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arxiv_dataset-82001702.05406 | Temperature Distribution and Heat Radiation of Patterned Surfaces at
Short Wave Lengths
cond-mat.mes-hall
We analyze the equilibrium spatial distribution of surface temperatures of
patterned surfaces. The surface is exposed to a constant external heat flux and
has a fixed internal temperature that is coupled to the outside heat fluxes by
finite heat conductivity across surface. It is assumed that the temperatures
are sufficiently high so that the thermal wavelength (a few microns at room
temperature) is short compared to all geometric length scales of the surface
patterns. Hence the radiosity method can be employed. A recursive multiple
scattering method is developed that enables rapid convergence to equilibrium
temperatures. While the temperature distributions show distinct dependence on
the detailed surface shapes (cuboids and cylinder are studied), we demonstrate
robust universal relations between the mean and the standard deviation of the
temperature distributions and quantities that characterize overall geometric
features of the surface shape.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-82011702.05506 | An Unsupervised Approach for Overlapping Cervical Cell Cytoplasm
Segmentation
cs.CV
The poor contrast and the overlapping of cervical cell cytoplasm are the
major issues in the accurate segmentation of cervical cell cytoplasm. This
paper presents an automated unsupervised cytoplasm segmentation approach which
can effectively find the cytoplasm boundaries in overlapping cells. The
proposed approach first segments the cell clumps from the cervical smear image
and detects the nuclei in each cell clump. A modified Otsu method with prior
class probability is proposed for accurate segmentation of nuclei from the cell
clumps. Using distance regularized level set evolution, the contour around each
nucleus is evolved until it reaches the cytoplasm boundaries. Promising results
were obtained by experimenting on ISBI 2015 challenge dataset.
| arxiv topic:cs.CV |
arxiv_dataset-82021702.05606 | On the global and local magnetic fields in flare stars. Study of YZ CMi
and OT Ser
astro-ph.SR
Global magnetic fields of flare stars can evolve rapidly, in time scale of
hundreds or dozens of days. We believe, that such changes result from rapid
superposition of local magnetic fields generated by differential rotation of
those stars. We discuss possible mechanisms of generation and dissipation of
local and global magnetic fields in sample flare stars OT Ser and YZ CMi. We
propose mechanism of magnetic braking of these stars, in which differential
rotation generates local magnetic fields, and eventually energy accumulated in
local fields is radiated away by flares. We obtained estimates of the
rotational energy and the energy of the global magnetic field of OT Ser and YZ
CMi. We also show that the energy of the local magnetic fields dissipated
during superflare of YZ CMi on 9 February 2008 (UT 20:22:00) did not influence
the global magnetic field of this star.
| arxiv topic:astro-ph.SR |
arxiv_dataset-82031702.05706 | Poisson Cluster Process: Bridging the Gap Between PPP and 3GPP HetNet
Models
cs.IT cs.NI math.IT
The growing complexity of heterogeneous cellular networks (HetNets) has
necessitated the need to consider variety of user and base station (BS)
configurations for realistic performance evaluation and system design. This is
directly reflected in the HetNet simulation models considered by
standardization bodies, such as the third generation partnership project
(3GPP). Complementary to these simulation models, stochastic geometry based
approach modeling the user and BS locations as independent and homogeneous
Poisson point processes (PPPs) has gained prominence in the past few years.
Despite its success in revealing useful insights, this PPP-based model is not
rich enough to capture all the spatial configurations that appear in real world
HetNet deployments (on which 3GPP simulation models are based). In this paper,
we bridge the gap between the 3GPP simulation models and the popular PPP-based
analytical model by developing a new unified HetNet model in which a fraction
of users and some BS tiers are modeled as Poisson cluster processes (PCPs).
This model captures both non-uniformity and coupling in the BS and user
locations. For this setup, we derive exact expression for downlink coverage
probability under maximum signal-to-interference ratio (SIR) cell association
model. As intermediate results, we define and evaluate sum-product functionals
for PPP and PCP. Special instances of the proposed model are shown to closely
resemble different configurations considered in 3GPP HetNet models. Our results
concretely demonstrate that the performance trends are highly sensitive to the
assumptions made on the user and SBS configurations.
| arxiv topic:cs.IT cs.NI math.IT |
arxiv_dataset-82041702.05806 | Topographically anisotropic photonics for broadband integrated
polarization diversity
physics.optics
Integrated polarimetric receivers have the potential to define a new
generation of lightweight, high-performance instrumentation for remote sensing.
To date, on-chip polarization-selective devices such as polarizing
beam-splitters have yet to even approach the necessary performance, due to
fundamental design limitations. Here, we propose, simulate and experimentally
demonstrate a method for realizing spatially-mapped birefringence onto
integrated photonic circuits, deemed topographically anisotropic photonics.
With this robust and widely tolerant approach, devices can be constructed with
strongly polarization-dependent modal properties and minimal wavelength
dependence. An integrated polarizing beam-splitter (PBS) is realized with
unprecedented performance: a record 0.52 octaves of fractional bandwidth (116
THz), maximum insertion loss of 1.4 +/- 0.8 dB, and a minimum extinction ratio
of 16 +/- 3 dB, pushing it into the realm of wideband spectroscopy and imaging
applications. Additionally, novel photonic structures such as
polarization-selective beam-taps and polarization-selective microring
resonators are demonstrated, enabling new on-chip polarimetric receiver
architectures.
| arxiv topic:physics.optics |
arxiv_dataset-82051702.05906 | Virtual photon polarization in ultrarelativistic heavy-ion collisions
nucl-th
The polarization of direct photons produced in an ultrarelativistic heavy-ion
collision reflects the momentum anisotropy of the quark-gluon plasma created in
the collision. This paper presents a general framework, based on the photon
spectral functions in the plasma, for analyzing the angular distribution and
thus the polarization of dileptons in terms of the plasma momentum
anisotropies. The rates of dilepton production depend, in general, on four
independent spectral functions, corresponding to two transverse polarizations,
one longitudinal polarization, and -- in plasmas in which the momentum
anisotropy is not invariant under parity in the local rest frame of the matter
-- a new spectral function, $\rho_n$, related to the anisotropy direction in
the collision. The momentum anisotropy appears in the difference of the two
transverse spectral functions, as well as in $\rho_n$. As an illustration, we
delineate the spectral functions for dilepton pairs produced in the lowest
order Drell-Yan process of quark-antiquark annihilation to a virtual photon.
| arxiv topic:nucl-th |
arxiv_dataset-82061702.06006 | Hierarchical star formation across the grand design spiral NGC1566
astro-ph.GA
We investigate how star formation is spatially organized in the grand-design
spiral NGC 1566 from deep HST photometry with the Legacy ExtraGalactic UV
Survey (LEGUS). Our contour-based clustering analysis reveals 890 distinct
stellar conglomerations at various levels of significance. These star-forming
complexes are organized in a hierarchical fashion with the larger congregations
consisting of smaller structures, which themselves fragment into even smaller
and more compact stellar groupings. Their size distribution, covering a wide
range in length-scales, shows a power-law as expected from scale-free
processes. We explain this shape with a simple "fragmentation and enrichment"
model. The hierarchical morphology of the complexes is confirmed by their
mass--size relation which can be represented by a power-law with a fractional
exponent, analogous to that determined for fractal molecular clouds. The
surface stellar density distribution of the complexes shows a log-normal shape
similar to that for supersonic non-gravitating turbulent gas. Between 50 and 65
per cent of the recently-formed stars, as well as about 90 per cent of the
young star clusters, are found inside the stellar complexes, located along the
spiral arms. We find an age-difference between young stars inside the complexes
and those in their direct vicinity in the arms of at least 10 Myr. This
timescale may relate to the minimum time for stellar evaporation, although we
cannot exclude the in situ formation of stars. As expected, star formation
preferentially occurs in spiral arms. Our findings reveal turbulent-driven
hierarchical star formation along the arms of a grand-design galaxy.
| arxiv topic:astro-ph.GA |
arxiv_dataset-82071702.06106 | An Attention-Based Deep Net for Learning to Rank
cs.LG
In information retrieval, learning to rank constructs a machine-based ranking
model which given a query, sorts the search results by their degree of
relevance or importance to the query. Neural networks have been successfully
applied to this problem, and in this paper, we propose an attention-based deep
neural network which better incorporates different embeddings of the queries
and search results with an attention-based mechanism. This model also applies a
decoder mechanism to learn the ranks of the search results in a listwise
fashion. The embeddings are trained with convolutional neural networks or the
word2vec model. We demonstrate the performance of this model with image
retrieval and text querying data sets.
| arxiv topic:cs.LG |
arxiv_dataset-82081702.06206 | Classification of systems with center-stable tori
math.DS
This paper gives a classification of partially hyperbolic systems in
dimension 3 which have at least one torus tangent to the center-stable bundle.
| arxiv topic:math.DS |
arxiv_dataset-82091702.06306 | Efficient single-pass third-harmonic generation at 520 nm for pumping
doubly-resonant OPO
physics.optics
A ~545 mW single-frequency tunable 520 nm green laser has been demonstrated
using a periodically-poled potassium titanyl phosphate (PPKTP) bulk crystal
based on single-pass third-harmonic generation (THG) of a 1560 nm laser via
single-pass second-harmonic generation (SHG) followed by single-pass
sum-frequency generation (SFG). In single-pass SHG, two cascaded
periodically-poled magnesium-oxide-doped lithium niobate (PPMgO:LN) crystals
were used, and ~3.5 W 780.25 nm doubled laser output is produced, corresponding
to maximum doubling efficiency of 26.8%. The system can provide a pump source
(520 nm) for an optical parametric oscillator for two-color entangled
continuous-variable optical field generation at 1560 and 780 nm and two-color
local oscillators for homodyne detection.
| arxiv topic:physics.optics |
arxiv_dataset-82101702.06406 | Edge states in non-Fermi liquids
cond-mat.str-el cond-mat.dis-nn
We devise an approach to the calculation of scaling dimensions of generic
operators describing scattering within multi-channel Luttinger liquid. The
local impurity scattering in an arbitrary configuration of conducting and
insulating channels is investigated and the problem is reduced to a single
algebraic matrix equation. In particular, the solution to this equation is
found for a finite array of chains described by Luttinger liquid models. It is
found that for a weak inter-chain hybridisation and intra-channel
electron-electron attraction the edge wires are robust against disorder whereas
bulk wires, on contrary, become insulating. Thus, the edge state may exist in a
finite sliding Luttinger liquid without time-reversal symmetry breaking
(quantum Hall systems) or spin-orbit interaction (topological insulators).
| arxiv topic:cond-mat.str-el cond-mat.dis-nn |
arxiv_dataset-82111702.06506 | PixelNet: Representation of the pixels, by the pixels, and for the
pixels
cs.CV cs.LG cs.RO
We explore design principles for general pixel-level prediction problems,
from low-level edge detection to mid-level surface normal estimation to
high-level semantic segmentation. Convolutional predictors, such as the
fully-convolutional network (FCN), have achieved remarkable success by
exploiting the spatial redundancy of neighboring pixels through convolutional
processing. Though computationally efficient, we point out that such approaches
are not statistically efficient during learning precisely because spatial
redundancy limits the information learned from neighboring pixels. We
demonstrate that stratified sampling of pixels allows one to (1) add diversity
during batch updates, speeding up learning; (2) explore complex nonlinear
predictors, improving accuracy; and (3) efficiently train state-of-the-art
models tabula rasa (i.e., "from scratch") for diverse pixel-labeling tasks. Our
single architecture produces state-of-the-art results for semantic segmentation
on PASCAL-Context dataset, surface normal estimation on NYUDv2 depth dataset,
and edge detection on BSDS.
| arxiv topic:cs.CV cs.LG cs.RO |
arxiv_dataset-82121702.06606 | Experimentally Obtaining Maximal Coherence Via Assisted Distillation Pro
cess
quant-ph physics.optics
Quantum coherence, which quantifies the superposition properties of a quantum
state, plays an indispensable role in quantum resource theory. A recent
theoretical work [Phys. Rev. Lett. \textbf{116}, 070402 (2016)] studied the
manipulation of quantum coherence in bipartite or multipartite systems under
the protocol Local Incoherent Operation and Classical Communication (LQICC).
Here we present the first experimental realization of obtaining maximal
coherence in assisted distillation protocol based on linear optical system. The
results of our work show that the optimal distillable coherence rate can be
reached even in one-copy scenario when the overall bipartite qubit state is
pure. Moreover, the experiments for mixed states showed that distillable
coherence can be increased with less demand than entanglement distillation. Our
work might be helpful in the remote quantum information processing and quantum
control.
| arxiv topic:quant-ph physics.optics |
arxiv_dataset-82131702.06706 | Voltage-induced suppression of weak localization in graphene
cond-mat.mes-hall cond-mat.dis-nn cond-mat.mtrl-sci
In this theoretical study, we explore the manner in which the quantum
correction due to weak localization is suppressed in weakly-disordered
graphene, when it is subjected to the application of a non-zero voltage. Using
a nonequilibrium Green function approach, we address the scattering generated
by the disorder up to the level of the maximally crossed diagrams, hereby
capturing the interference among different, impurity-defined, Feynman paths.
Our calculations of the charge current, and of the resulting differential
conductance, reveal the logarithmic divergence typical of weak localization in
linear transport. The main finding of our work is that the applied voltage
suppresses the weak localization contribution in graphene, by introducing a
dephasing time that decreases inversely with increasing voltage.
| arxiv topic:cond-mat.mes-hall cond-mat.dis-nn cond-mat.mtrl-sci |
arxiv_dataset-82141702.06806 | Introducing Context Awareness in Unmodified, Context-unaware Software
cs.SE cs.PL
Software tends to be highly configurable, but most applications are hardly
context aware. For example, a web browser provides many settings to configure
printers and proxies, but nevertheless it is unable to dynamically adapt to a
new workplace. In this paper we aim to empirically demonstrate that by dynamic
and automatic reconfiguration of unmodified software we can systematically
introduce context awareness. In 16 real-world applications comprising 50
million lines of code we empirically investigate which of the 2,683 run-time
configuration accesses (1) already take context into account, or (2) can be
manipulated at run-time to do so. The results show that context awareness can
be exploited far beyond the developers' initial intentions. Our tool Elektra
dynamically intercepts the run-time configuration accesses and replaces them
with a context aware implementation. Users only need to specify contexts and
add context sensors to make use of this potential.
| arxiv topic:cs.SE cs.PL |
arxiv_dataset-82151702.06906 | Bijections in de Bruijn Graphs
math.CO
A T-net of order $m$ is a graph with $m$ nodes and $2m$ directed edges, where
every node has indegree and outdegree equal to $2$. (A well known example of
T-nets are de Bruijn graphs.) Given a T-net $N$ of order $m$, there is the so
called "doubling" process that creates a T-net $N^*$ from $N$ with $2m$ nodes
and $4m$ edges. Let $|X|$ denote the number of Eulerian cycles in a graph $X$.
It is known that $| N^*|=2^{m-1}|N|$. In this paper we present a new proof of
this identity. Moreover we prove that $|N|\leq 2^{m-1}$. Let $\Theta(X)$ denote
the set of all Eulerian cycles in a graph $X$ and $S(n)$ the set of all binary
sequences of length $n$. Exploiting the new proof we construct a bijection
$\Theta(N)\times S(m-1)\rightarrow \Theta(N^*)$, which allows us to solve one
of Stanley's open questions: we find a bijection between de Bruijn sequences of
order $n$ and $S(2^{n-1})$.
| arxiv topic:math.CO |
arxiv_dataset-82161702.07006 | Synthesising Dynamic Textures using Convolutional Neural Networks
cs.CV
Here we present a parametric model for dynamic textures. The model is based
on spatiotemporal summary statistics computed from the feature representations
of a Convolutional Neural Network (CNN) trained on object recognition. We
demonstrate how the model can be used to synthesise new samples of dynamic
textures and to predict motion in simple movies.
| arxiv topic:cs.CV |
arxiv_dataset-82171702.07106 | More efficient formulas for efficiency correction of cumulants and
effect of using averaged efficiency
physics.data-an hep-ph nucl-ex nucl-th
We derive formulas for the efficiency correction of cumulants with many
efficiency bins. The derivation of the formulas is simpler than the previously
suggested method, but the numerical cost is drastically reduced from the naive
method. From analytical and numerical analyses in simple toy models, we show
that the use of the averaged efficiency in the efficiency correction can lead
to wrong corrected values, which have larger deviation for higher order
cumulants. These analyses show the importance of carrying out the efficiency
correction without taking the average.
| arxiv topic:physics.data-an hep-ph nucl-ex nucl-th |
arxiv_dataset-82181702.07206 | Cross Section Prediction for Inclusive Production of Z Boson in $pp$
Collisions at $\sqrt{s}$$=14$ TeV: A Study of Systematic Uncertainty Due to
Scale Dependence
hep-ph
Prediction of $Z\rightarrow l^{+}l^{-}$ production cross section (where
$l^{\pm} =e^{\pm},\mu^{\pm}$) in proton-proton collisions at $\sqrt{s}$=14 TeV
is estimated up to next-to-next-to-leading order (NNLO) in perturbative QCD
including next-to-leading order (NLO) electroweak (EW) corrections. The total
inclusive Z boson production cross section times leptonic branching ratio,
within the invariant mass window $66<m_{ll}<116$ GeV, is predicted using NNLO
HERAPDF2.0 at NNLO QCD and NLO EW as $\sigma_{Z}^{Tot}$=
2111.69$_{-26.92}^{+26.31}$ (PDF) $\pm11$ ($\alpha_{s}$) $\pm$17 (scale)
$^{+57.41}_{-30.98}$ (parameterization and model). Theoretical prediction of
the fiducial cross section is further computed with the latest modern PDF
models (CT14, MMHT2014, NNPDF3.0, HERAPDF2.0 and ABM12) at NNLO for QCD and NLO
for EW. The central values of the predictions are based on DYNNLO 1.5 program
and the uncertainties are extracted using FEWZ 3.1 program. In addition, the
cross section is also calculated as functions of $\mu_{R}$ and $\mu_{F}$
scales. The choice of $\mu_{R}$ and $\mu_{F}$ for scale variation uncertainty
is further discussed in details.
| arxiv topic:hep-ph |
arxiv_dataset-82191702.07306 | Causal Discovery Using Proxy Variables
stat.ML cs.LG
Discovering causal relations is fundamental to reasoning and intelligence. In
particular, observational causal discovery algorithms estimate the cause-effect
relation between two random entities $X$ and $Y$, given $n$ samples from
$P(X,Y)$.
In this paper, we develop a framework to estimate the cause-effect relation
between two static entities $x$ and $y$: for instance, an art masterpiece $x$
and its fraudulent copy $y$. To this end, we introduce the notion of proxy
variables, which allow the construction of a pair of random entities $(A,B)$
from the pair of static entities $(x,y)$. Then, estimating the cause-effect
relation between $A$ and $B$ using an observational causal discovery algorithm
leads to an estimation of the cause-effect relation between $x$ and $y$. For
example, our framework detects the causal relation between unprocessed
photographs and their modifications, and orders in time a set of shuffled
frames from a video.
As our main case study, we introduce a human-elicited dataset of 10,000 pairs
of casually-linked pairs of words from natural language. Our methods discover
75% of these causal relations. Finally, we discuss the role of proxy variables
in machine learning, as a general tool to incorporate static knowledge into
prediction tasks.
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-82201702.07406 | On permutations of order dividing a given integer
math.GR
We give a detailed analysis of the proportion of elements in the symmetric
group on $n$ points whose order divides $m$, for $n$ sufficiently large and $m
\ge n$ with $m = O(n)$.
| arxiv topic:math.GR |
arxiv_dataset-82211702.07506 | Out-of-plane easy-axis in thin films of diluted magnetic semiconductor
Ba1-xKx(Zn1-yMny)2As2
cond-mat.mtrl-sci
Single-phased, single-oriented thin films of Mn-doped ZnAs-based diluted
magnetic semiconductor (DMS) Ba1-xKx(Zn1-yMny)2As2 (x = 0.03, 0.08; y = 0.15)
have been deposited on Si, SrTiO3, LaAlO3, (La,Sr)(Al,Ta)O3, and MgAl2O4
substrates, respectively. Utilizing a combined synthesis and characterization
system excluding the air and further optimizing the deposition parameters,
high-quality thin films could be obtained and be measured showing that they can
keep inactive-in-air up to more than 90 hours characterized by electrical
transport measurements. In comparison with films of x = 0.03 which possess
relatively higher resistivity, weaker magnetic performances, and larger energy
gap, thin films of x = 0.08 show better electrical and magnetic performances.
Strong magnetic anisotropy was found in films of x = 0.08 grown on
(La,Sr)(Al,Ta)O3 substrate with their magnetic polarization aligned almost
solely on the film growth direction.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-82221702.07606 | Weyl points and Dirac lines protected by multiple screw rotations
cond-mat.mtrl-sci
In three-dimensional noncentrosymmetric materials two-fold screw rotation
symmetry forces electron's energy bands to have Weyl points at which two bands
touch. This is illustrated for space groups No. 19 ($P2_12_12_1$) and No. 198
($P2_13$), which have three orthogonal screw rotation axes. In the case of
space groups No. 61 ($Pbca$) and No. 205 ($P$a-3) that have extra inversion
symmetry, Weyl points are promoted to four-fold degenerate line nodes in
glide-invariant planes. The three-fold rotation symmetry present in the space
groups No. 198 and No. 205 allows Weyl and Dirac points, respectively, to
appear along its rotation axes in the Brillouin zone and generates four-fold
and six-fold degeneracy at the $\Gamma$ point and R point, respectively.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-82231702.07706 | The second law of thermodynamics at the microscopic scale
quant-ph cond-mat.stat-mech
In quantum statistical mechanics, equilibrium states have been shown to be
the typical states for a system that is entangled with its environment,
suggesting a possible identification between thermodynamic and von Neumann
entropies. In this paper, we investigate how the relaxation toward equilibrium
is made possible through interactions that do not lead to significant exchange
of energy, and argue for the validity of the second law of thermodynamics at
the microscopic scale.
| arxiv topic:quant-ph cond-mat.stat-mech |
arxiv_dataset-82241702.07806 | When Does Diversity of User Preferences Improve Outcomes in Selfish
Routing?
cs.GT
We seek to understand when heterogeneity in user preferences yields improved
outcomes in terms of overall cost. That this might be hoped for is based on the
common belief that diversity is advantageous in many settings. We investigate
this in the context of routing. Our main result is a sharp characterization of
the network settings in which diversity always helps, versus those in which it
is sometimes harmful. Specifically, we consider routing games, where diversity
arises in the way that users trade-off two criteria (such as time and money,
or, in the case of stochastic delays, expectation and variance of delay). Our
main contributions are the following: 1) A participant-oriented measure of cost
in the presence of user diversity, together with the identification of the
natural benchmark: the same cost measure for an appropriately defined average
of the diversity. 2) A full characterization of those network topologies for
which diversity always helps, for all latency functions and demands. For
single-commodity routings, these are series-parallel graphs, while for
multi-commodity routings, they are the newly-defined "block-matching" networks.
The latter comprise a suitable interweaving of multiple series-parallel graphs
each connecting a distinct source-sink pair. While the result for the
single-commodity case may seem intuitive in light of the well-known Braess
paradox, the two problems are different: there are instances where diversity
helps although the Braess paradox occurs, and vice-versa. But the main
technical challenge is to establish the "only if" direction of the result for
multi-commodity networks. This follows by constructing an instance where
diversity hurts, and showing how to embed it in any network which is not
block-matching, by carefully exploiting the way the simple source-sink paths of
the commodities intersect in the "non-block-matching" portion of the network.
| arxiv topic:cs.GT |
arxiv_dataset-82251702.07906 | Nonequilibrium thermodynamics and information theory: Basic concepts and
relaxing dynamics
cond-mat.stat-mech
Thermodynamics is based on the notions of energy and entropy. While energy is
the elementary quantity governing physical dynamics, entropy is the fundamental
concept in information theory. In this work, starting from first principles, we
give a detailed didactic account on the relations between energy and entropy
and thus physics and information theory. We show that thermodynamic process
inequalities, like the Second Law, are equivalent to the requirement that an
effective description for physical dynamics is strongly relaxing. From the
perspective of information theory, strongly relaxing dynamics govern the
irreversible convergence of a statistical ensemble towards the maximally
non-commital probability distribution that is compatible with thermodynamic
equilibrium parameters. In particular, Markov processes that converge to a
thermodynamic equilibrium state are strongly relaxing. Our framework
generalizes previous results to arbitrary open and driven systems, yielding
novel thermodynamic bounds for idealized and real processes.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-82261702.08006 | CRSTIP - An Assessment Scheme for Security Assessment Processes
cs.CR
Complex networked systems are an integral part of today's support
infrastructures. Due to their importance, these systems become more and more
the target for cyber-attacks, suffering a notable number of security incidents.
Also, they are subject to regulation by national and international legislation.
An operator of such an infrastructure or system is responsible for ensuring its
security and correct functioning in order to satisfy customers. In addition,
the entire process of risk and quality control needs to be efficient and
manageable. This short paper introduces the Compliance, Risk Assessment and
Security Testing Improvement Profiling (CRSTIP) scheme. CRSTIP is an evaluation
scheme that enables assessing the maturity of security assessment processes,
taking into consideration systematic use of formalisms, integration and
tool-support in the areas of compliance assessment, security risk assessment
and security testing. The paper describes the elements of the scheme and their
application to one of the case studies of the RASEN research project.
| arxiv topic:cs.CR |
arxiv_dataset-82271702.08106 | A New Concept for an Obstacle Avoidance System for the AUV "SLOCUM
Glider" Operation under Ice
cs.RO
This paper presents a concept for a control System for an autonomous
underwater vehicle under ice using a "SLOCUM" underwater glider. The project
concept, the separate working tasks for the next one-and-a-half years and the
first results will be presented. In this context the structure of the obstacle
avoidance system and a simulator structure with a sensor and environment
simulation as well as the interfaces to the glider hardware will be discussed.
As a first result of the main research, a graph-based algorithm for the path
planning in a time-varying environment (variable ocean field, moving obstacles)
will be described.
| arxiv topic:cs.RO |
arxiv_dataset-82281702.08206 | Critical and subcritical fractional Trudinger-Moser type inequalities on
$\mathbb{R}$
math.AP
In this paper, we are concerned with the critical and subcritical
Trudinger-Moser type inequalities for functions in a fractional Sobolev space
$H^{1/2,2}$ on the whole real line. We prove the relation between two
inequalities and discuss the attainability of the suprema.
| arxiv topic:math.AP |
arxiv_dataset-82291702.08306 | On-the-Fly Computation of Bisimilarity Distances
cs.LO
We propose a distance between continuous-time Markov chains (CTMCs) and study
the problem of computing it by comparing three different algorithmic
methodologies: iterative, linear program, and on-the-fly. In a work presented
at FoSSaCS'12, Chen et al. characterized the bisimilarity distance of
Desharnais et al. between discrete-time Markov chains as an optimal solution of
a linear program that can be solved by using the ellipsoid method. Inspired by
their result, we propose a novel linear program characterization to compute the
distance in the continuous-time setting. Differently from previous proposals,
ours has a number of constraints that is bounded by a polynomial in the size of
the CTMC. This, in particular, proves that the distance we propose can be
computed in polynomial time. Despite its theoretical importance, the proposed
linear program characterization turns out to be inefficient in practice.
Nevertheless, driven by the encouraging results of our previous work presented
at TACAS'13, we propose an efficient on-the-fly algorithm, which, unlike the
other mentioned solutions, computes the distances between two given states
avoiding an exhaustive exploration of the state space. This technique works by
successively refining over-approximations of the target distances using a
greedy strategy, which ensures that the state space is further explored only
when the current approximations are improved. Tests performed on a consistent
set of (pseudo)randomly generated CTMCs show that our algorithm improves, on
average, the efficiency of the corresponding iterative and linear program
methods with orders of magnitude.
| arxiv topic:cs.LO |
arxiv_dataset-82301702.08406 | Stability of Electrodeposition at Solid-Solid Interfaces and
Implications for Metal Anodes
cond-mat.mtrl-sci physics.chem-ph
We generalize the conditions for stable electrodeposition at isotropic
solid-solid interfaces using a kinetic model which incorporates the effects of
stresses and surface tension at the interface. We develop a stability diagram
that shows two regimes of stability: previously known pressure-driven mechanism
and a new density-driven stability mechanism that is governed by the relative
density of metal in the two phases. We show that inorganic solids and solid
polymers generally do not lead to stable electrodeposition, and provide design
guidelines for achieving stable electrodeposition.
| arxiv topic:cond-mat.mtrl-sci physics.chem-ph |
arxiv_dataset-82311702.08506 | Inferring processes of cultural transmission: the critical role of rare
variants in distinguishing neutrality from novelty biases
q-bio.PE
Neutral evolution assumes that there are no selective forces distinguishing
different variants in a population. Despite this striking assumption, many
recent studies have sought to assess whether neutrality can provide a good
description of different episodes of cultural change. One approach has been to
test whether neutral predictions are consistent with observed progeny
distributions, recording the number of variants that have produced a given
number of new instances within a specified time interval: a classic example is
the distribution of baby names. Using an overlapping generations model we show
that these distributions consist of two phases: a power law phase with a
constant exponent of -3/2, followed by an exponential cut-off for variants with
very large numbers of progeny. Maximum likelihood estimations of the model
parameters provide a direct way to establish whether observed empirical
patterns are consistent with neutral evolution. We apply our approach to a
complete data set of baby names from Australia. Crucially we show that analyses
based on only the most popular variants, as is often the case in studies of
cultural evolution, can provide misleading evidence for underlying transmission
hypotheses. While neutrality provides a plausible description of progeny
distributions of abundant variants, rare variants deviate from neutrality.
Further, we develop a simulation framework that allows for the detection of
alternative cultural transmission processes. We show that anti-novelty bias is
able to replicate the complete progeny distribution of the Australian data set.
| arxiv topic:q-bio.PE |
arxiv_dataset-82321702.08606 | The Active Atlas: Combining 3D Anatomical Models with Texture Detectors
cs.CV q-bio.NC q-bio.QM
While modern imaging technologies such as fMRI have opened exciting new
possibilities for studying the brain in vivo, histological sections remain the
best way to study the anatomy of the brain at the level of single neurons. The
histological atlas changed little since 1909 and localizing brain regions is a
still a labor intensive process performed only by experienced neuro-anatomists.
Existing digital atlases such as the Allen Brain atlas are limited to low
resolution images which cannot identify the detailed structure of the neurons.
We have developed a digital atlas methodology that combines information about
the 3D organization of the brain and the detailed texture of neurons in
different structures. Using the methodology we developed an atlas for the mouse
brainstem and mid-brain, two regions for which there are currently no good
atlases. Our atlas is "active" in that it can be used to automatically align a
histological stack to the atlas, thus reducing the work of the neuroanatomist.
| arxiv topic:cs.CV q-bio.NC q-bio.QM |
arxiv_dataset-82331702.08706 | On the role of magnetosonic solitons in perpendicular collisionless
shock reformation
physics.plasm-ph astro-ph.HE
The nature of the magnetic structure arising from ion specular reflection in
shock compression studies is examined by means of 1d particle in cell
simulations. Propagation speed, field profiles and supporting currents for this
magnetic structure are shown to be consistent with a magnetosonic soliton.
Coincidentally, this structure and its evolution are typical of foot structures
observed in perpendicular shock reformation. To reconcile these two
observations, we propose, for the first time, that shock reformation can be
explained as the result of the formation, growth and subsequent transition to a
super-critical shock of a magnetosonic soliton. This argument is further
supported by the remarkable agreement found between the period of the soliton
evolution cycle and classical reformation results. This new result suggests
that the unique properties of solitons can be used to shed new light on the
long-standing issue of shock non-stationarity and its role on particle
acceleration.
| arxiv topic:physics.plasm-ph astro-ph.HE |
arxiv_dataset-82341702.08806 | Wavelength selection beyond Turing
nlin.PS
Spatial patterns arising spontaneously due to internal processes are
ubiquitous in nature, varying from regular patterns of dryland vegetation to
complex structures of bacterial colonies. Many of these patterns can be
explained in the context of a Turing instability, where patterns emerge due to
two locally interacting components that diffuse with different speeds in the
medium. Turing patterns are multistable, such that many different patterns with
different wavelengths are possible for the same set of parameters, but in a
given region typically only one such wavelength is dominant. In the Turing
instability region, random initial conditions will mostly lead to a wavelength
that is similar to that of the leading eigenvector that arises from the linear
stability analysis, but when venturing beyond, little is known about the
pattern that will emerge. Using dryland vegetation as a case study, we use
different models of drylands ecosystems to study the wavelength pattern that is
selected in various scenarios beyond the Turing instability region, focusing
the phenomena of localized states and repeated local disturbances.
| arxiv topic:nlin.PS |
arxiv_dataset-82351702.08906 | On the energy landscape of spherical spin glasses
math.PR math-ph math.MP
We investigate the energy landscape of the spherical mixed even p-spin model
near its maximum energy. We relate the distance between pairs of near maxima to
the support of the Parisi measure at zero temperature. We then provide an
algebraic relation that characterizes one-step replica symmetric breaking
Parisi measures. For these measures, we show that any two nonparallel spin
configurations around the maximum energy are asymptotically orthogonal to each
other. In sharp contrast, we study models with full replica symmetry breaking
and show that all possible values of the asymptotic distance are attained near
the maximum energy.
| arxiv topic:math.PR math-ph math.MP |
arxiv_dataset-82361703.00096 | Gram-CTC: Automatic Unit Selection and Target Decomposition for Sequence
Labelling
cs.CL cs.LG cs.NE
Most existing sequence labelling models rely on a fixed decomposition of a
target sequence into a sequence of basic units. These methods suffer from two
major drawbacks: 1) the set of basic units is fixed, such as the set of words,
characters or phonemes in speech recognition, and 2) the decomposition of
target sequences is fixed. These drawbacks usually result in sub-optimal
performance of modeling sequences. In this pa- per, we extend the popular CTC
loss criterion to alleviate these limitations, and propose a new loss function
called Gram-CTC. While preserving the advantages of CTC, Gram-CTC automatically
learns the best set of basic units (grams), as well as the most suitable
decomposition of tar- get sequences. Unlike CTC, Gram-CTC allows the model to
output variable number of characters at each time step, which enables the model
to capture longer term dependency and improves the computational efficiency. We
demonstrate that the proposed Gram-CTC improves CTC in terms of both
performance and efficiency on the large vocabulary speech recognition task at
multiple scales of data, and that with Gram-CTC we can outperform the
state-of-the-art on a standard speech benchmark.
| arxiv topic:cs.CL cs.LG cs.NE |
arxiv_dataset-82371703.00196 | Incorporating Intra-Class Variance to Fine-Grained Visual Recognition
cs.CV
Fine-grained visual recognition aims to capture discriminative
characteristics amongst visually similar categories. The state-of-the-art
research work has significantly improved the fine-grained recognition
performance by deep metric learning using triplet network. However, the impact
of intra-category variance on the performance of recognition and robust feature
representation has not been well studied. In this paper, we propose to leverage
intra-class variance in metric learning of triplet network to improve the
performance of fine-grained recognition. Through partitioning training images
within each category into a few groups, we form the triplet samples across
different categories as well as different groups, which is called Group
Sensitive TRiplet Sampling (GS-TRS). Accordingly, the triplet loss function is
strengthened by incorporating intra-class variance with GS-TRS, which may
contribute to the optimization objective of triplet network. Extensive
experiments over benchmark datasets CompCar and VehicleID show that the
proposed GS-TRS has significantly outperformed state-of-the-art approaches in
both classification and retrieval tasks.
| arxiv topic:cs.CV |
arxiv_dataset-82381703.00296 | Rotationally time-resolved vis-spectroscopy of (3200) Phaethon
astro-ph.EP
Apollo-type NEA (3200) Phaethon, classified at the B/F-type taxonomy,
probably the main mass of the Phaethon-Geminid stream complex (PGC), can be the
most metamorphic C-complex asteroid in our solar system, since it is heated up
to ~1000 K by the solar radiation around its perihelion passages. Hence, its
surface material may be easily decomposed in near-sun environment. Phaethon's
spectrum exhibits extremely blue-slope in the VIS-NIR region (so-called
Phaethon Blue). Another candidate large member of the PGC, (155140) 2005 UD,
shows a B/F-type color, however with a C-type-like red color over its ~1/4
rotational part, which implies an exposition of less metamorphosed primordial
internal structure of the PGC precursor by a splitting or breakup event long
ago. If so, some rotational part of Phaethon should show the C-type color as
well as 2005 UD. Hence, we carried out the time-series VIS-spectroscopic
observations of Phaethon using 1-m telescope in order to detect such a
signature. Also, R-band photometries were simultaneously performed in order to
complement our spectroscopy. Consequently, we obtained a total of 68
VIS-spectrophotometric data, 78% of which show the B-type blue-color, as
against the rest of 22% showing the C-type red-color. We successfully acquired
rotationally time-resolved spectroscopic data, of which particular rotational
phase shows a red-spectral slope as the C-type color, as 2005 UD does,
suggesting longitudinal inhomogeneity on Phaethon's surface. We constrained
this C-type red-colored area in the mid-latitude in Phaethon's southern
hemisphere based on the rotationally time-resolved spectroscopy along with
Phaethon's axial rotation state, of which size suggests the impact-induced
origin of the PGC. We also surveyed the meteoritic analog of Phaethon's surface
blue-color, and found thermally metamorphosed CI/CM chondrites as likely
candidates.
| arxiv topic:astro-ph.EP |
arxiv_dataset-82391703.00396 | Patient Specific Congestive Heart Failure Detection From Raw ECG signal
stat.AP
In this study; in order to diagnose congestive heart failure (CHF) patients,
non-linear second-order difference plot (SODP) obtained from raw 256 Hz sampled
frequency and windowed record with different time of ECG records are used. All
of the data rows are labelled with their belongings to classify much more
realistically. SODPs are divided into different radius of quadrant regions and
numbers of the points fall in the quadrants are computed in order to extract
feature vectors. Fisher's linear discriminant, Naive Bayes, Radial basis
function, and artificial neural network are used as classifier. The results are
considered in two step validation methods as general k-fold cross-validation
and patient based cross-validation. As a result, it is shown that using neural
network classifier with features obtained from SODP, the constructed system
could distinguish normal and CHF patients with 100% accuracy rate. Keywords
| arxiv topic:stat.AP |
arxiv_dataset-82401703.00496 | The astrophysics of visible-light orbital phase curves in the space age
astro-ph.SR
The field of visible-light continuous time series photometry is now at its
golden age, manifested by the continuum of past (CoRoT, Kepler), present (K2),
and future (TESS, PLATO) space-based surveys delivering high precision data
with a long baseline for a large number of stars. The availability of the high
quality data has enabled astrophysical studies not possible before, including
for example detailed asteroseismic investigations and the study of the
exoplanet census including small planets. This has also allowed to study the
minute photometric variability following the orbital motion in stellar binaries
and star-planet systems which is the subject of this review. We focus on
systems with a main sequence primary and a low-mass secondary, from a small
star to a massive planet. The orbital modulations are induced by a combination
of gravitational and atmospheric processes, including the beaming effect, tidal
ellipsoidal distortion, reflected light, and thermal emission. Therefore, the
phase curve shape contains information about the companion's mass and
atmospheric characteristics, making phase curves a useful astrophysical tool.
For example, phase curves can be used to detect and measure the mass of
short-period low-mass companions orbiting hot fast-rotating stars, out of reach
of other detection methods. Another interesting application of phase curves is
using the orbital phase modulations to look for non-transiting systems, which
comprise the majority of stellar binary and star-planet systems. We discuss the
science done with phase curves, the first results obtained so far, and the
current difficulties and open questions related to this young and evolving
subfield.
| arxiv topic:astro-ph.SR |
arxiv_dataset-82411703.00596 | Cell survival probability in a spread-out Bragg peak for novel treatment
planning
physics.med-ph physics.bio-ph
The problem of variable cell survival probability along the spread-out Bragg
peak is one of the long standing problems in planning and optimisation of
ion-beam therapy. This problem is considered using the multiscale approach to
the physics of ion-beam therapy. The physical reasons for this problem are
analysed and understood on a quantitative level. A recipe of solution to this
problem is suggested using this approach. This recipe can be used in the design
of a novel treatment planning and optimisation based on fundamental science.
| arxiv topic:physics.med-ph physics.bio-ph |
arxiv_dataset-82421703.00696 | Artificial Noise-Aided Biobjective Transmitter Optimization for Service
Integration in Multi-User MIMO Gaussian Broadcast Channel
cs.IT math.IT
This paper considers an artificial noise (AN)-aided transmit design for
multi-user MIMO systems with integrated services. Specifically, two sorts of
service messages are combined and served simultaneously: one multicast message
intended for all receivers and one confidential message intended for only one
receiver and required to be perfectly secure from other unauthorized receivers.
Our interest lies in the joint design of input covariances of the multicast
message, confidential message and artificial noise (AN), such that the
achievable secrecy rate and multicast rate are simultaneously maximized. This
problem is identified as a secrecy rate region maximization (SRRM) problem in
the context of physical-layer service integration. Since this bi-objective
optimization problem is inherently complex to solve, we put forward two
different scalarization methods to convert it into a scalar optimization
problem. First, we propose to prefix the multicast rate as a constant, and
accordingly, the primal biobjective problem is converted into a secrecy rate
maximization (SRM) problem with quality of multicast service (QoMS) constraint.
By varying the constant, we can obtain different Pareto optimal points. The
resulting SRM problem can be iteratively solved via a provably convergent
difference-of-concave (DC) algorithm. In the second method, we aim to maximize
the weighted sum of the secrecy rate and the multicast rate. Through varying
the weighted vector, one can also obtain different Pareto optimal points. We
show that this weighted sum rate maximization (WSRM) problem can be recast into
a primal decomposable form, which is amenable to alternating optimization (AO).
Then we compare these two scalarization methods in terms of their overall
performance and computational complexity via theoretical analysis as well as
numerical simulation, based on which new insights can be drawn.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-82431703.00796 | Unsupervised Steganalysis Based on Artificial Training Sets
cs.MM cs.LG
In this paper, an unsupervised steganalysis method that combines artificial
training setsand supervised classification is proposed. We provide a formal
framework for unsupervisedclassification of stego and cover images in the
typical situation of targeted steganalysis (i.e.,for a known algorithm and
approximate embedding bit rate). We also present a completeset of experiments
using 1) eight different image databases, 2) image features based on
RichModels, and 3) three different embedding algorithms: Least Significant Bit
(LSB) matching,Highly undetectable steganography (HUGO) and Wavelet Obtained
Weights (WOW). Weshow that the experimental results outperform previous methods
based on Rich Models inthe majority of the tested cases. At the same time, the
proposed approach bypasses theproblem of Cover Source Mismatch -when the
embedding algorithm and bit rate are known-, since it removes the need of a
training database when we have a large enough testing set.Furthermore, we
provide a generic proof of the proposed framework in the machine
learningcontext. Hence, the results of this paper could be extended to other
classification problemssimilar to steganalysis.
| arxiv topic:cs.MM cs.LG |
arxiv_dataset-82441703.00896 | Lepton flavor violating Higgs boson decays in seesaw models: new
discussions
hep-ph
The lepton flavor violating decay of the Standard Model-like Higgs boson
(LFVHD), h->\mu\tau, is discussed in seesaw models at the one-loop level. Based
on particular analytic expressions of Passarino-Veltman functions, the two
unitary and 't Hooft Feynman gauges are used to compute the branching ratio of
LFVHD and compare with results reported recently. In the minimal seesaw (MSS)
model, the branching ratio was investigated in the whole valid range
10^{-9}-10^{15} GeV of new neutrino mass scale m_{n_6}. Using the Casas-Ibarra
parameterization, this branching ratio enhances with large and increasing
m_{n_6}. But the maximal value can reach only order of 10^{-11}. Interesting
relations of LFVHD predicted by the MSS and inverse seesaw (ISS) model are
discussed. The ratio between two LFVHD branching ratios predicted by the ISS
and MSS is simply m^2_{n_6}\mu^{-2}_X, where \mu_X is the small neutrino mass
scale in the ISS. The consistence between different calculations is shown
precisely from analytical approach.
| arxiv topic:hep-ph |
arxiv_dataset-82451703.00996 | Spectral Numerical Exterior Calculus Methods for Differential Equations
on Radial Manifolds
math.NA
We develop exterior calculus approaches for partial differential equations on
radial manifolds. We introduce numerical methods that approximate with spectral
accuracy the exterior derivative $\mathbf{d}$, Hodge star $\star$, and their
compositions. To achieve discretizations with high precision and symmetry, we
develop hyperinterpolation methods based on spherical harmonics and Lebedev
quadrature. We perform convergence studies of our numerical exterior derivative
operator $\overline{\mathbf{d}}$ and Hodge star operator $\overline{\star}$
showing each converge spectrally to $\mathbf{d}$ and $\star$. We show how the
numerical operators can be naturally composed to formulate general numerical
approximations for solving differential equations on manifolds. We present
results for the Laplace-Beltrami equations demonstrating our approach.
| arxiv topic:math.NA |
arxiv_dataset-82461703.01096 | Photo-association of trilobite Rydberg molecules via resonant spin-orbit
coupling
physics.atom-ph cond-mat.quant-gas
We report on a novel method for photo-association of strongly polar trilobite
Rydberg molecules. This exotic ultralong-range dimer, consisting of a
ground-state atom bound to the Rydberg electron via electron-neutral
scattering, inherits its polar character from the admixture of high angular
momentum electronic orbitals. The absence of low-$L$ character hinders standard
photo-association techniques. Here, we show that for suitable principal quantum
numbers resonant coupling of the orbital motion with the nuclear spin of the
perturber, mediated by electron-neutral scattering, hybridizes the trilobite
molecular potential with the more conventional ${\rm{S}}$-type molecular state.
This provides a general path to associate trilobite molecules with large
electric dipole moments, as demonstrated via high-resolution spectroscopy. We
find a dipole moment of 135(45) D for the trilobite state. Our results are
compared to theoretical predictions based on a Fermi-model.
| arxiv topic:physics.atom-ph cond-mat.quant-gas |
arxiv_dataset-82471703.01196 | Learning Identifiable Gaussian Bayesian Networks in Polynomial Time and
Sample Complexity
cs.LG stat.ML
Learning the directed acyclic graph (DAG) structure of a Bayesian network
from observational data is a notoriously difficult problem for which many
hardness results are known. In this paper we propose a provably polynomial-time
algorithm for learning sparse Gaussian Bayesian networks with equal noise
variance --- a class of Bayesian networks for which the DAG structure can be
uniquely identified from observational data --- under high-dimensional
settings. We show that $O(k^4 \log p)$ number of samples suffices for our
method to recover the true DAG structure with high probability, where $p$ is
the number of variables and $k$ is the maximum Markov blanket size. We obtain
our theoretical guarantees under a condition called Restricted Strong Adjacency
Faithfulness, which is strictly weaker than strong faithfulness --- a condition
that other methods based on conditional independence testing need for their
success. The sample complexity of our method matches the information-theoretic
limits in terms of the dependence on $p$. We show that our method out-performs
existing state-of-the-art methods for learning Gaussian Bayesian networks in
terms of recovering the true DAG structure while being comparable in speed to
heuristic methods.
| arxiv topic:cs.LG stat.ML |
arxiv_dataset-82481703.01296 | An Ordered Approach to Solving Parity Games in Quasi Polynomial Time and
Quasi Linear Space
cs.LO
Parity games play an important role in model checking and synthesis. In their
paper, Calude et al. have shown that these games can be solved in
quasi-polynomial time. We show that their algorithm can be implemented
efficiently: we use their data structure as a progress measure, allowing for a
backward implementation instead of a complete unravelling of the game. To
achieve this, a number of changes have to be made to their techniques, where
the main one is to add power to the antagonistic player that allows for
determining her rational move without changing the outcome of the game. We
provide a first implementation for a quasi-polynomial algorithm, test it on
small examples, and provide a number of side results, including minor
algorithmic improvements, a quasi bi-linear complexity in the number of states
and edges for a fixed number of colours, and matching lower bounds for the
algorithm of Calude et al.
| arxiv topic:cs.LO |
arxiv_dataset-82491703.01396 | Stacking-based Deep Neural Network: Deep Analytic Network on
Convolutional Spectral Histogram Features
cs.CV
Stacking-based deep neural network (S-DNN), in general, denotes a deep neural
network (DNN) resemblance in terms of its very deep, feedforward network
architecture. The typical S-DNN aggregates a variable number of individually
learnable modules in series to assemble a DNN-alike alternative to the targeted
object recognition tasks. This work likewise devises an S-DNN instantiation,
dubbed deep analytic network (DAN), on top of the spectral histogram (SH)
features. The DAN learning principle relies on ridge regression, and some key
DNN constituents, specifically, rectified linear unit, fine-tuning, and
normalization. The DAN aptitude is scrutinized on three repositories of varying
domains, including FERET (faces), MNIST (handwritten digits), and CIFAR10
(natural objects). The empirical results unveil that DAN escalates the SH
baseline performance over a sufficiently deep layer.
| arxiv topic:cs.CV |
arxiv_dataset-82501703.01496 | Weak-value amplification and optimal parameter estimation in the
presence of correlated noise
quant-ph
We analytically and numerically investigate the performance of weak-value
amplification (WVA) and related parameter estimation methods in the presence of
temporally correlated noise. WVA is a special instance of a general measurement
strategy that involves sorting data into separate subsets based on the outcome
of a second "partitioning" measurement. Using a simplified noise model that can
be analyzed exactly together with optimal statistical estimators, we compare
WVA to a conventional measurement method. We find that introducing WVA indeed
yields a much lower variance of the parameter of interest than does the
conventional technique, optimized in the absence of any partitioning
measurements. In contrast, a statistically optimal analysis that employs
partitioning measurements, incorporating all partitioned results and their
known correlations, is found to yield an improvement -- typically slight --
over the noise reduction achieved by WVA. This is because the simple WVA
technique is not tailored to a given noise environment and therefore does not
make use of correlations between the different partitions. We also compare WVA
to traditional background subtraction, a familiar technique where measurement
outcomes are partitioned to eliminate unknown offsets or errors in calibration.
Surprisingly, in our model background subtraction turns out to be a special
case of the optimal partitioning approach in the balanced case, possessing a
similar typically slight advantage over WVA. These results give deeper insight
into the role of partitioning measurements, with or without post-selection, in
enhancing measurement precision, which some have found puzzling. We finish by
presenting numerical results to model a more realistic laboratory situation of
time-decaying correlations, showing our conclusions hold for a wide range of
statistical models.
| arxiv topic:quant-ph |
arxiv_dataset-82511703.01596 | Protecting a nuclear spin from a noisy electron spin in diamond
quant-ph
Although a nuclear spin is weakly coupled to its environment, due to its
small gyromagnetic ratio, its coherence time is limited by the hyperfine
coupling to a nearby noisy electron. Here, we propose to utilize continuous
dynamical decoupling to refocus the coupling to the electron. If the random
phase accumulated by the nuclear spin through the reduced coupling terms is
sufficient small, we can increase the nuclear coherence time. Initially, we
demonstrate this on a simple case with a two-level electron spin, while taking
all relevant hyperfine coupling terms and noise terms into account. We then
extend the analysis to a nitrogen-vacancy center in diamond having a three
level structure.
| arxiv topic:quant-ph |
arxiv_dataset-82521703.01696 | Phonon-mediated repulsion, sharp transitions and (quasi)self-trapping in
the extended Peierls-Hubbard model
cond-mat.str-el cond-mat.quant-gas quant-ph
We study two identical fermions, or two hard-core bosons, in an infinite
chain and coupled to phonons by interactions that modulate their hopping as
described by the Peierls/Su-Schrieffer-Heeger (SSH) model. We show that
exchange of phonons generates effective nearest-neighbor repulsion between
particles and also gives rise to interactions that move the pair as a whole.
The two-polaron phase diagram exhibits two sharp transitions, leading to light
dimers at strong coupling and the flattening of the dimer dispersion at some
critical values of the parameters. This dimer (quasi)self-trapping occurs at
coupling strengths where single polarons are mobile. This illustrates that,
depending on the strength of the phonon-mediated interactions, the coupling to
phonons may completely suppress or strongly enhance quantum transport of
correlated particles.
| arxiv topic:cond-mat.str-el cond-mat.quant-gas quant-ph |
arxiv_dataset-82531703.01796 | Annihilators in $\mathbb{N}^k$-graded and $\mathbb{Z}^k$-graded rings
math.RA
It has been shown by McCoy that a right ideal of a polynomial ring with
several indeterminates has a non-trivial homogeneous right annihilator of
degree 0 provided its right annihilator is non-trivial to begin with. In this
note, it is documented that any $\mathbb{N}$-graded ring $R$ has a slightly
weaker property: the right annihilator of a right ideal contains a homogeneous
non-zero element, if it is non-trivial to begin with. If $R$ is a subring of a
$\mathbb{Z}^k$ -graded ring $S$ satisfying a certain non-annihilation property
(which is the case if $S$ is strongly graded, for example), then it is possible
to find annihilators of degree 0.
| arxiv topic:math.RA |
arxiv_dataset-82541703.01896 | Mutation supply and the repeatability of selection for antibiotic
resistance
q-bio.PE
Whether evolution can be predicted is a key question in evolutionary biology.
Here we set out to better understand the repeatability of evolution. We
explored experimentally the effect of mutation supply and the strength of
selective pressure on the repeatability of selection from standing genetic
variation. Different sizes of mutant libraries of an antibiotic resistance
gene, TEM-1 $\beta$-lactamase in Escherichia coli, were subjected to different
antibiotic concentrations. We determined whether populations went extinct or
survived, and sequenced the TEM gene of the surviving populations. The
distribution of mutations per allele in our mutant libraries- generated by
error-prone PCR- followed a Poisson distribution. Extinction patterns could be
explained by a simple stochastic model that assumed the sampling of beneficial
mutations was key for survival. In most surviving populations, alleles
containing at least one known large-effect beneficial mutation were present.
These genotype data also support a model which only invokes sampling effects to
describe the occurrence of alleles containing large-effect driver mutations.
Hence, evolution is largely predictable given cursory knowledge of mutational
fitness effects, the mutation rate and population size. There were no clear
trends in the repeatability of selected mutants when we considered all
mutations present. However, when only known large-effect mutations were
considered, the outcome of selection is less repeatable for large libraries, in
contrast to expectations. Furthermore, we show experimentally that alleles
carrying multiple mutations selected from large libraries confer higher
resistance levels relative to alleles with only a known large-effect mutation,
suggesting that the scarcity of high-resistance alleles carrying multiple
mutations may contribute to the decrease in repeatability at large library
sizes.
| arxiv topic:q-bio.PE |
arxiv_dataset-82551703.01996 | Strong supremacy of quantum systems as communication resource
quant-ph
We investigate the task of $d$-level random access codes ($d$-RACs) and
consider the possibility of encoding classical strings of $d$-level symbols
(dits) into a quantum system of dimension $d'$ strictly less than $d$. We show
that the average success probability of recovering one (randomly chosen) dit
from the encoded string can be larger than that obtained in the best classical
protocol for the task. Our result is intriguing as we know from Holevo's
theorem (and more recently from Frenkel-Weiner's result [Commun. Math. Phys.
340, 563 (2015)]) that there exist communication scenarios wherein quantum
resources prove to be of no advantage over classical resources. A
distinguishing feature of our protocol is that it establishes a stronger
quantum advantage in contrast to the existing quantum $d$-RACs where $d$-level
quantum systems are shown to be advantageous over their classical $d$-level
counterparts.
| arxiv topic:quant-ph |
arxiv_dataset-82561703.02096 | Structural and emission properties of Tb3+-doped nitrogen-rich silicon
oxynitride films
cond-mat.mtrl-sci physics.optics
Terbium doped silicon oxynitride host matrix is suitable for various
applications such as light emitters compatible with CMOS technology or
frequency converter systems for photovoltaic cells. In this study, amorphous
Tb3+ ion doped nitrogen-rich silicon oxynitride (NRSON) thin films were
fabricated using a reactive magnetron co-sputtering method, with various N2
flows and annealing conditions, in order to study their structural and emission
properties. Rutherford backscattering (RBS) measurements and refractive index
values confirmed the silicon oxynitride nature of the films. An electron
microscopy analysis conducted for different annealing temperatures (T A) was
also performed up to 1200 {\textdegree}C. Transmission electron microscopy
(TEM) images revealed two different sublayers. The top layer showed porosities
coming from a degassing of oxygen during deposition and annealing, while in the
region close to the substrate, a multilayer-like structure of SiO2 and Si3N4
phases appeared, involving a spinodal decomposition. Upon a 1200 {\textdegree}C
annealing treatment, a significant density of Tb clusters was detected,
indicating a higher thermal threshold of rare earth (RE) clusterization in
comparison to the silicon oxide matrix. With an opposite variation of the N2
flow during the deposition, the nitrogen excess parameter (Nex) estimated by
RBS measurements was introduced to investigate the Fourier transform infrared
(FTIR) spectrum behavior and emission properties. Different vibration modes of
the Si--N and Si--O bonds have been carefully identified from the FTIR spectra
characterizing such host matrices, especially the 'out-of-phase' stretching
vibration mode of the Si--O bond. The highest Tb3+ photoluminescence (PL)
intensity was obtained by optimizing the N incorporation and the annealing
conditions. In addition, according to these conditions, the integrated PL
intensity variation confirmed that the silicon nitride-based host matrix had a
higher thermal threshold of rare earth clusterization than its silicon oxide
counterpart. Analysis of time-resolved PL intensity versus T A showed the
impact of Tb clustering on decay times, in agreement with the TEM observations.
Finally, PL and PL excitation (PLE) experiments and comparison of the related
spectra between undoped and Tb-doped samples were carried out to investigate
the impact of the band tails on the excitation mechanism of Tb3+ ions.
| arxiv topic:cond-mat.mtrl-sci physics.optics |
arxiv_dataset-82571703.02196 | Cooperative Epistemic Multi-Agent Planning for Implicit Coordination
cs.AI cs.LO cs.MA
Epistemic planning can be used for decision making in multi-agent situations
with distributed knowledge and capabilities. Recently, Dynamic Epistemic Logic
(DEL) has been shown to provide a very natural and expressive framework for
epistemic planning. We extend the DEL-based epistemic planning framework to
include perspective shifts, allowing us to define new notions of sequential and
conditional planning with implicit coordination. With these, it is possible to
solve planning tasks with joint goals in a decentralized manner without the
agents having to negotiate about and commit to a joint policy at plan time.
First we define the central planning notions and sketch the implementation of a
planning system built on those notions. Afterwards we provide some case studies
in order to evaluate the planner empirically and to show that the concept is
useful for multi-agent systems in practice.
| arxiv topic:cs.AI cs.LO cs.MA |
arxiv_dataset-82581703.02296 | Low-rank model with covariates for count data analysis
stat.ME
Count data are collected in many scientific and engineering tasks including
image processing, single-cell RNA sequencing and ecological studies. Such data
sets often contain missing values, for example because some ecological sites
cannot be reached in a certain year. In addition, in many instances, side
information is also available, for example covariates about ecological sites or
species. Low-rank methods are popular to denoise and impute count data, and
benefit from a substantial theoretical background. Extensions accounting for
covariates have been proposed, but to the best of our knowledge their
theoretical and empirical properties have not been thoroughly studied, and few
softwares are available for practitioners. We propose a complete methodology
called LORI (Low-Rank Interaction), including a Poisson model, an algorithm,
and automatic selection of the regularization parameter, to analyze count
tables with covariates. We also derive an upper bound on the estimation error.
We provide a simulation study with synthetic data, revealing empirically that
LORI improves on state of the art methods in terms of estimation and imputation
of the missing values. We illustrate how the method can be interpreted through
visual displays with the analysis of a well-know plant abundance data set, and
show that the LORI outputs are consistent with known results. Finally we
demonstrate the relevance of the methodology by analyzing a water-birds
abundance table from the French national agency for wildlife and hunting
management (ONCFS). The method is available in the R package lori on the
Comprehensive Archive Network (CRAN).
| arxiv topic:stat.ME |
arxiv_dataset-82591703.02396 | The volume of the black holes - the constant curvature slicing of the
spherically symmetric spacetime
gr-qc
We consider the problem of determination of a volume of some bounded
space-like hypersurfaces in the case of spherically symmetric spacetimes. In
the case when the hypersurfaces is cut or bounded by a light-like hypersurface
the problem may not be well defined. In order to define properly the volume we
introduce the volume forms related to the given foliation (observer) of the
considered spacetime. In the case of the constant curvature slice the volume of
the hypersurface cut by the horizon (light-like surface) becomes composed of
the two parts, outer and inner, treated differently. We compute the
corresponding volumes outside and inside of the horizon of the ethernal
Schwarzschild black hole.
| arxiv topic:gr-qc |
arxiv_dataset-82601703.02496 | Effects of Hubbard term correction on the structural parameters and
electronic properties of wurtzite Zn
cond-mat.mtrl-sci
The effects of including the Hubbard on-site Coulombic correction to the
structural parameters and valence energy states of wurtzite ZnO was explored.
Due to the changes in the structural parameters caused by correction of
hybridization between Zn d states and O p states, suitable parameters of
Hubbard terms have to be determined for an accurate prediction of ZnO
properties. Using the LDA+${U}$ method by applying Hubbard corrections $U_p$ to
Zn 3d states and $U_p$ to O 2p states, the lattice constants were
underestimated for all tested Hubbard parameters. The combination of both $U_d$
and $U_p$ correction terms managed to widen the band gap of wurtzite ZnO to the
experimental value. Pairs of $U_p$ and $U_p$ parameters with the correct
positioning of d-band and accurate bandwidths were selected, in addition to
predicting an accurate band gap value. Inspection of vibrational properties,
however, revealed mismatches between the estimated gamma phonon frequencies and
experimental values. The selection of Hubbard terms based on electronic band
properties alone cannot ensure an accurate vibrational description in LDA+${U}$
calculation.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-82611703.02596 | Customer Lifetime Value Prediction Using Embeddings
cs.LG cs.CY cs.IR cs.NE stat.ML
We describe the Customer LifeTime Value (CLTV) prediction system deployed at
ASOS.com, a global online fashion retailer. CLTV prediction is an important
problem in e-commerce where an accurate estimate of future value allows
retailers to effectively allocate marketing spend, identify and nurture high
value customers and mitigate exposure to losses. The system at ASOS provides
daily estimates of the future value of every customer and is one of the
cornerstones of the personalised shopping experience. The state of the art in
this domain uses large numbers of handcrafted features and ensemble regressors
to forecast value, predict churn and evaluate customer loyalty. Recently,
domains including language, vision and speech have shown dramatic advances by
replacing handcrafted features with features that are learned automatically
from data. We detail the system deployed at ASOS and show that learning feature
representations is a promising extension to the state of the art in CLTV
modelling. We propose a novel way to generate embeddings of customers, which
addresses the issue of the ever changing product catalogue and obtain a
significant improvement over an exhaustive set of handcrafted features.
| arxiv topic:cs.LG cs.CY cs.IR cs.NE stat.ML |
arxiv_dataset-82621703.02696 | Anticorrelation between polar lattice instability and superconductivity
in the Weyl semimetal candidate MoTe2
cond-mat.supr-con
The relation between the polar structural instability and superconductivity
in a Weyl semimetal candidate MoTe2 has been clarified by finely controlled
physical and chemical pressure. The physical pressure as well as the chemical
pressure, i.e., the Se substitution for Te, enhances the superconducting
transition temperature Tc at around the critical pressure where the polar
structure transition disappears. From the heat capacity and thermopower
measurements, we ascribe the significant enhancement of Tc at the critical
pressure to a subtle modification of the phonon dispersion or the semimetallic
band structure upon the polar-to-nonpolar transition. On the other hand, the
physical pressure, which strongly reduces the interlayer distance, is more
effective on the suppression of the polar structural transition and the
enhancement of Tc as compared with the chemical pressure, which emphasizes the
importance of the interlayer coupling on the structural and superconducting
instability in MoTe2.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-82631703.02796 | The geometry of $m$-hyperconvex domains
math.CV math.CA
We study the geometry of $m$-regular domains within the
Caffarelli-Nirenberg-Spruck model in terms of barrier functions, envelopes,
exhaustion functions, and Jensen measures. We prove among other things that
every $m$-hyperconvex domain admits an exhaustion function that is negative,
smooth, strictly $m$-subharmonic, and has bounded $m$-Hessian measure.
| arxiv topic:math.CV math.CA |
arxiv_dataset-82641703.02896 | A Novel Thiophene-fused Ending Group Enabling an Excellent Small
Molecule Acceptor for High-performance Fullerene-free Polymer Solar Cells
with 11.8% Efficiency
physics.chem-ph
In this article, we designed and synthesized a novel small molecule acceptor
of ITCPTC with thiophene-fused ending group by employing a new active methylene
precursor of CPTCN. The ITCPTC based polymer solar cells with PBT1-EH as donor
achieved very high PCEs of up to 11.8% with a remarkably enhanced fill factor
(FF) of 0.751, a near 20% boost in PCE with respect to the ITIC based control
device. These values are among the highest PCEs and FFs for PSCs. In the whole
study, we made contrasts with ITIC to understand the reasons of excellent
performance of ITCPTC-based PSCs through various measurements, such as GIWAXS
and RSoXS. We revealed that the simple modification of ITIC into ITCPTC not
only change the material electronic structure, but also mediate the material
interactions and crystallization, which contribute together to the excellent
performance of ITCPTC based PSCs.
| arxiv topic:physics.chem-ph |
arxiv_dataset-82651703.02996 | Identity theorem for pro-$p$-groups
math.GR math.AG math.AT
We prove the Identity Theorem for pro-$p$-groups with a single defining
relation giving a positive feedback to a question of Serre on the structure of
relation modules. A construction of "conjurings" indicates finality of our
result in a certain sense.
| arxiv topic:math.GR math.AG math.AT |
arxiv_dataset-82661703.03096 | Normal State Gap in Parent Cuprate Pr2CuO4+/-{\delta}
cond-mat.supr-con
We present a tunneling study on single crystalline parent cuprate thin films,
i.e. a series of Pr2CuO4+/-{\delta}(PCO) with tunable superconducting
transition temperature. The zero-bias anomaly of differential conductance, well
reported in the normal state of R2-xCexCuO4 (R = Pr, Nd, La) and named as
normal state gap (NSG), is observed in the Ce-free samples. This NSG behaves
quite robust against the magnetic field up to 16 T, but fades away with
increasing the temperature. Most importantly, we find that the magnitude of the
NSG becomes larger with increasing point-contact junction resistance on the
superconducting films, which is further enhanced in the non-superconducting
samples of more oxygen disorders. The origination of NSG can be understood in
the framework of Altshuler-Aronov-Lee (AAL) theory, where the disorder-induced
electron-electron interactions suppress the density of states and thereby
result in a soft Coulomb gap.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-82671703.03196 | Prior-based Hierarchical Segmentation Highlighting Structures of
Interest
cs.CV
Image segmentation is the process of partitioning an image into a set of
meaningful regions according to some criteria. Hierarchical segmentation has
emerged as a major trend in this regard as it favors the emergence of important
regions at different scales. On the other hand, many methods allow us to have
prior information on the position of structures of interest in the images. In
this paper, we present a versatile hierarchical segmentation method that takes
into account any prior spatial information and outputs a hierarchical
segmentation that emphasizes the contours or regions of interest while
preserving the important structures in the image. Several applications are
presented that illustrate the method versatility and efficiency.
| arxiv topic:cs.CV |
arxiv_dataset-82681703.03296 | Levitation of heavy particles against gravity in asymptotically downward
flows
physics.flu-dyn nlin.CD
In the fluid transport of particles, it is generally expected that heavy
particles carried by a laminar fluid flow moving downward will also move
downward. We establish a theory to show, however, that particles can be
dynamically levitated and lifted by interacting vortices in such flows, thereby
moving against gravity and the asymptotic direction of the flow, even when they
are orders of magnitude denser than the fluid. The particle levitation is
rigorously demonstrated for potential flows and supported by simulations for
viscous flows. We suggest that this counterintuitive effect has potential
implications for the air-transport of water droplets and the lifting of
sediments in water.
| arxiv topic:physics.flu-dyn nlin.CD |
arxiv_dataset-82691703.03396 | A generic theory for Majorana zero modes in 2D superconductors
cond-mat.supr-con cond-mat.mes-hall quant-ph
It is well known that non-Abelian Majorana zero modes (MZM) harbor at vortex
cores in a $p_{x}+\text{i}p_{y}$ topological superconductor, which can be
realized in a 2D spin-orbit coupled system with a single Fermi surface and by
proximity coupling to an $s$-wave superconductor. Here we show that existence
of non-Abelian MZMs is unrelated to the bulk topology of a 2D superconductor,
and propose that such exotic modes can be resulted in much broader range of
superconductors, being topological or trivial. For a generic 2D system with
multiple Fermi surfaces and gapped out by superconducting pairings, we show
that at least a single MZM survives if there are only odd number of Fermi
surfaces of which the corresponding superconducting orders have vortices, and
such MZM is protected by an emergent Chern-Simons invariant, irrespective of
the bulk topology of the superconductor. This result may enrich new
experimental schemes for realizing non-Aelian MZMs. In particular, we propose a
minimal scheme to realize the MZMs in a 2D superconducting Dirac semimetal with
trivial bulk topology, which can be well achieved based on the recent cold atom
experiments.
| arxiv topic:cond-mat.supr-con cond-mat.mes-hall quant-ph |
arxiv_dataset-82701703.03496 | Momentum-Resolved View of Electron-Phonon Coupling in Multilayer WSe$_2$
cond-mat.mes-hall
We investigate the interactions of photoexcited carriers with lattice
vibrations in thin films of the layered transition metal dichalcogenide (TMDC)
WSe$_2$. Employing femtosecond electron diffraction with monocrystalline
samples and first principle density functional theory calculations, we obtain a
momentum-resolved picture of the energy-transfer from excited electrons to
phonons. The measured momentum-dependent phonon population dynamics are
compared to first principle calculations of the phonon linewidth and can be
rationalized in terms of electronic phase-space arguments. The relaxation of
excited states in the conduction band is dominated by intervalley scattering
between $\Sigma$ valleys and the emission of zone-boundary phonons.
Transiently, the momentum-dependent electron-phonon coupling leads to a
non-thermal phonon distribution, which, on longer timescales, relaxes to a
thermal distribution via electron-phonon and phonon-phonon collisions. Our
results constitute a basis for monitoring and predicting out of equilibrium
electrical and thermal transport properties for nanoscale applications of
TMDCs.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-82711703.03596 | High SNR Consistent Compressive Sensing
stat.ML cs.IT math.IT
High signal to noise ratio (SNR) consistency of model selection criteria in
linear regression models has attracted a lot of attention recently. However,
most of the existing literature on high SNR consistency deals with model order
selection. Further, the limited literature available on the high SNR
consistency of subset selection procedures (SSPs) is applicable to linear
regression with full rank measurement matrices only. Hence, the performance of
SSPs used in underdetermined linear models (a.k.a compressive sensing (CS)
algorithms) at high SNR is largely unknown. This paper fills this gap by
deriving necessary and sufficient conditions for the high SNR consistency of
popular CS algorithms like $l_0$-minimization, basis pursuit de-noising or
LASSO, orthogonal matching pursuit and Dantzig selector. Necessary conditions
analytically establish the high SNR inconsistency of CS algorithms when used
with the tuning parameters discussed in literature. Novel tuning parameters
with SNR adaptations are developed using the sufficient conditions and the
choice of SNR adaptations are discussed analytically using convergence rate
analysis. CS algorithms with the proposed tuning parameters are numerically
shown to be high SNR consistent and outperform existing tuning parameters in
the moderate to high SNR regime.
| arxiv topic:stat.ML cs.IT math.IT |
arxiv_dataset-82721703.03696 | Exotic Compact Objects and How to Quench their Ergoregion Instability
gr-qc astro-ph.HE hep-ph hep-th
Gravitational-wave astronomy can give us access to the structure of black
holes, potentially probing microscopic or even Planckian corrections at the
horizon scale, as those predicted by some quantum-gravity models of exotic
compact objects. A generic feature of these models is the replacement of the
horizon by a reflective surface. Objects with these properties are prone to the
so-called ergoregion instability when they spin sufficiently fast. We
investigate in detail a simple model consisting of scalar perturbations of a
Kerr geometry with a reflective surface near the horizon. The instability
depends on the spin, on the compactness, and on the reflectivity at the
surface. The instability time scale increases only logarithmically in the
black-hole limit and, for a perfectly reflecting object, this is not enough to
prevent the instability from occurring on dynamical time scales. However, we
find that an absorption rate at the surface as small as 0.4% (reflectivity
coefficient as large as $|{\cal R}|^2=0.996$) is sufficient to quench the
instability completely. Our results suggest that exotic compact objects are not
necessarily ruled out by the ergoregion instability.
| arxiv topic:gr-qc astro-ph.HE hep-ph hep-th |
arxiv_dataset-82731703.03796 | Controlled Flavour Changing Neutral Couplings in Two Higgs Doublet
Models
hep-ph hep-ex
We propose a class of Two Higgs Doublet Models where there are Flavour
Changing Neutral Currents (FCNC) at tree level, but under control due to the
introduction of a discrete symmetry in the full Lagrangian. It is shown that in
this class of models, one can have simultaneously FCNC in the up and down
sectors, in contrast to the situation encountered in BGL models. The intensity
of FCNC is analysed and it is shown that in this class of models one can
respect all the strong constraints from experiment without unnatural
fine-tuning. It is pointed out that the additional sources of flavour and CP
violation are such that they can enhance significantly the generation of the
Baryon Asymmetry of the Universe, with respect to the Standard Model.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-82741703.03896 | A degree version of the Hilton--Milner theorem
math.CO
An intersecting family of sets is trivial if all of its members share a
common element. Hilton and Milner proved a strong stability result for the
celebrated Erd\H{o}s--Ko--Rado theorem: when $n> 2k$, every non-trivial
intersecting family of $k$-subsets of $[n]$ has at most
$\binom{n-1}{k-1}-\binom{n-k-1}{k-1}+1$ members. One extremal family
$\mathcal{HM}_{n, k}$ consists of a $k$-set $S$ and all $k$-subsets of $[n]$
containing a fixed element $x\not\in S$ and at least one element of $S$. We
prove a degree version of the Hilton--Milner theorem: if $n=\Omega(k^2)$ and
$\mathcal{F}$ is a non-trivial intersecting family of $k$-subsets of $[n]$,
then $\delta(\mathcal{F})\le \delta(\mathcal{HM}_{n.k})$, where
$\delta(\mathcal{F})$ denotes the minimum (vertex) degree of $\mathcal{F}$. Our
proof uses several fundamental results in extremal set theory, the concept of
kernels, and a new variant of the Erd\H{o}s--Ko--Rado theorem.
| arxiv topic:math.CO |
arxiv_dataset-82751703.03996 | Stable Charged Antiparallel Domain Walls in Hyperferroelectrics
cond-mat.mtrl-sci
Charge-neutral 180$^\circ$ domain walls that separate domains of antiparallel
polarization directions are common structural topological defects in
ferroelectrics. In normal ferroelectrics, charged 180$^\circ$ domain walls
running perpendicular to the polarization directions are highly energetically
unfavorable because of the depolarization field and are difficult to stabilize.
We explore both neutral and charged 180$^\circ$ domain walls in
hyperferroelectrics, a class of proper ferroelectrics with persistent
polarization in the presence of a depolarization field, using density
functional theory. We obtain zero temperature equilibrium structures of
head-to-head and tail-to-tail walls in recently discovered $ABC$-type hexagonal
hyperferroelectrics. Charged domain walls can also be stabilized in canonical
ferroelectrics represented by LiNbO$_3$ without any dopants, defects or
mechanical clamping. First-principles electronic structure calculations show
that charged domain walls can reduce and even close the band gap of host
materials and support quasi-two-dimensional electron(hole) gas with enhanced
electrical conductivity.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-82761703.04096 | Improving Interpretability of Deep Neural Networks with Semantic
Information
cs.CV
Interpretability of deep neural networks (DNNs) is essential since it enables
users to understand the overall strengths and weaknesses of the models, conveys
an understanding of how the models will behave in the future, and how to
diagnose and correct potential problems. However, it is challenging to reason
about what a DNN actually does due to its opaque or black-box nature. To
address this issue, we propose a novel technique to improve the
interpretability of DNNs by leveraging the rich semantic information embedded
in human descriptions. By concentrating on the video captioning task, we first
extract a set of semantically meaningful topics from the human descriptions
that cover a wide range of visual concepts, and integrate them into the model
with an interpretive loss. We then propose a prediction difference maximization
algorithm to interpret the learned features of each neuron. Experimental
results demonstrate its effectiveness in video captioning using the
interpretable features, which can also be transferred to video action
recognition. By clearly understanding the learned features, users can easily
revise false predictions via a human-in-the-loop procedure.
| arxiv topic:cs.CV |
arxiv_dataset-82771703.04196 | Conditions of Full Disclosure:The Blockchain Remuneration Model
cs.CY
One of the fundamental applications for a practically useful system of money
is remuneration. Information pertaining to the amount of compensation awarded
to different individuals is often considered sensitive, commanding a certain
degree of privacy. As Bitcoin and similarly designed cryptocurrencies evolve
into a recognized medium of exchange for larger swaths of the world economy, an
increasing number of people will earn income in the form of blockchain-based
payments. The nature of these transactions is such that the minute details of
an affected individuals compensation package and spending habits will be
exposed to public scrutiny. In some cases this violates cultural norms which
respect the confidentiality of salaries, yet in other cases it could be
regarded as providing the benefits associated with greater transparency. In
this work we analyse the Bitcoin blockchain record of periodic payments
accruing to an individual address in exchange for goods or services rendered.
For differing levels of available information we seek to determine the extent
of insights that can be gleaned about the transacting counter-parties and the
privacy implications this entails.
| arxiv topic:cs.CY |
arxiv_dataset-82781703.04296 | Search for giant planets in M67 IV: survey results
astro-ph.EP
We present the results of a seven-year-long radial velocity survey of a
sample of 88 main-sequence and evolved stars to reveal signatures of
Jupiter-mass planets in the solar-age and solar-metallicity open cluster M67.
We aim at studying the frequency of giant planets in this cluster with respect
to the field stars. In addition, our sample is also ideal to perform a
long-term study to compare the chemical composition of stars with and without
giant planets in detail. We analyzed precise radial velocity (RV) measurements
obtained with five different instruments. We conducted Monte Carlo simulations
to estimate the occurrence rate of giant planets in our radial velocity survey.
All the planets previously announced in this RV campaign with their properties
are summarized here: 3 hot Jupiters around the main-sequence stars YBP1194,
YBP1514, and YBP401, and 1 giant planet around the evolved star S364. Two
additional planet candidates around the stars YBP778 and S978 are also analyzed
in the present work. We discuss stars that exhibit large RV variability or
trends individually. For 2 additional stars, long-term trends are compatible
with new binary candidates or substellar objects, which increases the total
number of binary candidates detected in our campaign to 14. Based on the
Doppler-detected planets discovered in this survey, we find an occurrence of
giant planets of ~18.0%(+12.0/-8.0%) in the selected period-mass range. This
frequency is slightly higher but consistent within the errors with the estimate
for the field stars, which leads to the general conclusion that open cluster
and field statistics agree. However, we find that the rate of hot Jupiters in
the cluster (~5.7%(+5.5/-3.0%)) is substantially higher than in the field.
| arxiv topic:astro-ph.EP |
arxiv_dataset-82791703.04396 | SMD-based numerical stochastic perturbation theory
hep-lat
The viability of a variant of numerical stochastic perturbation theory, where
the Langevin equation is replaced by the SMD algorithm, is examined. In
particular, the convergence of the process to a unique stationary state is
rigorously established and the use of higher-order symplectic integration
schemes is shown to be highly profitable in this context. For illustration, the
gradient-flow coupling in finite volume with Schr\"odinger functional boundary
conditions is computed to two-loop (i.e. NNL) order in the SU(3) gauge theory.
The scaling behaviour of the algorithm turns out to be rather favourable in
this case, which allows the computations to be driven close to the continuum
limit.
| arxiv topic:hep-lat |
arxiv_dataset-82801703.04496 | Comparison of echo state network output layer classification methods on
noisy data
cs.NE
Echo state networks are a recently developed type of recurrent neural network
where the internal layer is fixed with random weights, and only the output
layer is trained on specific data. Echo state networks are increasingly being
used to process spatiotemporal data in real-world settings, including speech
recognition, event detection, and robot control. A strength of echo state
networks is the simple method used to train the output layer - typically a
collection of linear readout weights found using a least squares approach.
Although straightforward to train and having a low computational cost to use,
this method may not yield acceptable accuracy performance on noisy data.
This study compares the performance of three echo state network output layer
methods to perform classification on noisy data: using trained linear weights,
using sparse trained linear weights, and using trained low-rank approximations
of reservoir states. The methods are investigated experimentally on both
synthetic and natural datasets. The experiments suggest that using regularized
least squares to train linear output weights is superior on data with low
noise, but using the low-rank approximations may significantly improve accuracy
on datasets contaminated with higher noise levels.
| arxiv topic:cs.NE |
arxiv_dataset-82811703.04596 | Perturbative solution for the spectral gap of the weakly asymmetric
exclusion process
math-ph cond-mat.stat-mech math.MP nlin.SI
We consider the weakly asymmetric exclusion process with $N=L/2$ particles on
a periodic lattice of $L$ sites, and hopping rates $1$ and $q=1-\mu/\sqrt{L}$
respectively in the forward and in the backward direction. Using Bethe ansatz,
we obtain a systematic perturbative expansion of the spectral gap near $\mu=0$
by solving order by order a simple functional equation. A key point is that
when $\mu\to0$, Bethe roots at a distance $1/\sqrt{L}$ from the edge of the
Fermi sea should not be considered as a continuum, but converge instead at
large $L$ to the complex zeroes of $1+\mathrm{erf}(x)$ after a rescaling by
$\sqrt{L}$.
| arxiv topic:math-ph cond-mat.stat-mech math.MP nlin.SI |
arxiv_dataset-82821703.04696 | On Quitting: Performance and Practice in Online Game Play
cs.CY
We study the relationship between performance and practice by analyzing the
activity of many players of a casual online game. We find significant
heterogeneity in the improvement of player performance, given by score, and
address this by dividing players into similar skill levels and segmenting each
player's activity into sessions, i.e., sequence of game rounds without an
extended break. After disaggregating data, we find that performance improves
with practice across all skill levels. More interestingly, players are more
likely to end their session after an especially large improvement, leading to a
peak score in their very last game of a session. In addition, success is
strongly correlated with a lower quitting rate when the score drops, and only
weakly correlated with skill, in line with psychological findings about the
value of persistence and "grit": successful players are those who persist in
their practice despite lower scores. Finally, we train an epsilon-machine, a
type of hidden Markov model, and find a plausible mechanism of game play that
can predict player performance and quitting the game. Our work raises the
possibility of real-time assessment and behavior prediction that can be used to
optimize human performance.
| arxiv topic:cs.CY |
arxiv_dataset-82831703.04796 | Collocation Methods for Exploring Perturbations in Linear Stability
Analysis
math.NA
Eigenvalue analysis is a well-established tool for stability analysis of
dynamical systems. However, there are situations where eigenvalues miss some
important features of physical models. For example, in models of incompressible
fluid dynamics, there are examples where linear stability analysis predicts
stability but transient simulations exhibit significant growth of infinitesimal
perturbations. This behavior can be predicted by pseudo-spectral analysis. In
this study, we show that an approach similar to pseudo-spectral analysis can be
performed inexpensively using stochastic collocation methods and the results
can be used to provide quantitative information about instability. In addition,
we demonstrate that the results of the perturbation analysis provide insight
into the behavior of unsteady flow simulations.
| arxiv topic:math.NA |
arxiv_dataset-82841703.04896 | Slit maps in the study of equal-strength cavities in $n$-connected
elastic planar domains
math.CV
The inverse problem of plane elasticity on $n$ equal-strength cavities in a
plane subjected to constant loading at infinity and in the cavities boundary is
analyzed. By reducing the governing boundary value problem to the
Riemann-Hilbert problem on a symmetric Riemann surface of genus $n-1$ a family
of conformal mappings from a parametric slit domain onto the $n$-connected
elastic domain is constructed. The conformal mappings are presented in terms of
hyperelliptic integrals and the zeros of the first derivative of the mappings
are analyzed. It is shown that for any $n\ge 1$ there always exists a set of
the loading parameters for which these zeros generate inadmissible poles of the
solution.
| arxiv topic:math.CV |
arxiv_dataset-82851703.04996 | Exceptionally strong phonon scattering by B substitution in cubic SiC
cond-mat.mtrl-sci
We use ab-initio calculations to predict the thermal conductivity of cubic
SiC with different types of defects. An excellent quantitative agreement with
previous experimental measurements is found. The results unveil that
B$_\mathrm{C}$ substitution has a much stronger effect than any of the other
defect types in 3C-SiC, including vacancies. This finding contradicts the
prediction of the classical mass-difference model of impurity scattering,
according to which the effects of B$_\mathrm{C}$ and N$_\mathrm{C}$ would be
similar and much smaller than that of the C vacancy. The strikingly different
behavior of the B$_\mathrm{C}$ defect arises from a unique pattern of resonant
phonon scattering caused by the broken structural symmetry around the B
impurity.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-82861703.05096 | The long-period binary central stars of the planetary nebulae NGC 1514
and LoTr 5
astro-ph.SR
The importance of long-period binaries on the formation and evolution of
planetary nebulae is still rather poorly understood, in part due to the lack of
central star systems known to comprise such long-period binaries.
Here, we report on the latest results from the on-going Mercator-HERMES
survey for variability in the central stars of planetary nebulae.
We present a study of the central stars of NGC 1514, BD+30$^\circ$623, the
spectrum of which shows features associated with a hot nebular progenitor as
well as a possible A-type companion. Cross-correlation of high-resolution
HERMES spectra against synthetic spectra shows the system to be a highly
eccentric ($e\sim0.5$), double-lined binary with a period of $\sim$3300 days.
Previous studies indicated that the cool component might be a Horizontal Branch
star of mass $\sim$0.55 M$_\odot$ but the observed radial velocity amplitudes
rule out such a low mass. Assuming the nebular symmetry axis and binary orbital
plane are perpendicular, the data are more consistent with a post-main-sequence
star ascending towards the Giant Branch.
We also present the continued monitoring of the central star of LoTr 5, HD
112313, which has now completed one full cycle, allowing the orbital period
(P$\sim$2700 days) and eccentricity ($e\sim0.3$) to be derived.
To date, the orbital periods of BD+30$^\circ$623 and HD 112313 are the
longest to have been measured spectroscopically in the central stars of
planetary nebulae. Furthermore, these systems, along with BD+33$^\circ$2642,
comprise the only spectroscopic wide-binary central stars currently known.
| arxiv topic:astro-ph.SR |
arxiv_dataset-82871703.05196 | A Comprehensive Library of X-ray Pulsars in the Small Magellanic Cloud:
Time Evolution of their Luminosities and Spin Periods
astro-ph.HE
We have collected and analyzed the complete archive of {\itshape XMM-Newton\}
(116), {\itshape Chandra\} (151), and {\itshape RXTE\} (952) observations of
the Small Magellanic Cloud (SMC), spanning 1997-2014. The resulting
observational library provides a comprehensive view of the physical, temporal
and statistical properties of the SMC pulsar population across the luminosity
range of $L_X= 10^{31.2}$--$10^{38}$~erg~s$^{-1}$. From a sample of 67 pulsars
we report $\sim$1654 individual pulsar detections, yielding $\sim$1260 pulse
period measurements. Our pipeline generates a suite of products for each pulsar
detection: spin period, flux, event list, high time-resolution light-curve,
pulse-profile, periodogram, and spectrum. Combining all three satellites, we
generated complete histories of the spin periods, pulse amplitudes, pulsed
fractions and X-ray luminosities. Some pulsars show variations in pulse period
due to the combination of orbital motion and accretion torques. Long-term
spin-up/down trends are seen in 12/11 pulsars respectively, pointing to
sustained transfer of mass and angular momentum to the neutron star on decadal
timescales. Of the sample 30 pulsars have relatively very small spin period
derivative and may be close to equilibrium spin. The distributions of
pulse-detection and flux as functions of spin-period provide interesting
findings: mapping boundaries of accretion-driven X-ray luminosity, and showing
that fast pulsars ($P<$10 s) are rarely detected, which yet are more prone to
giant outbursts. Accompanying this paper is an initial public release of the
library so that it can be used by other researchers. We intend the library to
be useful in driving improved models of neutron star magnetospheres and
accretion physics.
| arxiv topic:astro-ph.HE |
arxiv_dataset-82881703.05296 | On the perturbation algebra
math.QA math.RA math.RT
We introduce a certain differential graded bialgebra, neither commutative nor
cocommutative, that governs perturbations of a differential on complexes
supplied with an abstract Hodge decomposition. This leads to a conceptual
treatment of the Homological Perturbation Lemma and its multiplicative version.
As an application we give an explicit form of the decomposition theorem for
$A_\infty$ algebras and $A_\infty$ modules and, more generally, for twisted
objects in differential graded categories.
| arxiv topic:math.QA math.RA math.RT |
arxiv_dataset-82891703.05396 | Charge versus energy transfer in atomically-thin graphene-transition
metal dichalcogenide van der Waals heterostructures
cond-mat.mes-hall cond-mat.mtrl-sci physics.optics
Van der Waals heterostuctures, made from stacks of two-dimensional materials,
exhibit unique light-matter interactions and are promising for novel
optoelectronic devices. The performance of such devices is governed by
near-field coupling through, e.g., interlayer charge and/or energy transfer.
New concepts and experimental methodologies are needed to properly describe
two-dimensional heterointerfaces. Here, we report on interlayer charge and
energy transfer in atomically thin metal (graphene)/semiconductor (transition
metal dichalcogenide (TMD, here MoSe$_2$)) heterostructures using a combination
of photoluminescence and Raman scattering spectroscopies. The photoluminescence
intensity in graphene/MoSe$_2$ is quenched by more than two orders of magnitude
and rises linearly with the photon flux, demonstrating a drastically shortened
($\sim 1~\tr{ps}$) room temperature MoSe$_2$ exciton lifetime. Key
complementary insights are provided from analysis of the graphene and MoSe$_2$
Raman modes, which reveals net photoinduced electron transfer from MoSe$_2$ to
graphene and hole accumulation in MoSe$_2$. Remarkably, the steady state Fermi
energy of graphene saturates at $290\pm 15~\tr{meV}$ above the Dirac point.
This behavior is observed both in ambient air and in vacuum and is discussed in
terms of band offsets and environmental effects. In this saturation regime,
balanced photoinduced flows of electrons and holes may transfer to graphene, a
mechanism that effectively leads to energy transfer. Using a broad range of
photon fluxes and diverse environmental conditions, we find that the presence
of net photoinduced charge transfer has no measurable impact on the near-unity
photoluminescence quenching efficiency in graphene/MoSe$_2$. This absence of
correlation strongly suggests that energy transfer to graphene is the dominant
interlayer coupling mechanism between atomically-thin TMDs and graphene.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci physics.optics |
arxiv_dataset-82901703.05496 | Data Delivery by Mobile Agents with Energy Constraints over a fixed path
cs.DS
We consider $k$ mobile agents of limited energy that are initially located at
vertices of an edge-weighted graph $G$ and have to collectively deliver data
from a source vertex $s$ to a target vertex $t$. The data are to be collected
by an agent reaching $s$, who can carry and then hand them over another agent
etc., until some agent with the data reaches $t$. The data can be carried only
over a fixed $s-t$ path of $G$; each agent has an initial energy budget and
each time it passes an edge, it consumes the edge's weights in energy units and
stalls if its energy is not anymore sufficient to move. The main result of this
paper is a 3-approximation polynomial time algorithm for the data delivery
problem over a fixed $s-t$ path in the graph, for identical initial energy
budgets and at most one allowed data hand-over per agent.
| arxiv topic:cs.DS |
arxiv_dataset-82911703.05596 | Cosmetic contact surgeries along transverse knots and the knot
complement problem
math.GT math.SG
We study cosmetic contact surgeries along transverse knots in the standard
contact 3-sphere, i.e. contact surgeries that yield again the standard contact
3-sphere. The main result is that we can exclude non-trivial cosmetic contact
surgeries along all transverse knots not isotopic to the transverse unknot with
self-linking number -1. As a corollary it follows that every transverse knot in
the standard contact 3-sphere is determined by the contactomorphism type of its
exteriors. Moreover, we give counterexamples to this for transverse links in
the standard contact 3-sphere.
| arxiv topic:math.GT math.SG |
arxiv_dataset-82921703.05696 | Attitude and Gyro Bias Estimation Using GPS and IMU Measurements
math.OC
We propose an attitude and gyro-bias estimation scheme for accelerated rigid
body systems using an inertial measurement unit (IMU) and a global positioning
system (GPS). The proposed scheme allows to obtain attitude estimates directly
on the Special Orthogonal group $SO(3)$ while estimating the gyro bias and the
unknown apparent acceleration of the vehicle. We prove semi-global exponential
stability of the estimation errors. Furthermore, a new switching technique for
the attitude state is introduced which results in a velocity-aided hybrid
attitude observer with proven global exponential stability.
| arxiv topic:math.OC |
arxiv_dataset-82931703.05796 | Stellar binaries in galactic nuclei: tidally stimulated mergers followed
by tidal disruptions
astro-ph.HE astro-ph.GA
We investigate interactions of stellar binaries in galactic nuclear clusters
with a massive black hole (MBH). We consider binaries on highly eccentric
orbits around the MBH that change due to random gravitational interactions with
other stars in the nuclear stellar cluster. The pericenters of the orbits
perform a random walk, and we consider cases where this random walk slowly
brings the binary to the Hills tidal separation radius (the so-called empty
loss-cone regime). However, we find that in a majority of cases the expected
separation does not occur and instead the members of the binary merge together.
This happens because the binary's eccentricity is excited by tidal interactions
with the MBH, and the relative excursions of the internal eccentricity of the
binary far exceed those in its internal semimajor axis. This frequently reduces
the pericenter separation to values below typical stellar diameters, which
induces a significant fraction of such binaries to merge ($\gtrsim 75\%$ in our
set of numerical experiments). Stellar tides do not appreciably change the
total rate of mergers but circularise binaries, leading to a significant
fraction of low-eccentricity, low-impact-velocity mergers. Some of the stellar
merger products will then be tidally disrupted by the MBH within $\sim 10^6$
years. If the merger strongly enhances the magnetic field of the merger
product, this process could explain observations of prompt relativistic jet
formation in some tidal disruption events.
| arxiv topic:astro-ph.HE astro-ph.GA |
arxiv_dataset-82941703.05896 | Structural and magnetic properties of spin-$1/2$ dimer compound
Cu$_2$(IPA)$_2$(DMF)(H$_2$O) with a large spin gap
cond-mat.mtrl-sci cond-mat.str-el
We present the synthesis and a detailed investigation of structural and
magnetic properties of metal-organic compound Cu$_2$(IPA)$_2$(DMF)(H$_2$O) by
means of x-ray diffraction, magnetization, and heat capacity measurements.
Single crystals of the title compound were synthesized by judicious selection
of organic ligand and employing a selective hydrothermal reaction route. It
crystallizes in an orthorhombic structure with space group $Cmca$. The
structural analysis revealed that two Cu$^{2+}$ ions are held together by the
organic component (-O-C-O-) in a square paddle-wheel to form spin dimers which
are aligned perpendicular to each other and are further coupled through organic
ligands (isophthalic acid) forming two-dimensional layers. Temperature
dependent magnetic susceptibility $\chi(T)$ could be described well using
spin-$1/2$ dimer model. The spin susceptibility $\chi_{\rm spin} (T)$ shows an
exponential decrease in the low temperature region, below the broad maximum,
confirming the singlet ground state with a large spin gap of $\Delta/k_{\rm B}
\simeq 409$~K. The heat capacity $C_{\rm p}$ measured as a function of
temperature also confirms the absence of magnetic long-range-order down to 2~K.
| arxiv topic:cond-mat.mtrl-sci cond-mat.str-el |
arxiv_dataset-82951703.05996 | Energy Efficient Precoding C-RAN Downlink with Compression at Fronthaul
cs.IT math.IT
This paper considers a downlink transmission of cloud radio access network
(C-RAN) in which precoded baseband signals at a common baseband unit are
compressed before being forwarded to radio units (RUs) through limited
fronthaul capacity links. We investigate the joint design of precoding,
multivariate compression and RU-user selection which maximizes the energy
efficiency of downlink C-RAN networks. The considered problem is inherently a
rank-constrained mixed Boolean nonconvex program for which a globally optimal
solution is difficult and computationally expensive to find. In order to derive
practically appealing solutions, we invoke some useful relaxation and
transformation techniques to arrive at a more tractable (but still nonconvex)
continuous program. To solve the relaxation problem, we propose an iterative
procedure based on DC algorithms which is provably convergent. Numerical
results demonstrate the superior of the proposed solution in terms of
achievable energy efficiency compared to existing schemes.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-82961703.06096 | A minimally invasive neurostimulation method for controlling epilepsy
seizures
nlin.AO
Many coordination phenomena in Nature are grounded on a synchronisation
regime. In the case of brain dynamics, such self-organised process allows the
neurons of particular brain regions to behave as a whole and thus directly
controlling the neural activity, the muscles and finally the whole human body.
However, not always such synchronised collective behaviour is the desired one,
this is the case of neurodegenerative diseases such as Parkinson's or epilepsy
where abnormal synchronisation induces undesired effects such as tremors and
epileptic seizures. In this paper we propose an innovative, minimally invasive,
control method able to effectively desynchronise the interested brain zones and
thus to reduce the onset of undesired behaviour.
| arxiv topic:nlin.AO |
arxiv_dataset-82971703.06196 | Understanding the High Temperature Thermoelectric Properties of
La$_{0.82}$Ba$_{0.18}$CoO$_{3}$ Compound using DFT+U Method
cond-mat.str-el
Normally, understanding the temperature dependent transport properties of
strongly correlated electron systems remains challenging task due to complex
electronic structure and its variations (around E$_{F}$) with temperature.
Here, we report the applicability of DFT+U in explaining thermopower ($\alpha$)
and electrical conductivity ($\sigma$) in high temperature region. We have
measured temperature dependent $\alpha$ and $\sigma$ in the 300-600 K range.
The non-monotonic temperature dependent behavior of $\alpha$ and metallic
behavior of $\sigma$ were observed. The value of $\alpha$ at 300 K was
$\sim$15.80 $\mu$V/K and it decreases upto $\sim$477 K ($\sim$11.6 $\mu$V/K)
and it further increases with temperature to the $\sim$14.8 $\mu$V/K at 600 K,
whereas the values of $\sigma$ were found to be $\sim$1.42 $\times$10$^{5}$
$\Omega$$^{-1}$ m$^{-1}$ and $\sim$0.20 $\times$10$^{5}$ $\Omega$$^{-1}$
m$^{-1}$ at 300 and 600 K, respectively. Combining the WIEN2k and BoltzTraP
code, the electronic structure and temperature dependent transport coefficients
were calculated. The ferromagnetic ground state electronic structure with
half-metallic character obtained from the DFT+U calculations, U = 3.1 eV,
provides better explanation of high-temperature transport behavior. Two current
model was used for calculation of $\alpha$ and $\sigma$ where the temperature
dependent values of relaxation time ($\tau$), almost linear for up-spin,
$\tau$$_{up}$, and non-linear for dn-spin, $\tau$$_{dn}$, were used and
estimated values were found to be in good agreement with experimentally
reported values.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-82981703.06296 | Geometric RTT realization of $U_v(gl_n)^+$
math.QA math.RT
In this paper, we give a BLM realization of the positive part of the quantum
group of $U_v(gl_n)$ with respect to RTT relations.
| arxiv topic:math.QA math.RT |
arxiv_dataset-82991703.06396 | Radial Variations of the Volume- and Surface-Star Formation Laws in the
Galaxy
astro-ph.GA
Variation of the volume- and surface-Schmidt laws (star-formation or SF law)
with the galacto-centric distance R was investigated using 3D distributions of
HII regions, HI, and molecular (H_2) gases in the Milky Way. Both the power-law
index and SF coefficient were found to be variable with R. The index is flatter
in the inner disc than in the outer Galaxy, and the coefficient is larger in
the inner disc, decreasing steeply outward. There is also a mutual
anti-correlation between the index and SF coefficient, and the SF law can be
expressed by a single-parameter function of the SF coefficient. The variable SF
law is discussed in relation to the self-regulation star formation.
| arxiv topic:astro-ph.GA |
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