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Boson-vortex duality in compressible spin-orbit coupled BECs | Using a (1+2)-dimensional boson-vortex duality between non-linear
electrodynamics and a two-component compressible Bose-Einstein condensate (BEC)
with spin-orbit (SO) coupling, we obtain generalised versions of the
hydrodynamic continuity and Euler equations where the phase defect and
non-defect degrees of freedom enter separately. We obtain the generalised
Magnus force on vortices under SO coupling, and associate the linear
confinement of vortices due to SO coupling with instanton fluctuations of the
dual theory.
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Communicating Correlated Sources Over an Interference Channel | A new coding technique, based on \textit{fixed block-length} codes, is
proposed for the problem of communicating a pair of correlated sources over a
$2-$user interference channel. Its performance is analyzed to derive a new set
of sufficient conditions. The latter is proven to be strictly less binding than
the current known best, which is due to Liu and Chen [Dec, 2011]. Our findings
are inspired by Dueck's example [March, 1981].
| 1 | 0 | 0 | 0 | 0 | 0 |
Simulating polaron biophysics with Rydberg atoms | Transport of excitations along proteins can be formulated in a quantum
physics context, based on the periodicity and vibrational modes of the
structures. Exact solutions are very challenging to obtain on classical
computers, however, approximate solutions based on the Davydov ansatz have
demonstrated the possibility of stabilized solitonic excitations along the
protein. We propose an alternative study based on a chain of ultracold atoms.
We investigate the experimental parameters to control such a quantum simulator
based on dressed Rydberg atoms. We show that there is a feasible range of
parameters where a quantum simulator can directly mimic the Davydov equations
and their solutions. Such a quantum simulator opens up new directions for the
study of transport phenomena in a biophysical context.
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Solubility limit of methyl red and methylene blue in microemulsions and liquid crystals of water, sds and pentanol systems | Solubility of dyes in amphiphilic association structures of water, SDS and
penthanol system (i.e. in the phases of microemulsions and liquid crystals) was
attracted much interest due to its wide industrial and technological
applications. This research was focused on understanding the solubility
limitation of methyl red and methylene blue in microemulsion and liquid crystal
phases. Experimental results showed that the highest solubility of methyl red
was in LLC, followed by w/o microemulsion and o/w microemulsion, respectively,
whereas the highest solubility of methylene blue was in w/o microemulsion,
followed by o/w microemulsion and LLC, respectively. Hence, a chemical dynamics
strongly played an important role in the solubility limitation of methyl red
and methylene blue in microemulsions and liquid crystal phases.
| 0 | 1 | 0 | 0 | 0 | 0 |
Towards Visual Ego-motion Learning in Robots | Many model-based Visual Odometry (VO) algorithms have been proposed in the
past decade, often restricted to the type of camera optics, or the underlying
motion manifold observed. We envision robots to be able to learn and perform
these tasks, in a minimally supervised setting, as they gain more experience.
To this end, we propose a fully trainable solution to visual ego-motion
estimation for varied camera optics. We propose a visual ego-motion learning
architecture that maps observed optical flow vectors to an ego-motion density
estimate via a Mixture Density Network (MDN). By modeling the architecture as a
Conditional Variational Autoencoder (C-VAE), our model is able to provide
introspective reasoning and prediction for ego-motion induced scene-flow.
Additionally, our proposed model is especially amenable to bootstrapped
ego-motion learning in robots where the supervision in ego-motion estimation
for a particular camera sensor can be obtained from standard navigation-based
sensor fusion strategies (GPS/INS and wheel-odometry fusion). Through
experiments, we show the utility of our proposed approach in enabling the
concept of self-supervised learning for visual ego-motion estimation in
autonomous robots.
| 1 | 0 | 0 | 0 | 0 | 0 |
Sequential Prediction of Social Media Popularity with Deep Temporal Context Networks | Prediction of popularity has profound impact for social media, since it
offers opportunities to reveal individual preference and public attention from
evolutionary social systems. Previous research, although achieves promising
results, neglects one distinctive characteristic of social data, i.e.,
sequentiality. For example, the popularity of online content is generated over
time with sequential post streams of social media. To investigate the
sequential prediction of popularity, we propose a novel prediction framework
called Deep Temporal Context Networks (DTCN) by incorporating both temporal
context and temporal attention into account. Our DTCN contains three main
components, from embedding, learning to predicting. With a joint embedding
network, we obtain a unified deep representation of multi-modal user-post data
in a common embedding space. Then, based on the embedded data sequence over
time, temporal context learning attempts to recurrently learn two adaptive
temporal contexts for sequential popularity. Finally, a novel temporal
attention is designed to predict new popularity (the popularity of a new
user-post pair) with temporal coherence across multiple time-scales.
Experiments on our released image dataset with about 600K Flickr photos
demonstrate that DTCN outperforms state-of-the-art deep prediction algorithms,
with an average of 21.51% relative performance improvement in the popularity
prediction (Spearman Ranking Correlation).
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Key Management and Learning based Two Level Data Security for Metering Infrastructure of Smart Grid | In the smart grid, smart meters, and numerous control and monitoring
applications employ bidirectional wireless communication, where security is a
critical issue. In key management based encryption method for the smart grid,
the Trusted Third Party (TTP), and links between the smart meter and the third
party are assumed to be fully trusted and reliable. However, in wired/wireless
medium, a man-in-middle may want to interfere, monitor and control the network,
thus exposing its vulnerability. Acknowledging this, in this paper, we propose
a novel two level encryption method based on two partially trusted simple
servers (constitutes the TTP) which implement this method without increasing
packet overhead. One server is responsible for data encryption between the
meter and control center/central database, and the other server manages the
random sequence of data transmission. Numerical calculation shows that the
number of iterations required to decode a message is large which is quite
impractical. Furthermore, we introduce One-class support vector machine
(machine learning) algorithm for node-to-node authentication utilizing the
location information and the data transmission history (node identity, packet
size and frequency of transmission). This secures data communication privacy
without increasing the complexity of the conventional key management scheme.
| 1 | 0 | 0 | 0 | 0 | 0 |
A numerical study of the homogeneous elliptic equation with fractional order boundary conditions | We consider the homogeneous equation ${\mathcal A} u=0$, where ${\mathcal A}$
is a symmetric and coercive elliptic operator in $H^1(\Omega)$ with $\Omega$
bounded domain in ${\mathbb R}^d$. The boundary conditions involve fractional
power $\alpha$, $ 0 < \alpha <1$, of the Steklov spectral operator arising in
Dirichlet to Neumann map. For such problems we discuss two different numerical
methods: (1) a computational algorithm based on an approximation of the
integral representation of the fractional power of the operator and (2)
numerical technique involving an auxiliary Cauchy problem for an
ultra-parabolic equation and its subsequent approximation by a time stepping
technique. For both methods we present numerical experiment for a model
two-dimensional problem that demonstrate the accuracy, efficiency, and
stability of the algorithms.
| 0 | 0 | 1 | 0 | 0 | 0 |
Effects of soft interactions and bound mobility on diffusion in crowded environments: a model of sticky and slippery obstacles | Crowded environments modify the diffusion of macromolecules, generally
slowing their movement and inducing transient anomalous subdiffusion. The
presence of obstacles also modifies the kinetics and equilibrium behavior of
tracers. While previous theoretical studies of particle diffusion have
typically assumed either impenetrable obstacles or binding interactions that
immobilize the particle, in many cellular contexts bound particles remain
mobile. Examples include membrane proteins or lipids with some entry and
diffusion within lipid domains and proteins that can enter into membraneless
organelles or compartments such as the nucleolus. Using a lattice model, we
studied the diffusive movement of tracer particles which bind to soft
obstacles, allowing tracers and obstacles to occupy the same lattice site. For
sticky obstacles, bound tracer particles are immobile, while for slippery
obstacles, bound tracers can hop without penalty to adjacent obstacles. In both
models, binding significantly alters tracer motion. The type and degree of
motion while bound is a key determinant of the tracer mobility: slippery
obstacles can allow nearly unhindered diffusion, even at high obstacle filling
fraction. To mimic compartmentalization in a cell, we examined how obstacle
size and a range of bound diffusion coefficients affect tracer dynamics. The
behavior of the model is similar in two and three spatial dimensions. Our work
has implications for protein movement and interactions within cells.
| 0 | 1 | 0 | 0 | 0 | 0 |
Thermodynamics of a Quantum Ising system coupled to a spin bath: Zero Temperature Results | We study the effect of coupling a spin bath environment to a system which, at
low energies, can be modeled as a quantum Ising system. A field theoretic
formalism incorporating both thermal and quantum fluctuations is developed to
derive results for the thermodynamic properties and response functions, both
for a toy model and for the $LiHoF_4$ system, in which spin-8 electronic spins
couple to a spin-$7/2$ nuclear spin bath: the phase transition then occurs in a
system of electronuclear degrees of freedom, coupled by long-range dipolar
interactions. The quantum Ising phase transition still exists, and one
hybridized mode of the Ising and bath spins always goes soft at the transition.
| 0 | 1 | 0 | 0 | 0 | 0 |
Observation of a Lamb band gap in a polymer waveguide with periodic cross-like cavities | The quest for large and low frequency band gaps is one of the principal
objectives pursued in a number of engineering applications, ranging from noise
absorption to vibration control, to seismic wave abatement. For this purpose, a
plethora of complex architectures (including multi-phase materials) and
multi-physics approaches have been proposed in the past, often involving
difficulties in their practical realization.
To address this issue, in this work we propose an easy-to-manufacture design
able to open large, low frequency complete Lamb band gaps exploiting a suitable
arrangement of masses and stiffnesses produced by cavities in a monolithic
material. The performance of the designed structure is evaluated by numerical
simulations and confirmed by Scanning Laser Doppler Vibrometer (SLDV)
measurements on an isotropic polyvinyl chloride plate in which a square ring
region of cross-like cavities is fabricated. The full wave field reconstruction
clearly confirms the ability of even a limited number of unit cell rows of the
proposed design to efficiently attenuate Lamb waves. In addition, numerical
simulations show that the structure allows to shift of the central frequency of
the BG through geometrical modifications. The design may be of interest for
applications in which large BGs at low frequencies are required.
| 0 | 1 | 0 | 0 | 0 | 0 |
Search for nucleon decays with EXO-200 | A search for instability of nucleons bound in $^{136}$Xe nuclei is reported
with 223 kg$\cdot$yr exposure of $^{136}$Xe in the EXO-200 experiment. Lifetime
limits of 3.3$\times 10^{23}$ and 1.9$\times 10^{23}$ yrs are established for
nucleon decay to $^{133}$Sb and $^{133}$Te, respectively. These are the most
stringent to date, exceeding the prior decay limits by a factor of 9 and 7,
respectively.
| 0 | 1 | 0 | 0 | 0 | 0 |
The multiplicity of massive stars: a 2016 view | Massive stars like company. Here, we provide a brief overview of progresses
made over the last 5 years by a number of medium and large surveys. These
results provide new insights on the observed and intrinsic multiplicity
properties of main sequence massive stars and on the initial conditions for
their future evolution. They also bring new interesting constraints on the
outcome of the massive star formation process.
| 0 | 1 | 0 | 0 | 0 | 0 |
Principal Eigenvalue of Mixed Problem for the Fractional Laplacian: Moving the Boundary Conditions | We analyze the behavior of the eigenvalues of the following non local mixed
problem $\left\{ \begin{array}{rcll} (-\Delta)^{s} u &=& \lambda_1(D) \ u
&\inn\Omega,\\ u&=&0&\inn D,\\ \mathcal{N}_{s}u&=&0&\inn N. \end{array}\right $
Our goal is to construct different sequences of problems by modifying the
configuration of the sets $D$ and $N$, and to provide sufficient and necessary
conditions on the size and the location of these sets in order to obtain
sequences of eigenvalues that in the limit recover the eigenvalues of the
Dirichlet or Neumann problem. We will see that the non locality plays a crucial
role here, since the sets $D$ and $N$ can have infinite measure, a phenomenon
that does not appear in the local case (see for example \cite{D,D2,CP}).
| 0 | 0 | 1 | 0 | 0 | 0 |
Two-dimensional Bose and Fermi gases beyond weak coupling | Using a formalism based on the two-body S-matrix we study two-dimensional
Bose and Fermi gases with both attractive and repulsive interactions.
Approximate analytic expressions, valid at weak coupling and beyond, are
developed and applied to the Berezinskii-Kosterlitz-Thouless (BKT) transition.
We successfully recover the correct logarithmic functional form of the critical
chemical potential and density for the Bose gas. For fermions, the BKT critical
temperature is calculated in BCS and BEC regimes through consideration of Tan's
contact.
| 0 | 1 | 0 | 0 | 0 | 0 |
Anisotropy of magnetic interactions and symmetry of the order parameter in unconventional superconductor Sr$_{2}$RuO$_{4}$ | Sr$_2$RuO$_4$ is the best candidate for spin-triplet superconductivity, an
unusual and elusive superconducting state of fundamental importance. In the
last three decades Sr$_2$RuO$_4$ has been very carefully studied and despite
its apparent simplicity when compared with strongly correlated high-$T_{c}$
cuprates, for which the pairing symmetry is understood, there is no scenario
that can explain all the major experimental observations, a conundrum that has
generated tremendous interest. Here we present a density-functional based
analysis of magnetic interactions in Sr$_{2}$RuO$_{4}$ and discuss the role of
magnetic anisotropy in its unconventional superconductivity. Our goal is
twofold. First, we access the possibility of the superconducting order
parameter rotation in an external magnetic field of 200 Oe, and conclude that
the spin-orbit interaction in this material is several orders of magnitude too
strong to be consistent with this hypothesis. Thus, the observed invariance of
the Knight shift across $T_{c}$ has no plausible explanation, and casts doubt
on using the Knight shift as an ultimate litmus paper for the pairing symmetry.
Second, we propose a quantitative double-exchange-like model for combining
itinerant fermions with an anisotropic Heisenberg magnetic Hamiltonian. This
model is complementary to the Hubbard-model-based calculations published so
far, and forms an alternative framework for exploring superconducting symmetry
in Sr$_{2}$RuO$_{4}.$ As an example, we use this model to analyze the
degeneracy between various $p-$triplet states in the simplest mean-field
approximation, and show that it splits into a single and two doublets with the
ground state defined by the competition between the "Ising" and "compass"
anisotropic terms.
| 0 | 1 | 0 | 0 | 0 | 0 |
Loss of Regularity of Solutions of the Lighthill Problem for Shock Diffraction for Potential Flow | We are concerned with the regularity of solutions of the Lighthill problem
for shock diffraction by a convex corned wedge, which can be formulated as a
free boundary problem. In this paper, we prove that there is no regular
solution that is subsonic up to the wedge corner for potential flow. This
indicates that, if the solution is subsonic at the wedge corner, at least a
characteristic discontinuity (vortex sheet or entropy wave) is expected to be
generated, which is consistent with the experimental and computational results.
In order to achieve the non-existence result, a weak maximum principle for the
solution is established, and several other mathematical techniques are
developed. The methods and techniques developed here are also useful to the
other problems with similar difficulties.
| 0 | 0 | 1 | 0 | 0 | 0 |
Stage 4 validation of the Satellite Image Automatic Mapper lightweight computer program for Earth observation Level 2 product generation, Part 1 Theory | The European Space Agency (ESA) defines an Earth Observation (EO) Level 2
product as a multispectral (MS) image corrected for geometric, atmospheric,
adjacency and topographic effects, stacked with its scene classification map
(SCM), whose legend includes quality layers such as cloud and cloud-shadow. No
ESA EO Level 2 product has ever been systematically generated at the ground
segment. To contribute toward filling an information gap from EO big data to
the ESA EO Level 2 product, an original Stage 4 validation (Val) of the
Satellite Image Automatic Mapper (SIAM) lightweight computer program was
conducted by independent means on an annual Web-Enabled Landsat Data (WELD)
image composite time-series of the conterminous U.S. The core of SIAM is a one
pass prior knowledge based decision tree for MS reflectance space
hyperpolyhedralization into static color names presented in literature in
recent years. For the sake of readability this paper is split into two. The
present Part 1 Theory provides the multidisciplinary background of a priori
color naming in cognitive science, from linguistics to computer vision. To cope
with dictionaries of MS color names and land cover class names that do not
coincide and must be harmonized, an original hybrid guideline is proposed to
identify a categorical variable pair relationship. An original quantitative
measure of categorical variable pair association is also proposed. The
subsequent Part 2 Validation discusses Stage 4 Val results collected by an
original protocol for wall-to-wall thematic map quality assessment without
sampling where the test and reference map legends can differ. Conclusions are
that the SIAM-WELD maps instantiate a Level 2 SCM product whose legend is the 4
class taxonomy of the FAO Land Cover Classification System at the Dichotomous
Phase Level 1 vegetation/nonvegetation and Level 2 terrestrial/aquatic.
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Performance Analysis of MEC Approach for Haplotype Assembly | The Minimum Error Correction (MEC) approach is used as a metric for
reconstruction of haplotypes from NGS reads. In this paper, we show that the
MEC may encounter with imprecise reconstructed haplotypes for some NGS devices.
Specifically, using mathematical derivations, we evaluate this approach for the
SOLiD, Illumina, 454, Ion, Pacific BioSciences, Oxford Nanopore, and 10X
Genomics devices. Our results reveal that the MEC yields inexact haplotypes for
the Illumina MiniSeq, 454 GS Junior+, Ion PGM 314, and Oxford Nanopore MK 1
MinION.
| 0 | 0 | 0 | 0 | 1 | 0 |
Opinion Recommendation using Neural Memory Model | We present opinion recommendation, a novel task of jointly predicting a
custom review with a rating score that a certain user would give to a certain
product or service, given existing reviews and rating scores to the product or
service by other users, and the reviews that the user has given to other
products and services. A characteristic of opinion recommendation is the
reliance of multiple data sources for multi-task joint learning, which is the
strength of neural models. We use a single neural network to model users and
products, capturing their correlation and generating customised product
representations using a deep memory network, from which customised ratings and
reviews are constructed jointly. Results show that our opinion recommendation
system gives ratings that are closer to real user ratings on Yelp.com data
compared with Yelp's own ratings, and our methods give better results compared
to several pipelines baselines using state-of-the-art sentiment rating and
summarization systems.
| 1 | 0 | 0 | 0 | 0 | 0 |
Distributed Optimization of Multi-Beam Directional Communication Networks | We formulate an optimization problem for maximizing the data rate of a common
message transmitted from nodes within an airborne network broadcast to a
central station receiver while maintaining a set of intra-network rate demands.
Assuming that the network has full-duplex links with multi-beam directional
capability, we obtain a convex multi-commodity flow problem and use a
distributed augmented Lagrangian algorithm to solve for the optimal flows
associated with each beam in the network. For each augmented Lagrangian
iteration, we propose a scaled gradient projection method to minimize the local
Lagrangian function that incorporates the local topology of each node in the
network. Simulation results show fast convergence of the algorithm in
comparison to simple distributed primal dual methods and highlight performance
gains over standard minimum distance-based routing.
| 0 | 0 | 1 | 0 | 0 | 0 |
Mean conservation for density estimation via diffusion using the finite element method | We propose boundary conditions for the diffusion equation that maintain the
initial mean and the total mass of a discrete data sample in the density
estimation process. A complete study of this framework with numerical
experiments using the finite element method is presented for the one
dimensional diffusion equation, some possible applications of this results are
presented as well. We also comment on a similar methodology for the
two-dimensional diffusion equation for future applications in two-dimensional
domains.
| 0 | 0 | 1 | 0 | 0 | 0 |
Asymptotic properties of maximum likelihood estimator for the growth rate of a stable CIR process based on continuous time observations | We consider a stable Cox--Ingersoll--Ross process driven by a standard Wiener
process and a spectrally positive strictly stable Lévy process, and we study
asymptotic properties of the maximum likelihood estimator (MLE) for its growth
rate based on continuous time observations. We distinguish three cases:
subcritical, critical and supercritical. In all cases we prove strong
consistency of the MLE in question, in the subcritical case asymptotic
normality, and in the supercritical case asymptotic mixed normality are shown
as well. In the critical case the description of the asymptotic behavior of the
MLE in question remains open.
| 0 | 0 | 1 | 1 | 0 | 0 |
Indoor Office Wideband Penetration Loss Measurements at 73 GHz | This paper presents millimeter wave (mmWave) penetration loss measurements
and analysis at 73 GHz using a wideband sliding correlator channel sounder in
an indoor office environment. Penetration loss was measured using a carefully
controlled measurement setup for many common indoor building materials such as
glass doors, glass windows, closet doors, steel doors, and whiteboard writing
walls. Measurements were conducted using narrowbeam transmitter (TX) and
receiver (RX) horn antennas that were boresight-aligned with a test material
between the antennas. Overall, 21 different locations were measured for 6
different materials such that the same type of material was tested in at least
two locations in order to characterize the effect of penetration loss for
materials with similar composition. As shown here, attenuation through common
materials ranged between 0.8 dB/cm and 9.9 dB/cm for co-polarized antennas,
while cross-polarized antennas exhibited similar attenuation for most
materials, but up to 23.4 dB/cm of attenuation for others. The penetration loss
results presented here are useful for site-specific planning tools that will
model indoor mmWave networks, without the need for expensive measurement
campaigns.
| 1 | 0 | 0 | 0 | 0 | 0 |
The SPEDE spectrometer | The electron spectrometer, SPEDE, has been developed and will be employed in
conjunction with the Miniball spectrometer at the HIE-ISOLDE facility, CERN.
SPEDE allows for direct measurement of internal conversion electrons emitted
in-flight, without employing magnetic fields to transport or momentum filter
the electrons. Together with the Miniball spectrometer, it enables simultaneous
observation of {\gamma} rays and conversion electrons in Coulomb-excitation
experiments using radioactive ion beams.
| 0 | 1 | 0 | 0 | 0 | 0 |
Global Stabilization of Triangular Systems with Time-Delayed Dynamic Input Perturbations | A control design approach is developed for a general class of uncertain
strict-feedback-like nonlinear systems with dynamic uncertain input
nonlinearities with time delays. The system structure considered in this paper
includes a nominal uncertain strict-feedback-like subsystem, the input signal
to which is generated by an uncertain nonlinear input unmodeled dynamics that
is driven by the entire system state (including unmeasured state variables) and
is also allowed to depend on time delayed versions of the system state variable
and control input signals. The system also includes additive uncertain
nonlinear functions, coupled nonlinear appended dynamics, and uncertain dynamic
input nonlinearities with time-varying uncertain time delays. The proposed
control design approach provides a globally stabilizing delay-independent
robust adaptive output-feedback dynamic controller based on a dual dynamic
high-gain scaling based structure.
| 1 | 0 | 1 | 0 | 0 | 0 |
Multifractal Analysis of Pulsar Timing Residuals: Assessment of Gravitational Wave Detection | We introduce a pipeline including multifractal detrended cross-correlation
analysis (MF-DXA) modified by either singular value decomposition or the
adaptive method to examine the statistical properties of the pulsar timing
residual ($PTR$) induced by a gravitational wave (GW) signal. We propose a new
algorithm, the so-called irregular-MF-DXA, to deal with irregular data
sampling. Inspired by the quadrupolar nature of the spatial cross-correlation
function of a gravitational wave background, a new cross-correlation function,
$\bar{\sigma}_{\times}$, derived from irregular-MF-DXA will be introduced. We
show that, this measure reveals the quadrupolar signature in the $PTRs$ induced
by stochastic GWB. We propose four strategies based on the $y$-intercept of
fluctuation functions, the generalized Hurst exponent, and the width of the
singularity spectrum to determine the dimensionless amplitude and power-law
exponent of the characteristic strain spectrum as
$\mathcal{H}_c(f)\sim\mathcal{A}_{yr}(f/f_{yr})^{\zeta}$ for stochastic GWB.
Using the value of Hurst exponent, one can clarify the type of GWs. We apply
our pipeline to explore 20 millisecond pulsars observed by Parkes Pulsar Timing
Array. The computed scaling exponents confirm that all data are classified into
a nonstationary class implying the universality feature. The value of the Hurst
exponent is in the range $H\in [0.56,0.87]$. The $q$-dependency of the
generalized Hurst exponent demonstrates that the observed $PTRs$ have
multifractal behavior, and the source of this multifractality is mainly
attributed to the correlation of data which is another universality of the
observed datasets. Multifractal analysis of available $PTRs$ datasets reveals
an upper bound on the dimensionless amplitude of the GWB, $\mathcal{A}_{yr}<
2.0\times 10^{-15}$.
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Recovery of Bennu's Orientation for the OSIRIS-REx Mission: Implications for the Spin State Accuracy and Geolocation Errors | The goal of the OSIRIS-REx mission is to return a sample of asteroid material
from Near-Earth Asteroid (101955) Bennu. The role of the navigation and flight
dynamics team is critical for the spacecraft to execute a precisely planned
sampling maneuver over a specifically-selected landing site. In particular, the
orientation of Bennu needs to be recovered with good accuracy during orbital
operations to contribute as small an error as possible to the landing error
budget. Although Bennu is well characterized from Earth-based radar
observations, its orientation dynamics are not sufficiently known to exclude
the presence of a small wobble. To better understand this contingency and
evaluate how well the orientation can be recovered in the presence of a large
1$^{\circ}$ wobble, we conduct a comprehensive simulation with the NASA GSFC
GEODYN orbit determination and geodetic parameter estimation software. We
describe the dynamic orientation modeling implemented in GEODYN in support of
OSIRIS-REx operations, and show how both altimetry and imagery data can be used
as either undifferenced (landmark, direct altimetry) or differenced (image
crossover, altimetry crossover) measurements. We find that these two different
types of data contribute differently to the recovery of instrument pointing or
planetary orientation. When upweighted, the absolute measurements help reduce
the geolocation errors, despite poorer astrometric (inertial) performance. We
find that with no wobble present, all the geolocation requirements are met.
While the presence of a large wobble is detrimental, the recovery is still
reliable thanks to the combined use of altimetry and imagery data.
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Energy Scale of Lorentz Violation in Rainbow Gravity | We modify the standard relativistic dispersion relation in a way which breaks
Lorentz symmetry - the effect is predicted in a high-energy regime of some
modern theories of quantum gravity. We show that it is possible to realise this
scenario within the framework of Rainbow Gravity which introduces two new
energy-dependent functions $f_1(E)$ and $f_2(E)$ into the dispersion relation.
Additionally, we assume that the gravitational constant $G$ and the
cosmological constant $\Lambda$ also depend on energy $E$ and introduce the
scaling function $h(E)$ in order to express this dependence. For cosmological
applications we specify the functions $f_1$ and $f_2$ in order to fit massless
particles which allows us to derive modified cosmological equations. Finally,
by using Hubble+SNIa+BAO(BOSS+Lyman $\alpha$)+CMB data, we constrain the energy
scale $E_{LV}$ to be at least of the order of $10^{16}$ GeV at $1\sigma$ which
is the GUT scale or even higher $10^{17}$ GeV at $3\sigma$. Our claim is that
this energy can be interpreted as the decoupling scale of massless particles
from spacetime Lorentz violating effects.
| 0 | 1 | 0 | 0 | 0 | 0 |
How to construct wavelets on local fields of positive characteristic | We present an algorithm for construction step wavelets on local fields of
positive characteristic.
| 0 | 0 | 1 | 0 | 0 | 0 |
Fates of the dense cores formed by fragmentation of filaments: do they fragment again or not? | Fragmentation of filaments into dense cores is thought to be an important
step in forming stars. The bar-mode instability of spherically collapsing cores
found in previous linear analysis invokes a possibility of re-fragmentation of
the cores due to their ellipsoidal (prolate or oblate) deformation. To
investigate this possibility, here we perform three-dimensional
self-gravitational hydrodynamics simulations that follow all the way from
filament fragmentation to subsequent core collapse. We assume the gas is
polytropic with index \gamma, which determines the stability of the bar-mode.
For the case that the fragmentation of isolated hydrostatic filaments is
triggered by the most unstable fragmentation mode, we find the bar mode grows
as collapse proceeds if \gamma < 1.1, in agreement with the linear analysis.
However, it takes more than ten orders-of-magnitude increase in the central
density for the distortion to become non-linear. In addition to this fiducial
case, we also study non-fiducial ones such as the fragmentation is triggered by
a fragmentation mode with a longer wavelength and it occurs during radial
collapse of filaments and find the distortion rapidly grows. In most of
astrophysical applications, the effective polytropic index of collapsing gas
exceeds 1.1 before ten orders-of-magnitude increase in the central density.
Thus, supposing the fiducial case of filament fragmentation, re-fragmentation
of dense cores would not be likely and their final mass would be determined
when the filaments fragment.
| 0 | 1 | 0 | 0 | 0 | 0 |
Inference Related to Common Breaks in a Multivariate System with Joined Segmented Trends with Applications to Global and Hemispheric Temperatures | What transpires from recent research is that temperatures and radiative
forcing seem to be characterized by a linear trend with two changes in the rate
of growth. The first occurs in the early 60s and indicates a very large
increase in the rate of growth of both temperature and radiative forcing
series. This was termed as the "onset of sustained global warming". The second
is related to the more recent so-called hiatus period, which suggests that
temperatures and total radiative forcing have increased less rapidly since the
mid-90s compared to the larger rate of increase from 1960 to 1990. There are
two issues that remain unresolved. The first is whether the breaks in the slope
of the trend functions of temperatures and radiative forcing are common. This
is important because common breaks coupled with the basic science of climate
change would strongly suggest a causal effect from anthropogenic factors to
temperatures. The second issue relates to establishing formally via a proper
testing procedure that takes into account the noise in the series, whether
there was indeed a `hiatus period' for temperatures since the mid 90s. This is
important because such a test would counter the widely held view that the
hiatus is the product of natural internal variability. Our paper provides tests
related to both issues. The results show that the breaks in temperatures and
radiative forcing are common and that the hiatus is characterized by a
significant decrease in their rate of growth. The statistical results are of
independent interest and applicable more generally.
| 0 | 0 | 0 | 1 | 0 | 0 |
How to Stop Consensus Algorithms, locally? | This paper studies problems on locally stopping distributed consensus
algorithms over networks where each node updates its state by interacting with
its neighbors and decides by itself whether certain level of agreement has been
achieved among nodes. Since an individual node is unable to access the states
of those beyond its neighbors, this problem becomes challenging. In this work,
we first define the stopping problem for generic distributed algorithms. Then,
a distributed algorithm is explicitly provided for each node to stop consensus
updating by exploring the relationship between the so-called local and global
consensus. Finally, we show both in theory and simulation that its
effectiveness depends both on the network size and the structure.
| 1 | 0 | 0 | 0 | 0 | 0 |
Seoul National University Camera II (SNUCAM-II): The New SED Camera for the Lee Sang Gak Telescope (LSGT) | We present the characteristics and the performance of the new CCD camera
system, SNUCAM-II (Seoul National University CAMera system II) that was
installed on the Lee Sang Gak Telescope (LSGT) at the Siding Spring Observatory
in 2016. SNUCAM-II consists of a deep depletion chip covering a wide wavelength
from 0.3 {\mu}m to 1.1 {\mu}m with high sensitivity (QE at > 80% over 0.4 to
0.9 {\mu}m). It is equipped with the SDSS ugriz filters and 13 medium band
width (50 nm) filters, enabling us to study spectral energy distributions
(SEDs) of diverse objects from extragalactic sources to solar system objects.
On LSGT, SNUCAM-II offers 15.7 {\times} 15.7 arcmin field-of-view (FOV) at a
pixel scale of 0.92 arcsec and a limiting magnitude of g = 19.91 AB mag and
z=18.20 AB mag at 5{\sigma} with 180 sec exposure time for point source
detection.
| 0 | 1 | 0 | 0 | 0 | 0 |
A Bridge Between Hyperparameter Optimization and Larning-to-learn | We consider a class of a nested optimization problems involving inner and
outer objectives. We observe that by taking into explicit account the
optimization dynamics for the inner objective it is possible to derive a
general framework that unifies gradient-based hyperparameter optimization and
meta-learning (or learning-to-learn). Depending on the specific setting, the
variables of the outer objective take either the meaning of hyperparameters in
a supervised learning problem or parameters of a meta-learner. We show that
some recently proposed methods in the latter setting can be instantiated in our
framework and tackled with the same gradient-based algorithms. Finally, we
discuss possible design patterns for learning-to-learn and present encouraging
preliminary experiments for few-shot learning.
| 1 | 0 | 0 | 1 | 0 | 0 |
Accelerating Prototype-Based Drug Discovery using Conditional Diversity Networks | Designing a new drug is a lengthy and expensive process. As the space of
potential molecules is very large (10^23-10^60), a common technique during drug
discovery is to start from a molecule which already has some of the desired
properties. An interdisciplinary team of scientists generates hypothesis about
the required changes to the prototype. In this work, we develop an algorithmic
unsupervised-approach that automatically generates potential drug molecules
given a prototype drug. We show that the molecules generated by the system are
valid molecules and significantly different from the prototype drug. Out of the
compounds generated by the system, we identified 35 FDA-approved drugs. As an
example, our system generated Isoniazid - one of the main drugs for
Tuberculosis. The system is currently being deployed for use in collaboration
with pharmaceutical companies to further analyze the additional generated
molecules.
| 0 | 0 | 0 | 1 | 0 | 0 |
Convex and non-convex regularization methods for spatial point processes intensity estimation | This paper deals with feature selection procedures for spatial point
processes intensity estimation. We consider regularized versions of estimating
equations based on Campbell theorem derived from two classical functions:
Poisson likelihood and logistic regression likelihood. We provide general
conditions on the spatial point processes and on penalty functions which ensure
consistency, sparsity and asymptotic normality. We discuss the numerical
implementation and assess finite sample properties in a simulation study.
Finally, an application to tropical forestry datasets illustrates the use of
the proposed methods.
| 0 | 0 | 1 | 1 | 0 | 0 |
Glass Transition in Supercooled Liquids with Medium Range Crystalline Order | The origins of rapid dynamical slow down in glass forming liquids in the
growth of static length scales, possibly associated with identifiable
structural ordering, is a much debated issue. Growth of medium range
crystalline order (MRCO) has been observed in various model systems to be
associated with glassy behaviour. Such observations raise the question about
the eventual state reached by a glass former, if allowed to relax for
sufficiently long times. Is a slowly growing crystalline order responsible for
slow dynamics? Are the molecular mechanisms for glass transition in liquids
with and without MRCO the same? If yes, glass formers with MRCO provide a
paradigm for understanding glassy behaviour generically. If not, systems with
MRCO form a new class of glass forming materials whose molecular mechanism for
slow dynamics may be easier to understand in terms of growing crystalline
order, and should be approached in that manner, even while they will not
provide generic insights. In this study we perform extensive molecular dynamics
simulations of a number of glass forming liquids in two dimensions and show
that the static and dynamic properties of glasses with MRCO are different from
other glass forming liquids with no predominant local order. We also resolve an
important issue regarding the so-called Point-to-set method for determining
static length scales, and demonstrate it to be a robust, order agnostic, method
for determining static correlation lengths in glass formers.
| 0 | 1 | 0 | 0 | 0 | 0 |
Natural and Artificial Spectral Edges in Exoplanets | Technological civilizations may rely upon large-scale photovoltaic arrays to
harness energy from their host star. Photovoltaic materials, such as silicon,
possess distinctive spectral features, including an "artificial edge" that is
characteristically shifted in wavelength shortwards of the "red edge" of
vegetation. Future observations of reflected light from exoplanets would be
able to detect both natural and artificial edges photometrically, if a
significant fraction of the planet's surface is covered by vegetation or
photovoltaic arrays respectively. The stellar energy thus tapped can be
utilized for terraforming activities by transferring heat and light from the
day side to the night side on tidally locked exoplanets, thereby producing
detectable artifacts.
| 0 | 1 | 0 | 0 | 0 | 0 |
The damage inflicted by a computer virus: A new estimation method | This paper addressed the issue of estimating the damage caused by a computer
virus. First, an individual-level delayed SIR model capturing the spreading
process of a digital virus is derived. Second, the damage inflicted by the
virus is modeled as the sum of the economic losses and the cost for developing
the antivirus. Next, the impact of different factors, including the delay and
the network structure, on the damage is explored by means of computer
simulations. Thereby some measures of reducing the damage of a virus are
recommended. To our knowledge, this is the first time the antivirus-developing
cost is taken into account when estimating the damage of a virus.
| 1 | 1 | 0 | 0 | 0 | 0 |
Deep Fault Analysis and Subset Selection in Solar Power Grids | Non-availability of reliable and sustainable electric power is a major
problem in the developing world. Renewable energy sources like solar are not
very lucrative in the current stage due to various uncertainties like weather,
storage, land use among others. There also exists various other issues like
mis-commitment of power, absence of intelligent fault analysis, congestion,
etc. In this paper, we propose a novel deep learning-based system for
predicting faults and selecting power generators optimally so as to reduce
costs and ensure higher reliability in solar power systems. The results are
highly encouraging and they suggest that the approaches proposed in this paper
have the potential to be applied successfully in the developing world.
| 1 | 0 | 0 | 1 | 0 | 0 |
Hirzebruch L-polynomials and multiple zeta values | We express the coefficients of the Hirzebruch L-polynomials in terms of
certain alternating multiple zeta values. In particular, we show that every
monomial in the Pontryagin classes appears with a non-zero coefficient, with
the expected sign. Similar results hold for the polynomials associated to the
A-hat genus.
| 0 | 0 | 1 | 0 | 0 | 0 |
On Nontrivial Zeros of Riemann Zeta Function | Let {\Xi} be a function relating to the Riemann zeta function with . In this
paper, we construct a function containing and {\Xi} , and prove that satisfies
a nonadjoint boundary value problem to a nonsingular differential equation if
is any nontrivial zero of {\Xi} . Inspecting properties of and using known
results of nontrivial zeros of , we derive that nontrivial zeros of all have
real part equal to , which concludes that Riemann Hypothesis is true.
| 0 | 0 | 1 | 0 | 0 | 0 |
The reliability of a nutritional meta-analysis study | Background: Many researchers have studied the relationship between diet and
health. There are papers showing an association between the consumption of
sugar-sweetened beverages and Type 2 diabetes. Many meta-analyses use
individual studies that do not adjust for multiple testing or multiple modeling
and thus provide biased estimates of effect. Hence the claims reported in a
meta-analysis paper may be unreliable if the primary papers do not ensure
unbiased estimates of effect. Objective: Determine the statistical reliability
of 10 papers and indirectly the reliability of the meta-analysis study. Method:
Ten primary papers used in a meta-analysis paper and counted the numbers of
outcomes, predictors, and covariates. We estimated the size of the potential
analysis search space available to the authors of these papers; i.e. the number
of comparisons and models available. Since we noticed that there were
differences between predictors and covariates cited in the abstract and in the
text, we applied this formula to information found in the abstracts, Space A,
as well as the text, Space T, of each primary paper. Results: The median and
range of the number of comparisons possible across the primary papers are 6.5
and (2-12,288) for abstracts, and 196,608 and (3,072-117,117,952) the texts.
Note that the median of 6.5 for Space A is misleading as each primary study has
60-165 foods not mentioned in the abstract. Conclusion: Given that testing is
at the 0.05 level and the number of comparisons is very large, nominal
statistical significance is very weak support for a claim. The claims in these
papers are not statistically supported and hence are unreliable. Thus, the
claims of the meta-analysis paper lack evidentiary confirmation.
| 0 | 0 | 0 | 1 | 0 | 0 |
Composite Fermions on a Torus | We achieve an explicit construction of the lowest Landau level (LLL)
projected wave functions for composite fermions in the periodic (torus)
geometry. To this end, we first demonstrate how the vortex attachment of the
composite fermion (CF) theory can be accomplished in the torus geometry to
produce the "unprojected" wave functions satisfying the correct
(quasi-)periodic boundary conditions. We then consider two methods for
projecting these wave functions into the LLL. The direct projection produces
valid wave functions but can be implemented only for very small systems. The
more powerful and more useful projection method of Jain and Kamilla fails in
the torus geometry because it does not preserve the periodic boundary
conditions and thus takes us out of the original Hilbert space. We have
succeeded in constructing a modified projection method that is consistent with
both the periodic boundary conditions and the general structure of the CF
theory. This method is valid for a large class of states of composite fermions,
called "proper states," which includes the incompressible ground states at
electron filling factors $\nu=\frac{n}{2pn+ 1}$, their charged and neutral
excitations, and also the quasidegenerate ground states at arbitrary filling
factors of the form $\nu=\frac{\nu^*}{2p\nu^*+ 1}$, where $n$ and $p$ are
integers and $\nu^*$ is the CF filling factor. Comparison with exact results
known for small systems for the ground and excited states at filling factors
$\nu=1/3$, 2/5 and 3/7 demonstrates our LLL-projected wave functions to be
extremely accurate representations of the actual Coulomb eigenstates. Our
construction enables the study of large systems of composite fermions on the
torus, thereby opening the possibility of investigating numerous interesting
questions and phenomena.
| 0 | 1 | 0 | 0 | 0 | 0 |
ROCKER: A Refinement Operator for Key Discovery | The Linked Data principles provide a decentral approach for publishing
structured data in the RDF format on the Web. In contrast to structured data
published in relational databases where a key is often provided explicitly,
finding a set of properties that allows identifying a resource uniquely is a
non-trivial task. Still, finding keys is of central importance for manifold
applications such as resource deduplication, link discovery, logical data
compression and data integration. In this paper, we address this research gap
by specifying a refinement operator, dubbed ROCKER, which we prove to be
finite, proper and non-redundant. We combine the theoretical characteristics of
this operator with two monotonicities of keys to obtain a time-efficient
approach for detecting keys, i.e., sets of properties that describe resources
uniquely. We then utilize a hash index to compute the discriminability score
efficiently. Therewith, we ensure that our approach can scale to very large
knowledge bases. Results show that ROCKER yields more accurate results, has a
comparable runtime, and consumes less memory w.r.t. existing state-of-the-art
techniques.
| 1 | 0 | 0 | 0 | 0 | 0 |
Double-slit Fraunhofer pattern as the signature of the Josephson effect between Berezinskii superconductors through the ferromagnetic vortex | I apply the recently developed formalism of generalized quasiclassical theory
to show that using hybrid superconducting systems with non-collinear strong
ferromagnets one can realize the Josephson junction between Berezinskii-type
superconductors. The reported calculation reproduces main features observed in
the recent experiment, namely the the slightly asymmetric double-slit
Fraunhofer interference pattern of the Josephson current through the
ferromagnetic vortex. The double-slit structure results from the spatially
inhomogeneous Berezinskii state with the amplitude controlled by the local
angle between magnetic moments in two ferromagnetic layers. The critical
current asymmetry by the sign of magnetic field can signal the presence of
spontaneous supercurrents generated by the non-coplanar magnetic texture near
the core of the ferromagnetic vortex core. I demonstrate that ferromagnetic
vortex can induce spontaneous vorticity in the odd-frequency order parameter
manifesting the possibility of the emergent magnetic field to create
topological defects.
| 0 | 1 | 0 | 0 | 0 | 0 |
A class of differential quadratic algebras and their symmetries | We study a multi-parametric family of quadratic algebras in four generators,
which includes coordinate algebras of noncommutative four-planes and, as
quotient algebras, noncommutative three spheres. Particular subfamilies
comprise Sklyanin algebras and Connes--Dubois-Violette planes. We determine
quantum groups of symmetries for the general algebras and construct
finite-dimensional covariant differential calculi.
| 0 | 0 | 1 | 0 | 0 | 0 |
Introduction to compact and discrete quantum groups | These are notes from introductory lectures at the graduate school
"Topological Quantum Groups" in Będlewo (June 28--July 11, 2015). The notes
present the passage from Hopf algebras to compact quantum groups and sketch the
notion of discrete quantum groups viewed as duals of compact quantum groups.
| 0 | 0 | 1 | 0 | 0 | 0 |
An optimization approach to adaptive multi-dimensional capital management | Firms should keep capital to offer sufficient protection against the risks
they are facing. In the insurance context methods have been developed to
determine the minimum capital level required, but less so in the context of
firms with multiple business lines including allocation. The individual capital
reserve of each line can be represented by means of classical models, such as
the conventional Cramér-Lundberg model, but the challenge lies in soundly
modelling the correlations between the business lines. We propose a simple yet
versatile approach that allows for dependence by introducing a common
environmental factor. We present a novel Bayesian approach to calibrate the
latent environmental state distribution based on observations concerning the
claim processes. The calibration approach is adjusted for an environmental
factor that changes over time. The convergence of the calibration procedure
towards the true environmental state is deduced. We then point out how to
determine the optimal initial capital of the different business lines under
specific constraints on the ruin probability of subsets of business lines. Upon
combining the above findings, we have developed an easy-to-implement approach
to capital risk management in a multi-dimensional insurance risk model.
| 0 | 0 | 0 | 0 | 0 | 1 |
Low Energy Phonons in $Bi_2Sr_2CaCu_2O_{8+δ}$ and their Possible Interaction with Electrons Measured by Inelastic Neutron Scattering | Angle-resolved photoemission (ARPES) experiments on copper oxide
superconductors revealed enigmatic kinks in electronic dispersions near 10 meV
presumably due to phonons or impuritites. We used inelastic neutron scattering
to measure phonon branches below 15 meV in a large single crystal sample of
optimally-doped $Bi_2Sr_2CaCu_2O_{8+\delta}$ (BSCCO). The high quality dataset
covered several Brilloiun zones with different final energies. In addition to
acoustic branches, optic branches disperse from 4 meV and 7 meV zone center
energies. The 4 meV branch interacts with acoustic phonons at small
wavevectors, which destroys the LA character of the acoustic branch beyond
~0.15 reciprocal lattice units. We propose a mechanism that explains the low
energy electronic dispersion features based on this observation.
| 0 | 1 | 0 | 0 | 0 | 0 |
Spectral properties of complex Airy operator on the semi-axis | We prove the theorem on the completeness of the root functions of the
Schroedinger operator $L=-d^2/dx^2+p(x)$ on the semi-axis $\mathbb R_+$ with a
complex--valued potential $p(x)$. It is assumed that the potential $p = q \pm
ir$ is such that the real functions $q$ and $r$ are subject the conditions $$
q(x) \geqslant c r(x), \quad r(x) \geqslant c_0+ c_1 x^\alpha, \quad \alpha >0,
$$ where the constants $c, \ c_0\in \mathbb R$, $c_1>0$ and $\arg(\pm i+c) <
2\alpha\pi/(2+\alpha)$. For the case of the Airy operator $L_c=-d^2/dx^2+cx$,
$c=const$, this theorem imply the completeness of the system of the
eigenfunctions of this operator if $|\arg c|<2\pi/3$. Using another technique
based on the asymptotic behavior of the Airy functions we prove that the
completeness theorem for the operator $L_c$ remains valid, provided that $|\arg
c|<5\pi/6$.
| 0 | 0 | 1 | 0 | 0 | 0 |
Webs and $q$-Howe dualities in types $\mathbf{B}\mathbf{C}\mathbf{D}$ | We define web categories describing intertwiners for the orthogonal and
symplectic Lie algebras, and, in the quantized setup, for certain orthogonal
and symplectic coideal subalgebras. They generalize the Brauer category, and
allow us to prove quantum versions of some classical type
$\mathbf{B}\mathbf{C}\mathbf{D}$ Howe dualities.
| 0 | 0 | 1 | 0 | 0 | 0 |
Structural Controllability of Linear Time-invariant Systems | One version of the concept of structural controllability defined for
single-input systems by Lin and subsequently generalized to multi-input systems
by others, states that a parameterized matrix pair $(A, B)$ whose nonzero
entries are distinct parameters, is structurally controllable if values can be
assigned to the parameters which cause the resulting matrix pair to be
controllable. In this paper the concept of structural controllability is
broadened to allow for the possibility that a parameter may appear in more than
one location in the pair $(A, B)$. Subject to a certain condition on the
parameterization called the "binary assumption", an explicit graph-theoretic
characterization of such matrix pairs is derived.
| 1 | 0 | 0 | 0 | 0 | 0 |
Structure of martingale transports in finite dimensions | We study the structure of martingale transports in finite dimensions. We
consider the family $\mathcal{M}(\mu,\nu) $ of martingale measures on
$\mathbb{R}^N \times \mathbb{R}^N$ with given marginals $\mu,\nu$, and
construct a family of relatively open convex sets $\{C_x:x\in \mathbb{R}^N \}$,
which forms a partition of $\mathbb{R}^N$, and such that any martingale
transport in $\mathcal{M}(\mu,\nu) $ sends mass from $x$ to within
$\overline{C_x}$, $\mu(dx)$--a.e. Our results extend the analogous
one-dimensional results of M. Beiglböck and N. Juillet (2016) and M.
Beiglböck, M. Nutz, and N. Touzi (2015). We conjecture that the decomposition
is canonical and minimal in the sense that it allows to characterise the
martingale polar sets, i.e. the sets which have zero mass under all measures in
$\mathcal{M}(\mu,\nu)$, and offers the martingale analogue of the
characterisation of transport polar sets proved in M. Beiglböck, M.
Goldstern, G. Maresch, and W. Schachermayer (2009).
| 0 | 0 | 1 | 0 | 0 | 0 |
Simplifying branched covering surface-knots by chart moves involving black vertices | A branched covering surface-knot is a surface-knot in the form of a branched
covering over an oriented surface-knot $F$, where we include the case when the
covering has no branch points. A branched covering surface-knot is presented by
a graph called a chart on a surface diagram of $F$. We can simplify a branched
covering surface-knot by an addition of 1-handles with chart loops to a form
such that its chart is the union of free edges and 1-handles with chart loops.
We investigate properties of such simplifications for the case when branched
covering surface-knots have a non-zero number of branch points, using chart
moves involving black vertices.
| 0 | 0 | 1 | 0 | 0 | 0 |
$K$-surfaces with free boundaries | A well-known question in classical differential geometry and geometric
analysis asks for a description of possible boundaries of $K$-surfaces, which
are smooth, compact hypersurfaces in $\mathbb{R}^d$ having constant Gauss
curvature equal to $K \geq 0$. This question generated a considerable amount of
remarkable results in the last few decades. Motivated by these developments
here we study the question of determining a $K$-surface when only part of its
boundary is fixed, and in addition the surface hits a given manifold at some
fixed angle. While this general setting is out of reach for us at the present,
we settle a model case of the problem, which in its analytic formulation
reduces to a Bernoulli type free boundary problem for the Monge-Ampère
equation. We study both the cases of 0-curvature and of positive curvature. The
formulation of the free boundary condition and its regularity are the most
delicate and challenging questions addressed in this work. In this regard we
introduce a notion of a Blaschke extension of a solution which might be of
independent interest.
The problem we study can also be interpreted as the Alt-Caffarelli problem
for the Monge-Ampère equation. Moreover, it also relates to the problem of
isometric embedding of a positive metric on the annulus with partially
prescribed boundary and optimal transport with free mass.
| 0 | 0 | 1 | 0 | 0 | 0 |
The graphs of join-semilattices and the shape of congruence lattices of particle lattices | We attach to each $\langle 0, \vee \rangle$-semilattice a graph
$\boldsymbol{G}_{\boldsymbol{S}}$ whose vertices are join-irreducible elements
of $\boldsymbol{S}$ and whose edges correspond to the reflexive dependency
relation. We study properties of the graph $\boldsymbol{G}_{\boldsymbol{S}}$
both when $\boldsymbol{S}$ is a join-semilattice and when it is a lattice. We
call a $\langle 0, \vee \rangle$-semilattice $\boldsymbol{S}$ particle provided
that the set of its join-irreducible elements join-generates $\boldsymbol{S}$
and it satisfies DCC. We prove that the congruence lattice of a particle
lattice is anti-isomorphic to the lattice of hereditary subsets of the
corresponding graph that are closed in a certain zero-dimensional topology.
Thus we extend the result known for principally chain finite lattices.
| 0 | 0 | 1 | 0 | 0 | 0 |
Optimal Quasi-Gray Codes: The Alphabet Matters | A quasi-Gray code of dimension $n$ and length $\ell$ over an alphabet
$\Sigma$ is a sequence of distinct words $w_1,w_2,\dots,w_\ell$ from $\Sigma^n$
such that any two consecutive words differ in at most $c$ coordinates, for some
fixed constant $c>0$. In this paper we are interested in the read and write
complexity of quasi-Gray codes in the bit-probe model, where we measure the
number of symbols read and written in order to transform any word $w_i$ into
its successor $w_{i+1}$.
We present construction of quasi-Gray codes of dimension $n$ and length $3^n$
over the ternary alphabet $\{0,1,2\}$ with worst-case read complexity $O(\log
n)$ and write complexity $2$. This generalizes to arbitrary odd-size alphabets.
For the binary alphabet, we present quasi-Gray codes of dimension $n$ and
length at least $2^n - 20n$ with worst-case read complexity $6+\log n$ and
write complexity $2$. This complements a recent result by Raskin [Raskin '17]
who shows that any quasi-Gray code over binary alphabet of length $2^n$ has
read complexity $\Omega(n)$.
Our results significantly improve on previously known constructions and for
the odd-size alphabets we break the $\Omega(n)$ worst-case barrier for
space-optimal (non-redundant) quasi-Gray codes with constant number of writes.
We obtain our results via a novel application of algebraic tools together with
the principles of catalytic computation [Buhrman et al. '14, Ben-Or and Cleve
'92, Barrington '89, Coppersmith and Grossman '75].
| 1 | 0 | 0 | 0 | 0 | 0 |
Revisiting the pre-main-sequence evolution of stars I. Importance of accretion efficiency and deuterium abundance | Recent theoretical work has shown that the pre-main-sequence (PMS) evolution
of stars is much more complex than previously envisioned. Instead of the
traditional steady, one-dimensional solution, accretion may be episodic and not
necessarily symmetrical, thereby affecting the energy deposited inside the star
and its interior structure. Given this new framework, we want to understand
what controls the evolution of accreting stars. We use the MESA stellar
evolution code with various sets of conditions. In particular, we account for
the (unknown) efficiency of accretion in burying gravitational energy into the
protostar through a parameter, $\xi$, and we vary the amount of deuterium
present. We confirm the findings of previous works that the evolution changes
significantly with the amount of energy that is lost during accretion. We find
that deuterium burning also regulates the PMS evolution. In the low-entropy
accretion scenario, the evolutionary tracks in the H-R diagram are
significantly different from the classical tracks and are sensitive to the
deuterium content. A comparison of theoretical evolutionary tracks and
observations allows us to exclude some cold accretion models ($\xi\sim 0$) with
low deuterium abundances. We confirm that the luminosity spread seen in
clusters can be explained by models with a somewhat inefficient injection of
accretion heat. The resulting evolutionary tracks then become sensitive to the
accretion heat efficiency, initial core entropy, and deuterium content. In this
context, we predict that clusters with a higher D/H ratio should have less
scatter in luminosity than clusters with a smaller D/H. Future work on this
issue should include radiation-hydrodynamic simulations to determine the
efficiency of accretion heating and further observations to investigate the
deuterium content in star-forming regions. (abbrev.)
| 0 | 1 | 0 | 0 | 0 | 0 |
Surface-assisted carrier excitation in plasmonic nanostructure | We present a quantum-mechanical model for surface-assisted carrier excitation
by optical fields in plasmonic nanostructures of arbitrary shape. We derive an
explicit expression, in terms of local fields inside the metal structure, for
surface absorbed power and surface scattering rate that determine the
enhancement of carrier excitation efficiency near the metal-dielectric
interface. We show that surface scattering is highly sensitive to the local
field polarization, and can be incorporated into metal dielectric function
along with phonon and impurity scattering. We also show that the obtained
surface scattering rate describes surface-assisted plasmon decay (Landau
damping) in nanostructures larger than the nonlocality scale. Our model can be
used for calculations of plasmon-assisted hot carrier generation rates in
photovoltaics and photochemistry applications.
| 0 | 1 | 0 | 0 | 0 | 0 |
Existence of global weak solutions to the kinetic Hookean dumbbell model for incompressible dilute polymeric fluids | We explore the existence of global weak solutions to the Hookean dumbbell
model, a system of nonlinear partial differential equations that arises from
the kinetic theory of dilute polymers, involving the unsteady incompressible
Navier--Stokes equations in a bounded domain in two or three space dimensions,
coupled to a Fokker--Planck-type parabolic equation. We prove the existence of
large-data global weak solutions in the case of two space dimensions.
Indirectly, our proof also rigorously demonstrates that, in two space
dimensions at least, the Oldroyd-B model is the macroscopic closure of the
Hookean dumbbell model. In three space dimensions, we prove the existence of
large-data global weak subsolutions to the model, which are weak solutions with
a defect measure, where the defect measure appearing in the Navier--Stokes
momentum equation is the divergence of a symmetric positive semidefinite
matrix-valued Radon measure.
| 0 | 0 | 1 | 0 | 0 | 0 |
Tight Bounds for Online Coloring of Basic Graph Classes | We resolve a number of long-standing open problems in online graph coloring.
More specifically, we develop tight lower bounds on the performance of online
algorithms for fundamental graph classes. An important contribution is that our
bounds also hold for randomized online algorithms, for which hardly any results
were known. Technically, we construct lower bounds for chordal graphs. The
constructions then allow us to derive results on the performance of randomized
online algorithms for the following further graph classes: trees, planar,
bipartite, inductive, bounded-treewidth and disk graphs. It shows that the best
competitive ratio of both deterministic and randomized online algorithms is
$\Theta(\log n)$, where $n$ is the number of vertices of a graph. Furthermore,
we prove that this guarantee cannot be improved if an online algorithm has a
lookahead of size $O(n/\log n)$ or access to a reordering buffer of size
$n^{1-\epsilon}$, for any $0<\epsilon\leq 1$. A consequence of our results is
that, for all of the above mentioned graph classes except bipartite graphs, the
natural $\textit{First Fit}$ coloring algorithm achieves an optimal
performance, up to constant factors, among deterministic and randomized online
algorithms.
| 1 | 0 | 0 | 0 | 0 | 0 |
Comparison of PCA with ICA from data distribution perspective | We performed an empirical comparison of ICA and PCA algorithms by applying
them on two simulated noisy time series with varying distribution parameters
and level of noise. In general, ICA shows better results than PCA because it
takes into account higher moments of data distribution. On the other hand, PCA
remains quite sensitive to the level of correlations among signals.
| 0 | 0 | 0 | 1 | 0 | 0 |
The Special Polarization Characteristic Features of a Three-Dimensional Terahertz Photonic Crystal with a Silicon Inverse Diamond Structure | The band structure of a Si inverse diamond structure whose lattice point
shape was vacant regular octahedrons was calculated using plane wave expansion
method and a complete photonic band gap was theoretically confirmed at around
0.4 THz. It is said that three-dimensional photonic crystals have no
polarization anisotropy in photonic band gap (stop gap, stop band) of high
symmetry points in normal incidence. However, it was experimentally confirmed
that the polarization orientation of a reflected light was different from that
of a incident light, {I(X,Y)}, where (X,Y) is the coordinate system fixed in
the photonic crystal. It was studied on a plane (001) at around X point's
photonic band gap (0.36 - 0.44 THz) for incident light direction [001]
($\Gamma$-X direction) by rotating a sample in the plane (001), relatively. The
polarization orientation of the reflected light was parallel to that of the
incident light for the incident polarization orientation I(1,1), I(1,-1). In
contrast, the former was perpendicular to the latter for the incident
polarization orientation I(1,0), I(0,-1) in the vicinity of 0.38 THz. As far as
the photonic crystal in this work is concerned, method of resolution and
synthesis of the incident polarization vector isn't apparently able to apply to
the analysis of experimental results.
| 0 | 1 | 0 | 0 | 0 | 0 |
Toward Finding Latent Cities with Non-Negative Matrix Factorization | In the last decade, digital footprints have been used to cluster population
activity into functional areas of cities.
However, a key aspect has been overlooked: we experience our cities not only
by performing activities at specific destinations, but also by moving from one
place to another.
In this paper, we propose to analyze and cluster the city based on how people
move through it. Particularly, we introduce Mobilicities, automatically
generated travel patterns inferred from mobile phone network data using NMF, a
matrix factorization model.
We evaluate our method in a large city and we find that mobilicities reveal
latent but at the same time interpretable mobility structures of the city. Our
results provide evidence on how clustering and visualization of aggregated
phone logs could be used in planning systems to interactively analyze city
structure and population activity.
| 1 | 0 | 0 | 0 | 0 | 0 |
Time-Sensitive Networking for robotics | We argue that Time-Sensitive Networking (TSN) will become the de facto
standard for real-time communications in robotics. We present a review and
classification of the different communication standards which are relevant for
the field and introduce the typical problems with traditional switched Ethernet
networks. We discuss some of the TSN features relevant for deterministic
communications and evaluate experimentally one of the shaping mechanisms in an
exemplary robotic scenario. In particular, and based on our results, we claim
that many of the existing real-time industrial solutions will slowly be
replaced by TSN. And that this will lead towards a unified landscape of
physically interoperable robot and robot components.
| 1 | 0 | 0 | 0 | 0 | 0 |
Active Orthogonal Matching Pursuit for Sparse Subspace Clustering | Sparse Subspace Clustering (SSC) is a state-of-the-art method for clustering
high-dimensional data points lying in a union of low-dimensional subspaces.
However, while $\ell_1$ optimization-based SSC algorithms suffer from high
computational complexity, other variants of SSC, such as Orthogonal Matching
Pursuit-based SSC (OMP-SSC), lose clustering accuracy in pursuit of improving
time efficiency. In this letter, we propose a novel Active OMP-SSC, which
improves clustering accuracy of OMP-SSC by adaptively updating data points and
randomly dropping data points in the OMP process, while still enjoying the low
computational complexity of greedy pursuit algorithms. We provide heuristic
analysis of our approach, and explain how these two active steps achieve a
better tradeoff between connectivity and separation. Numerical results on both
synthetic data and real-world data validate our analyses and show the
advantages of the proposed active algorithm.
| 1 | 0 | 0 | 1 | 0 | 0 |
Experimental and theoretical study of AC losses in variable asymmetrical magnetic environments | Measurements of AC losses in a HTS-tape placed in between of two bulk
magnetic shields of high permeability were performed by applying calorimetric
techniques for various asymmetrical shielding arrangements. The experiment was
supported by analytical calculations and finite-element simulations of the
field and current distributions, based on the Bean model of the critical state.
The simulated current and field profiles perfectly reproduce the analytic
solutions known for certain shielding geometries. The evaluation of the
consequent AC losses exhibits good agreement with measurements for the central
position of the tape between the magnets but increasing discrepancy when the
tape is approaching the shields. This can be explained by the increasing
contribution of the eddy currents and magnetic hysteresis losses in the
conducting shields.
| 0 | 1 | 0 | 0 | 0 | 0 |
Robustness of semiparametric efficiency in nearly-true models for two-phase samples | We examine the performance of efficient and AIPW estimators under two-phase
sampling when the complete-data model is nearly correctly specified, in the
sense that the misspecification is not reliably detectable from the data by any
possible diagnostic or test. Asymptotic results for these nearly true models
are obtained by representing them as sequences of misspecified models that are
mutually contiguous with a correctly specified model. We find that for the
least-favourable direction of model misspecification the bias in the efficient
estimator induced can be comparable to the extra variability in the AIPW
estimator, so that the mean squared error of the efficient estimator is no
longer lower. This can happen when the most-powerful test for the model
misspecification still has modest power. We verify that the theoretical results
agree with simulation in three examples: a simple informative-sampling model
for a Normal mean, logistic regression in the classical case-control design,
and linear regression in a two-phase design.
| 0 | 0 | 1 | 1 | 0 | 0 |
A* CCG Parsing with a Supertag and Dependency Factored Model | We propose a new A* CCG parsing model in which the probability of a tree is
decomposed into factors of CCG categories and its syntactic dependencies both
defined on bi-directional LSTMs. Our factored model allows the precomputation
of all probabilities and runs very efficiently, while modeling sentence
structures explicitly via dependencies. Our model achieves the state-of-the-art
results on English and Japanese CCG parsing.
| 1 | 0 | 0 | 0 | 0 | 0 |
Numerical studies of Thompson's group F and related groups | We have developed polynomial-time algorithms to generate terms of the
cogrowth series for groups $\mathbb{Z}\wr \mathbb{Z},$ the lamplighter group,
$(\mathbb{Z}\wr \mathbb{Z})\wr \mathbb{Z}$ and the Navas-Brin group $B.$ We
have also given an improved algorithm for the coefficients of Thompson's group
$F,$ giving 32 terms of the cogrowth series. We develop numerical techniques to
extract the asymptotics of these various cogrowth series. We present improved
rigorous lower bounds on the growth-rate of the cogrowth series for Thompson's
group $F$ using the method from \cite{HHR15} applied to our extended series. We
also generalise their method by showing that it applies to loops on any locally
finite graph. Unfortunately, lower bounds less than 16 do not help in
determining amenability.
Again for Thompson's group $F$ we prove that, if the group is amenable, there
cannot be a sub-dominant stretched exponential term in the
asymptotics\footnote{ }. Yet the numerical data provides compelling evidence
for the presence of such a term. This observation suggests a potential path to
a proof of non-amenability: If the universality class of the cogrowth sequence
can be determined rigorously, it will likely prove non-amenability.
We estimate the asymptotics of the cogrowth coefficients of $F$ to be $$ c_n
\sim c \cdot \mu^n \cdot \kappa^{n^\sigma \log^\delta{n}} \cdot n^g,$$ where
$\mu \approx 15,$ $\kappa \approx 1/e,$ $\sigma \approx 1/2,$ $\delta \approx
1/2,$ and $g \approx -1.$ The growth constant $\mu$ must be 16 for amenability.
These two approaches, plus a third based on extrapolating lower bounds, support
the conjecture \cite{ERvR15, HHR15} that the group is not amenable.
| 0 | 0 | 1 | 0 | 0 | 0 |
The modularity of action and perception revisited using control theory and active inference | The assumption that action and perception can be investigated independently
is entrenched in theories, models and experimental approaches across the brain
and mind sciences. In cognitive science, this has been a central point of
contention between computationalist and 4Es (enactive, embodied, extended and
embedded) theories of cognition, with the former embracing the "classical
sandwich", modular, architecture of the mind and the latter actively denying
this separation can be made. In this work we suggest that the modular
independence of action and perception strongly resonates with the separation
principle of control theory and furthermore that this principle provides formal
criteria within which to evaluate the implications of the modularity of action
and perception. We will also see that real-time feedback with the environment,
often considered necessary for the definition of 4Es ideas, is not however a
sufficient condition to avoid the "classical sandwich". Finally, we argue that
an emerging framework in the cognitive and brain sciences, active inference,
extends ideas derived from control theory to the study of biological systems
while disposing of the separation principle, describing non-modular models of
behaviour strongly aligned with 4Es theories of cognition.
| 0 | 0 | 0 | 0 | 1 | 0 |
Clique-based Method for Social Network Clustering | In this article, we develop a clique-based method for social network
clustering. We introduce a new index to evaluate the quality of clustering
results, and propose an efficient algorithm based on recursive bipartition to
maximize an objective function of the proposed index. The optimization problem
is NP-hard, so we approximate the semi-optimal solution via an implicitly
restarted Lanczos method. One of the advantages of our algorithm is that the
proposed index of each community in the clustering result is guaranteed to be
higher than some predetermined threshold, $p$, which is completely controlled
by users. We also account for the situation that $p$ is unknown. A statistical
procedure of controlling both under-clustering and over-clustering errors
simultaneously is carried out to select localized threshold for each
subnetwork, such that the community detection accuracy is optimized.
Accordingly, we propose a localized clustering algorithm based on binary tree
structure. Finally, we exploit the stochastic blockmodels to conduct simulation
studies and demonstrate the accuracy and efficiency of our algorithms, both
numerically and graphically.
| 1 | 0 | 0 | 1 | 0 | 0 |
Fermionic Matrix Product States and One-Dimensional Short-Range Entangled Phases with Anti-Unitary Symmetries | We extend the formalism of Matrix Product States (MPS) to describe
one-dimensional gapped systems of fermions with both unitary and anti-unitary
symmetries. Additionally, systems with orientation-reversing spatial symmetries
are considered. The short-ranged entangled phases of such systems are
classified by three invariants, which characterize the projective action of the
symmetry on edge states. We give interpretations of these invariants as
properties of states on the closed chain. The relationship between fermionic
MPS systems at an RG fixed point and equivariant algebras is exploited to
derive a group law for the stacking of fermionic phases. The result generalizes
known classifications to symmetry groups that are non-trivial extensions of
fermion parity and time-reversal.
| 0 | 1 | 0 | 0 | 0 | 0 |
How tracer particles sample the complexity of turbulence | On their roller coaster ride through turbulence, tracer particles sample the
fluctuations of the underlying fields in space and time. Quantitatively
relating particle and field statistics remains a fundamental challenge in a
large variety of turbulent flows. We quantify how tracer particles sample
turbulence by expressing their temporal velocity fluctuations in terms of an
effective probabilistic sampling of spatial velocity field fluctuations. To
corroborate our theory, we investigate an extensive suite of direct numerical
simulations of hydrodynamic turbulence covering a Taylor-scale Reynolds number
range from 150 to 430. Our approach allows the assessment of particle
statistics from the knowledge of flow field statistics only, therefore opening
avenues to a new generation of models for transport in complex flows.
| 0 | 1 | 0 | 0 | 0 | 0 |
Rare Nash Equilibria and the Price of Anarchy in Large Static Games | We study a static game played by a finite number of agents, in which agents
are assigned independent and identically distributed random types and each
agent minimizes its objective function by choosing from a set of admissible
actions that depends on its type. The game is anonymous in the sense that the
objective function of each agent depends on the actions of other agents only
through the empirical distribution of their type-action pairs. We study the
asymptotic behavior of Nash equilibria, as the number of agents tends to
infinity, first by deriving laws of large numbers characterizes almost sure
limit points of Nash equilibria in terms of so-called Cournot-Nash equilibria
of an associated nonatomic game. Our main results are large deviation
principles that characterize the probability of rare Nash equilibria and
associated conditional limit theorems describing the behavior of equilibria
conditioned on a rare event. The results cover situations when neither the
finite-player game nor the associated nonatomic game has a unique equilibrium.
In addition, we study the asymptotic behavior of the price of anarchy,
complementing existing worst-case bounds with new probabilistic bounds in the
context of congestion games, which are used to model traffic routing in
networks.
| 1 | 0 | 1 | 0 | 0 | 0 |
Componentwise different tail solutions for bivariate stochastic recurrence equations -- with application to GARCH(1,1) processes -- | We study bivariate stochastic recurrence equations (SREs) motivated by
applications to GARCH(1,1) processes. If coefficient matrices of SREs have
strictly positive entries, then the Kesten result applies and it gives
solutions with regularly varying tails. Moreover, the tail indices are the same
for all coordinates. However, for applications, this framework is too
restrictive. We study SREs when coefficients are triangular matrices and prove
that the coordinates of the solution may exhibit regularly varying tails with
different indices. We also specify each tail index together with its constant.
The results are used to characterize regular variations of bivariate stationary
GARCH(1,1) processes.
| 0 | 0 | 1 | 1 | 0 | 0 |
Partial constraint singularities in elastic rods | We present a unified classical treatment of partially constrained elastic
rods. Partial constraints often entail singularities in both shapes and
reactions. Our approach encompasses both sleeve and adhesion problems, and
provides simple and unambiguous derivations of counterintuitive results in the
literature. Relationships between reaction forces and moments, geometry, and
adhesion energies follow from the balance of energy during quasistatic motion.
We also relate our approach to the balance of material momentum and the concept
of a driving traction. The theory is generalizable and can be applied to a wide
array of contact, adhesion, gripping, and locomotion problems.
| 0 | 1 | 0 | 0 | 0 | 0 |
Personalization in Goal-Oriented Dialog | The main goal of modeling human conversation is to create agents which can
interact with people in both open-ended and goal-oriented scenarios. End-to-end
trained neural dialog systems are an important line of research for such
generalized dialog models as they do not resort to any situation-specific
handcrafting of rules. However, incorporating personalization into such systems
is a largely unexplored topic as there are no existing corpora to facilitate
such work. In this paper, we present a new dataset of goal-oriented dialogs
which are influenced by speaker profiles attached to them. We analyze the
shortcomings of an existing end-to-end dialog system based on Memory Networks
and propose modifications to the architecture which enable personalization. We
also investigate personalization in dialog as a multi-task learning problem,
and show that a single model which shares features among various profiles
outperforms separate models for each profile.
| 1 | 0 | 0 | 0 | 0 | 0 |
Maximum Margin Principal Components | Principal Component Analysis (PCA) is a very successful dimensionality
reduction technique, widely used in predictive modeling. A key factor in its
widespread use in this domain is the fact that the projection of a dataset onto
its first $K$ principal components minimizes the sum of squared errors between
the original data and the projected data over all possible rank $K$
projections. Thus, PCA provides optimal low-rank representations of data for
least-squares linear regression under standard modeling assumptions. On the
other hand, when the loss function for a prediction problem is not the
least-squares error, PCA is typically a heuristic choice of dimensionality
reduction -- in particular for classification problems under the zero-one loss.
In this paper we target classification problems by proposing a straightforward
alternative to PCA that aims to minimize the difference in margin distribution
between the original and the projected data. Extensive experiments show that
our simple approach typically outperforms PCA on any particular dataset, in
terms of classification error, though this difference is not always
statistically significant, and despite being a filter method is frequently
competitive with Partial Least Squares (PLS) and Lasso on a wide range of
datasets.
| 1 | 0 | 0 | 1 | 0 | 0 |
A New self-propelled magnetic bearing with helical windings | In this work a design is proposed for an active, permanent magnet based,
self-propelled magnetic bearing i.e. levitating motor having the following
features : (a) simple winding structure, (b) high load supporting capacity, (c)
no eccentricity sensors, (d) stable confinement in all translational
dimensions, (e) stable confinement in all rotational dimensions and (f) high
efficiency. This design uses an architecture consisting of a helically wound
three-phase stator, and a rotor with the magnets also arranged in a helical
manner. Active control is used to excite the rotor at a torque angle lying in
the second quadrant. This torque angle is independent of the rotor's position
inside the stator cavity hence the control algorithm is similar to that of a
conventional permanent magnet synchronous motor. It is motivated through a
physical argument that the bearing rotor develops a lift force proportional to
the output torque and that it remains stably confined in space. These
assertions are then proved rigorously through a calculation of the magnetic
fields, forces and torques. The stiffness matrix of the system is presented and
a discussion of stable and unstable operating regions is given.
| 0 | 1 | 0 | 0 | 0 | 0 |
A-Fast-RCNN: Hard Positive Generation via Adversary for Object Detection | How do we learn an object detector that is invariant to occlusions and
deformations? Our current solution is to use a data-driven strategy -- collect
large-scale datasets which have object instances under different conditions.
The hope is that the final classifier can use these examples to learn
invariances. But is it really possible to see all the occlusions in a dataset?
We argue that like categories, occlusions and object deformations also follow a
long-tail. Some occlusions and deformations are so rare that they hardly
happen; yet we want to learn a model invariant to such occurrences. In this
paper, we propose an alternative solution. We propose to learn an adversarial
network that generates examples with occlusions and deformations. The goal of
the adversary is to generate examples that are difficult for the object
detector to classify. In our framework both the original detector and adversary
are learned in a joint manner. Our experimental results indicate a 2.3% mAP
boost on VOC07 and a 2.6% mAP boost on VOC2012 object detection challenge
compared to the Fast-RCNN pipeline. We also release the code for this paper.
| 1 | 0 | 0 | 0 | 0 | 0 |
Non-thermalization in trapped atomic ion spin chains | Linear arrays of trapped and laser cooled atomic ions are a versatile
platform for studying emergent phenomena in strongly-interacting many-body
systems. Effective spins are encoded in long-lived electronic levels of each
ion and made to interact through laser mediated optical dipole forces. The
advantages of experiments with cold trapped ions, including high spatiotemporal
resolution, decoupling from the external environment, and control over the
system Hamiltonian, are used to measure quantum effects not always accessible
in natural condensed matter samples. In this review we highlight recent work
using trapped ions to explore a variety of non-ergodic phenomena in long-range
interacting spin-models which are heralded by memory of out-of-equilibrium
initial conditions. We observe long-lived memory in static magnetizations for
quenched many-body localization and prethermalization, while memory is
preserved in the periodic oscillations of a driven discrete time crystal state.
| 0 | 1 | 0 | 0 | 0 | 0 |
Generalized Uniformity Testing | In this work, we revisit the problem of uniformity testing of discrete
probability distributions. A fundamental problem in distribution testing,
testing uniformity over a known domain has been addressed over a significant
line of works, and is by now fully understood.
The complexity of deciding whether an unknown distribution is uniform over
its unknown (and arbitrary) support, however, is much less clear. Yet, this
task arises as soon as no prior knowledge on the domain is available, or
whenever the samples originate from an unknown and unstructured universe. In
this work, we introduce and study this generalized uniformity testing question,
and establish nearly tight upper and lower bound showing that -- quite
surprisingly -- its sample complexity significantly differs from the
known-domain case. Moreover, our algorithm is intrinsically adaptive, in
contrast to the overwhelming majority of known distribution testing algorithms.
| 1 | 0 | 1 | 1 | 0 | 0 |
Refraction in exoplanet atmospheres: Photometric signatures, implications for transmission spectroscopy, and search in Kepler data | Refraction deflects photons that pass through atmospheres, which affects
transit light curves. Refraction thus provides an avenue to probe physical
properties of exoplanet atmospheres and to constrain the presence of clouds and
hazes. In addition, an effective surface can be imposed by refraction, thereby
limiting the pressure levels probed by transmission spectroscopy. The main
objective of the paper is to model the effects of refraction on photometric
light curves for realistic planets and to explore the dependencies on
atmospheric physical parameters. We also explore under which circumstances
transmission spectra are significantly affected by refraction. Finally, we
search for refraction signatures in photometric residuals in Kepler data. We
use the model of Hui & Seager (2002) to compute deflection angles and
refraction transit light curves, allowing us to explore the parameter space of
atmospheric properties. The observational search is performed by stacking large
samples of transit light curves from Kepler. We find that out-of-transit
refraction shoulders are the most easily observable features, which can reach
peak amplitudes of ~10 parts per million (ppm) for planets around Sun-like
stars. More typical amplitudes are a few ppm or less for Jovians and at the
sub-ppm level for super-Earths. Interestingly, the signal-to-noise ratio of any
refraction residuals for planets orbiting Sun-like hosts are expected to be
similar for planets orbiting red dwarfs. We also find that the maximum depth
probed by transmission spectroscopy is not limited by refraction for weakly
lensing planets, but that the incidence of refraction can vary significantly
for strongly lensing planets. We find no signs of refraction features in the
stacked Kepler light curves, which is in agreement with our model predictions.
| 0 | 1 | 0 | 0 | 0 | 0 |
Balancing Efficiency and Coverage in Human-Robot Dialogue Collection | We describe a multi-phased Wizard-of-Oz approach to collecting human-robot
dialogue in a collaborative search and navigation task. The data is being used
to train an initial automated robot dialogue system to support collaborative
exploration tasks. In the first phase, a wizard freely typed robot utterances
to human participants. For the second phase, this data was used to design a GUI
that includes buttons for the most common communications, and templates for
communications with varying parameters. Comparison of the data gathered in
these phases show that the GUI enabled a faster pace of dialogue while still
maintaining high coverage of suitable responses, enabling more efficient
targeted data collection, and improvements in natural language understanding
using GUI-collected data. As a promising first step towards interactive
learning, this work shows that our approach enables the collection of useful
training data for navigation-based HRI tasks.
| 1 | 0 | 0 | 0 | 0 | 0 |
Reinforcement Learning Based Argument Component Detection | Argument component detection (ACD) is an important sub-task in argumentation
mining. ACD aims at detecting and classifying different argument components in
natural language texts. Historical annotations (HAs) are important features the
human annotators consider when they manually perform the ACD task. However, HAs
are largely ignored by existing automatic ACD techniques. Reinforcement
learning (RL) has proven to be an effective method for using HAs in some
natural language processing tasks. In this work, we propose a RL-based ACD
technique, and evaluate its performance on two well-annotated corpora. Results
suggest that, in terms of classification accuracy, HAs-augmented RL outperforms
plain RL by at most 17.85%, and outperforms the state-of-the-art supervised
learning algorithm by at most 11.94%.
| 1 | 0 | 0 | 0 | 0 | 0 |
VUNet: Dynamic Scene View Synthesis for Traversability Estimation using an RGB Camera | We present VUNet, a novel view(VU) synthesis method for mobile robots in
dynamic environments, and its application to the estimation of future
traversability. Our method predicts future images for given virtual robot
velocity commands using only RGB images at previous and current time steps. The
future images result from applying two types of image changes to the previous
and current images: 1) changes caused by different camera pose, and 2) changes
due to the motion of the dynamic obstacles. We learn to predict these two types
of changes disjointly using two novel network architectures, SNet and DNet. We
combine SNet and DNet to synthesize future images that we pass to our
previously presented method GONet to estimate the traversable areas around the
robot. Our quantitative and qualitative evaluation indicate that our approach
for view synthesis predicts accurate future images in both static and dynamic
environments. We also show that these virtual images can be used to estimate
future traversability correctly. We apply our view synthesis-based
traversability estimation method to two applications for assisted
teleoperation.
| 1 | 0 | 0 | 0 | 0 | 0 |
Bayesian hypothesis tests with diffuse priors: Can we have our cake and eat it too? | We introduce a new class of priors for Bayesian hypothesis testing, which we
name "cake priors". These priors circumvent Bartlett's paradox (also called the
Jeffreys-Lindley paradox); the problem associated with the use of diffuse
priors leading to nonsensical statistical inferences. Cake priors allow the use
of diffuse priors (having one's cake) while achieving theoretically justified
inferences (eating it too). We demonstrate this methodology for Bayesian
hypotheses tests for scenarios under which the one and two sample t-tests, and
linear models are typically derived. The resulting Bayesian test statistic
takes the form of a penalized likelihood ratio test statistic. By considering
the sampling distribution under the null and alternative hypotheses we show for
independent identically distributed regular parametric models that Bayesian
hypothesis tests using cake priors are Chernoff-consistent, i.e., achieve zero
type I and II errors asymptotically. Lindley's paradox is also discussed. We
argue that a true Lindley's paradox will only occur with small probability for
large sample sizes.
| 0 | 0 | 1 | 1 | 0 | 0 |
On a Novel Speech Representation Using Multitapered Modified Group Delay Function | In this paper, a novel multitaper modified group delay function-based
representation for speech signals is proposed. With a set of phoneme-based
experiments, it is shown that the proposed method performs better that an
existing multitaper magnitude (MT-MAG) estimation technique, in terms of
variance and MSE, both in spectral- and cepstral-domains. In particular, the
performance of MT-MOGDF is found to be the best with the Thomson tapers.
Additionally, the utility of the MT-MOGDF technique is highlighted in a speaker
recognition experimental setup, where an improvement of around $20\%$ compared
to the next-best technique is obtained. Moreover, the computational
requirements of the proposed technique is comparable to that of MT-MAG. The
proposed feature can be used in for many speech-related applications; in
particular, it is best suited among those that require information of speaker
and speech.
| 1 | 0 | 0 | 0 | 0 | 0 |
Persistent Flows and Non-Reciprocal Interactions in Deterministic Networks | This paper studies deterministic consensus networks with discrete-time
dynamics under persistent flows and non-reciprocal agent interactions. An arc
describing the interaction strength between two agents is said to be persistent
if its weight function has an infinite $l_1$ norm. We discuss two balance
conditions on the interactions between agents which generalize the arc-balance
and cut-balance conditions in the literature respectively. The proposed
conditions require that such a balance should be satisfied over each time
window of a fixed length instead of at each time instant. We prove that in both
cases global consensus is reached if and only if the persistent graph, which
consists of all the persistent arcs, contains a directed spanning tree. The
convergence rates of the system to consensus are also provided in terms of the
interactions between agents having taken place. The results are obtained under
a weak condition without assuming the existence of a positive lower bound of
all the nonzero weights of arcs and are compared with the existing results.
Illustrative examples are provided to show the critical importance of the
nontrivial lower boundedness of the self-confidence of the agents.
| 1 | 0 | 0 | 0 | 0 | 0 |
Linking Fluid and Kinetic Scales in Solar Wind Turbulence | We investigate possible links between the large-scale and small-scale
features of solar wind fluctuations across the frequency break separating fluid
and kinetic regimes. The aim is to correlate the magnetic field fluctuations
polarization at dissipative scales with the particular state of turbulence
within the inertial range of fluctuations. We found clear correlations between
each type of polarization within the kinetic regime and fluid parameters within
the inertial range. Moreover, for the first time in literature, we showed that
left-handed and right-handed polarized fluctuations occupy different areas of
the plasma instabilities-temperature anisotropy plot, as expected for
Alfv$\acute{\textrm{e}}$n Ion Cyclotron and Kinetic Alfv$\acute{\textrm{e}}$n
waves, respectively.
| 0 | 1 | 0 | 0 | 0 | 0 |
Thresholds For Detecting An Anomalous Path From Noisy Environments | We consider the "searching for a trail in a maze" composite hypothesis
testing problem, in which one attempts to detect an anomalous directed path in
a lattice 2D box of side n based on observations on the nodes of the box. Under
the signal hypothesis, one observes independent Gaussian variables of unit
variance at all nodes, with zero, mean off the anomalous path and mean \mu_n on
it. Under the null hypothesis, one observes i.i.d. standard Gaussians on all
nodes. Arias-Castro et al. (2008) showed that if the unknown directed path
under the signal hypothesis has known the initial location, then detection is
possible (in the minimax sense) if \mu_n >> 1/\sqrt log n, while it is not
possible if \mu_n << 1/ log n\sqrt log log n. In this paper, we show that this
result continues to hold even when the initial location of the unknown path is
not known. As is the case with Arias-Castro et al. (2008), the upper bound here
also applies when the path is undirected. The improvement is achieved by
replacing the linear detection statistic used in Arias-Castro et al. (2008)
with a polynomial statistic, which is obtained by employing a multi-scale
analysis on a quadratic statistic to bootstrap its performance. Our analysis is
motivated by ideas developed in the context of the analysis of random polymers
in Lacoin (2010).
| 0 | 0 | 1 | 1 | 0 | 0 |
On the topology of real Bott manifolds | The main aim of this article is to give a necessary and sufficient condition
for a real Bott manifold to admit a spin structure and further give a
combinatorial characterization for the spin structure in terms of the
associated acyclic digraph.
| 0 | 0 | 1 | 0 | 0 | 0 |
Relative Error Tensor Low Rank Approximation | We consider relative error low rank approximation of $tensors$ with respect
to the Frobenius norm: given an order-$q$ tensor $A \in
\mathbb{R}^{\prod_{i=1}^q n_i}$, output a rank-$k$ tensor $B$ for which
$\|A-B\|_F^2 \leq (1+\epsilon)$OPT, where OPT $= \inf_{\textrm{rank-}k~A'}
\|A-A'\|_F^2$. Despite the success on obtaining relative error low rank
approximations for matrices, no such results were known for tensors. One
structural issue is that there may be no rank-$k$ tensor $A_k$ achieving the
above infinum. Another, computational issue, is that an efficient relative
error low rank approximation algorithm for tensors would allow one to compute
the rank of a tensor, which is NP-hard. We bypass these issues via (1)
bicriteria and (2) parameterized complexity solutions:
(1) We give an algorithm which outputs a rank $k' = O((k/\epsilon)^{q-1})$
tensor $B$ for which $\|A-B\|_F^2 \leq (1+\epsilon)$OPT in $nnz(A) + n \cdot
\textrm{poly}(k/\epsilon)$ time in the real RAM model. Here $nnz(A)$ is the
number of non-zero entries in $A$.
(2) We give an algorithm for any $\delta >0$ which outputs a rank $k$ tensor
$B$ for which $\|A-B\|_F^2 \leq (1+\epsilon)$OPT and runs in $ ( nnz(A) + n
\cdot \textrm{poly}(k/\epsilon) + \exp(k^2/\epsilon) ) \cdot n^\delta$ time in
the unit cost RAM model.
For outputting a rank-$k$ tensor, or even a bicriteria solution with
rank-$Ck$ for a certain constant $C > 1$, we show a $2^{\Omega(k^{1-o(1)})}$
time lower bound under the Exponential Time Hypothesis.
Our results give the first relative error low rank approximations for tensors
for a large number of robust error measures for which nothing was known, as
well as column row and tube subset selection. We also obtain new results for
matrices, such as $nnz(A)$-time CUR decompositions, improving previous
$nnz(A)\log n$-time algorithms, which may be of independent interest.
| 1 | 0 | 0 | 0 | 0 | 0 |
Bayesian Boolean Matrix Factorisation | Boolean matrix factorisation aims to decompose a binary data matrix into an
approximate Boolean product of two low rank, binary matrices: one containing
meaningful patterns, the other quantifying how the observations can be
expressed as a combination of these patterns. We introduce the OrMachine, a
probabilistic generative model for Boolean matrix factorisation and derive a
Metropolised Gibbs sampler that facilitates efficient parallel posterior
inference. On real world and simulated data, our method outperforms all
currently existing approaches for Boolean matrix factorisation and completion.
This is the first method to provide full posterior inference for Boolean Matrix
factorisation which is relevant in applications, e.g. for controlling false
positive rates in collaborative filtering and, crucially, improves the
interpretability of the inferred patterns. The proposed algorithm scales to
large datasets as we demonstrate by analysing single cell gene expression data
in 1.3 million mouse brain cells across 11 thousand genes on commodity
hardware.
| 1 | 0 | 0 | 1 | 0 | 0 |
Global existence and convergence of $Q$-curvature flow on manifolds of even dimension | Using a negative gradient flow approach, we generalize and unify some
existence theorems for the problem of prescribing $Q$-curvature first by Baird,
Fardoun, and Regbaoui (Calc. Var. 27 75-104) for $4$-manifolds with a possible
sign-changing curvature candidate then by Brendle (Ann. Math. 158 323-343) for
$n$-manifolds with even $n$ with positive curvature candidate to the case of
$n$-manifolds of all even dimension with sign-changing curvature candidates.
Making use of the \L ojasiewicz--Simon inequality, we also address the rate of
the convergence.
| 0 | 0 | 1 | 0 | 0 | 0 |
Group Embeddings with Algorithmic Properties | We show that every countable group H with solvable word problem (=computable
group) can be subnormally embedded into a 2-generated group G which also has
solvable word problem. Moreover, the membership problem for H < G is also
solvable. We also give estimates of time and space complexity of the word
problem in G and of the membership problem for H < G.
| 0 | 0 | 1 | 0 | 0 | 0 |
General purpose graphics-processing-unit implementation of cosmological domain wall network evolution | Topological defects unavoidably form at symmetry breaking phase transitions
in the early Universe. To probe the parameter space of theoretical models and
set tighter experimental constraints (exploiting the recent advances in
astrophysical observations), one requires more and more demanding simulations,
and therefore more hardware resources and computation time. Improving the speed
and efficiency of existing codes is essential. Here we present a General
Purpose Graphics Processing Unit implementation of the canonical
Press-Ryden-Spergel algorithm for the evolution of cosmological domain wall
networks. This is ported to the Open Computing Language standard, and as a
consequence significant speed-ups are achieved both in 2D and 3D simulations.
| 0 | 1 | 0 | 0 | 0 | 0 |
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