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arxiv_dataset-72001604.00833 | Obstacle Avoidance Strategy using Onboard Stereo Vision on a Flapping
Wing MAV
cs.RO
The development of autonomous lightweight MAVs, capable of navigating in
unknown indoor environments, is one of the major challenges in robotics. The
complexity of this challenge comes from constraints on weight and power
consumption of onboard sensing and processing devices. In this paper we propose
the "Droplet" strategy, an avoidance strategy based on stereo vision inputs
that outperforms reactive avoidance strategies by allowing constant speed
maneuvers while being computationally extremely efficient, and which does not
need to store previous images or maps. The strategy deals with nonholonomic
motion constraints of most fixed and flapping wing platforms, and with the
limited field-of-view of stereo camera systems. It guarantees obstacle-free
flight in the absence of sensor and motor noise. We first analyze the strategy
in simulation, and then show its robustness in real-world conditions by
implementing it on a 20-gram flapping wing MAV.
| arxiv topic:cs.RO |
arxiv_dataset-72011604.00933 | Entity Type Recognition using an Ensemble of Distributional Semantic
Models to Enhance Query Understanding
cs.CL cs.IR
We present an ensemble approach for categorizing search query entities in the
recruitment domain. Understanding the types of entities expressed in a search
query (Company, Skill, Job Title, etc.) enables more intelligent information
retrieval based upon those entities compared to a traditional keyword-based
search. Because search queries are typically very short, leveraging a
traditional bag-of-words model to identify entity types would be inappropriate
due to the lack of contextual information. Our approach instead combines clues
from different sources of varying complexity in order to collect real-world
knowledge about query entities. We employ distributional semantic
representations of query entities through two models: 1) contextual vectors
generated from encyclopedic corpora like Wikipedia, and 2) high dimensional
word embedding vectors generated from millions of job postings using word2vec.
Additionally, our approach utilizes both entity linguistic properties obtained
from WordNet and ontological properties extracted from DBpedia. We evaluate our
approach on a data set created at CareerBuilder; the largest job board in the
US. The data set contains entities extracted from millions of job
seekers/recruiters search queries, job postings, and resume documents. After
constructing the distributional vectors of search entities, we use supervised
machine learning to infer search entity types. Empirical results show that our
approach outperforms the state-of-the-art word2vec distributional semantics
model trained on Wikipedia. Moreover, we achieve micro-averaged F 1 score of
97% using the proposed distributional representations ensemble.
| arxiv topic:cs.CL cs.IR |
arxiv_dataset-72021604.01033 | Classification of topological phonons in linear mechanical metamaterials
cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.soft
Topological phononic crystals, alike their electronic counterparts, are
characterized by a bulk-edge correspondence where the interior of a material
dictates the existence of stable surface or boundary modes. In the mechanical
setup, such surface modes can be used for various applications such as
wave-guiding, vibration isolation, or the design of static properties such as
stable floppy modes where parts of a system move freely. Here, we provide a
classification scheme of topological phonons based on local symmetries. We
import and adapt the classification of non-interacting electron systems and
embed it into the mechanical setup. Moreover, we provide an extensive set of
examples that illustrate our scheme and can be used to generate new models in
unexplored symmetry classes. Our works unifies the vast recent literature on
topological phonons and paves the way to future applications of topological
surface modes in mechanical metamaterials.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci cond-mat.soft |
arxiv_dataset-72031604.01133 | Classical deformations of noncompact surfaces and their moduli of
instantons
math.AG hep-th math.CV
We describe semiuniversal deformation spaces for the noncompact surfaces $Z_k
:= \operatorname{Tot} (\mathcal O_{\mathbb P^1} (-k))$ and prove that any
nontrivial deformation $Z_k (\tau)$ of $Z_k$ is affine.
It is known that the moduli spaces of instantons of charge $j$ on $Z_k$ are
quasi-projective varieties of dimension $2j-k-2$. In contrast, our results
imply that the moduli spaces of instantons on any nontrivial deformation $Z_k
(\tau)$ are empty.
| arxiv topic:math.AG hep-th math.CV |
arxiv_dataset-72041604.01233 | Construction of Simultaneous Confidence Bands for Multiple Logistic
Regression Models over Restricted Regions
math.ST stat.ME stat.TH
This article presents methods for constructing an asymptotic hyperbolic band
under the multiple logistic regression model when the predictor variables are
restricted to a specific region $\mathscr{X}$. Scheff\'{e}'s method yields
unnecessarily wide, and hence conservative, bands if the predictor variables
can be restricted to a certain region. Piegorsch and Casella (1988) developed a
procedure to build an asymptotic confidence band for the multiple logistic
regression model over particular regions. Those regions are shown to be special
cases of the region $\mathscr{X}$, which was first investigated by Seppanen and
Uusipaikka (1992) in the multiple linear regression context. This article also
provides methods for constructing conservative confidence bands when the
restricted region is not of the specified form. Particularly, rectangular
restricted regions, which are commonly encountered in practice, are considered.
Two examples are given to illustrate the proposed methodology, and one example
shows that the proposed procedure outperforms the method given by Piegorsch and
Casella (1988).
| arxiv topic:math.ST stat.ME stat.TH |
arxiv_dataset-72051604.01333 | Invariant quantities of a nondepolarizing Mueller matrix
physics.optics
Orthogonal Mueller matrices can be considered either as corresponding to
retarders or to generalized transformations of the polarization basis for the
representation of Stokes vectors, so that they constitute the only type of
Mueller matrices that preserve the degree of polarization and the intensity of
any partially-polarized input Stokes vector. The physical quantities which
remain invariant when a nondepolarizing Mueller matrix is transformed through
its product by different types of orthogonal Mueller matrices are identified
and interpreted, providing a better knowledge of the information contained in a
nondepolarizing Mueller matrix.
| arxiv topic:physics.optics |
arxiv_dataset-72061604.01433 | Collaborative Information Bottleneck
cs.IT math.IT stat.ML
This paper investigates a multi-terminal source coding problem under a
logarithmic loss fidelity which does not necessarily lead to an additive
distortion measure. The problem is motivated by an extension of the Information
Bottleneck method to a multi-source scenario where several encoders have to
build cooperatively rate-limited descriptions of their sources in order to
maximize information with respect to other unobserved (hidden) sources. More
precisely, we study fundamental information-theoretic limits of the so-called:
(i) Two-way Collaborative Information Bottleneck (TW-CIB) and (ii) the
Collaborative Distributed Information Bottleneck (CDIB) problems. The TW-CIB
problem consists of two distant encoders that separately observe marginal
(dependent) components $X_1$ and $X_2$ and can cooperate through multiple
exchanges of limited information with the aim of extracting information about
hidden variables $(Y_1,Y_2)$, which can be arbitrarily dependent on
$(X_1,X_2)$. On the other hand, in CDIB there are two cooperating encoders
which separately observe $X_1$ and $X_2$ and a third node which can listen to
the exchanges between the two encoders in order to obtain information about a
hidden variable $Y$. The relevance (figure-of-merit) is measured in terms of a
normalized (per-sample) multi-letter mutual information metric (log-loss
fidelity) and an interesting tradeoff arises by constraining the complexity of
descriptions, measured in terms of the rates needed for the exchanges between
the encoders and decoders involved. Inner and outer bounds to the
complexity-relevance region of these problems are derived from which optimality
is characterized for several cases of interest. Our resulting theoretical
complexity-relevance regions are finally evaluated for binary symmetric and
Gaussian statistical models.
| arxiv topic:cs.IT math.IT stat.ML |
arxiv_dataset-72071604.01533 | Characterisation of the turbulent electromotive force and its
magnetically-mediated quenching in a global EULAG-MHD simulation of solar
convection
astro-ph.SR
We perform a mean-field analysis of the EULAG-MHD millenium simulation of
global magnetohydrodynamical convection presented in Passos et al. 2014. The
turbulent electromotive force operating in the simulation is assumed to be
linearly related to the cyclic axisymmetric mean magnetic field and its first
spatial derivatives. At every grid point in the simulation's meridional plane,
this assumed relationship involves 27 independent tensorial coefficients.
Expanding on Racine et al. 2011, we extract these coefficients from the
simulation data through a least-squares minimization procedure based on
singular value decomposition. The reconstructed alpha-tensor shows good
agreement with that obtained by Racine et al. 2011, who did not include
derivatives of the mean-field in their fit, as well as with the alpha-tensor
extracted by Augustson et al. 2015 from a distinct ASH MHD simulation. The
isotropic part of the turbulent magnetic diffusivity tensor beta is positive
definite and reaches values of 5.0x10^7 m2s-1 in the middle of the convecting
fluid layers. The spatial variations of both alpha_phiphi and beta_phiphi
component are well reproduced by expressions obtained under the SOCA, with a
good matching of amplitude requiring a turbulent correlation time about five
times smaller than the estimated turnover time of the small-scale turbulent
flow. We find the magnetic quenching of the alpha-effect to be driven primarily
by a reduction of the small-scale flow's kinetic helicity, with variations of
the current helicity playing a lesser role in most locations in the simulation
domain. Our measurements of turbulent diffusivity quenching are restricted to
the beta_phiphi component, but indicate a weaker quenching, by a factor of
1.36, than of the alpha effect, which in our simulation drops by a factor of
three between the minimum and maximum phases of the magnetic cycle.
| arxiv topic:astro-ph.SR |
arxiv_dataset-72081604.01633 | Coherent Charge Transport in Ballistic InSb Nanowire Josephson Junctions
cond-mat.mes-hall
Hybrid InSb nanowire-superconductor devices are promising for investigating
Majorana modes and topological quantum computation in solid-state devices. An
experimental realisation of ballistic, phase-coherent superconductor-nanowire
hybrid devices is a necessary step towards engineering topological
superconducting electronics. Here, we report on a low-temperature transport
study of Josephson junction devices fabricated from InSb nanowires grown by
molecular-beam epitaxy and provide a clear evidence for phase-coherent,
ballistic charge transport through the nanowires in the junctions. We
demonstrate that our devices show gate-tunable proximity-induced supercurrent
and clear signatures of multiple Andreev reflections in the differential
conductance, indicating phase-coherent transport within the junctions. We also
observe periodic modulations of the critical current that can be associated
with the Fabry-P\'{e}rot interference in the nanowires in the ballistic
transport regime. Our work shows that the InSb nanowires grown by
molecular-beam epitaxy are of excellent material quality and hybrid
superconducting devices made from these nanowires are highly desirable for
investigation of the novel physics in topological states of matter and for
applications in topological quantum electronics.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-72091604.01733 | A U-statistic Approach to Hypothesis Testing for Structure Discovery in
Undirected Graphical Models
stat.ML math.ST stat.TH
Structure discovery in graphical models is the determination of the topology
of a graph that encodes conditional independence properties of the joint
distribution of all variables in the model. For some class of probability
distributions, an edge between two variables is present if and only if the
corresponding entry in the precision matrix is non-zero. For a finite sample
estimate of the precision matrix, entries close to zero may be due to low
sample effects, or due to an actual association between variables; these two
cases are not readily distinguishable. %Fisher provided a hypothesis test based
on a parametric approximation to the distribution of an entry in the precision
matrix of a Gaussian distribution, but this may not provide valid upper bounds
on $p$-values for non-Gaussian distributions. Many related works on this topic
consider potentially restrictive distributional or sparsity assumptions that
may not apply to a data sample of interest, and direct estimation of the
uncertainty of an estimate of the precision matrix for general distributions
remains challenging. Consequently, we make use of results for $U$-statistics
and apply them to the covariance matrix. By probabilistically bounding the
distortion of the covariance matrix, we can apply Weyl's theorem to bound the
distortion of the precision matrix, yielding a conservative, but sound test
threshold for a much wider class of distributions than considered in previous
works. The resulting test enables one to answer with statistical significance
whether an edge is present in the graph, and convergence results are known for
a wide range of distributions. The computational complexities is linear in the
sample size enabling the application of the test to large data samples for
which computation time becomes a limiting factor. We experimentally validate
the correctness and scalability of the test on multivariate distributions for
which the distributional assumptions of competing tests result in
underestimates of the false positive ratio. By contrast, the proposed test
remains sound, promising to be a useful tool for hypothesis testing for diverse
real-world problems.
| arxiv topic:stat.ML math.ST stat.TH |
arxiv_dataset-72101604.01833 | System for Filtering Messages on Social Media Content
cs.SI
The social networking era has left us with little privacy. The details of the
social network users are published on Social Networking sites. Vulnerability
has reached new heights due to the overpowering effects of social networking.
The sites like Facebook, Twitter are having a huge set of users who publish
their files, comments, messages in other users walls. These messages and
comments could be of any nature. Even friends could post a comment that would
harm a persons integrity. Thus there has to be a system which will monitor the
messages and comments that are posted on the walls. If the messages are found
to be neutral (does not have any harmful content), then it can be published. If
the messages are found to have non-neutral content in them, then these messages
would be blocked by the social network manager. The messages that are
non-neutral would be of sexual, offensive, hatred, pun intended nature. Thus
the social network manager can classify content as neutral and non-neutral and
notify the user if there seems to be messages of non-neutral behavior.
| arxiv topic:cs.SI |
arxiv_dataset-72111604.01933 | Universal amorphous-amorphous transition in GexSe1-x glasses under
pressure
cond-mat.mtrl-sci
Pressure induced structural modifications in vitreous Ge$_{x}$Se$_{100-x}$
(where 10 $\leq$ x $\leq$ 25)are investigated using X-ray absorption
spectroscopy (XAS) along with supplementary X-ray diffraction (XRD) experiments
and ab initio molecular dynamics (AIMD) simulations. Universal changes in
distances and angle distributions are observed when scaled to reduced
densities. All compositions are observed to remain amorphous under pressure
values up to 42 GPa. The Ge-Se interatomic distances extracted from XAS data
show a two-step response to the applied pressure; a gradual decrease followed
by an increase at around 15-20 GPa, depending on the composition. This increase
is attributed to the metallization event that can be traced with the red shift
in Ge K edge energy which is also identified by the principal peak position of
the structure factor. The densification mechanisms are studied in details by
means of AIMD simulations and compared to the experimental results. The
evolution of bond angle distributions, interatomic distances and coordination
numbers are examined and lead to similar pressure-induced structural changes
for any composition.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-72121604.02033 | A remark on a converse theorem of Cogdell and Piatetski-Shapiro
math.NT math.RT
In this paper, we reprove a global converse theorem of Cogdell and
Piatetski-Shapiro using purely global methods.
| arxiv topic:math.NT math.RT |
arxiv_dataset-72131604.02133 | Revising Incompletely Specified Convex Probabilistic Belief Bases
cs.AI
We propose a method for an agent to revise its incomplete probabilistic
beliefs when a new piece of propositional information is observed. In this
work, an agent's beliefs are represented by a set of probabilistic formulae --
a belief base. The method involves determining a representative set of
'boundary' probability distributions consistent with the current belief base,
revising each of these probability distributions and then translating the
revised information into a new belief base. We use a version of Lewis Imaging
as the revision operation. The correctness of the approach is proved. The
expressivity of the belief bases under consideration are rather restricted, but
has some applications. We also discuss methods of belief base revision
employing the notion of optimum entropy, and point out some of the benefits and
difficulties in those methods. Both the boundary distribution method and the
optimum entropy method are reasonable, yet yield different results.
| arxiv topic:cs.AI |
arxiv_dataset-72141604.02233 | Accurate selfcorrection of errors in long reads using de Bruijn graphs
q-bio.GN
New long read sequencing technologies, like PacBio SMRT and Oxford NanoPore,
can produce sequencing reads up to 50,000 bp long but with an error rate of at
least 15%. Reducing the error rate is necessary for subsequent utilisation of
the reads in, e.g., de novo genome assembly. The error correction problem has
been tackled either by aligning the long reads against each other or by a
hybrid approach that uses the more accurate short reads produced by second
generation sequencing technologies to correct the long reads. We present an
error correction method that uses long reads only. The method consists of two
phases: first we use an iterative alignment-free correction method based on de
Bruijn graphs with increasing length of k-mers, and second, the corrected reads
are further polished using long-distance dependencies that are found using
multiple alignments. According to our experiments the proposed method is the
most accurate one relying on long reads only for read sets with high coverage.
Furthermore, when the coverage of the read set is at least 75x, the throughput
of the new method is at least 20% higher. LoRMA is freely available at
http://www.cs.helsinki.fi/u/lmsalmel/LoRMA/.
| arxiv topic:q-bio.GN |
arxiv_dataset-72151604.02333 | Information Theoretic Caching: The Multi-User Case
cs.IT math.IT
In this paper, we consider a cache aided network in which each user is
assumed to have individual caches, while upon users' requests, an update
message is sent though a common link to all users. First, we formulate a
general information theoretic setting that represents the database as a
discrete memoryless source, and the users' requests as side information that is
available everywhere except at the cache encoder. The decoders' objective is to
recover a function of the source and the side information. By viewing cache
aided networks in terms of a general distributed source coding problem and
through information theoretic arguments, we present inner and outer bounds on
the fundamental tradeoff of cache memory size and update rate. Then, we
specialize our general inner and outer bounds to a specific model of content
delivery networks: File selection networks, in which the database is a
collection of independent equal-size files and each user requests one of the
files independently. For file selection networks, we provide an outer bound and
two inner bounds (for centralized and decentralized caching strategies). For
the case when the user request information is uniformly distributed, we
characterize the rate vs. cache size tradeoff to within a multiplicative gap of
4. By further extending our arguments to the framework of Maddah-Ali and
Niesen, we also establish a new outer bound and two new inner bounds in which
it is shown to recover the centralized and decentralized strategies, previously
established by Maddah-Ali and Niesen. Finally, in terms of rate vs. cache size
tradeoff, we improve the previous multiplicative gap of 72 to 4.7 for the
average case with uniform requests.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-72161604.02433 | A Parallax-based Distance Estimator for Spiral Arm Sources
astro-ph.GA
The spiral arms of the Milky Way are being accurately located for the first
time via trigonometric parallaxes of massive star forming regions with the
BeSSeL Survey, using the Very Long Baseline Array and the European VLBI
Network, and with the Japanese VERA project. Here we describe a computer
program that leverages these results to significantly improve the accuracy and
reliability of distance estimates to other sources that are known to follow
spiral structure. Using a Bayesian approach, sources are assigned to arms based
on their (l,b,v) coordinates with respect to arm signatures seen in CO and HI
surveys. A source's kinematic distance, displacement from the plane, and
proximity to individual parallax sources are also considered in generating a
full distance probability density function. Using this program to estimate
distances to large numbers of star forming regions, we generate a realistic
visualization of the Milky Way's spiral structure as seen from the northern
hemisphere.
| arxiv topic:astro-ph.GA |
arxiv_dataset-72171604.02533 | Joint Data Purchasing and Data Placement in a Geo-Distributed Data
Market
cs.DC
This paper studies two design tasks faced by a geo-distributed cloud data
market: which data to purchase (data purchasing) and where to place/replicate
the data for delivery (data placement). We show that the joint problem of data
purchasing and data placement within a cloud data market can be viewed as a
facility location problem, and is thus NP-hard. However, we give a provably
optimal algorithm for the case of a data market made up of a single data
center, and then generalize the structure from the single data center setting
in order to develop a near-optimal, polynomial-time algorithm for a
geo-distributed data market. The resulting design, Datum, decomposes the joint
purchasing and placement problem into two subproblems, one for data purchasing
and one for data placement, using a transformation of the underlying bandwidth
costs. We show, via a case study, that Datum is near-optimal (within 1.6%) in
practical settings.
| arxiv topic:cs.DC |
arxiv_dataset-72181604.02633 | Ground state properties of quantum Kagome ice hardcore bosons
cond-mat.str-el
We study the quantum Kagom\'e ice hardcore bosons, which corresponds to the
XY limit of quantum spin ice Hamiltonian. We estimate the values of the
zero-temperature thermodynamic quantities using the large-$S$ expansion. We
show that our semi-classical analysis is consistent with finite temperature
quantum Monte Carlo estimates.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-72191604.02733 | Bacterial cartels at steady supply
q-bio.PE q-bio.MN
Metagenomics has revealed hundreds of bacterial species in almost all
microbiota. In a few well-studied cases, bacterial communities have been
observed to coordinate their metabolic fluxes. In principle, bacteria can
divide tasks to reap the benefits of specialization, as in human economies.
However, the benefits and stability of an economy of bacterial specialists are
far from obvious. Here, we physically model the population dynamics of bacteria
that compete for steadily supplied resources. Importantly, we explicitly model
the metabolic fluxes yielding cellular biomass production under the constraint
of a limited enzyme budget. In our framework, we find that population dynamics
generally leads to the coexistence of different metabolic types, which satisfy
an extended competitive exclusion principle (even allowing for adaptive
mutation). We establish that these consortia act as cartels, whereby population
dynamics pins down resource concentrations at values for which no other
strategy can invade. Finally, we propose that at steady supply, cartels of
competing strategies automatically yield maximum biomass, thereby achieving a
collective optimum.
| arxiv topic:q-bio.PE q-bio.MN |
arxiv_dataset-72201604.02833 | Efficiently Enumerating Minimal Triangulations
cs.DS
We present an algorithm that enumerates all the minimal triangulations of a
graph in incremental polynomial time. Consequently, we get an algorithm for
enumerating all the proper tree decompositions, in incremental polynomial time,
where "proper" means that the tree decomposition cannot be improved by removing
or splitting a bag. The algorithm can incorporate any method for (ordinary,
single result) triangulation or tree decomposition, and can serve as an anytime
algorithm to improve such a method. We describe an extensive experimental study
of an implementation on real data from different fields. Our experiments show
that the algorithm improves upon central quality measures over the underlying
tree decompositions, and is able to produce a large number of high-quality
decompositions.
| arxiv topic:cs.DS |
arxiv_dataset-72211604.02933 | A class of square-free monomial ideals associated to two integer
sequences
math.AC
Given two finite sequences of positive integers $\alpha$ and $\beta$, we
associate a square free monomial ideal $I_{\alpha,\beta}$ in a ring of
polynomials $S$, and we recursively compute the algebraic invariants of
$S/I_{\alpha,\beta}$. Also, we give precise formulas in special cases.
| arxiv topic:math.AC |
arxiv_dataset-72221604.03033 | Untwisting information from Heegaard Floer homology
math.GT
The unknotting number of a knot is the minimum number of crossings one must
change to turn that knot into the unknot. We work with a generalization of
unknotting number due to Mathieu-Domergue, which we call the untwisting number.
The p-untwisting number is the minimum number (over all diagrams of a knot) of
full twists on at most 2p strands of a knot, with half of the strands oriented
in each direction, necessary to transform that knot into the unknot. In
previous work, we showed that the unknotting and untwisting numbers can be
arbitrarily different. In this paper, we show that a common route for
obstructing low unknotting number, the Montesinos trick, does not generalize to
the untwisting number. However, we use a different approach to get conditions
on the Heegaard Floer correction terms of the branched double cover of a knot
with untwisting number one. This allows us to obstruct several 10 and
11-crossing knots from being unknotted by a single positive or negative twist.
We also use the Ozsv\'ath-Szab\'o tau invariant and the Rasmussen s invariant
to differentiate between the p- and q-untwisting numbers for certain p,q > 1.
| arxiv topic:math.GT |
arxiv_dataset-72231604.03133 | An Update on Local Universality Limits for Correlation Functions
Generated by Unitary Ensembles
math.CA
We survey the current status of universality limits for $m$-point correlation
functions in the bulk and at the edge for unitary ensembles, primarily when the
limiting kernels are Airy, Bessel, or Sine kernels. In particular, we consider
underlying measures on compact intervals, and fixed and varying exponential
weights, as well as universality limits for a variety of orthogonal systems.
The scope of the survey is quite narrow: we do not consider $\beta$ ensembles
for $\beta \neq 2$, nor general Hermitian matrices with independent entries,
let alone more general settings. We include some open problems.
| arxiv topic:math.CA |
arxiv_dataset-72241604.03233 | Precision Ephemerides For Gravitational Wave Searches: II. Cyg X-2
astro-ph.HE
Accreting neutron stars in low-mass X-ray binaries (LMXBs) are candidate
high-frequency persistent gravitational wave sources. These may be detectable
with next generation interferometers such as Advanced LIGO/VIRGO within this
decade. However, the search sensitivity is expected to be limited principally
by the uncertainty in the binary system parameters. We combine new optical
spectroscopy of Cyg X-2 obtained with the Liverpool Telescope (LT) with
available historical radial velocity data, which gives us improved orbital
parameter uncertainties based on a 44-year baseline. We obtained an improvement
of a factor of 2.6 in the orbital period precision and a factor of 2 in the
epoch of inferior conjunction T_0. The updated orbital parameters imply a mass
function of 0.65 +/- 0.01 M_sun, leading to a primary mass (M_1) of 1.67 +/-
0.22 M_sun (for i=62.5 +/- 4 deg). In addition, we estimate the likely orbital
parameter precision through to the expected Advanced LIGO and VIRGO detector
observing period and quantify the corresponding improvement in sensitivity via
the required number of templates.
| arxiv topic:astro-ph.HE |
arxiv_dataset-72251604.03333 | Hybridization and spin-orbit coupling effects in quasi-one-dimensional
spin-1/2 magnet Ba3Cu3Sc4O12
cond-mat.str-el
We study electronic and magnetic properties of the quasi-one-dimensional
spin-1/2 magnet Ba3Cu3Sc4O12 with a distinct orthogonal connectivity of CuO4
plaquettes. An effective low-energy model taking into account spin-orbit
coupling was constructed by means of first-principles calculations. On this
basis a complete microscopic magnetic model of Ba3Cu3Sc4O12, including
symmetric and antisymmetric anisotropic exchange interactions, is derived. The
anisotropic exchanges are obtained from a distinct first-principles numerical
scheme combining, on one hand, the local density approximation taking into
account spin-orbit coupling, and, on the other hand, projection procedure along
with the microscopic theory by Toru Moriya. The resulting tensors of the
symmetric anisotropy favor collinear magnetic order along the structural chains
with the leading ferromagnetic coupling J1 = -9.88 meV. The interchain
interactions J8 = 0.21 meV and J5 = 0.093 meV are antiferromagnetic. Quantum
Monte Carlo simulations demonstrated that the proposed model reproduces the
experimental Neel temperature, magnetization and magnetic susceptibility data.
The modeling of neutron diffraction data reveals an important role of the
covalent Cu-O bonding in Ba3Cu3Sc4O12.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-72261604.03433 | Nonabelian Cohen-Lenstra Heuristics over Function Fields
math.NT
Boston, Bush, and Hajir have developed heuristics, extending the
Cohen-Lenstra heuristics, that conjecture the distribution of the Galois groups
of the maximal unramified pro-p extensions of imaginary quadratic number fields
for p an odd prime. In this paper, we find the moments of their proposed
distribution, and further prove there is a unique distribution with those
moments. Further, we show that in the function field analog, for imaginary
quadratic extensions of F_q(t), the Galois groups of the maximal unramified
pro-p extensions, as q goes to infinity, have the moments predicted by the
Boston, Bush, and Hajir heuristics. In fact, we determine the moments of the
Galois groups of the maximal unramified pro-odd extensions of imaginary
quadratic function fields, leading to a conjecture on Galois groups of the
maximal unramified pro-odd extensions of imaginary quadratic number fields.
| arxiv topic:math.NT |
arxiv_dataset-72271604.03533 | Consistency relations for sharp inflationary non-Gaussian features
astro-ph.CO gr-qc hep-th
If cosmic inflation suffered tiny time-dependent deviations from the
slow-roll regime, these would induce the existence of small scale-dependent
features imprinted in the primordial spectra, with their shapes and sizes
revealing information about the physics that produced them. Small sharp
features could be suppressed at the level of the two-point correlation
function, making them undetectable in the power spectrum, but could be
amplified at the level of the three-point correlation function, offering us a
window of opportunity to uncover them in the non-Gaussian bispectrum. In this
article, we show that sharp features may be analyzed using only data coming
from the three point correlation function parametrizing primordial
non-Gaussianity. More precisely, we show that if features appear in a
particular non-Gaussian triangle configuration (e.g. equilateral, folded,
squeezed), these must reappear in every other configuration according to a
specific relation allowing us to correlate features across the non-Gaussian
bispectrum. As a result, we offer a method to study scale-dependent features
generated during inflation that depends only on data coming from measurements
of non-Gaussianity, allowing us to omit data from the power spectrum.
| arxiv topic:astro-ph.CO gr-qc hep-th |
arxiv_dataset-72281604.03633 | Cooperation and Underlay Mode Selection in Cognitive Radio Network
cs.NI cs.IT math.IT
In this research, we proposes a new method for cooperation and underlay mode
selection in cognitive radio networks. We characterize the maximum achievable
throughput of our proposed method of hybrid spectrum sharing. Hybrid spectrum
sharing is assumed where the Secondary User (SU) can access the Primary User
(PU) channel in two modes, underlay mode or cooperative mode with admission
control. In addition to access the channel in the overlay mode, secondary user
is allowed to occupy the channel currently occupied by the primary user but
with small transmission power. Adding the underlay access modes attains more
opportunities to the secondary user to transmit data. It is proposed that the
secondary user can only exploits the underlay access when the channel of the
primary user direct link is good or predicted to be in non-outage state.
Therefore, the secondary user could switch between underlay spectrum sharing
and cooperation with the primary user. Hybrid access is regulated through
monitoring the state of the primary link. By observing the simulation results,
the proposed model attains noticeable improvement in the system performance in
terms of maximum secondary user throughput than the conventional cooperation
and non-cooperation schemes.
| arxiv topic:cs.NI cs.IT math.IT |
arxiv_dataset-72291604.03733 | Contact inhibition of locomotion and mechanical cross-talk between
cell-cell and cell-substrate adhesion determines the pattern of junctional
tension in epithelial cell aggregates
physics.bio-ph q-bio.CB q-bio.TO
We generated a computational approach to analyze the biomechanics of
epithelial cell aggregates, either island or stripes or entire monolayers, that
combines both vertex and contact-inhibition-of-locomotion models to include
both cell-cell and cell-substrate adhesion. Examination of the distribution of
cell protrusions (adhesion to the substrate) in the model predicted high order
profiles of cell organization that agree with those previously seen
experimentally. Cells acquired an asymmetric distribution of basal protrusions,
traction forces and apical aspect ratios that decreased when moving from the
edge to the island center. Our in silico analysis also showed that tension on
cell-cell junctions and apical stress is not homogeneous across the island.
Instead, these parameters are higher at the island center and scales up with
island size, which we confirmed experimentally using laser ablation assays and
immunofluorescence. Without formally being a 3-dimensional model, our approach
has the minimal elements necessary to reproduce the distribution of cellular
forces and mechanical crosstalk as well as distribution of principal stress in
cells within epithelial cell aggregates. By making experimental testable
predictions, our approach would benefit the mechanical analysis of epithelial
tissues, especially when local changes in cell-cell and/or cell-substrate
adhesion drive collective cell behavior.
| arxiv topic:physics.bio-ph q-bio.CB q-bio.TO |
arxiv_dataset-72301604.03833 | On closest isotropic tensors and their norms
physics.geo-ph
An anisotropic elasticity tensor can be approximated by the closest tensor
belonging to a higher symmetry class. The closeness of tensors depends on the
choice of a criterion. We compare the closest isotropic tensors obtained using
four approaches: the Frobenius 36-component norm, the Frobenius 21-component
norm, the operator norm and the L2 slowness-curve fit. We find that the
isotropic tensors are similar to each other within the range of expected
measurement errors.
| arxiv topic:physics.geo-ph |
arxiv_dataset-72311604.03933 | Kato's Inequality for Magnetic Relativistic Schr\"odinger Operators
math.AP
Kato's inequality is shown for the magnetic relativistic Schr\"odinger
operator $H_{A,m}$ defined as the operator theoretical {\it square root} of the
selfadjoint, magnetic nonrelativistic Schr\"odinger operator
$(-i\nabla-A(x))^2+m^2$ with an $L^{2}_{\text{\rm loc}}$ vector potential
$A(x)$.
| arxiv topic:math.AP |
arxiv_dataset-72321604.04033 | From dripline to dripline: Nuclear astrophysics in the laboratory
nucl-ex
For the better part of a century the field of nuclear astrophysics has aimed
to answer fundamental questions about nature, such as the origin of the
elements and the behavior of high-density, low-temperature matter. Sustained
and concerted efforts in nuclear experiment have been key to achieving progress
in these areas and will continue to be so. Here I will briefly review recent
accomplishments and open questions in experimental nuclear astrophysics.
| arxiv topic:nucl-ex |
arxiv_dataset-72331604.04133 | Scaling Theory of the Mechanical Properties of Amorphous Nano-Films
cond-mat.soft
Numerical Simulations are employed to create amorphous nano-films of a chosen
thickness on a crystalline substrate which induces strain on the film. The
films are grown by a vapor deposition technique which was recently developed to
create very stable glassy films. Using the exact relations between the Hessian
matrix and the shear and bulk moduli we explore the mechanical properties of
the nano-films as a function of the density of the substrate and the film
thickness. The existence of the substrate dominates the mechanical properties
of the combined substrate-film system. Scaling concepts are then employed to
achieve data collapse in a wide range of densities and film thicknesses.
| arxiv topic:cond-mat.soft |
arxiv_dataset-72341604.04233 | Neutrino oscillations in discrete-time quantum walk framework
quant-ph hep-lat
Here we present neutrino oscillation in the frame-work of quantum walks.
Starting from a one spatial dimensional discrete-time quantum walk we present a
scheme of evolutions that will simulate neutrino oscillation. The set of
quantum walk parameters which is required to reproduce the oscillation
probability profile obtained in both, long range and short range neutrino
experiment is explicitly presented. Our scheme to simulate three-generation
neutrino oscillation from quantum walk evolution operators can be physically
realized in any low energy experimental set-up with access to control a single
six-level system, a multiparticle three-qubit or a qubit-qutrit system. We also
present the entanglement between spins and position space, during neutrino
propagation that will quantify the wave function delocalization around
instantaneous average position of the neutrino. This work will contribute
towards understanding neutrino oscillation in the framework of the quantum
information perspective.
| arxiv topic:quant-ph hep-lat |
arxiv_dataset-72351604.04333 | Latent Model Ensemble with Auto-localization
cs.CV
Deep Convolutional Neural Networks (CNN) have exhibited superior performance
in many visual recognition tasks including image classification, object
detection, and scene label- ing, due to their large learning capacity and
resistance to overfit. For the image classification task, most of the current
deep CNN- based approaches take the whole size-normalized image as input and
have achieved quite promising results. Compared with the previously dominating
approaches based on feature extraction, pooling, and classification, the deep
CNN-based approaches mainly rely on the learning capability of deep CNN to
achieve superior results: the burden of minimizing intra-class variation while
maximizing inter-class difference is entirely dependent on the implicit feature
learning component of deep CNN; we rely upon the implicitly learned filters and
pooling component to select the discriminative regions, which correspond to the
activated neurons. However, if the irrelevant regions constitute a large
portion of the image of interest, the classification performance of the deep
CNN, which takes the whole image as input, can be heavily affected. To solve
this issue, we propose a novel latent CNN framework, which treats the most
discriminate region as a latent variable. We can jointly learn the global CNN
with the latent CNN to avoid the aforementioned big irrelevant region issue,
and our experimental results show the evident advantage of the proposed latent
CNN over traditional deep CNN: latent CNN outperforms the state-of-the-art
performance of deep CNN on standard benchmark datasets including the CIFAR-10,
CIFAR- 100, MNIST and PASCAL VOC 2007 Classification dataset.
| arxiv topic:cs.CV |
arxiv_dataset-72361604.04433 | Quantum simulations and many-body physics with light
quant-ph
In this review we discuss the works in the area of quantum simulation and
many-body physics with light, from the early proposals on equilibrium models to
the more recent works in driven dissipative platforms. We start by describing
the founding works on Jaynes-Cummings-Hubbard model and the corresponding
photon-blockade induced Mott transitions and continue by discussing the
proposals to simulate effective spin models and fractional quantum Hall states
in coupled resonator arrays (CRAs). We also analyze the recent efforts to study
out-of-equilibrium many-body effects using driven CRAs, including the
predictions for photon fermionization and crystallization in driven rings of
CRAs as well as other dynamical and transient phenomena. We try to summarise
some of the relatively recent results predicting exotic phases such as
super-solidity and Majorana like modes and then shift our attention to
developments involving one dimensional nonlinear slow light setups. There the
simulation of strongly correlated phases characterising Tonks-Girardeau gases,
Luttinger liquids, and interacting relativistic fermionic models is described.
We review the major theory results and also briefly outline recent developments
in ongoing experimental efforts involving different platforms in circuit QED,
photonic crystals and nanophotonic fibers interfaced with cold atoms.
| arxiv topic:quant-ph |
arxiv_dataset-72371604.04533 | Universal critical behavior of the 2d Ising spin glass
cond-mat.dis-nn
We use finite size scaling to study Ising spin glasses in two spatial
dimensions. The issue of universality is addressed by comparing discrete and
continuous probability distributions for the quenched random couplings. The
sophisticated temperature dependency of the scaling fields is identified as the
major obstacle that has impeded a complete analysis. Once temperature is
relinquished in favor of the correlation length as the basic variable, we
obtain a reliable estimation of the anomalous dimension and of the thermal
critical exponent. Universality among binary and Gaussian couplings is
confirmed to a high numerical accuracy.
| arxiv topic:cond-mat.dis-nn |
arxiv_dataset-72381604.04633 | Kinetics of Deposition in the Diffusion-Controlled Limit
cond-mat.stat-mech cond-mat.soft
The adsorption of particles diffusing in a half-space bounded by the
substrate and irreversibly sticking to the substrate upon contacts is
investigated. We show that when absorbing particles are planar disks diffusing
in the three-dimensional half-space, the coverage approaches its saturated
jamming value as $t^{-1}$ in the large time limit [generally as $t^{-1/(d-1)}$
when the substrate is $d$ dimensional and $d>1$, and as $e^{-t/\ln(t)}$ when
$d=1$]. We also analyze the asymptotic behavior when particles are spherical
and when particles are planar aligned squares.
| arxiv topic:cond-mat.stat-mech cond-mat.soft |
arxiv_dataset-72391604.04733 | Symplectic Involutions, quadratic pairs and function fields of conics
math.RA
In this paper we study symplectic involutions and quadratic pairs that become
hyperbolic over the function field of a conic. In particular, we classify them
in degree 4 and deduce results on 5 dimensional minimal quadratic forms, thus
extending to arbitrary fields some results of [24], which were only known in
characteristic different from 2.
| arxiv topic:math.RA |
arxiv_dataset-72401604.04833 | Subgroups of the Torelli group generated by two symmetric bounding pair
maps
math.GT
Let {a,b} and {c,d} be two pairs of bounding simple closed curves on an
oriented surface which intersect nontrivialy. We prove that if these pairs are
invariant under the action of an orientation reversing involution, then the
corresponding bounding pair maps generate a free group. This supports the
conjecture stated by C. Leininger and D. Margalit that any pair of elements of
the Torelli group either commute or generate a free group.
| arxiv topic:math.GT |
arxiv_dataset-72411604.04933 | On plane polynomial automorphisms commuting with simple derivations
math.AC
We consider the subgroup Aut(D) consisting of automorphisms of K[x,y]
commuting with a derivation D, where K is an algebraically closed field of
characteristic 0. We prove that if D is simple (i.e. D does not stabilize
non-trivial ideals), then Aut(D)=1, in the case where D is of Shamsuddin type
this result was proven by R.Baltazar in 2014 (arXiv:1412.8373). Moreover, we
describe Aut(D) for Shamsuddin type derivations and deduce that Aut(D)=1 for a
general such derivation implies D is simple.
| arxiv topic:math.AC |
arxiv_dataset-72421604.05033 | Fingerprints of Majorana fermions in spin-resolved subgap spectroscopy
cond-mat.mes-hall
When a strongly correlated quantum dot is tunnel-coupled to a superconductor,
it leads to the formation of Shiba bound states inside the superconducting gap.
They have been measured experimentally in a superconductor-quantum dot-normal
lead setup. Side coupling the quantum dot to a topological superconducting wire
that supports Majorana bound states at its ends, drastically affects the
structure of the Shiba states and induces supplementary in-gap states. The
anomalous coupling between the Majorana bound states and the quantum dot gives
rise to a characteristic imbalance in the spin resolved spectral functions for
the dot operators. These are clear fingerprints for the existence of Majorana
fermions and they can be detected experimentally in transport measurements. In
terms of methods employed, we have used analytical approaches combined with the
numerical renormalization group approach.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-72431604.05133 | Spatial dependent spontaneous emission of an atom in a semi-infinite
waveguide of rectangular cross section
quant-ph
We study a quantum electrodynamics (QED) system made of an two-level atom and
a semi-infinite rectangular waveguide, which behaves as a perfect mirror in one
end. The spatial dependence of the atomic spontaneous emission has been
included in the coupling strength relevant to the eigenmodes of the waveguide.
The role of retardation is studied for the atomic transition frequency far away
from the cutoff frequencies. The atom-mirror distance introduces different
phases and retardation times into the dynamics of the atom interacting
resonantly with the corresponding transverse modes. It is found that the upper
state population decreases from its initial as long as the atom-mirror distance
does not vanish, and is lowered and lowered when more and more transverse modes
are resonant with the atom. The atomic spontaneous emission can be either
suppressed or enhanced by adjusting the atomic location for short retardation
time. There are partial revivals and collapses due to the photon reabsorbed and
re-emitted by the atom for long retardation time.
| arxiv topic:quant-ph |
arxiv_dataset-72441604.05233 | On the possibility of determining the distance to the Galactic center
from the geometry of spiral arm segments
astro-ph.GA
A new approach to determining the solar galactocentric distance, $R_0$, from
the geometry of spiral-arm segments is proposed. Geometric aspects of the
problem are analyzed and a simplified three-point method for estimating $R_0$
from objects in a spiral segment is developed in order to test the proposed
approach. An estimate of $R_0 = 8.44 \pm 0.45$ kpc is obtained by applying the
method to masers with measured trigonometric parallaxes, and statistical
properties of the $R_0$ estimation from spiral segments are analyzed.
| arxiv topic:astro-ph.GA |
arxiv_dataset-72451604.05333 | Stellar and Black Hole Mass Densities as Empirical Tracers of
Co-evolution Show Lock-step Growth since $z{\sim}3$
astro-ph.GA
At redshifts beyond $z{\sim}1$ measuring the black hole galaxy relations
proves to be a difficult task. The bright light of the AGN aggravates
deconvolution of black hole and galaxy properties. On the other hand high
redshift data on these relations is vital to understand in what ways galaxies
and black holes co-evolve and in what ways they don't. In this work we use
black hole (BHMDs) and stellar mass densities (SMDs) to constrain the possible
co-evolution of black holes with their host galaxies since $z{\sim}5$. The
BHMDs are calculated from quasar luminosity functions (QLF) using the Soltan
argument, while we use integrals over stellar mass functions (SMFs) or the star
formation rate density to obtain values for the stellar mass density. We find
that both quantities grow in lock-step below redshifts of $z{\sim}3$ with a
non-evolving BHMD to SMD ratio. A fit to the data assuming a power law relation
between the BHMD and the SMD yields exponents around unity ($1.0{-}1.5$). Up to
$z{\sim}5$ the BHMD to SMD ratio doesn't show a strong evolution given the
larger uncertainty in the completeness of high-redshift datasets. Our results,
always applying the same analysis technique, seem to be consistent across all
adopted data sets.
| arxiv topic:astro-ph.GA |
arxiv_dataset-72461604.05433 | Uniform approximation of Bloch functions and the boundedness of the
integration operator on $H^\infty$
math.CV math.CA math.FA
We obtain a necessary and sufficient condition for the operator of
integration to be bounded on $H^\infty$ in a simply connected domain. The main
ingredient of the proof is a new result on uniform approximation of Bloch
functions. This gives a full characterization of symbols of certain Volterra
operators that act on bounded analytic functions in the disc if the symbol is
assumed to be univalent. Without this assumption the answer is not known, and
as the example at the end of the paper shows, the natural answer is definitely
false.
| arxiv topic:math.CV math.CA math.FA |
arxiv_dataset-72471604.05533 | On Arakawa-Kaneko zeta-functions associated with $GL_2(\mathbb{C})$ and
their functional relations
math.NT
We construct a certain class of Arakawa--Kaneko zeta-functions associated
with $GL_2(\mathbb{C})$, which includes the ordinary Arakawa--Kaneko
zeta-function. We also define poly-Bernoulli polynomials associated with
$GL_2(\mathbb{C})$ which appear in their special values of these
zeta-functions. We prove some functional relations for these zeta-functions,
which are regarded as interpolation formulas of various relations among
poly-Bernoulli numbers. Considering their special values, we prove difference
relations and duality relations for poly-Bernoulli polynomials associated with
$GL_2(\mathbb{C})$.
| arxiv topic:math.NT |
arxiv_dataset-72481604.05633 | Online Human Action Detection using Joint Classification-Regression
Recurrent Neural Networks
cs.CV
Human action recognition from well-segmented 3D skeleton data has been
intensively studied and has been attracting an increasing attention. Online
action detection goes one step further and is more challenging, which
identifies the action type and localizes the action positions on the fly from
the untrimmed stream data. In this paper, we study the problem of online action
detection from streaming skeleton data. We propose a multi-task end-to-end
Joint Classification-Regression Recurrent Neural Network to better explore the
action type and temporal localization information. By employing a joint
classification and regression optimization objective, this network is capable
of automatically localizing the start and end points of actions more
accurately. Specifically, by leveraging the merits of the deep Long Short-Term
Memory (LSTM) subnetwork, the proposed model automatically captures the complex
long-range temporal dynamics, which naturally avoids the typical sliding window
design and thus ensures high computational efficiency. Furthermore, the subtask
of regression optimization provides the ability to forecast the action prior to
its occurrence. To evaluate our proposed model, we build a large streaming
video dataset with annotations. Experimental results on our dataset and the
public G3D dataset both demonstrate very promising performance of our scheme.
| arxiv topic:cs.CV |
arxiv_dataset-72491604.05733 | The Solar Twin Planet Search III. The [Y/Mg] clock: estimating stellar
ages of solar-type stars
astro-ph.SR
Solar twins are stars with similar stellar (surface) parameters to the Sun
that can have a wide range of ages. This provide an opportunity to analyze the
variation of their chemical abundances with age. Nissen (2015) recently
suggested that the abundances of the s-process element Y and the
$\alpha$-element Mg could be used to estimate stellar ages. This paper aims to
determine with high precision the Y, Mg, and Fe abundances for a sample of 88
solar twins that span a broad age range ($0.3-10.0$\,Gyr) and investigate their
use for estimating ages. We obtained high-quality Magellan Inamori Kyocera
Echelle (MIKE) spectra and determined Y and Mg abundances using equivalent
widths and a line-by-line differential method within a 1D LTE framework.
Stellar parameters and iron abundances were measured in Paper I of this series
for all stars, but a few (three) required a small revision. The [Y/Mg] ratio
shows a strong correlation with age. It has a slope of -0.041$\pm$0.001 dex/Gyr
and a significance of 41 $\sigma$. This is in excellent agreement with the
relation first proposed by Nissen (2015). We found some outliers that turned
out to be binaries where mass transfer may have enhanced the yttrium abundance.
Given a precise measurement of [Y/Mg] with typical error of 0.02 dex in solar
twins, our formula can be used to determine a stellar age with $\sim$0.8 Gyr
precision in the 0 to 10 Gyr range.
| arxiv topic:astro-ph.SR |
arxiv_dataset-72501604.05833 | Concepts of Ferrovalley Material and Anomalous Valley Hall Effect
cond-mat.mtrl-sci cond-mat.mes-hall
Valleytronics rooted in the valley degree of freedom is of both theoretical
and technological importance as it offers additional opportunities for
information storage and electronic, magnetic and optical switches. In analogy
to ferroelectric materials with spontaneous charge polarization in electronics,
as well as ferromagnetic materials with spontaneous spin polarization in
spintronics, here we introduce a new member of ferroic-family, i.e. a
ferrovalley material with spontaneous valley polarization. Combining a two-band
kp model with first-principles calculations, we show that 2H-VSe2 monolayer,
where the spin-orbit coupling coexists with the intrinsic exchange interaction
of transition-metal-d electrons, is such a room-temperature ferrovalley
material. We further predict that such system could demonstrate many
distinctive properties, for example, chirality-dependent optical band gap and
more interestingly, anomalous valley Hall effect. On account of the latter, a
series of functional devices based on ferrovalley materials, such as
valley-based nonvolatile random access memory, valley filter, are contemplated
for valleytronic applications.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall |
arxiv_dataset-72511604.05933 | Parametric Object Motion from Blur
cs.CV
Motion blur can adversely affect a number of vision tasks, hence it is
generally considered a nuisance. We instead treat motion blur as a useful
signal that allows to compute the motion of objects from a single image.
Drawing on the success of joint segmentation and parametric motion models in
the context of optical flow estimation, we propose a parametric object motion
model combined with a segmentation mask to exploit localized, non-uniform
motion blur. Our parametric image formation model is differentiable w.r.t. the
motion parameters, which enables us to generalize marginal-likelihood
techniques from uniform blind deblurring to localized, non-uniform blur. A
two-stage pipeline, first in derivative space and then in image space, allows
to estimate both parametric object motion as well as a motion segmentation from
a single image alone. Our experiments demonstrate its ability to cope with very
challenging cases of object motion blur.
| arxiv topic:cs.CV |
arxiv_dataset-72521604.06033 | A Lindblad Model of Quantum Brownian Motion
quant-ph cond-mat.quant-gas
The theory of quantum Brownian motion describes the properties of a large
class of open quantum systems. Nonetheless, its description in terms of a
Born-Markov master equation, widely used in the literature, is known to violate
the positivity of the density operator at very low temperatures. We study an
extension of existing models, leading to an equation in the Lindblad form,
which is free of this problem. We study the dynamics of the model, including
the detailed properties of its stationary solution, for both constant and
position-dependent coupling of the Brownian particle to the bath, focusing in
particular on the correlations and the squeezing of the probability
distribution induced by the environment
| arxiv topic:quant-ph cond-mat.quant-gas |
arxiv_dataset-72531604.06133 | Embedded all relevant feature selection with Random Ferns
cs.LG
Many machine learning methods can produce variable importance scores
expressing the usability of each feature in context of the produced model;
those scores on their own are yet not sufficient to generate feature selection,
especially when an all relevant selection is required. Although there are
wrapper methods aiming to solve this problem, they introduce a substantial
increase in the required computational effort.
In this paper I investigate an idea of incorporating all relevant selection
within the training process by producing importance for implicitly generated
shadows, attributes irrelevant by design. I propose and evaluate such a method
in context of random ferns classifier. Experiment results confirm the
effectiveness of such approach, although show that fully stochastic nature of
random ferns limits its applicability either to small dimensions or as a part
of a broader feature selection procedure.
| arxiv topic:cs.LG |
arxiv_dataset-72541604.06233 | Interaction of two magnetic resonance modes in polar phase of superfluid
3He
cond-mat.other
We report results of low frequency nuclear magnetic resonance (NMR)
experiments in the superfluid polar phase of 3He which is stabilized by a new
type of "nematic" aerogel - nafen. We have found that an interaction between
transverse and longitudinal NMR modes may essentially influence the spin
dynamics. Theoretical formulas for NMR resonant frequencies are derived and
applied for interpretation of the experimental results.
| arxiv topic:cond-mat.other |
arxiv_dataset-72551604.06333 | Submanifolds and differential forms on Carnot manifolds, after M. Gromov
and M. Rumin
math.DG math.MG
The purpose of these notes is to explain parts of Gromov's survey of
Carnot-Carathedory spaces, in the light of subsequent results of M. Rumin.
Among the rich material provided by Gromov, most of which pertains to analysis
on metric spaces, we choose to concentrate on the H{\"o}lder equivalence
problem for Carnot manifolds. The notes go to some extent into the PDE
technique used by Gromov in order to construct horizontal submanifolds. Rumin's
complex is explained too. The upshot is that both methods yield more or less
the same conclusions as far as the H{\"o}lder equivalence problem is concerned.
| arxiv topic:math.DG math.MG |
arxiv_dataset-72561604.06433 | Walk and Learn: Facial Attribute Representation Learning from Egocentric
Video and Contextual Data
cs.CV
The way people look in terms of facial attributes (ethnicity, hair color,
facial hair, etc.) and the clothes or accessories they wear (sunglasses, hat,
hoodies, etc.) is highly dependent on geo-location and weather condition,
respectively. This work explores, for the first time, the use of this
contextual information, as people with wearable cameras walk across different
neighborhoods of a city, in order to learn a rich feature representation for
facial attribute classification, without the costly manual annotation required
by previous methods. By tracking the faces of casual walkers on more than 40
hours of egocentric video, we are able to cover tens of thousands of different
identities and automatically extract nearly 5 million pairs of images connected
by or from different face tracks, along with their weather and location
context, under pose and lighting variations. These image pairs are then fed
into a deep network that preserves similarity of images connected by the same
track, in order to capture identity-related attribute features, and optimizes
for location and weather prediction to capture additional facial attribute
features. Finally, the network is fine-tuned with manually annotated samples.
We perform an extensive experimental analysis on wearable data and two standard
benchmark datasets based on web images (LFWA and CelebA). Our method
outperforms by a large margin a network trained from scratch. Moreover, even
without using manually annotated identity labels for pre-training as in
previous methods, our approach achieves results that are better than the state
of the art.
| arxiv topic:cs.CV |
arxiv_dataset-72571604.06533 | A New Non-Planetary Interpretation of the Microlensing Event
OGLE-2013-BLG-0723
astro-ph.EP
Recently, the discovery of a Venus-mass planet orbiting a brown-dwarf host in
a binary system was reported from the analysis of the microlensing event
OGLE-2013-BLG-0723. We reanalyze the event considering the possibility of other
interpretations. From this, we find a new solution where the lens is composed
of 2 bodies in contrast to the 3-body solution of the previous analysis. The
new solution better explains the observed light curve than the previous
solution with $\Delta\chi^2\sim 202$, suggesting that the new solution is a
correct model for the event. From the estimation of the physical parameters
based on the new interpretation, we find that the lens system is composed of
two low-mass stars with $\sim 0.2\ M_\odot$ and $\sim 0.1\ M_\odot$ and located
at a distance $\sim 3$ kpc. The fact that the physical parameters correspond to
those of the most common lens population located at a distance with a large
lensing probability further supports the likelihood of the new interpretation.
Considering that two dramatically different solutions can approximately explain
the observed light curve, the event suggests the need of carefully testing all
possible lens-system geometries.
| arxiv topic:astro-ph.EP |
arxiv_dataset-72581604.06633 | Phase reduction theory for hybrid nonlinear oscillators
nlin.AO
Hybrid dynamical systems characterized by discrete switching of smooth
dynamics have been used to model various rhythmic phenomena. However, the phase
reduction theory, a fundamental framework for analyzing the synchronization of
limit-cycle oscillations in rhythmic systems, has mostly been restricted to
smooth dynamical systems. Here we develop a general phase reduction theory for
weakly perturbed limit cycles in hybrid dynamical systems that facilitates
analysis, control, and optimization of nonlinear oscillators whose smooth
models are unavailable or intractable. On the basis of the generalized theory,
we analyze injection locking of hybrid limit-cycle oscillators by periodic
forcing and reveal their characteristic synchronization properties, such as
ultrafast and robust entrainment to the periodic forcing and logarithmic
scaling at the synchronization transition. We also illustrate the theory by
analyzing the synchronization dynamics of a simple physical model of biped
locomotion.
| arxiv topic:nlin.AO |
arxiv_dataset-72591604.06733 | Cascading Failures in AC Electricity Grids
nlin.AO cs.SY
Sudden failure of a single transmission element in a power grid can induce a
domino effect of cascading failures, which can lead to the isolation of a large
number of consumers or even to the failure of the entire grid. Here we present
results of the simulation of cascading failures in power grids, using an
alternating current (AC) model. We first apply this model to a regular square
grid topology. For a random placement of consumers and generators on the grid,
the probability to find more than a certain number of unsupplied consumers
decays as a power law and obeys a scaling law with respect to system size.
Varying the transmitted power threshold above which a transmission line fails
does not seem to change the power law exponent $q \approx 1.6$. Furthermore, we
study the influence of the placement of generators and consumers on the number
of affected consumers and demonstrate that large clusters of generators and
consumers are especially vulnerable to cascading failures. As a real-world
topology we consider the German high-voltage transmission grid. Applying the
dynamic AC model and considering a random placement of consumers, we find that
the probability to disconnect more than a certain number of consumers depends
strongly on the threshold. For large thresholds the decay is clearly
exponential, while for small ones the decay is slow, indicating a power law
decay.
| arxiv topic:nlin.AO cs.SY |
arxiv_dataset-72601604.06833 | Counting odd cycles in locally dense graphs
math.CO
We prove that for any given $\varepsilon>0$ and $d\in [0,1]$, every
sufficiently large $(\varepsilon, d)$-dense graph $G$ contains for each odd
integer $r$ at least $(d^r-\varepsilon)|V(G)|^r$ cycles of length $r$. Here,
$G$ being $(\varepsilon, d)$-dense means that every set $X$ containing at
least~$\varepsilon\,|V(G)|$ vertices spans at least $\tfrac d2\, |X|^2$ edges,
and what we really count is the number of homomorphisms from an $r$-cycle into
$G$.
The result adresses a question of Y. Kohayakawa, B. Nagle, V. R\"odl, and M.
Schacht.
| arxiv topic:math.CO |
arxiv_dataset-72611604.06933 | The discrete sign problem: uniqueness, recovery algorithms and phase
retrieval applications
math.NA
In this paper we consider the following real-valued and finite dimensional
specific instance of the 1-D classical phase retrieval problem. Let ${\bf
F}\in\mathbb{R}^N$ be an $N$-dimensional vector, whose discrete Fourier
transform has a compact support. The sign problem is to recover ${\bf F}$ from
its magnitude $|{\bf F}|$. First, in contrast to the classical 1-D phase
problem which in general has multiple solutions, we prove that with sufficient
over-sampling, the sign problem admits a unique solution. Next, we show that
the sign problem can be viewed as a special case of a more general piecewise
constant phase problem. Relying on this result, we derive a computationally
efficient and robust to noise sign recovery algorithm. In the noise-free case
and with a sufficiently high sampling rate, our algorithm is guaranteed to
recover the true sign pattern. Finally, we present two phase retrieval
applications of the sign problem: (i) vectorial phase retrieval with three
measurement vectors; and (ii) recovery of two well separated 1-D objects.
| arxiv topic:math.NA |
arxiv_dataset-72621604.07033 | MOCCA code for star cluster simulations - V. Initial globular cluster
conditions influence on blue stragglers
astro-ph.GA astro-ph.IM physics.comp-ph
The paper presents an analysis of properties of populations of blue
stragglers (BSs) in evolving globular clusters, based on numerical simulations
done with the MOCCA code for various initial globular clusters conditions.
We find that various populations of BSs strongly depend on the initial
semi-major axes distributions. With a significant number of compact binaries,
the number of evolutionary BSs can be also significant. In turn, for semi-major
axes distributions preferring binaries with wider orbits, dynamical BSs are the
dominant ones. Their formation scenario is very distinct: for wide binaries the
number of dynamical interactions is significantly larger. Most interactions are
weak and increase only slightly the eccentricities. However, due to a large
number of such interactions, the eccentricities of a number of binaries finally
get so large that the stars collide.
We study how larger initial clusters' concentrations influence the BSs.
Besides the expected increase of the number of dynamically created BSs (for
denser GCs the probabilities of strong dynamical interactions and collisions
are higher), we find that the number of the evolutionary BSs is not affected
even by very high initial concentrations. This has a very important implication
on observations - it supports the theory that the evolutionary BSs are the
result of the unperturbed evolution of the primordial binaries.
In addition, the paper presents the evolution of the ratio between the number
of BSs in binaries and as single stars R_B/S. For a vast diversity of models,
the ratio R_B/S approaches the value ~0.4. Additionally, we identified two
subgroups which differ in the initial semi-major axes distributions. The first
group starts with a high ratio R_B/S, it decreases with time and settles around
0.4. The second group starts with lower values of the ratio R_B/S ... . (etc.,
abstract continues)
| arxiv topic:astro-ph.GA astro-ph.IM physics.comp-ph |
arxiv_dataset-72631604.07133 | Spectrum of commuting graphs of some classes of finite groups
math.GR
In this paper, we initiate the study of spectrum of the commuting graphs of
finite non-abelian groups. We first compute the spectrum of this graph for
several classes of finite groups, in particular AC-groups. We show that the
commuting graphs of finite non-abelian AC-groups are integral. We also show
that the commuting graph of a finite non-abelian group $G$ is integral if $G$
is not isomorphic to the symmetric group of degree $4$ and the commuting graph
of $G$ is planar. Further it is shown that the commuting graph of $G$ is
integral if the commuting graph of $G$ is toroidal.
| arxiv topic:math.GR |
arxiv_dataset-72641604.07233 | Dependence of GAMA galaxy halo masses on the cosmic web environment from
100 square degrees of KiDS weak lensing data
astro-ph.GA
Galaxies and their dark matter haloes are part of a complex network of mass
structures, collectively called the cosmic web. Using the tidal tensor
prescription these structures can be classified into four cosmic environments:
voids, sheets, filaments and knots. As the cosmic web may influence the
formation and evolution of dark matter haloes and the galaxies they host, we
aim to study the effect of these cosmic environments on the average mass of
galactic haloes. To this end we measure the galaxy-galaxy lensing profile of
91,195 galaxies, within 0.039 < z < 0.263, from the spectroscopic Galaxy And
Mass Assembly (GAMA) survey, using ~100 square degrees of overlapping data from
the Kilo-Degree Survey (KiDS). In each of the four cosmic environments we model
the contributions from group centrals, satellites and neighbouring groups to
the stacked galaxy-galaxy lensing profiles. After correcting the lens samples
for differences in the stellar mass distribution, we find no dependence of the
average halo mass of central galaxies on their cosmic environment. We do find a
significant increase in the average contribution of neighbouring groups to the
lensing profile in increasingly dense cosmic environments. We show, however,
that the observed effect can be entirely attributed to the galaxy density at
much smaller scales (within 4 Mpc/h), which is correlated with the density of
the cosmic environments. Within our current uncertainties we find no direct
dependence of galaxy halo mass on their cosmic environment.
| arxiv topic:astro-ph.GA |
arxiv_dataset-72651604.07333 | A filtration on rings of representations of non-Archimedean $GL_n$
math.RT
Let $F$ be a $p$-adic field. Let $\mathcal{R}$ be the Grothendieck ring of
complex smooth finite-length representations of the groups
$\{GL_n(F)\}_{n=0}^\infty$ taken together, with multiplication defined in the
sense of parabolic induction. We introduce a width invariant for elements of
$\mathcal{R}$ and show that it gives an increasing filtration on the ring.
Irreducible representations of width $1$ are precisely those known as ladder
representations. We thus obtain a necessary condition on irreducible factors of
a product of two ladder representations. For such a product we further
establish a multiplicity-one phenomenon, which was previously observed in
special cases.
| arxiv topic:math.RT |
arxiv_dataset-72661604.07433 | CN Zeeman and dust polarization in a high-mass cold clump
astro-ph.GA
We report on the young massive clump (G35.20w) in W48 that previous molecular
line and dust observations have revealed to be in the very early stages of star
formation. Based on virial analysis, we find that a strong field of ~1640
microG is required to keep the clump in pressure equilibrium. We performed a
deep Zeeman effect measurement of the 113 GHz CN (1-0) line towards this clump
with the IRAM 30 m telescope. We combine simultaneous fitting of all CN
hyperfines with Monte Carlo simulations for a large range in realization of the
magnetic field to obtain a constraint on the line-of-sight field strength of
-687 +/- 420 microG. We also analyze archival dust polarization observations
towards G35.20w. A strong magnetic field is implied by the remarkably ordered
field orientation that is perpendicular to the longest axis of the clump. Based
on this, we also estimate the plane-of-sky component of the magnetic field to
be ~740 microG. This allows for a unique comparison of the two orthogonal
measurements of magnetic field strength of the same region and at similar
spatial scales. The expected total field strength shows no significant conflict
between the observed field and that required for pressure equilibrium. By
producing a probability distribution for a large range in field geometries, we
show that plane-of-sky projections are much closer to the true field strengths
than line-of-sight projections. This can present a significant challenge for
Zeeman measurements of magnetized structures, even with ALMA. We also show that
CN molecule does not suffer from depletion on the observed scales in the
predominantly cold and highly deuterated core in an early stage of high-mass
star formation and is thus a good tracer of the dense gas.
| arxiv topic:astro-ph.GA |
arxiv_dataset-72671604.07533 | A Characterisation of the Fourier transform on the Schwartz-Bruhat space
of locally compact Abelian groups
math.FA math.CA
We obtain a characterisation of the Fourier transform on the space of
Schwartz-Bruhat functions on locally compact Abelian groups. The result states
that any appropriately additive bijection of the Schwartz space onto itself,
which interchanges convolution and pointwise products is essentially the
Fourier transform. The proof of this result is very similar to that obtained by
the author recently for the Euclidean Fourier transform.
| arxiv topic:math.FA math.CA |
arxiv_dataset-72681604.07633 | Relativistic corrections to the pair $B_c$-meson production in $e^+e^-$
annihilation
hep-ph
Relativistic corrections to the pair $B_c$-meson production in
$e^+e^-$-annihilation are calculated. We investigate a production of pair
pseudoscalar, vector and pseudoscalar+vector $B_c$-mesons in the leading order
perturbative quantum chromodynamics and relativistic quark model. Relativistic
expressions of the pair production cross sections are obtained. Their numerical
evaluation shows that relativistic effects in the production amplitudes and
bound state wave functions three times reduce nonrelativistic results at the
center-of-mass energy s=22 GeV.
| arxiv topic:hep-ph |
arxiv_dataset-72691604.07733 | On relations between the classes $\mathcal S$ and $\mathcal U$
math.CV
Let ${\mathcal A}$ denote the family of all functions $f$ analytic in the
unit disk $\ID$ and satisfying the normalization $f(0)=0= f'(0)-1$. Let
$\mathcal{S}$ denote the subclass of ${\mathcal A}$ consisting of univalent
functions in $\ID$. We consider the subclass $\mathcal{U} $ of $\mathcal{S}$
that is defined by the condition that for its members $f$ the condition $$\left
|\left (\frac{z}{f(z)} \right )^{2}f'(z)-1\right | < 1 ~\mbox{ for $z\in \ID$}
$$ holds. To theses relations belong striking similarities and on the other
hand big differences. We show that some results about $\mathcal{S}$ can be
improved for $\mathcal{U}$, while others cannot.
| arxiv topic:math.CV |
arxiv_dataset-72701604.07833 | Spectral Line De-confusion in an Intensity Mapping Survey
astro-ph.CO
Spectral line intensity mapping has been proposed as a promising tool to
efficiently probe the cosmic reionization and the large-scale structure.
Without detecting individual sources, line intensity mapping makes use of all
available photons and measures the integrated light in the source confusion
limit, to efficiently map the three-dimensional matter distribution on large
scales as traced by a given emission line. One particular challenge is the
separation of desired signals from astrophysical continuum foregrounds and line
interlopers. Here we present a technique to extract large-scale structure
information traced by emission lines from different redshifts, embedded in a
three-dimensional intensity mapping data cube. The line redshifts are
distinguished by the anisotropic shape of the power spectra when projected onto
a common coordinate frame. We consider the case where high-redshift [CII] lines
are confused with multiple low-redshift CO rotational lines. We present a
semi-analytic model for [CII] and CO line estimates based on the cosmic
infrared background measurements, and show that with a modest instrumental
noise level and survey geometry, the large-scale [CII] and CO power spectrum
amplitudes can be successfully extracted from a confusion-limited data set,
without external information. We discuss the implications and limits of this
technique for possible line intensity mapping experiments.
| arxiv topic:astro-ph.CO |
arxiv_dataset-72711604.07933 | Spin dynamics of large-spin (spinor) fermions in a harmonic trap
cond-mat.quant-gas
Understanding the collective dynamics in a many-body system has been a
central task in condensed matter physics. To achieve this task, we develop a
Hartree-Fock theory to study the collective oscillations of spinor Fermi
system, motivated by recent experiment on spin-9/2 fermions. We observe an
oscillation period shoulder for small rotation angles. Different from previous
studies, where the shoulder is found connected to the resonance from periodic
to running phase, here the system is always in a running phase in the two-body
phase space. This shoulder survives even in the many-body oscillations, which
could be tested in the experiments. We also show how these collective
oscillations evolve from two- to many-body. Our theory provides an alternative
way to understand the collective dynamics in large-spin Fermi systems.
| arxiv topic:cond-mat.quant-gas |
arxiv_dataset-72721604.08033 | Polyelectrolyte assisted charge titration spectrometry: applications to
latex and oxide nanoparticles
cond-mat.mtrl-sci cond-mat.soft
The electrostatic charge density of particles is of paramount importance for
the control of the dispersion stability. Conventional methods use
potentiometric, conductometric or turbidity titration but require large amount
of samples. Here we report a simple and cost-effective method called
polyelectrolyte assisted charge titration spectrometry or PACTS. The technique
takes advantage of the propensity of oppositely charged polymers and particles
to assemble upon mixing, leading to aggregation or phase separation. The mixed
dispersions exhibit a maximum in light scattering as a function of the
volumetric ratio X, and the peak position XMax is linked to the particle charge
density according to {\sigma} ~ D0 XMax where D0 is the particle diameter. The
PACTS is successfully applied to organic latex, aluminum and silicon oxide
particles of positive or negative charge using poly(diallyldimethylammonium
chloride) and poly(sodium 4-styrenesulfonate). The protocol is also optimized
with respect to important parameters such as pH and concentration, and to the
polyelectrolyte molecular weight. The advantages of the PACTS technique are
that it requires minute amounts of sample and that it is suitable to a broad
variety of charged nano-objects.
| arxiv topic:cond-mat.mtrl-sci cond-mat.soft |
arxiv_dataset-72731604.08133 | Reflection Of Propagating Slow Magneto-acoustic Waves In Hot Coronal
Loops : Multi-instrument Observations and Numerical Modelling
astro-ph.SR
Slow MHD waves are important tools for understanding the coronal structures
and dynamics. In this paper, we report a number of observations, from X-Ray
Telescope (XRT) on board HINODE and SDO/AIA of reflecting longitudinal waves in
hot coronal loops. To our knowledge, this is the first report of this kind as
seen from the XRT and simultaneously with the AIA. The wave appears after a
micro-flare occurs at one of the footpoints. We estimate the density and the
temperature of the loop plasma by performing DEM analysis on the AIA image
sequence. The estimated speed of propagation is comparable or lower than the
local sound speed suggesting it to be a propagating slow wave. The intensity
perturbation amplitudes, in every case, falls very rapidly as the perturbation
moves along the loop and eventually vanishes after one or more reflections. To
check the consistency of such reflection signatures with the obtained loop
parameters, we perform a 2.5D MHD simulation, which uses the parameters
obtained from our observation as inputs and performed forward modelling to
synthesize AIA 94~\r{A} images. Analyzing the synthesized images, we obtain the
same properties of the observables as for the real observation. From the
analysis we conclude that a footpoint heating can generate slow wave which then
reflects back and forth in the coronal loop before fading out. Our analysis on
the simulated data shows that the main agent for this damping is the
anisotropic thermal conduction.
| arxiv topic:astro-ph.SR |
arxiv_dataset-72741604.08233 | Simple and Accurate Oscillation Probabilities for Three Coupled
Neutrinos Propagating in Matter
hep-ph
Within a conventional Hamiltonian description, we find accurate closed-form
expressions for the oscillation probabilities of three coupled neutrinos
propagating in matter. Subtle cancelations that occur in coefficients of our
formulation are avoided for all transitions $\nu_a \to \nu_b$ by transforming
to a different set of coefficients presented in an appendix of this paper. The
neutrino mass eigenvalues are easily obtained numerically as the solution of a
cubic equation. Our methods are illustrated for flavor-changing transitions in
the $(\nu_e,\nu_\mu)$ sector. The resulting analytic expressions oscillation
probabilities, which are particularly simple, are also accurate to a few
percent over all regions of interest at present and the envisioned future
neutrino facilities. While somewhat less accurate than numerical simulations,
our approximate expressions are sufficiently accuracy to obviate the need for
exact computer simulations in many circumstances.
| arxiv topic:hep-ph |
arxiv_dataset-72751604.08333 | Cancellation of Infrared Divergence in Inclusive Production of Lepton
Pair Near the Threshold of Heavy Quarkonia
hep-ph
The detailed proof of cancellation of topologically unfactorized infrared
divergences in the inclusive production of lepton pair close to the threshold
of heavy quarkonia is presented. To make the effects of transition between
states containing heavy quark pairs, which is important in such cancellation,
the final detected states are constrained to be lepton pair near the threshold
of the heavy quarkonia instead of heavy quarkonia themselves. Such cancellation
is crucial for the NRQCD factorization of these processes.
| arxiv topic:hep-ph |
arxiv_dataset-72761604.08433 | From almost (para)-complex structures to affine structures on Lie groups
math.DG
Let $G=H\ltimes K$ denote a semidirect product Lie group with Lie algebra
$\mathfrak g=\mathfrak h \oplus \mathfrak k$, where $\mathfrak k$ is an ideal
and $\mathfrak h$ is a subalgebra of the same dimension as $\mathfrak k$. There
exist some natural split isomorphisms $S$ with $S^2=\pm \,Id$ on $\mathfrak g$:
given any linear isomorphism $j:\mathfrak h \to \mathfrak k$, we have the
almost complex structure $J(x,v)=(-j^{-1}v, jx)$ and the almost paracomplex
structure $E(x,v)=(j^{-1}v, jx)$. In this work we show that the integrability
of the structures $J$ and $E$ above is equivalent to the existence of a
left-invariant torsion-free connection $\nabla$ on $G$ such that $\nabla
J=0=\nabla E$ and also to the existence of an affine structure on $H$.
Applications include complex, paracomplex and symplectic geometries.
| arxiv topic:math.DG |
arxiv_dataset-72771604.08533 | Exact two-body quantum dynamics of an electron-hole pair in
semiconductor coupled quantum wells: a time-dependent approach
cond-mat.mes-hall
We simulate the time-dependent coherent dynamics of a spatially indirect
exciton (an electron-hole pair with the two particles confined in different
layers) in a GaAs coupled quantum well system. We use a unitary wave-packet
propagation method taking into account in full the four degrees of freedom of
the two particles in a two-dimensional system, including both the long-range
Coulomb attraction and arbitrary two-dimensional electrostatic potentials
affecting the electron and/or the hole separately. The method has been
implemented for massively parallel architectures to cope with the huge
numerical problem, showing good scaling properties and allowing evolution for
tens of picoseconds. We have investigated both transient time phenomena and
asymptotic time transmission and reflection coefficients for potential profiles
consisting of i) extended barriers and wells and ii) a single-slit geometry. We
found clear signatures of the internal two-body dynamics, with transient
phenomena in the picosecond time-scale which might be revealed by optical
spectroscopy. Exact results have been compared with mean-field approaches
which, neglecting dynamical correlations by construction, turn out to be
inadequate to describe the electron-hole pair evolution in realistic
experimental conditions.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-72781604.08633 | Word Ordering Without Syntax
cs.CL
Recent work on word ordering has argued that syntactic structure is
important, or even required, for effectively recovering the order of a
sentence. We find that, in fact, an n-gram language model with a simple
heuristic gives strong results on this task. Furthermore, we show that a long
short-term memory (LSTM) language model is even more effective at recovering
order, with our basic model outperforming a state-of-the-art syntactic model by
11.5 BLEU points. Additional data and larger beams yield further gains, at the
expense of training and search time.
| arxiv topic:cs.CL |
arxiv_dataset-72791604.08733 | Sufficient conditions for Hamiltonian cycles in bipartite digraphs
math.CO
We prove two sharp sufficient conditions for hamiltonian cycles in balanced
bipartite directed graph. Let $D$ be a strongly connected balanced bipartite
directed graph of order $2a$. Let $x,y$ be distinct vertices in $D$. $\{x,y\}$
dominates a vertex $z$ if $x\rightarrow z$ and $y\rightarrow z$; in this case,
we call the pair $\{x,y\}$ dominating.
(i) {\it If $a\geq 4$ and $max \{d(x), d(y)\}\geq 2a-1$ for every dominating
pair of vertices $\{x,y\}$, then either $D$ is hamiltonian or $D$ is isomorphic
to one exceptional digraph of order eight.}
(ii) {\it If $a\geq 5$ and $d(x)+d(y)\geq 4a-3$ for every dominating pair of
vertices $\{x,y\}$, then $D$ is hamiltonian.}
The first result improves a theorem of R. Wang (arXiv:1506.07949 [math.CO]),
the second result, in particular, establishes a conjecture due to Bang-Jensen,
Gutin and Li (J. Graph Theory , 22(2), 1996) for strongly connected balanced
bipartite digraphs of order at least ten.
| arxiv topic:math.CO |
arxiv_dataset-72801604.08833 | Viewpoint: Opportunities and challenges of two-dimensional magnetic van
der Waals materials: magnetic graphene?
cond-mat.mtrl-sci cond-mat.mes-hall cond-mat.str-el
There has been a huge increase of interests in two-dimensional van der Waals
materials over the past ten years or so with the conspicuous absence of one
particular class of materials: magnetic van der Waals systems. In this
Viewpoint, we point it out and illustrate how we might be able to benefit from
exploring these so-far neglected materials.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall cond-mat.str-el |
arxiv_dataset-72811604.08933 | Quantum transitions and quantum entanglement from Dirac-like dynamics
simulated by trapped ions
quant-ph hep-th
Quantum transition probabilities and quantum entanglement for two-qubit
states of a four level trapped ion quantum system are computed for
time-evolving ionic states driven by Jaynes-Cummings Hamiltonians with
interactions mapped onto a $\mbox{SU}(2)\otimes \mbox{SU}(2)$ group structure.
Using the correspondence of the method of simulating a $3+1$ dimensional
Dirac-like Hamiltonian for bi-spinor particles into a single trapped ion, one
preliminarily obtains the analytical tools for describing ionic state
transition probabilities as a typical quantum oscillation feature. For
Dirac-like structures driven by generalized Poincar\'e classes of coupling
potentials, one also identifies the $\mbox{SU}(2)\otimes \mbox{SU}(2)$ internal
degrees of freedom corresponding to intrinsic parity and spin polarization as
an adaptive platform for computing the quantum entanglement between the
internal quantum subsystems which define two-qubit ionic states. The obtained
quantum correlational content is then translated into the quantum entanglement
of two-qubit ionic states with quantum numbers related to the total angular
momentum and to its projection onto the direction of the trapping magnetic
field. Experimentally, the controllable parameters simulated by ion traps can
be mapped into a Dirac-like system in the presence of an electrostatic field
which, in this case, is associated to ionic carrier interactions. Besides
exhibiting a complete analytical profile for ionic quantum transitions and
quantum entanglement, our results indicate that carrier interactions actively
drive an overall suppression of the quantum entanglement.
| arxiv topic:quant-ph hep-th |
arxiv_dataset-72821605.00085 | Usage of Cloud Computing Simulators and Future Systems For Computational
Research
cs.DC
Cloud Computing is an Internet based computing, whereby shared resources,
software and information, are provided to computers and devices on demand, like
the electricity grid. Currently, IaaS (Infrastructure as a Service), PaaS
(Platform as a Service) and SaaS (Software as a Service) are used as a business
model for Cloud Computing. Nowadays, the adoption and deployment of Cloud
Computing is increasing in various domains, forcing researchers to conduct
research in the area of Cloud Computing globally. Setting up the research
environment is critical for the researchers in the developing countries to
evaluate the research outputs. Currently, modeling, simulation technology and
access of resources from various university data centers has become a useful
and powerful tool in cloud computing research. Several cloud simulators have
been specifically developed by various universities to carry out Cloud
Computing research, including CloudSim, SPECI, Green Cloud and Future Systems
(the Indiana University machines India, Bravo, Delta, Echo and Foxtrot)
supports leading edge data science research and a broad range of
computing-enabled education as well as integration of ideas from cloud and HPC
systems. In this paper, the features, suitability, adaptability and the
learning curve of the existing Cloud Computing simulators and Future Systems
are reviewed and analyzed.
| arxiv topic:cs.DC |
arxiv_dataset-72831605.00185 | Constrained Nonlinear and Mixed Effects Differential Equation Models for
Dynamic Cell Polarity Signaling
stat.ME
The key of tip growth in eukaryotes is the polarized distribution on plasma
membrane of a particle named ROP1. This distribution is the result of a
positive feedback loop, whose mechanism can be described by a Differential
Equation parametrized by two meaningful parameters kpf and knf . We introduce a
mechanistic Integro-Differential Equation (IDE) derived from a spatiotemporal
model of cell polarity and we show how this model can be fitted to real data,
i.e., ROP1 intensities measured on pollen tubes. At first, we provide an
existence and uniqueness result for the solution of our IDE model under certain
conditions. Interestingly, this analysis gives a tractable expression for the
likelihood, and our approach can be seen as the estimation of a constrained
nonlinear model. Moreover, we introduce a population variability by a
constrained nonlinear mixed model. We then propose a constrained Least Squares
method to fit the model for the single pollen tube case, and two methods,
constrained Methods of Moments and constrained Restricted Maximum Likelihood
(REML) to fit the model for the multiple pollen tubes case. The performances of
all three methods are studied through simulations and are used on an in-house
multiple pollen tubes dataset generated at UC Riverside.
| arxiv topic:stat.ME |
arxiv_dataset-72841605.00285 | The Borell-Ehrhard Game
math.PR math.FA math.MG
A precise description of the convexity of Gaussian measures is provided by
sharp Brunn-Minkowski type inequalities due to Ehrhard and Borell. We show that
these are manifestations of a game-theoretic mechanism: a minimax variational
principle for Brownian motion. As an application, we obtain a Gaussian
improvement of Barthe's reverse Brascamp-Lieb inequality.
| arxiv topic:math.PR math.FA math.MG |
arxiv_dataset-72851605.00385 | A geometric formulation of exceptional field theory
hep-th
We formulate the full bosonic SL(5) exceptional field theory in a
coordinate-invariant manner. Thereby we interpret the 10-dimensional extended
space as a manifold with $\mathrm{SL}(5)\times\mathbb{R}^+$-structure. We show
that the algebra of generalised diffeomorphisms closes subject to a set of
closure constraints which are reminiscent of the quadratic and linear
constraints of maximal seven-dimensional gauged supergravities, as well as the
section condition. We construct an action for the full bosonic SL(5)
exceptional field theory, even when the
$\mathrm{SL}(5)\times\mathbb{R}^+$-structure is not locally flat.
| arxiv topic:hep-th |
arxiv_dataset-72861605.00485 | From Reaction-Diffusion Systems to Confined Brownian Motion
physics.chem-ph nlin.PS
In this note, we demonstrated for the first time that one can derive an
expression for the effective diffusion coefficient, equal to the Lifson-Jackson
formula, using a subsequent homogenization of the 1D
reaction-diffusion-advection equation. The latter has been derived by applying
asymptotic perturbation analysis to the underlying 3D reaction-diffusion
equation with spatially dependent no-flux boundary conditions and incorporates
the effects of boundary interactions on the reactants via a boundary-induced
advection term [S. Martens et al, Phys. Rev. E 91, 022902 (2015)].
| arxiv topic:physics.chem-ph nlin.PS |
arxiv_dataset-72871605.00585 | Probing gaugino coannihilation with displaced vertex searches
hep-ph
Bino-like dark matter in supersymmetric theories tends to suffer from
over-production. This problem can be evaded if there is another gaugino which
has a mass close to the bino mass so that it enhances the annihilation rate of
bino dark matter through coannihilation. We study such possibilities in
high-scale supersymmetric models, and show that searches for long-lived
particles with displaced vertices can test the bino-gaugino coannihilation
scenario in the forthcoming LHC experiments.
| arxiv topic:hep-ph |
arxiv_dataset-72881605.00685 | Potential tuning in the S-W system. (i) Bringing Tc,2 to ambient
pressure, and (ii) colliding Tc,2 with the liquid-vapor spinodal
cond-mat.dis-nn
Following Vasisht et al's identification of the second critical point
(Tc2,Pc2) for liquid silicon in the Stillinger-Weber (S-W) model for silicon,
we study the variation of Tc2,Pc2 with tetrahedral repulsion parameter in an
extension of the earlier "potential tuning" study of this system. We use the
simple isochoric cooling approach to identify the location of the second
critical point as a function of the "tuning" or "tetrahedrality", parameter
{\lambda}, and identify two phenomena of high interest content. The first is
that the second critical point pressure Pc2, becomes less negative as {\lambda}
decreases from the silicon value (meaning the drive to high tetrahedrality is
decreased) and reaches zero pressure at the same value of lambda as earlier
found to mark the onset of glassforming ability in an earlier study of this
tunable system. The second is that, as the Tc,2 approaches the temperature of
the liquid-gas spinodal, {\lambda}>22, the behavior of the temperature of
maximum density TMD switches from the behavior seen in most current water pair
potential models (locus of TMDs has a maximum), to the behavior seen in
empirical engineering multiparameter equations of state (EoS) (and also by two
parameter Speedy isothermal expansion EoS) for water, according to which the
locus of TMDs of HDL phase has no maximum, and the EoS for HDL has no second
critical point. At {\lambda}= 23 the behavior is isomorphic with that of the mW
model of water, which is now seen to conform to the "critical point free"
scenario for water.
| arxiv topic:cond-mat.dis-nn |
arxiv_dataset-72891605.00785 | Stochastic completeness and gradient representations for sub-Riemannian
manifolds
math.DG math.PR
Given a second order partial differential operator $L$ satisfying the strong
H\"ormander condition with corresponding heat semigroup $P_t$, we give two
different stochastic representations of $dP_t f$ for a bounded smooth function
$f$. We show that the first identity can be used to prove infinite lifetime of
a diffusion of $\frac{1}{2} L$, while the second one is used to find an
explicit pointwise bound for the horizontal gradient on a Carnot group. In both
cases, the underlying idea is to consider the interplay between sub-Riemannian
geometry and connections compatible with this geometry.
| arxiv topic:math.DG math.PR |
arxiv_dataset-72901605.00885 | Conjugated liquid layers driven by the short-wavelength
B\'enard-Marangoni instability: experiment and numerical simulation
physics.flu-dyn cond-mat.soft
The coupled dynamics of two conjugated liquid layers of disparate
thicknesses, which coat a solid substrate and are subjected to a transverse
temperature gradient, is investigated. The upper liquid layer evolves under the
short-wavelength (SW) B\'enard-Marangoni (BM) instability, whereas the lower,
much thinner film undergoes a shear-driven long-wavelength deformation.
Although the lubricating film should reduce the viscous stresses acting on the
up to one hundred times thicker upper layer by only 10%, it is found that the
critical Marangoni number of marginal stability may be as low as if a
stress-free boundary condition were applied at the bottom of the upper layer,
i.e. much lower than the classical value of 79.6 known for a single film.
Furthermore, it is experimentally verified that the deformation of the
liquid-liquid interface, albeit small, has a non-negligible effect on the
temperature distribution along the liquid-gas interface of the upper layer.
This stabilizes the hexagonal pattern symmetry towards external disturbances
and indicates a two-way coupling of the different layers. The experiments also
demonstrate how convection patterns formed in a liquid film can be used to
pattern a second conjugated film. The experimental findings are verified by a
numerical model of the coupled layers.
| arxiv topic:physics.flu-dyn cond-mat.soft |
arxiv_dataset-72911605.00985 | Alternating Arm Exponents for the Critical Planar Ising Model
math.PR
We derive the alternating arm exponents of critical Ising model. We obtain
six different patterns of alternating boundary arm exponents which correspond
to the boundary conditions $(\ominus\oplus)$, $(\ominus\text{free})$ and
$(\text{free}\text{free})$, and the alternating interior arm exponents.
| arxiv topic:math.PR |
arxiv_dataset-72921605.01085 | Numerical Computations and Computer Assisted Proofs of Periodic Orbits
of the Kuramoto-Sivashinsky Equation
math.DS math.AP
We present numerical results and computer assisted proofs of the existence of
periodic orbits for the Kuramoto-Sivashinky equation. These two results are
based on writing down the existence of periodic orbits as zeros of functionals.
This leads to the use of Newton's algorithm for the numerical computation of
the solutions and, with some a posteriori analysis in combination with rigorous
interval arithmetic, to the rigorous verification of the existence of
solutions. This is a particular case of the methodology developed in [19] for
several types of orbits. An independent implementation, covering overlapping
but different ground, using different functional setups appears in [33].
| arxiv topic:math.DS math.AP |
arxiv_dataset-72931605.01185 | Linear Bandit algorithms using the Bootstrap
stat.ML cs.LG
This study presents two new algorithms for solving linear stochastic bandit
problems. The proposed methods use an approach from non-parametric statistics
called bootstrapping to create confidence bounds. This is achieved without
making any assumptions about the distribution of noise in the underlying
system. We present the X-Random and X-Fixed bootstrap bandits which correspond
to the two well-known approaches for conducting bootstraps on models, in the
literature. The proposed methods are compared to other popular solutions for
linear stochastic bandit problems, namely, OFUL, LinUCB and Thompson Sampling.
The comparisons are carried out using a simulation study on a hierarchical
probability meta-model, built from published data of experiments, which are run
on real systems. The model representing the response surfaces is conceptualized
as a Bayesian Network which is presented with varying degrees of noise for the
simulations. One of the proposed methods, X-Random bootstrap, performs better
than the baselines in-terms of cumulative regret across various degrees of
noise and different number of trials. In certain settings the cumulative regret
of this method is less than half of the best baseline. The X-Fixed bootstrap
performs comparably in most situations and particularly well when the number of
trials is low. The study concludes that these algorithms could be a preferred
alternative for solving linear bandit problems, especially when the
distribution of the noise in the system is unknown.
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-72941605.01285 | Shape recovery from sparse tomographic X-ray data
math.NA
A two-dimensional tomographic problem is studied. The target is assumed to be
a homogeneous object bounded by a smooth curve. A Non Uniform Rational Basis
Splines (NURBS) curve is used as computational representation of the boundary.
This approach conveniently provides the result in a format readily compatible
with computer-aided design (CAD) software. However, the linear tomography task
becomes a nonlinear inverse problem due to the NURBS-based parameterization.
Therefore, Bayesian inversion with Markov chain Monte Carlo (MCMC) sampling is
used for calculating an estimate of the NURBS control points. The
reconstruction method is tested with both simulated data and measured X-ray
projection data. The proposed method recovers the shape and the attenuation
coefficient significantly better than the baseline algorithm (optimally
thresholded total variation regularization), but at the cost of heavier
computation.
| arxiv topic:math.NA |
arxiv_dataset-72951605.01385 | Shift-preserving maps on $\omega^*$
math.GN
The shift map $\sigma$ on $\omega^*$ is the continuous self-map of $\omega^*$
induced by the function $n \mapsto n+1$ on $\omega$. Given a compact Hausdorff
space $X$ and a continuous function $f: X \rightarrow X$, we say that $(X,f)$
is a quotient of $(\omega^*,\sigma)$ whenever there is a continuous surjection
$Q: \omega^* \to X$ such that $Q \circ \sigma = f \circ Q$.
Our main theorem states that if the weight of $X$ is at most $\aleph_1$, then
$(X,f)$ is a quotient of $(\omega^*,\sigma)$ if and only if $f$ is weakly
incompressible (which means that no nontrivial open $U \subseteq X$ has
$f(\bar{U}) \subseteq U$). Under CH, this gives a complete characterization of
the quotients of $(\omega^*,\sigma)$ and implies, for example, that
$(\omega^*,\sigma^{-1})$ is a quotient of $(\omega^*,\sigma)$.
In the language of topological dynamics, our theorem states that a dynamical
system of weight $\aleph_1$ is an abstract $\omega$-limit set if and only if it
is weakly incompressible.
We complement these results by proving $(1)$ our main theorem remains true
when $\aleph_1$ is replaced by any $\kappa < \mathfrak{p}$, $(2)$ consistently,
the theorem becomes false if we replace $\aleph_1$ by $\aleph_2$, and $(3)$
OCA+MA implies that $(\omega^*,\sigma^{-1})$ is not a quotient of
$(\omega^*,\sigma)$.
| arxiv topic:math.GN |
arxiv_dataset-72961605.01485 | Matrix-Variate Regressions and Envelope Models
stat.ME math.ST stat.TH
Modern technology often generates data with complex structures in which both
response and explanatory variables are matrix-valued. Existing methods in the
literature are able to tackle matrix-valued predictors but are rather limited
for matrix-valued responses. In this article, we study matrix-variate
regressions for such data, where the response Y on each experimental unit is a
random matrix and the predictor X can be either a scalar, a vector, or a
matrix, treated as non-stochastic in terms of the conditional distribution Y|X.
We propose models for matrix-variate regressions and then develop envelope
extensions of these models. Under the envelope framework, redundant variation
can be eliminated in estimation and the number of parameters can be notably
reduced when the matrix-variate dimension is large, possibly resulting in
significant gains in efficiency. The proposed methods are applicable to high
dimensional settings.
| arxiv topic:stat.ME math.ST stat.TH |
arxiv_dataset-72971605.01585 | Finite groups with non-trivial intersections of kernels of all but one
irreducible characters
math.GR
In this paper we consider finite groups G satisfying the following condition:
G has two columns in its character table which differ by exactly one entry. It
turns out that such groups exist and they are exactly the finite groups with a
non-trivial intersection of the kernels of all but one irreducible characters
or, equivalently, finite groups with an irreducible character vanishing on all
but two conjugacy classes. We investigate such groups and in particular we
characterize their subclass, which properly contains all finite groups with
non-linear characters of distinct degrees, which were characterized by
Berkovich, Chillag and Herzog in 1992.
| arxiv topic:math.GR |
arxiv_dataset-72981605.01685 | Partial flag incidence algebras
math.CO
The $n^{th}$ partial flag incidence algebra of a poset $P$ is the set of
functions from $P^n$ to some ring which are zero on non-partial flag vectors.
These partial flag incidence algebras for $n>2$ are not commutative, not
unitary, and not associative. However, partial flag incidence algebras contain
generalized zeta, delta, and M\"obius functions which are finer and more
delicate invariants than their classical analogues. We also study some
generalized characteristic polynomials of posets which are not evaluations of
Tutte polynomials and compute them for Boolean lattices. Motivation for this
work came from studying the matroid Kazhdan-Lusztig polynomials where partial
flag Whitney numbers play a central role.
| arxiv topic:math.CO |
arxiv_dataset-72991605.01785 | A First Targeted Search for Gravitational-Wave Bursts from Core-Collapse
Supernovae in Data of First-Generation Laser Interferometer Detectors
gr-qc astro-ph.HE
We present results from a search for gravitational-wave bursts coincident
with a set of two core-collapse supernovae observed between 2007 and 2011. We
employ data from the Laser Interferometer Gravitational-wave Observatory
(LIGO), the Virgo gravitational-wave observatory, and the GEO 600
gravitational-wave observatory. The targeted core-collapse supernovae were
selected on the basis of (1) proximity (within approximately 15 Mpc), (2)
tightness of observational constraints on the time of core collapse that
defines the gravitational-wave search window, and (3) coincident operation of
at least two interferometers at the time of core collapse. We find no plausible
gravitational-wave candidates. We present the probability of detecting signals
from both astrophysically well-motivated and more speculative
gravitational-wave emission mechanisms as a function of distance from Earth,
and discuss the implications for the detection of gravitational waves from
core-collapse supernovae by the upgraded Advanced LIGO and Virgo detectors.
| arxiv topic:gr-qc astro-ph.HE |
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