explore a large phase space. When
this effect takes place for a significant number of orbits it will be
manifested in the density distribution as an approach to a rounder
configuration. As a consequence, the influence of the central mass on the shape
of the phase space decreases with increasing distance from the center. We
discuss the importance of future analysis of controlled experiments (i.e. using
analytic potentials instead of live DM halos) to better decipher the dynamics
of this phenomenon.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 07:32:22 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Maccio'",
"Andrea V.",
"",
"MPIA"
],
[
"Sideris",
"Ioannis",
"",
"Zurich"
],
[
"Miranda",
"Marco",
"",
"Zurich"
],
[
"Moore",
"Ben",
"",
"Zurich"
],
[
"Jesseit",
"Roland",
"",
"Munich Obs."
]
] |
0704.3079 | Ilia Solov'yov | Alexander V. Yakubovich, Ilia A. Solov'yov, Andrey V. Solov'yov and
Walter Greiner | Ab initio theory of helix-coil phase transition | 24 pages, 3 figures | null | 10.1140/epjd/e2007-00328-9 | null | physics.bio-ph physics.chem-ph | null | In this paper we suggest a theoretical method based on the statistical
mechanics for treating the alpha-helix-random coil transition in alanine
polypeptides. We consider this process as a first-order phase transition and
develop a theory which is free of model parameters and is based solely on
fundamental physical principles. It describes essential thermodynamical
properties of the system such as heat capacity, the phase transition
temperature and others from the analysis of the polypeptide potential energy
surface calculated as a function of two dihedral angles, responsible for the
polypeptide twisting. The suggested theory is general and with some
modification can be applied for the description of phase transitions in other
complex molecular systems (e.g. proteins, DNA, nanotubes, atomic clusters,
fullerenes).
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:10:04 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Yakubovich",
"Alexander V.",
""
],
[
"Solov'yov",
"Ilia A.",
""
],
[
"Solov'yov",
"Andrey V.",
""
],
[
"Greiner",
"Walter",
""
]
] |
0704.3080 | Takuya Okuda | Jaume Gomis and Takuya Okuda | D-branes as a Bubbling Calabi-Yau | 32 pages; v.2 reference added | JHEP0707:005,2007 | 10.1088/1126-6708/2007/07/005 | CPHT-RR022.0407, NSF-KITP-07-106 | hep-th math.DG | null | We prove that the open topological string partition function on a D-brane
configuration in a Calabi-Yau manifold X takes the form of a closed topological
string partition function on a different Calabi-Yau manifold X_b. This
identification shows that the physics of D-branes in an arbitrary background X
of topological string theory can be described either by open+closed string
theory in X or by closed string theory in X_b. The physical interpretation of
the ''bubbling'' Calabi-Yau X_b is as the space obtained by letting the
D-branes in X undergo a geometric transition. This implies, in particular, that
the partition function of closed topological string theory on certain bubbling
Calabi-Yau manifolds are invariants of knots in the three-sphere.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 17:02:59 GMT"
},
{
"version": "v2",
"created": "Fri, 15 Jun 2007 20:31:42 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Gomis",
"Jaume",
""
],
[
"Okuda",
"Takuya",
""
]
] |
0704.3081 | Andrei Gruzinov | Andrei Gruzinov | Directed Relativistic Blast Wave | 9 pages | null | null | null | astro-ph | null | A spherically symmetrical ultra-relativistic blast wave is not an attractor
of a generic asymmetric explosion. Spherical symmetry is reached only by the
time the blast wave slows down to non-relativistic velocities, when the
Sedov-Taylor-von Neumann attractor solution sets in. We show however, that a
directed relativistic explosion, with the explosion momentum close to the
explosion energy, produces a blast wave with a universal intermediate
asymptotic -- a selfsimilar directed ultra-relativistic blast wave. This
universality might be of interest for the astrophysics of gamma-ray burst
afterglows.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:11:08 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Gruzinov",
"Andrei",
""
]
] |
0704.3082 | Plamen Bozhilov | P. Bozhilov | Neumann and Neumann-Rosochatius integrable systems from membranes on
AdS_4xS^7 | LaTeX, 17 pages, no figures;v2: comments and citations added;v3: 20
pages, new subsection, explanations, comments and references added; v4: some
typos fixed, to appear in JHEP | JHEP0708:073,2007 | 10.1088/1126-6708/2007/08/073 | null | hep-th nlin.SI | null | It is known that large class of classical string solutions in the type IIB
AdS_5xS^5 background is related to the Neumann and Neumann-Rosochatius
integrable systems, including spiky strings and giant magnons. It is also
interesting if these integrable systems can be associated with some membrane
configurations in M-theory. We show here that this is indeed the case by
presenting explicitly several types of membrane embedding in AdS_4xS^7 with the
searched properties.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:14:00 GMT"
},
{
"version": "v2",
"created": "Sat, 28 Apr 2007 08:25:36 GMT"
},
{
"version": "v3",
"created": "Tue, 17 Jul 2007 08:54:05 GMT"
},
{
"version": "v4",
"created": "Fri, 24 Aug 2007 20:09:17 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Bozhilov",
"P.",
""
]
] |
0704.3083 | Alberto Buzzoni | Alberto Buzzoni (INAF, Osservatorio Astronomico di Bologna, Italy) | Late stages of stellar evolution and their impact on spectrophotometric
properties of galaxies | 8 pages and 6 figures (macro asp2006.sty included). An invited
contribution to the intl. conference "From Stars to Galaxies: Building the
pieces to build up the Universe" (Venezia, Italy, 16-20/Oct/2006). ASP Conf.
Series, eds. A. Vallenari, R. Tantalo, L. Portinari and A. Moretti. Further
info at author's web site (see http://www.bo.astro.it/~eps/home.html) | null | null | null | astro-ph | null | The connection between AGB evolution of stellar populations and infrared vs.
ultraviolet properties of the parent galaxies is reviewed relying on the
updated lookout provided by population-synthesis theory. In particular,
planetary-nebula events and hot horizontal-branch evolution are assessed in a
unitary view to outline a plain general picture of galaxy spectrophotometric
evolution. This will include a brief discussion of relevant phenomena such as
the "UV upturn" in ellipticals and the stellar mass loss properties along the
galaxy morphological sequence.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:18:24 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Buzzoni",
"Alberto",
"",
"INAF, Osservatorio Astronomico di Bologna, Italy"
]
] |
0704.3084 | Joshua Erlich | Christopher D. Carone, Joshua Erlich, and Marc Sher | Holographic Electroweak Symmetry Breaking from D-branes | REVTeX, 25 pages, 8 eps figures, version published in PRD | Phys.Rev.D76:015015,2007 | 10.1103/PhysRevD.76.015015 | null | hep-th hep-ph | null | We observe several interesting phenomena in a technicolor-like model of
electroweak symmetry breaking based on the D4-D8-D8bar system of Sakai and
Sugimoto. The benefit of holographic models based on D-brane configurations is
that both sides of the holographic duality are well understood. We find that
the lightest technicolor resonances contribute negatively to the
Peskin-Takeuchi S-parameter, but heavy resonances do not decouple and lead
generically to large, positive values of S, consistent with standard estimates
in QCD-like theories. We study how the S parameter and the masses and decay
constants of the vector and axial-vector techni-resonances vary over a
one-parameter family of D8-brane configurations. We discuss possibilities for
the consistent truncation of the theory to the first few resonances and suggest
some generic predictions of stringy holographic technicolor models.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 18:13:40 GMT"
},
{
"version": "v2",
"created": "Thu, 21 Jun 2007 15:08:29 GMT"
}
] | 2008-11-26T00:00:00 | [
[
"Carone",
"Christopher D.",
""
],
[
"Erlich",
"Joshua",
""
],
[
"Sher",
"Marc",
""
]
] |
0704.3085 | Ilia Solov'yov | Ilia A. Solov'yov, Alexander V. Yakubovich, Andrey V. Solov'yov and
Walter Greiner | Alpha helix-coil phase transition: analysis of ab initio theory
predictions | 34 pages, 12 figures | null | 10.1140/epjd/e2007-00327-x | null | physics.bio-ph physics.chem-ph | null | In the present paper we present results of calculations obtained with the use
of the theoretical method described in our preceding paper [1] and perform
detail analysis of alpha helix-random coil transition in alanine polypeptides
of different length. We have calculated the potential energy surfaces of
polypeptides with respect to their twisting degrees of freedom and construct a
parameter-free partition function of the polypeptide using the suggested method
[1]. From the build up partition function we derive various thermodynamical
characteristics for alanine polypeptides of different length as a function of
temperature. Thus, we analyze the temperature dependence of the heat capacity,
latent heat and helicity for alanine polypeptides consisting of 21, 30, 40, 50
and 100 amino acids. Alternatively, we have obtained same thermodynamical
characteristics from the use of molecular dynamics simulations and compared
them with the results of the new statistical mechanics approach. The comparison
proves the validity of the statistical mechanic approach and establishes its
accuracy.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:28:38 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Solov'yov",
"Ilia A.",
""
],
[
"Yakubovich",
"Alexander V.",
""
],
[
"Solov'yov",
"Andrey V.",
""
],
[
"Greiner",
"Walter",
""
]
] |
0704.3086 | Marek Biskup | Marek Biskup, Herbert Spohn | Scaling limit for a class of gradient fields with nonconvex potentials | Published in at http://dx.doi.org/10.1214/10-AOP548 the Annals of
Probability (http://www.imstat.org/aop/) by the Institute of Mathematical
Statistics (http://www.imstat.org) | Annals of Probability 2011, Vol. 39, No. 1, 224-251 | 10.1214/10-AOP548 | IMS-AOP-AOP548 | math.PR math-ph math.MP | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider gradient fields $(\phi_x:x\in \mathbb{Z}^d)$ whose law takes the
Gibbs--Boltzmann form $Z^{-1}\exp\{-\sum_{< x,y>}V(\phi_y-\phi_x)\}$, where the
sum runs over nearest neighbors. We assume that the potential $V$ admits the
representation \[V(\eta):=-\log\int\varrho({d}\kappa)\exp\biggl[-{1/2}\kappa\et
a^2\biggr],\] where $\varrho$ is a positive measure with compact support in
$(0,\infty)$. Hence, the potential $V$ is symmetric, but nonconvex in general.
While for strictly convex $V$'s, the translation-invariant, ergodic gradient
Gibbs measures are completely characterized by their tilt, a nonconvex
potential as above may lead to several ergodic gradient Gibbs measures with
zero tilt. Still, every ergodic, zero-tilt gradient Gibbs measure for the
potential $V$ above scales to a Gaussian free field.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:45:20 GMT"
},
{
"version": "v2",
"created": "Thu, 10 Sep 2009 20:20:03 GMT"
},
{
"version": "v3",
"created": "Wed, 8 Dec 2010 12:58:35 GMT"
}
] | 2010-12-09T00:00:00 | [
[
"Biskup",
"Marek",
""
],
[
"Spohn",
"Herbert",
""
]
] |
0704.3087 | Dierk Schleicher | Mihai Bailesteanu, Vlad Balan, Dierk Schleicher | Hausdorff Dimension of Exponential Parameter Rays and Their Endpoints | 10 pages | Nonlinearity 21 (2008), 113-120 | 10.1088/0951-7715/21/1/006 | null | math.DS | null | We investigate the set $I$ of parameters $\kappa$ for which the singular
value of $z\mapsto e^z+\kappa$ converges to $\infty$. The set $I$ consists of
uncountably many parameter rays, plus landing points of some of these rays. We
show that the parameter rays have Hausdorff dimension 1, while the ray
endpoints in $I$ alone have dimension 2. Analogous results were known for
dynamical planes of exponential maps; our result shows that this also holds in
parameter space.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:58:35 GMT"
},
{
"version": "v2",
"created": "Fri, 16 Nov 2007 08:49:20 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Bailesteanu",
"Mihai",
""
],
[
"Balan",
"Vlad",
""
],
[
"Schleicher",
"Dierk",
""
]
] |
0704.3088 | Henrique R. Schmitt | N. E. Kassim, T. J. W. Lazio, W. C. Erickson, R. A. Perley, W. D.
Cotton, E. W. Greisen, A. S. Cohen, B. Hicks, H. R. Schmitt, D. Katz | The 74MHz System on the Very Large Array | 73 pages, 46 jpeg figures, to appear in ApJS | null | 10.1086/519022 | null | astro-ph | null | The Naval Research Laboratory and the National Radio Astronomy Observatory
completed implementation of a low frequency capability on the VLA at 73.8 MHz
in 1998. This frequency band offers unprecedented sensitivity (~25 mJy/beam)
and resolution (~25 arcsec) for low-frequency observations. We review the
hardware, the calibration and imaging strategies, comparing them to those at
higher frequencies, including aspects of interference excision and wide-field
imaging. Ionospheric phase fluctuations pose the major difficulty in
calibrating the array. Over restricted fields of view or at times of extremely
quiescent ionospheric ``weather'', an angle-invariant calibration strategy can
be used. In this approach a single phase correction is devised for each
antenna, typically via self-calibration. Over larger fields of view or at times
of more normal ionospheric ``weather'' when the ionospheric isoplanatic patch
size is smaller than the field of view, we adopt a field-based strategy in
which the phase correction depends upon location within the field of view. This
second calibration strategy was implemented by modeling the ionosphere above
the array using Zernike polynomials. Images of 3C sources of moderate strength
are provided as examples of routine, angle-invariant calibration and imaging.
Flux density measurements indicate that the 74 MHz flux scale at the VLA is
stable to a few percent, and tied to the Baars et al. value of Cygnus A at the
5 percent level. We also present an example of a wide-field image, devoid of
bright objects and containing hundreds of weaker sources, constructed from the
field-based calibration. We close with a summary of lessons the 74 MHz system
offers as a model for new and developing low-frequency telescopes. (Abridged)
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 20:59:04 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Kassim",
"N. E.",
""
],
[
"Lazio",
"T. J. W.",
""
],
[
"Erickson",
"W. C.",
""
],
[
"Perley",
"R. A.",
""
],
[
"Cotton",
"W. D.",
""
],
[
"Greisen",
"E. W.",
""
],
[
"Cohen",
"A. S.",
""
],
[
"Hicks",
"B.",
""
],
[
"Schmitt",
"H. R.",
""
],
[
"Katz",
"D.",
""
]
] |
0704.3089 | H. A. Dye | H. A. Dye | Pure Virtual Braids Homotopic to the Identity Braid | 18 pages, 17 figures Final version, accepted by Fundamenta
Mathematicae | null | null | null | math.GT math.AT | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Two virtual link diagrams are homotopic if one may be transformed into the
other by a sequence of virtual Reidemeister moves, classical Reidemeister
moves, and self crossing changes. We recall the pure virtual braid group. We
then describe the set of pure virtual braids that are homotopic to the identity
braid.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 21:10:16 GMT"
},
{
"version": "v2",
"created": "Thu, 21 Aug 2008 12:33:35 GMT"
}
] | 2008-08-21T00:00:00 | [
[
"Dye",
"H. A.",
""
]
] |
0704.3090 | Benoit Fresse | Benoit Fresse | Modules over operads and functors | This book project has been withdrawn from arXiv. Final version to
appear as a Springer-Verlag Lecture Notes with significant additions and
corrections. The preprint on arXiv will not be updated | null | null | null | math.AT | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | In the theory of operads we consider functors of generalized symmetric powers
defined by sums of coinvariant modules under actions of symmetric groups. One
observes classically that the construction of symmetric functors provides an
isomorphism from the category of symmetric modules to a subcategory of the
category of functors on the base category. The purpose of this book is to
obtain a similar relationship for functors on a category of algebras over an
operad.
We observe that right modules over operads, symmetric modules equipped with a
right operad action, give rise to functors on categories of algebras and we
prove that this construction yields an embedding of categories. Then we check
that right modules over operads form a model category. In addition we prove
that weak-equivalences of right modules correspond to pointwise
weak-equivalences at the functor level. As a conclusion, we obtain that right
modules over operads supply good models for the homotopy of associated functors
on algebras over operads.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 13:28:01 GMT"
},
{
"version": "v2",
"created": "Tue, 29 May 2007 15:31:57 GMT"
},
{
"version": "v3",
"created": "Thu, 8 Nov 2007 22:38:10 GMT"
},
{
"version": "v4",
"created": "Fri, 18 Jan 2008 10:45:08 GMT"
},
{
"version": "v5",
"created": "Wed, 25 Feb 2009 09:29:30 GMT"
}
] | 2009-02-25T00:00:00 | [
[
"Fresse",
"Benoit",
""
]
] |
0704.3091 | David Richter | David A. Richter | Triacontagonal coordinates for the E(8) root system | 4 pages, 2 figures | null | null | null | math.GM | null | This note gives an explicit formula for the elements of the E(8) root system.
The formula is triacontagonally symmetric in that one may clearly see an action
by the cyclic group with 30 elements. The existence of such a formula is due to
the fact that the Coxeter number of E(8) is 30.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 19:35:29 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Richter",
"David A.",
""
]
] |
0704.3092 | David P. Blecher | David P. Blecher and Maureen K. Royce | Extensions of operator algebras I | null | null | 10.1016/j.jmaa.2007.07.065 | null | math.OA math.FA | null | We transcribe a portion of the theory of extensions of C*-algebras to general
operator algebras. We also include several new general facts about
approximately unital ideals in operator algebras and the C*-algebras which they
generate.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 21:21:43 GMT"
},
{
"version": "v2",
"created": "Wed, 1 Aug 2007 20:08:22 GMT"
}
] | 2015-05-13T00:00:00 | [
[
"Blecher",
"David P.",
""
],
[
"Royce",
"Maureen K.",
""
]
] |
0704.3093 | Jean-Baptiste Meilhan | Jean-Baptiste Meilhan and Akira Yasuhara | Whitehead double and Milnor invariants | 9 pages, 5 figures. Some minor modifications in this final version | Osaka J. Math. 48 No. 2 (2011), 371-381 | null | null | math.GT | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | We consider the operation of Whitehead double on a component of a link and
study the behavior of Milnor invariants under this operation. We show that this
operation turns a link whose Milnor invariants of length < k are all zero into
a link with vanishing Milnor invariants of length < 2k, and we provide formulas
for the first non-vanishing ones.
As a consequence, we obtain statements relating the notions of link-homotopy
and self Delta-equivalence via the Whitehead double operation. By using our
result, we show that a Brunnian link L is link-homotopic to the unlink if and
only if a link L with a single component Whitehed doubled is self
Delta-equivalent to the unlink.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 21:24:47 GMT"
},
{
"version": "v2",
"created": "Wed, 29 Feb 2012 10:57:47 GMT"
}
] | 2012-03-01T00:00:00 | [
[
"Meilhan",
"Jean-Baptiste",
""
],
[
"Yasuhara",
"Akira",
""
]
] |
0704.3094 | Olympia Hadjiliadis | Olympia Hadjiliadis and H.Vincent Poor | Detection of two-sided alternatives in a Brownian motion model | 4 pages, to appear in the Proceedings of the 56th Session of the
International Statistical Institute, Lisbon, Portugal, August 22- 29, 2007 | null | null | null | cs.IT math.IT | null | This work examines the problem of sequential detection of a change in the
drift of a Brownian motion in the case of two-sided alternatives. Applications
to real life situations in which two-sided changes can occur are discussed.
Traditionally, 2-CUSUM stopping rules have been used for this problem due to
their asymptotically optimal character as the mean time between false alarms
tends to $\infty$. In particular, attention has focused on 2-CUSUM harmonic
mean rules due to the simplicity in calculating their first moments. In this
paper, we derive closed-form expressions for the first moment of a general
2-CUSUM stopping rule. We use these expressions to obtain explicit upper and
lower bounds for it. Moreover, we derive an expression for the rate of change
of this first moment as one of the threshold parameters changes. Based on these
expressions we obtain explicit upper and lower bounds to this rate of change.
Using these expressions we are able to find the best 2-CUSUM stopping rule with
respect to the extended Lorden criterion. In fact, we demonstrate not only the
existence but also the uniqueness of the best 2-CUSUM stopping both in the case
of a symmetric change and in the case of a non-symmetric case. Furthermore, we
discuss the existence of a modification of the 2-CUSUM stopping rule that has a
strictly better performance than its classical 2-CUSUM counterpart for small
values of the mean time between false alarms. We conclude with a discussion on
the open problem of strict optimality in the case of two-sided alternatives.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 22:28:30 GMT"
}
] | 2007-07-13T00:00:00 | [
[
"Hadjiliadis",
"Olympia",
""
],
[
"Poor",
"H. Vincent",
""
]
] |
0704.3095 | David P. Blecher | David P. Blecher, Kay Kirkpatrick, Matthew Neal, Wend Werner | Ordered involutive operator spaces | 11 pages. To appear, Positivity | null | null | null | math.OA math.FA | null | This is a companion to recent papers of the authors; here we construct the
`noncommutative
Shilov boundary' of a (possibly nonunital) selfadjoint ordered space of
Hilbert space operators. The morphisms in the universal property of the
boundary preserve order.
As an application, we consider `maximal' and `minimal' unitizations of such
ordered operator spaces.
| [
{
"version": "v1",
"created": "Mon, 23 Apr 2007 21:29:18 GMT"
}
] | 2007-05-23T00:00:00 | [
[
"Blecher",
"David P.",
""
],
[
"Kirkpatrick",
"Kay",
""
],
[
"Neal",
"Matthew",
""
],
[
"Werner",
"Wend",
""
]
] |
0704.3096 | Vincent Bouchard | Vincent Bouchard and Ron Donagi | On a class of non-simply connected Calabi-Yau threefolds | 50 pages; v3: version published in CNTP | Comm. Numb. Theor. Phys. 2 (2008) 1-61 | null | null | math.AG hep-th | null | We obtain a detailed classification for a class of non-simply connected
Calabi-Yau threefolds which are of potential interest for a wide range of
problems in string phenomenology. These threefolds arise as quotients of
Schoen's Calabi-Yau threefolds, which are fiber products over P1 of two
rational elliptic surfaces. The quotient is by a freely acting finite abelian
group preserving the fibrations. Our work involves a classification of
restricted finite automorphism groups of rational elliptic surfaces.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 18:05:55 GMT"
},
{
"version": "v2",
"created": "Thu, 3 May 2007 18:42:49 GMT"
},
{
"version": "v3",
"created": "Mon, 14 Apr 2008 17:56:58 GMT"
}
] | 2008-04-14T00:00:00 | [
[
"Bouchard",
"Vincent",
""
],
[
"Donagi",
"Ron",
""
]
] |
0704.3097 | Sarah Brough | S. Brough (Swinburne University), R. Proctor (Swin), D. Forbes (Swin),
W. Couch (Swin), C. Collins (Liverpool John Moores), D. Burke (CfA), R. Mann
(ROE) | Spatially resolved kinematics and stellar populations of brightest
cluster and group galaxies | 21 pages plus appendices, accepted for publication in MNRAS | Mon.Not.Roy.Astron.Soc.378:1507-1530,2007 | 10.1111/j.1365-2966.2007.11900.x | null | astro-ph | null | We present an examination of the kinematics and stellar populations of a
sample of 3 Brightest Group Galaxies (BGGs) and 3 Brightest Cluster Galaxies
(BCGs) in X-ray groups and clusters. We have obtained high signal-to-noise
Gemini/GMOS (Gemini South Multi-Object Spectrograph) long-slit spectra of these
galaxies and use Lick indices to determine ages, metallicities and
alpha-element abundance ratios out to at least their effective radii. We find
that the BGGs and BCGs have very uniform masses, central ages and central
metallicities. Examining the radial dependence of their stellar populations, we
find no significant velocity dispersion, age, or alpha-enhancement gradients.
However, we find a wide range of metallicity gradients, suggesting a variety of
formation mechanisms. The range of metallicity gradients observed is surprising
given the homogeneous environment these galaxies probe and their uniform
central stellar populations. However, our results are inconsistent with any
single model of galaxy formation and emphasize the need for more theoretical
understanding of both the origins of metallicity gradients and galaxy formation
itself. We postulate two possible physical causes for the different formation
mechanisms.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 00:39:38 GMT"
}
] | 2009-06-23T00:00:00 | [
[
"Brough",
"S.",
"",
"Swinburne University"
],
[
"Proctor",
"R.",
"",
"Swin"
],
[
"Forbes",
"D.",
"",
"Swin"
],
[
"Couch",
"W.",
"",
"Swin"
],
[
"Collins",
"C.",
"",
"Liverpool John Moores"
],
[
"Burke",
"D.",
"",
"CfA"
],
[
"Mann",
"R.",
"",
"ROE"
]
] |
0704.3098 | Amaury Lambert | Amaury Lambert (PMA) | The contour of splitting trees is a L\'evy process | null | null | null | null | math.PR | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | Splitting trees are those random trees where individuals give birth at
constant rate during a lifetime with general distribution, to i.i.d. copies of
themselves. The width process of a splitting tree is then a binary, homogeneous
Crump--Mode--Jagers (CMJ) process, and is not Markovian unless the lifetime
distribution is exponential. Here, we allow the birth rate to be infinite, that
is, pairs of birth times and lifespans of newborns form a Poisson point process
along the lifetime of their mother, with possibly infinite intensity measure. A
splitting tree is a random (so-called) chronological tree. Each element of a
chronological tree is a (so-called) existence point $(v,\tau)$ of some
individual $v$ (vertex) in a discrete tree, where $\tau$ is a nonnegative real
number called chronological level (time). We introduce a total order on
existence points, called linear order, and a mapping $\varphi$ from the tree
into the real line which preserves this order. The inverse of $\varphi$ is
called the exploration process, and the projection of this inverse on
chronological levels the contour process. For splitting trees truncated up to
level $\tau$, we prove that thus defined contour process is a L\'evy process
reflected below $\tau$ and killed upon hitting 0. This allows to derive
properties of (i) splitting trees: conceptual proof of Le Gall--Le Jan's
theorem in the finite variation case, exceptional points, coalescent point
process, age distribution; (ii) CMJ processes: one-dimensional marginals,
conditionings, limit theorems, asymptotic numbers of individuals with infinite
vs finite descendances.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 13:34:17 GMT"
},
{
"version": "v2",
"created": "Mon, 9 Feb 2009 11:00:30 GMT"
}
] | 2009-02-09T00:00:00 | [
[
"Lambert",
"Amaury",
"",
"PMA"
]
] |
0704.3099 | Vyacheslav P. Spiridonov | V.P. Spiridonov | Elliptic hypergeometric functions | 27 pp., a complement to the book by G.E. Andrews, R. Askey, and R.
Roy, Special Functions, Encyclopedia of Math. Appl. 71, Cambridge Univ.
Press, Cambridge, 1999, written for its Russian edition: Moscow, MCCME, 2013,
pp. 577-606 | null | null | null | math.CA | http://arxiv.org/licenses/nonexclusive-distrib/1.0/ | This is a brief overview of the status of the theory of elliptic
hypergeometric functions to the end of 2012 written as a complementary chapter
to the Russian edition of the book by G.E. Andrews, R. Askey, and R. Roy,
Special Functions, Encycl. of Math. Appl. 71, Cambridge Univ. Press, 1999.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 13:25:31 GMT"
},
{
"version": "v2",
"created": "Wed, 28 Dec 2016 19:22:16 GMT"
}
] | 2016-12-30T00:00:00 | [
[
"Spiridonov",
"V. P.",
""
]
] |
0704.3100 | Kristian Finlator | K. Finlator, R. Dave | The Origin of the Galaxy Mass-Metallicity Relation and Implications for
Galactic Outflows | 28 pages, 15 figures, accepted by MNRAS with minor revisions. The
definitive version is available at www.blackell-synergy.com | null | 10.1111/j.1365-2966.2008.12991.x | null | astro-ph | null | (Abridged) Using cosmological hydrodynamic simulations in combination with
analytic modeling, we show that the galaxy stellar mass-metallicity relation
(MZR) provides strong constraints on galactic outflows across cosmic time. We
compare three outflow models: No outflows, a "constant wind" (cw) model that
emulates the popular Dekel & Silk (1986) scenario, and a ``momentum-driven
wind" (vzw) model. We find that only the vzw scaling reproduces the observed
z~2 MZR's slope, amplitude, and scatter. Comparing our fully three-dimensional
simulations with a simple one-zone chemical evolution model, we find that the
MZR can be understood in terms of three parameters: (1) The equilibrium
metallicity Z_eq=y*SFR/ACC (where y=true yield), reflecting the enrichment
balance between star formation rate SFR and gas accretion rate ACC; (2) the
dilution time t_d=M_g/ACC, representing the timescale for a galaxy to return to
Z_eq after a metallicity-perturbing interaction; and (3) the blowout mass
M_blowout, which is the galaxy stellar mass above which winds can escape its
halo. When outflows with mass loading factor MLF are present, galaxies below
M_blowout obey Z_eq = y/(1+MLF), while above M_blowout, Z_eq->y. Our cw model
has M_blowout ~ 10^10 M_sun, which yields a sharp upturn in the MZR above this
scale and a flat MZR with large scatter below it, in strong disagreement with
observations. Our vzw model reproduces the observed Z_g \propto M_*^0.3 because
Z_eq \propto MLF^-1 \propto M_*^1/3 when MLF >> 1 (i.e. at low masses). The
flattening of the MZR at M_* > 10^10.5 M_sun observed by Tremonti et al. (2004)
reflects the mass scale where MLF~1, rather than a characteristic wind speed.
The tight observed MZR scatter is ensured when t_d<1 dynamical time, which is
only satisified at all masses and epochs in our momentum-driven wind model.
| [
{
"version": "v1",
"created": "Tue, 24 Apr 2007 01:11:35 GMT"
},
{
"version": "v2",
"created": "Tue, 22 Jan 2008 00:08:53 GMT"
}
] | 2009-11-13T00:00:00 | [
[
"Finlator",
"K.",
""
],
[
"Dave",
"R.",
""
]
] |
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