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arxiv_dataset-101001808.00854 | A finitely presented ${E}_{\infty}$-prop I: algebraic context
math.AT
We introduce a finitely presented prop $\mathcal{S} = \{\mathcal{S}(n,m)\}$
in the category of differential graded modules whose associated operad
$U(\mathcal{S})=\{\mathcal{S}(1,m)\}$ is a model for the $E_\infty$-operad.
This finite presentation allows us to describe a natural $E_\infty$-coalgebra
structure on the chains of any simplicial set in terms of only three maps: the
Alexander-Whitney diagonal, the augmentation map, and an algebraic version of
the join of simplices. The first appendix connects our construction to the
Surjection operad of McClure-Smith and Berger-Fresse. The second establishes a
duality between the join and AW maps for augmented and non-augmented simplicial
sets. A follow up paper constructs a prop corresponding to $\mathcal{S}$ in the
category of $CW$-complexes.
| arxiv topic:math.AT |
arxiv_dataset-101011808.00954 | Semi-inclusive back-to-back production of a hadron pair and a single
hadron in $e^+e^-$ annihilation
hep-ph hep-ex nucl-th
Inclusive hadron production in $e^+e^-$ annihilation has long been used to
study both single hadron fragmentation functions (FF) and dihadron
fragmentation functions (DiFF). In particular, the polarized DiFFs can be
accessed in electron-positron annihilation by measuring azimuthal correlations
between two back-to-back pairs of hadrons in the center of mass system, where
the relevant structure functions can be expressed as convolutions of two
(polarized) DiFFs. Here we explore the advantages of measuring the inclusive
back-to-back production of a single hadron on one side against a hadron pair on
the opposite side of the detector in two jet events. The leading twist cross
section for this process contains convolutions of the corresponding single
hadron FFs on one side and the DiFFs for the hadron pair on the other side,
which furnishes several interesting new opportunities. A measurement of the
unpolarized cross section with a number of different types of observed hadrons
will help in untangling the quark flavor dependence of the unpolarized DiFFs,
when the results are analyzed together with the inclusive measurements of
dihadron pairs, such as those recently performed by the $\texttt{BELLE}$
collaboration. Even more interesting, with a polarized hyperon on one side we
can study the quark spin-dependent DiFFs of an unpolarized hadron pair on the
other side. This, in turn, will allow us to test the universality of the
spin-dependent DiFFs entering the cross sections of electron-positron
annihilation and semi-inclusive deep inelastic scattering processes.
| arxiv topic:hep-ph hep-ex nucl-th |
arxiv_dataset-101021808.01054 | Partitioned Density Matrices and Entanglement Correlators
quant-ph cond-mat.other
The density matrix of a non-relativistic quantum system, divided into $N$
sub-systems, is rewritten in terms of the set of all partitioned density
matrices for the system. For the case where the different sub-systems are
distinguishable, we derive a hierarchy of equations of motion linking the
dynamics of all the partitioned density matrices, analogous to the
"Schwinger-Dyson" hierarchy in quantum field theory. The special case of a set
of $N$ coupled spin-$1/2$ "qubits" is worked out in detail. The equations are
then rewritten in terms of a set of "entanglement correlators", which comprise
all the possible correlation functions for the system - this case is worked out
for coupled spin systems. The equations of motion for these correlators can be
written in terms of a first-order differential equation for an entanglement
correlator supervector.
| arxiv topic:quant-ph cond-mat.other |
arxiv_dataset-101031808.01154 | Unitary equivalence between the Green's function and Schr\"odinger
approaches for quantum graphs
quant-ph math-ph math.MP
In a previous work [Andrade \textit{et al.}, Phys. Rep. \textbf{647}, 1
(2016)], it was shown that the exact Green's function (GF) for an arbitrarily
large (although finite) quantum graph is given as a sum over scattering paths,
where local quantum effects are taken into account through the reflection and
transmission scattering amplitudes. To deal with general graphs, two
simplifying procedures were developed: regrouping of paths into families of
paths and the separation of a large graph into subgraphs. However, for less
symmetrical graphs with complicated topologies as, for instance, random graphs,
it can become cumbersome to choose the subgraphs and the families of paths. In
this work, an even more general procedure to construct the energy domain GF for
a quantum graph based on its adjacency matrix is presented. This new
construction allows us to obtain the secular determinant, unraveling a unitary
equivalence between the scattering Schr\"odinger approach and the Green's
function approach. It also enables us to write a trace formula based on the
Green's function approach. The present construction has the advantage that it
can be applied directly for any graph, going from regular to random topologies.
| arxiv topic:quant-ph math-ph math.MP |
arxiv_dataset-101041808.01254 | The geometry of generalized Cheeger-Gromoll metrics on the total space
of transitive Euclidean Lie algebroids
math.DG
Natural metrics (Sasaki metric, Cheeger-Gromoll metric, Kaluza-Klein metrics
etc.. ) on the tangent bundle of a Riemannian manifold is a central topic in
Riemannian geometry. Generalized Cheeger-Gromoll metrics is a family of natural
metrics $h_{p,q}$ depending on two parameters with $p\in\mathbb{R}$ and
$q\geq0$. This family has been introduced recently and possesses interesting
geometric properties. If $p=q=0$ we recover the Sasaki metric and when $p=q=1$
we recover the classical Cheeger-Gromoll metric. A transitive Euclidean Lie
algebroid is a transitive Lie algebroid with an Euclidean product on its total
space.
In this paper, we show that natural metrics can be built in a natural way on
the total space of transitive Euclidean Lie algebroids. Then we study the
properties of generalized Cheeger-Gromoll metrics on this new context. We show
a rigidity result of this metrics which generalizes so far all rigidity results
known in the case of the tangent bundle. We show also that considering natural
metrics on the total space of transitive Euclidean Lie algebroids opens new
interesting horizons.
For instance, Atiyah Lie algebroids constitute an important class of
transitive Lie algebroids and we will show that natural metrics on the total
space of Atiyah Euclidean Lie algebroids have interesting properties. In
particular, if $M$ is a Riemannian manifold of dimension $n$, then the Atiyah
Lie algebroid associated to the $\mathrm{O}(n)$-principal bundle of orthonormal
frames over $M$ possesses a family depending on a parameter $k>0$ of transitive
Euclidean Lie algebroids structures say $AO(M,k)$. When $M$ is a space form of
constant curvature $c$, we show that there exists two constants $C_n<0$ and
$K(n,c)>0$ such that $(AO(M,k),h_{1,1})$ is a Riemannian manifold with positive
scalar curvature if and only if $c>C_n$ and $0<k\leq K(n,c)$.
| arxiv topic:math.DG |
arxiv_dataset-101051808.01354 | Resonance Raman spectroscopy of silicene and germanene
cond-mat.mtrl-sci
We model Raman processes in silicene and germanene involving scattering of
quasiparticles by, either, two phonons, or, one phonon and one point defect. We
compute the resonance Raman intensities and lifetimes for laser excitations
between 1 and 3$\,$eV using a newly developed third-nearest neighbour
tight-binding model parametrized from first principles density functional
theory. We identify features in the Raman spectra that are unique to the
studied materials or the defects therein. We find that in silicene, a new Raman
resonance arises from the $2.77\,\rm$eV $\pi-\sigma$ plasmon at the M point,
measurably higher than the Raman resonance originating from the $2.12\,\rm$eV
$\pi$ plasmon energy. We show that in germanene, the lifetimes of charge
carriers, and thereby the linewidths of the Raman peaks, are influenced by
spin-orbit splittings within the electronic structure. We use our model to
predict scattering cross sections for defect induced Raman scattering involving
adatoms, substitutional impurities, Stone-Wales pairs, and vacancies, and argue
that the presence of each of these defects in silicene and germanene can be
qualitatively matched to specific features in the Raman response.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-101061808.01454 | T2Net: Synthetic-to-Realistic Translation for Solving Single-Image Depth
Estimation Tasks
cs.CV
Current methods for single-image depth estimation use training datasets with
real image-depth pairs or stereo pairs, which are not easy to acquire. We
propose a framework, trained on synthetic image-depth pairs and unpaired real
images, that comprises an image translation network for enhancing realism of
input images, followed by a depth prediction network. A key idea is having the
first network act as a wide-spectrum input translator, taking in either
synthetic or real images, and ideally producing minimally modified realistic
images. This is done via a reconstruction loss when the training input is real,
and GAN loss when synthetic, removing the need for heuristic
self-regularization. The second network is trained on a task loss for synthetic
image-depth pairs, with extra GAN loss to unify real and synthetic feature
distributions. Importantly, the framework can be trained end-to-end, leading to
good results, even surpassing early deep-learning methods that use real paired
data.
| arxiv topic:cs.CV |
arxiv_dataset-101071808.01554 | Synchronization and extinction in a high-infectivity spatial SIRS with
long-range links
physics.soc-ph
A numerical study of synchronization and extinction is done for a SIRS model
with fixed infective and refractory periods, in the regime of high infectivity,
on one- and two-dimensional networks for which the connectivity probability
decays as $r^{-\alpha}$ with distance. In both one and two dimensions, a
long-lasting synchronized state is reached when $\alpha < d$ but not when
$\alpha > d$. Three dynamical stages are identified for small $\alpha$,
respectively: a short period of initial synchronization, followed by a long
oscillatory stage of random duration, and finally a third phase of rapid
increase in synchronization that invariably leads to dynamical extinction. For
large $\alpha$, the second stage is not synchronized, but is instead a
long-lasting endemic state of incoherent activity. Dynamical extinction is in
this case still preceded by a short third stage of rapidly intensifying
synchronized oscillations. A simple model of noise-induced escape from a
potential barrier is introduced, that explains the main characteristics of the
observed three-stage dynamical structure before extinction. This model
additionally provides specific predictions regarding the size-scaling of the
different timescales for the observed dynamical stages, which are found to be
consistent with our numerical results.
| arxiv topic:physics.soc-ph |
arxiv_dataset-101081808.01654 | The simplest way to get a cluster's parameters in the Gaia era (Dolidze
41)
astro-ph.GA
The astro-photometric parameters of the open star cluster Dolidze 41, which
located in the constellation of Cygnus, have been investigated using the
Gaia-ESO DR2 large Survey merging with the near Infrared Two Micron All Sky
Survey 2MASS database. The radial density distribution (limited, core and tidal
radii), color-magnitude diagrams, the galactocentric coordinates, distances,
color excess, and age of Dolidze 41 are presented. Thanks to Gaia DR2
astrometry, which help us to define the membership of the cluster stars easily.
The luminosity & mass functions, the entire luminosity & mass, and the repose
time of the cluster have been estimated as well.
| arxiv topic:astro-ph.GA |
arxiv_dataset-101091808.01754 | GAMA/G10-COSMOS/3D-HST: Evolution of the galaxy stellar mass function
over 12.5Gyrs
astro-ph.GA
Using a combined and consistently analysed GAMA, G10-COSMOS, and 3D-HST
dataset we explore the evolution of the galaxy stellar-mass function over
lookback times $t_{\rm L} \in \left[0.2,12.5\right] {\rm h^{-1}_{70} Gyr}$. We
use a series of volume limited samples to fit Schechter functions in bins of
$\sim\!$constant lookback time and explore the evolution of the best-fit
parameters in both single and two-component cases. In all cases, we employ a
fitting procedure that is robust to the effects of Eddington bias and sample
variance. Surprisingly, when fitting a two-component Schechter function, we
find essentially no evidence of temporal evolution in $M_\star$, the two
$\alpha$ slope parameters, or the normalisation of the low-mass component.
Instead, our fits suggest that the various shape parameters have been
exceptionally stable over cosmic time, as has the normalisation of the low-mass
component, and that the evolution of the stellar-mass function is well
described by a simple build up of the high-mass component over time. When
fitting a single component Schechter function, there is an observed evolution
in both $M_\star$ and $\alpha$, however this is interpreted as being an
artefact. Finally, we find that the evolution of the stellar-mass function, and
the observed stellar mass density, can be well described by a simple model of
constant growth in the high-mass source density over the last $11 {\rm
h^{-1}_{70} Gyr}$.
| arxiv topic:astro-ph.GA |
arxiv_dataset-101101808.01854 | Quasi-projective manifolds with negative holomorphic sectional curvature
math.DG math.AG
Let $(M,\omega)$ be a compact K\"ahler manifold with negative holomorphic
sectional curvature. It was proved by Wu-Yau and Tosatti-Yang that $M$ is
necessarily projective and has ample canonical bundle. In this paper, we show
that any irreducible subvariety of $M$ is of general type. Moreover, we can
extend the theorem to the quasi-negative curvature case building on earlier
results of Diverio-Trapani. Finally, we investigate the more general setting of
a quasi-projective manifold $X^{\circ}$ endowed with a K\"ahler metric with
negative holomorphic sectional curvature and we prove that such a manifold
$X^{\circ}$ is necessarily of log general type.
| arxiv topic:math.DG math.AG |
arxiv_dataset-101111808.01954 | Cooperation of dual modes of cell motility promotes epithelial stress
relaxation to accelerate wound healing
physics.bio-ph cond-mat.soft q-bio.CB q-bio.TO
Collective cell migration in cohesive units is vital for tissue
morphogenesis, wound repair, and immune response. While the fundamental driving
forces for collective cell motion stem from contractile and protrusive
activities of individual cells, it remains unknown how their balance is
optimized to maintain tissue cohesiveness and the fluidity for motion. Here we
present a cell-based computational model for collective cell migration during
wound healing that incorporates mechanochemical coupling of cell motion and
adhesion kinetics with stochastic transformation of active motility forces. We
show that a balance of protrusive motility and actomyosin contractility is
optimized for accelerating the rate of wound repair, which is robust to
variations in cell and substrate mechanical properties. This balance underlies
rapid collective cell motion during wound healing, resulting from a tradeoff
between tension mediated collective cell guidance and active stress relaxation
in the tissue.
| arxiv topic:physics.bio-ph cond-mat.soft q-bio.CB q-bio.TO |
arxiv_dataset-101121808.02054 | Temperature dependence of butterfly effect in a classical many-body
system
cond-mat.stat-mech
We study the chaotic dynamics in a classical many-body system of interacting
spins on the kagome lattice. We characterise many-body chaos via the butterfly
effect as captured by an appropriate out-of-time-ordered correlator. Due to the
emergence of a spin liquid phase, the chaotic dynamics extends all the way to
zero temperature. We thus determine the full temperature dependence of two
complementary aspects of the butterfly effect: the Lyapunov exponent, $\mu$,
and the butterfly speed, $v_b$, and study their interrelations with usual
measures of spin dynamics such as the spin-diffusion constant, $D$ and
spin-autocorrelation time, $\tau$. We find that they all exhibit power law
behaviour at low temperature, consistent with scaling of the form $D\sim
v_b^2/\mu$ and $\tau^{-1}\sim T$. The vanishing of $\mu\sim T^{0.48}$ is
parametrically slower than that of the corresponding quantum bound, $\mu\sim
T$, raising interesting questions regarding the semi-classical limit of such
spin systems.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-101131808.02154 | Detector Backgrounds at the Higgs Factory Muon Collider: MARS vs FLUKA
physics.ins-det
Simulations for the 125-GeV Higgs Factory (HF) Muon Collider (MC) have shown
large background particle loads on the collider detector. To verify level,
source and composition of background calculations were performed using FLUKA
and MARS codes for two shielding configurations. After comprehensive tuning of
muon beam parameters, geometry setups and scoring procedures, background
particle distributions at the detector entrance were simulated and compared.
The spatial distributions and energy spectra of background particles obtained
by two codes are rather similar. Average numbers of background particles
simulated using MARS and FLUKA agree within a factor of two.
| arxiv topic:physics.ins-det |
arxiv_dataset-101141808.02254 | Performance-Aware Management of Cloud Resources: A Taxonomy and Future
Directions
cs.DC
Dynamic nature of the cloud environment has made distributed resource
management process a challenge for cloud service providers. The importance of
maintaining the quality of service in accordance with customer expectations as
well as the highly dynamic nature of cloud-hosted applications add new levels
of complexity to the process. Advances to the big data learning approaches have
shifted conventional static capacity planning solutions to complex
performance-aware resource management methods. It is shown that the process of
decision making for resource adjustment is closely related to the behaviour of
the system including the utilization of resources and application components.
Therefore, a continuous monitoring of system attributes and performance metrics
provide the raw data for the analysis of problems affecting the performance of
the application. Data analytic methods such as statistical and machine learning
approaches offer the required concepts, models and tools to dig into the data,
find general rules, patterns and characteristics that define the functionality
of the system. Obtained knowledge form the data analysis process helps to find
out about the changes in the workloads, faulty components or problems that can
cause system performance to degrade. A timely reaction to performance
degradations can avoid violations of the service level agreements by performing
proper corrective actions including auto-scaling or other resource adjustment
solutions. In this paper, we investigate the main requirements and limitations
in cloud resource management including a study of the approaches in workload
and anomaly analysis in the context of the performance management in the cloud.
A taxonomy of the works on this problem is presented which identifies the main
approaches in existing researches from data analysis side to resource
adjustment techniques.
| arxiv topic:cs.DC |
arxiv_dataset-101151808.02354 | Objective and Subjective Solomonoff Probabilities in Quantum Mechanics
quant-ph cs.AI
Algorithmic probability has shown some promise in dealing with the
probability problem in the Everett interpretation, since it provides an
objective, single-case probability measure. Many find the Everettian cosmology
to be overly extravagant, however, and algorithmic probability has also
provided improved models of subjective probability and Bayesian reasoning. I
attempt here to generalize algorithmic Everettianism to more Bayesian and
subjectivist interpretations. I present a general framework for applying
generative probability, of which algorithmic probability can be considered a
special case. I apply this framework to two commonly vexing thought experiments
that have immediate application to quantum probability: the Sleeping Beauty and
Replicator experiments.
| arxiv topic:quant-ph cs.AI |
arxiv_dataset-101161808.02454 | Two decades of Exoplanetary Science with Adaptive Optics
astro-ph.EP
As astronomers, we are living an exciting time for what concerns the search
for other worlds. Recent discoveries have already deeply impacted our vision of
planetary formation and architectures. Future bio-signature discoveries will
probably deeply impact our scientific and philosophical understanding of life
formation and evolution. In that unique perspective, the role of observation is
crucial to extend our understanding of the formation and physics of giant
planets shaping planetary systems. With the development of high contrast
imaging techniques and instruments over more than two decades, vast efforts
have been devoted to detect and characterize lighter, cooler and closer
companions to nearby stars, and ultimately image new planetary systems.
Complementary to other planet-hunting techniques, this approach has opened a
new astrophysical window to study the physical properties and the formation
mechanisms of brown dwarfs and planets. I will briefly review the different
observing techniques and strategies used, the main samples of targeted stars,
the key discoveries and surveys, to finally address the main results obtained
so far about the physics and the mechanisms of formation and evolution of young
giant planets and planetary system architectures.
| arxiv topic:astro-ph.EP |
arxiv_dataset-101171808.02554 | Raman scattering from the bulk inactive out-of-plane B$^{1}_{2\text{g}}$
mode in few-layer MoTe$_{2}$
cond-mat.mtrl-sci
Raman scattering from the out-of-plane vibrational modes
(A$_{1\text{g}}$/A'$_{1}$), which originate from the bulk-inactive out-of-plane
B$^{1}_{2\text{g}}$ mode, are studied in few-layer MoTe$_{2}$.
Temperature-dependent measurements reveal a doublet structure of the
corresponding peaks in the Raman scattering spectra of tetralayer and
pentalayer samples. A strong enhancement of their lower energy components is
recorded at low temperature for 1.91 eV and 1.96 eV laser excitation. We
discuss the attribution of the peaks to the inner modes of the respective
Raman-active vibrations. The temperature evolution of their intensity strongly
suggests a resonant character of the employed excitation, which leads to the
mode enhancement at low temperature. The resonance of the laser light with the
singularity of the electronic density of states at the $M$ point of the
Brillouin zone in MoTe$_{2}$ is proposed to be responsible for the observed
effects.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-101181808.02654 | Randomized Core Reduction for Discrete Ill-Posed Problem
math.NA
In this paper, we apply randomized algorithms to approximate the total least
squares (TLS) solution of the problem $Ax\approx b$ in the large-scale discrete
ill-posed problems. A regularization technique, based on the multiplicative
randomization and the subspace iteration, is proposed to obtain the approximate
core problem.In the error analysis, we provide upper bounds %in terms of the
$(k\!\!+\!\!1)$-th singular value of $A$ for the errors of the solution and the
residual of the randomized core reduction. Illustrative numerical examples and
comparisons are presented.
| arxiv topic:math.NA |
arxiv_dataset-101191808.02754 | Ground states of Nicolai and $\mathbb{Z}_2$ Nicolai models
math-ph math.MP
We derive explicit recursions for the ground state generating functions of
the one-dimensional Nicolai model and $\mathbb{Z}_2$ Nicolai model. Both are
examples of lattice models with $\mathcal{N}=2$ supersymmetry. The relations
that we obtain for the $\mathbb{Z}_2$ model were numerically predicted by
Sannomiya, Katsura, and Nakayama.
| arxiv topic:math-ph math.MP |
arxiv_dataset-101201808.02854 | Convenient Partial Poisson Manifolds
math.DG
We introduce the concept of partial Poisson structure on a manifold $M$
modelled on a convenient space. This is done by specifying a (weak) subbundle
$T^{\prime}M$ of $T^{\ast}M$ and an antisymmetric morphism
$P:T^{\prime}M\rightarrow TM$ such that the bracket $\{f,g\}_{P}=-<df,P(dg)>$
defines a Poisson bracket on the algebra $\mathcal{A}$ of smooth functions $f$
on $M$ whose differential $df$ induces a section of $T^{\prime}M$. In
particular, to each such function $f\in\mathcal{A}$ is associated a hamiltonian
vector field $P(df)$. This notion takes naturally place in the framework of
infinite dimensional weak symplectic manifolds and Lie algebroids. After having
defined this concept, we will illustrate it by a lot of natural examples. We
will also consider the particular situations of direct (resp. projective)
limits of such Banach structures. Finally, we will also give some results on
the existence of (weak) symplectic foliations naturally associated to some
particular partial Poisson structures.
| arxiv topic:math.DG |
arxiv_dataset-101211808.02954 | Nonlinear optics of graphene and other 2D materials in layered
structures
physics.optics cond-mat.mes-hall
We present a theoretical framework for nonlinear optics of graphene and other
2D materials in layered structures. We derive a key equation to find the
effective electric field and the sheet current density in the 2D material for
given incident light beams. Our approach takes into account the effect of the
surrounding environment and characterizes its contribution as a structure
factor. We apply our approach to two experimental setups, and discuss the
structure factors for several nonlinear optical processes including second
harmonic generation, third harmonic generation, and parametric frequency
conversion. Our systematic study gives a strict extraction method for the
nonlinear coefficients, and provides new insights in how layered structures
influence the nonlinear signal observed from 2D materials.
| arxiv topic:physics.optics cond-mat.mes-hall |
arxiv_dataset-101221808.03054 | De Donder Construction for Higher Jets
math-ph math.MP
In this paper, we generalize De Donder approach to construct boundary forms
that depend on the adapted coordinate system used. In continuum mechanics, use
of boundary forms leads to splitting of the total force acting on the body into
body force and surface traction. Moreover, this splitting is independent of the
choice of the boundary form used. In calculus of variations, use of boundary
forms leads to equations in exterior differential forms that are equivalent to
the Euler-Lagrange equations. Infinitesimal symmetries of the theory lead to
conservation laws valid for any choice of the boundary form used. In an
example, we show that the boundary conditions lead to independence of constants
of motion of the choice of the boundary form.
| arxiv topic:math-ph math.MP |
arxiv_dataset-101231808.03154 | Derivation of vector-valued complex interpolation scales
math.FA
We study complex interpolation scales obtained by vector valued amalgamation
and the derivations they generate. We study their trivial and singular
character and obtain examples showing that the hypotheses in the main theorems
of [J.M.F. Castillo, V. Ferenczi and M. Gonz\'alez, \emph{Singular exact
sequences generated by complex interpolation}, Trans. Amer. Math. Soc. 369
(2017) 4671--4708] are not necessary.
| arxiv topic:math.FA |
arxiv_dataset-101241808.03254 | On asymptotically uniformly smoothness and nonlinear geometry of Banach
spaces
math.FA
These notes concern the nonlinear geometry of Banach spaces, asymptotic
uniform smoothness and several Banach-Saks-like properties. We study the
existence of certain concentration inequalities in asymptotically uniformly
smooth Banach spaces as well as weakly sequentially continuous coarse
(Lipschitz) embeddings into those spaces. Some results concerning the
descriptive set theoretical complexity of those properties are also obtained.
We finish the paper with a list of open problem.
| arxiv topic:math.FA |
arxiv_dataset-101251808.03354 | Sequence-Based OOK for Orthogonal Multiplexing of Wake-up Radio Signals
and OFDM Waveforms
eess.SP cs.IT math.IT
In this study, we propose an approach to constructing on-off keying (OOK)
symbols for wake-up radios (WURs) by using sequences in the frequency domain.
The proposed method enables orthogonal multiplexing of wake-up signals (WUSs)
and orthogonal frequency division multiplexing (OFDM) waveforms. We optimize
the sequences with a tractable algorithm by considering the reliability of WUSs
in fading channels. The proposed algorithm relies on an alternating
minimization technique, i.e. cyclic algorithm-new (CAN), which was originally
proposed for obtaining a unimodular sequence with good aperiodic correlation
properties. In this study, we extend CAN to generate OOK waveforms with
Manchester coding. We demonstrate the performance of four optimized sequences
and compare with state-of-the-art approaches. We show that the proposed scheme
improves the wake-up radio receiver (WURx) performance by controlling the
energy distribution in frequency domain while removing the interference-floor
at the OFDM receiver.
| arxiv topic:eess.SP cs.IT math.IT |
arxiv_dataset-101261808.03454 | AIQ: Measuring Intelligence of Business AI Software
cs.AI
Focusing on Business AI, this article introduces the AIQ quadrant that
enables us to measure AI for business applications in a relative comparative
manner, i.e. to judge that software A has more or less intelligence than
software B. Recognizing that the goal of Business software is to maximize value
in terms of business results, the dimensions of the quadrant are the key
factors that determine the business value of AI software: Level of Output
Quality (Smartness) and Level of Automation. The use of the quadrant is
illustrated by several software solutions to support the real life business
challenge of field service scheduling. The role of machine learning and
conversational digital assistants in increasing the business value are also
discussed and illustrated with a recent integration of existing intelligent
digital assistants for factory floor decision making with the new version of
Google Glass. Such hands free AI solutions elevate the AIQ level to its
ultimate position.
| arxiv topic:cs.AI |
arxiv_dataset-101271808.03554 | Integrated gallium phosphide nonlinear photonics
physics.app-ph physics.optics
Gallium phosphide (GaP) is an indirect bandgap semiconductor used widely in
solid-state lighting. Despite numerous intriguing optical
properties---including large $\chi^{(2)}$ and $\chi^{(3)}$ coefficients, a high
refractive index ($>3$), and transparency from visible to long-infrared
wavelengths ($0.55-11\,\mu$m)---its application as an integrated photonics
material has been little studied. Here we introduce GaP-on-insulator as a
platform for nonlinear photonics, exploiting a direct wafer bonding approach to
realize integrated waveguides with 1.2 dB/cm loss in the telecommunications
C-band (on par with Si-on-insulator). High quality $(Q> 10^5)$, grating-coupled
ring resonators are fabricated and studied. Employing a modulation transfer
approach, we obtain a direct experimental estimate of the nonlinear index of
GaP at telecommunication wavelengths: $n_2=1.2(5)\times
10^{-17}\,\text{m}^2/\text{W}$. We also observe Kerr frequency comb generation
in resonators with engineered dispersion. Parametric threshold powers as low as
3 mW are realized, followed by broadband ($>100$ nm) frequency combs with
sub-THz spacing, frequency-doubled combs and, in a separate device, efficient
Raman lasing. These results signal the emergence of GaP-on-insulator as a novel
platform for integrated nonlinear photonics.
| arxiv topic:physics.app-ph physics.optics |
arxiv_dataset-101281808.03654 | How low does it go? Too few Galactic satellites with standard
reionization quenching
astro-ph.GA
A standard prediction of galaxy formation theory is that the ionizing
background suppresses galaxy formation in haloes with peak circular velocities
smaller than Vpeak ~ 20 km/s, rendering the majority of haloes below this scale
completely dark. We use a suite of cosmological zoom simulations of Milky
Way-like haloes that include central Milky Way disk galaxy potentials to
investigate the relationship between subhaloes and ultrafaint galaxies. We find
that there are far too few subhaloes within 50 kpc of the Milky Way that had
Vpeak > 20 km/s to account for the number of ultrafaint galaxies already known
within that volume today. In order to match the observed count, we must
populate subhaloes down to Vpeak ~ 6 km/s with ultrafaint dwarfs. The required
haloes have peak virial temperatures as low as 1,500 K, well below the atomic
hydrogen cooling limit of 10^4 K. Allowing for the possibility that the Large
Magellanic Cloud contributes several of the satellites within 50 kpc could
potentially raise this threshold to 10 km/s (4,000 K), still below the atomic
cooling limit and far below the nominal reionization threshold.
| arxiv topic:astro-ph.GA |
arxiv_dataset-101291808.03754 | Quasi-homogeneity of superpotentials
math.AG math.QA math.RA
In this article, we study the quasi-homogeneity of a superpotential in a
complete free algebra over an algebraic closed field of characteristic zero. We
prove that a superpotential with finite dimensional Jacobi algebra is right
equivalent to a weighted homogeneous superpotential if and only if the
corresponding class in the 0-th Hochschlid homology group of the Jacobi algebra
is zero. This result can be viewed as a noncommutative version of the famous
theorem of Kyoji Saito on isolated hypersurface singularities.
| arxiv topic:math.AG math.QA math.RA |
arxiv_dataset-101301808.03854 | Adversarial vs cooperative quantum estimation
quant-ph
We address the estimation of a one-parameter family of isometries taking one
input into two output systems. This primarily allows us to consider imperfect
estimation by accessing only one output system, i.e. through a quantum channel.
Then, on the one hand, we consider separate and adversarial control of the two
output systems to introduce the concept of \emph{privacy of estimation}. On the
other hand we conceive the possibility of separate but cooperative control of
the two output systems. Optimal estimation strategies are found according to
the minimum mean square error. This also implies the generalization of
Personik's theorem to the case of local measurements. Finally, applications to
two-qubit unitaries (with one qubit in a fixed input state) are discussed.
| arxiv topic:quant-ph |
arxiv_dataset-101311808.03954 | Unsteady fluid--structure interactions in a soft-walled microchannel: A
one-dimensional lubrication model for finite Reynolds number
physics.flu-dyn physics.comp-ph
We develop a one-dimensional model for the unsteady fluid--structure
interaction (FSI) between a soft-walled microchannel and viscous fluid flow
within it. A beam equation, which accounts for both transverse bending rigidity
and nonlinear axial tension, is coupled to a one-dimensional fluid model
obtained from depth-averaging the two-dimensional incompressible Navier--Stokes
equations across the channel height. Specifically, the Navier--Stokes equations
are scaled in the viscous lubrication limit relevant to microfluidics. The
resulting set of coupled nonlinear partial differential equations is solved
numerically through a segregated approach employing fully-implicit time
stepping. We explore both the static and dynamic FSI behavior of this example
microchannel system by varying a reduced Reynolds number $Re$, which
necessarily changes the Strouhal number $St$, while we keep the geometry and a
modified dimensionless Young's modulus $\Sigma$ fixed. At steady state, an
order-of-magnitude analysis (balancing argument) shows that the
axially-averaged pressure in the flow, $\langle P\rangle$, exhibits two
different scaling regimes, while the maximum deformation of the top wall of the
channel, $H_{\mathrm{max}}$, can fall into four different regimes, depending on
the magnitudes of $Re$ and $\Sigma$. These regimes are physically explained as
resulting from the competition between the inertial and viscous forces in the
fluid flow as well as the bending resistance and tension in the elastic wall.
Finally, the linear stability of the steady inflated microchannel shape is
assessed via a modal analysis, showing the existence of many highly oscillatory
but stable modes, which further highlights the computational challenge of
simulating unsteady FSIs.
| arxiv topic:physics.flu-dyn physics.comp-ph |
arxiv_dataset-101321808.04054 | Constructing Non-isomorphic Signless Laplacian Cospectral Graphs
math.CO cs.DM
In this article, we generate large families of non-isomorphic and signless
Lalacian cospectral graphs using partial transpose on graphs. Our constructions
are significantly powerful. More than $70\%$ of non-isomorphic
signless-Laplacian cospectral graphs can be generated with partial transpose
when number of vertices is $\le 8$. We have also produced numerous examples of
non-isomorphic signless Laplacian cospectral graphs.
| arxiv topic:math.CO cs.DM |
arxiv_dataset-101331808.04154 | Topological terms in Composite Higgs Models
hep-ph hep-th
We apply a recent classification of topological action terms to Composite
Higgs models based on a variety of coset spaces $G/H$ and discuss their
phenomenology. The topological terms, which can all be obtained by integrating
(possibly only locally-defined) differential forms, come in one of two types,
with substantially differing consequences for phenomenology. The first type of
term (which appears in the minimal model based on $SO(5)/SO(4)$) is a field
theory generalization of the Aharonov-Bohm phase in quantum mechanics. The
phenomenological effects of such a term arise only at the non-perturbative
level, and lead to $P$ and $CP$ violation in the Higgs sector. The second type
of term (which appears in the model based on $SO(6)/SO(5)$) is a field theory
generalization of the Dirac monopole in quantum mechanics and has physical
effects even at the classical level. Perhaps most importantly, measuring the
coefficient of such a term can allow one to probe the structure of the
underlying microscopic theory. A particularly rich topological structure, with
6 distinct terms, is uncovered for the model based on $SO(6)/SO(4)$, containing
2 Higgs doublets and a singlet. Of the corresponding couplings, one is an
integer and one is a phase.
| arxiv topic:hep-ph hep-th |
arxiv_dataset-101341808.04254 | Homophonic Quotients of Linguistic Free Groups: German, Korean, and
Turkish
math.GR cs.CL
In 1993, the homophonic quotient groups for French and English (the quotient
of the free group generated by the French (respectively English) alphabet
determined by relations representing standard pronunciation rules) were
explicitly characterized [5]. In this paper we apply the same methodology to
three different language systems: German, Korean, and Turkish. We argue that
our results point to some interesting differences between these three languages
(or at least their current script systems).
| arxiv topic:math.GR cs.CL |
arxiv_dataset-101351808.04354 | Dynamics of solitons for nonlinear quantum walks
quant-ph math-ph math.AP math.MP nlin.PS
We present some numerical results for nonlinear quantum walks (NLQWs) studied
by the authors analytically \cite{MSSSS18DCDS, MSSSS18QIP}. It was shown that
if the nonlinearity is weak, then the long time behavior of NLQWs are
approximated by linear quantum walks. In this paper, we observe the linear
decay of NLQWs for range of nonlinearity wider than studied in
\cite{MSSSS18DCDS}. In addition, we treat the strong nonlinear regime and show
that the solitonic behavior of solutions appears. There are several kinds of
soliton solutions and the dynamics becomes complicated. However, we see that
there are some special cases so that we can calculate explicit form of
solutions. In order to understand the nonlinear dynamics, we systematically
study the collision between soliton solutions. We can find a relationship
between our model and a nonlinear differential equation.
| arxiv topic:quant-ph math-ph math.AP math.MP nlin.PS |
arxiv_dataset-101361808.04454 | A Feature Selection Method for High Impedance Fault Detection
eess.SP cs.SY
High impedance fault (HIF) has been a challenging task to detect in
distribution networks. On one hand, although several types of HIF models are
available for HIF study, they are still not exhibiting satisfactory fault
waveforms. On the other hand, utilizing historical data has been a trend
recently for using machine learning methods to improve HIF detection.
Nonetheless, most proposed methodologies address the HIF issue starting with
investigating a limited group of features and can hardly provide a practical
and implementable solution. This paper, however, proposes a systematic design
of feature extraction, based on an HIF detection and classification method. For
example, features are extracted according to when, how long, and what magnitude
the fault events create. Complementary power expert information is also
integrated into the feature pools. Subsequently, we propose a ranking procedure
in the feature pool for balancing the information gain and the complexity to
avoid over-fitting. For implementing the framework, we create an HIF detection
logic from a practical perspective. Numerical methods show the proposed HIF
detector has very high dependability and security performance under multiple
fault scenarios comparing with other traditional methods.
| arxiv topic:eess.SP cs.SY |
arxiv_dataset-101371808.04554 | Three-particle electron-hole complexes in two-dimensional electron
systems
cond-mat.str-el cond-mat.mes-hall cond-mat.quant-gas
Three-particle complexes consisting of two holes in the completely filled
zero electron Landau level and an excited electron in the unoccupied first
Landau level are investigated in a quantum Hall insulator. The distinctive
features of these three-particle complexes are an electron-hole mass symmetry
and the small energy gap of the quantum Hall insulator itself. Theoretical
calculations of the trion energy spectrum in a quantizing magnetic field
predict that, besides the ground state, trions feature a hierarchy of excited
bound states. In agreement with the theoretical simulations, we observe new
photoluminescence lines related to the excited trion states. A relatively small
energy gap allows the binding of three-particle complexes with magnetoplasma
oscillations and formation of plasmarons. The plasmaron properties are
investigated experimentally.
| arxiv topic:cond-mat.str-el cond-mat.mes-hall cond-mat.quant-gas |
arxiv_dataset-101381808.04654 | Low-power continuous-wave second harmonic generation in semiconductor
nanowires
physics.optics
Semiconductor nanowires (NWs) are promising for realizing various on-chip
nonlinear optical devices, due to their nanoscale lateral confinement and
strong light-matter interaction. However, high-intensity pulsed pump lasers are
typically needed to exploit their optical nonlinearity because light couples
poorly with nanometric-size wires. Here, we demonstrate microwatts
continuous-wave light pumped second harmonic generation (SHG) in AlGaAs NWs by
integrating them with silicon planar photonic crystal cavities. Light-NW
coupling is enhanced effectively by the extremely localized cavity mode at the
subwavelength scale. Strong SHG is obtained even with a continuous-wave laser
excitation with a pump power down to ~3 uW, and the cavity-enhancement factor
is estimated around 150. Additionally, in the integrated device, the NW's SHG
is more than two-order of magnitude stronger than third harmonic generations in
the silicon slab, though the NW only couple s with less than 1% of the cavity
mode. This significantly reduced power-requirement of NW's nonlinear frequency
conversion would promote NW-based building blocks for nonlinear optics,
specially in chip-integrated coherent light sources, entangled photon-pairs and
signal processing devices.
| arxiv topic:physics.optics |
arxiv_dataset-101391808.04754 | Treepedia 2.0: Applying Deep Learning for Large-scale Quantification of
Urban Tree Cover
cs.CV
Recent advances in deep learning have made it possible to quantify urban
metrics at fine resolution, and over large extents using street-level images.
Here, we focus on measuring urban tree cover using Google Street View (GSV)
images. First, we provide a small-scale labelled validation dataset and propose
standard metrics to compare the performance of automated estimations of street
tree cover using GSV. We apply state-of-the-art deep learning models, and
compare their performance to a previously established benchmark of an
unsupervised method. Our training procedure for deep learning models is novel;
we utilize the abundance of openly available and similarly labelled
street-level image datasets to pre-train our model. We then perform additional
training on a small training dataset consisting of GSV images. We find that
deep learning models significantly outperform the unsupervised benchmark
method. Our semantic segmentation model increased mean intersection-over-union
(IoU) from 44.10% to 60.42% relative to the unsupervised method and our
end-to-end model decreased Mean Absolute Error from 10.04% to 4.67%. We also
employ a recently developed method called gradient-weighted class activation
map (Grad-CAM) to interpret the features learned by the end-to-end model. This
technique confirms that the end-to-end model has accurately learned to identify
tree cover area as key features for predicting percentage tree cover. Our paper
provides an example of applying advanced deep learning techniques on a
large-scale, geo-tagged and image-based dataset to efficiently estimate
important urban metrics. The results demonstrate that deep learning models are
highly accurate, can be interpretable, and can also be efficient in terms of
data-labelling effort and computational resources.
| arxiv topic:cs.CV |
arxiv_dataset-101401808.04854 | Dark matter bound states via emission of scalar mediators
hep-ph
If dark matter (DM) couples to a force carrier that is much lighter than
itself, then it may form bound states in the early universe and inside haloes.
While bound-state formation via vector emission is known to be efficient and
have a variety of phenomenological implications, the capture via scalar
emission typically requires larger couplings and is relevant to more limited
parameter space, due to cancellations in the radiative amplitude. However, this
result takes into account only the trilinear DM-DM-mediator coupling. Theories
with scalar mediators include also a scalar potential, whose couplings may
participate in the radiative transitions. We compute the contributions of these
couplings to the radiative capture, and determine the parameter space in which
they are important.
| arxiv topic:hep-ph |
arxiv_dataset-101411808.04954 | Rainbow matchings in properly-colored hypergraphs
math.CO
A hypergraph $H$ is properly colored if for every vertex $v\in V(H)$, all the
edges incident to $v$ have distinct colors. In this paper, we show that if
$H_{1}$, \cdots, $H_{s}$ are properly-colored $k$-uniform hypergraphs on $n$
vertices, where $n\geq3k^{2}s$, and $e(H_{i})>{{n}\choose {k}}-{{n-s+1}\choose
{k}}$, then there exists a rainbow matching of size $s$, containing one edge
from each $H_i$. This generalizes some previous results on the Erd\H{o}s
Matching Conjecture.
| arxiv topic:math.CO |
arxiv_dataset-101421808.05054 | Shedding Light on Black Box Machine Learning Algorithms: Development of
an Axiomatic Framework to Assess the Quality of Methods that Explain
Individual Predictions
cs.LG stat.ML
From self-driving vehicles and back-flipping robots to virtual assistants who
book our next appointment at the hair salon or at that restaurant for dinner -
machine learning systems are becoming increasingly ubiquitous. The main reason
for this is that these methods boast remarkable predictive capabilities.
However, most of these models remain black boxes, meaning that it is very
challenging for humans to follow and understand their intricate inner workings.
Consequently, interpretability has suffered under this ever-increasing
complexity of machine learning models. Especially with regards to new
regulations, such as the General Data Protection Regulation (GDPR), the
necessity for plausibility and verifiability of predictions made by these black
boxes is indispensable. Driven by the needs of industry and practice, the
research community has recognised this interpretability problem and focussed on
developing a growing number of so-called explanation methods over the past few
years. These methods explain individual predictions made by black box machine
learning models and help to recover some of the lost interpretability. With the
proliferation of these explanation methods, it is, however, often unclear,
which explanation method offers a higher explanation quality, or is generally
better-suited for the situation at hand. In this thesis, we thus propose an
axiomatic framework, which allows comparing the quality of different
explanation methods amongst each other. Through experimental validation, we
find that the developed framework is useful to assess the explanation quality
of different explanation methods and reach conclusions that are consistent with
independent research.
| arxiv topic:cs.LG stat.ML |
arxiv_dataset-101431808.05154 | A differential algebra based importance sampling method for impact
probability computation on Earth resonant returns of Near Earth Objects
astro-ph.EP
A differential algebra based importance sampling method for uncertainty
propagation and impact probability computation on the first resonant returns of
Near Earth Objects is presented in this paper. Starting from the results of an
orbit determination process, we use a differential algebra based automatic
domain pruning to estimate resonances and automatically propagate in time the
regions of the initial uncertainty set that include the resonant return of
interest. The result is a list of polynomial state vectors, each mapping
specific regions of the uncertainty set from the observation epoch to the
resonant return. Then, we employ a Monte Carlo importance sampling technique on
the generated subsets for impact probability computation. We assess the
performance of the proposed approach on the case of asteroid (99942) Apophis. A
sensitivity analysis on the main parameters of the technique is carried out,
providing guidelines for their selection. We finally compare the results of the
proposed method to standard and advanced orbital sampling techniques.
| arxiv topic:astro-ph.EP |
arxiv_dataset-101441808.05254 | Zero-momentum trajectories inside a black hole and high energy particle
collisions
gr-qc astro-ph.HE hep-th
We consider properties of the trajectory with the zero momentum inside a
spherically symmetric black hole. We work mostly in the Painlev\'{e}%
-Gullstrand frame and use the concept of the "river model of black hole". This
consept allows us to decompose (in a "cosmological manner") the geodesic motion
of a test particle into a "flow" of the frame and a peculiar motion with
respect to this frame. After this decomposition the application of standard
formulae of special relativity for kinematic processes becomes possible. The
present paper expands the notion of peculiar velocities to the region under the
horzion and exploits it for the description of two physical processess - high
energy collisions and redshift. Using this approach we (i) present a novel
description of particle collisions occuring near black hole horizons inside the
event horizon. In particular, we show that the trajectory under discussion is
relevant for ultra-high energy collisions. (ii) In the framework of the river
model, we derive a simple formula (both outside and inside the horizon) for the
redshift in the case of radial motion. It represents the product of two
factors. One of them is responsible for pure gravitational part whereas the
other one gives the Doppler shift due to peculiar motion with respect to the
"flow".
| arxiv topic:gr-qc astro-ph.HE hep-th |
arxiv_dataset-101451808.05354 | The lower $p$-central series of a free profinite group and the shuffle
algebra
math.NT math.KT math.RA
For a prime number $p$ and a free profinite group $S$ on the basis $X$, let
$S^{(n,p)}$, $n=1,2,\ldots$ be the lower $p$-central filtration of $S$. For
$p>n$, we give a combinatorial description of $H^2(S/S^{(n,p)},\mathbb{Z}/p)$
in terms of the Shuffle algebra on $X$.
| arxiv topic:math.NT math.KT math.RA |
arxiv_dataset-101461808.05454 | Atomic basis functions for molecular electronic structure calculations
physics.chem-ph
Electronic structure methods for accurate calculation of molecular properties
have a high cost that grows steeply with the problem size, therefore, it is
helpful to have the underlying atomic basis functions that are less in number
but of higher quality. Following our earlier work [Chem. Phys. Lett. 416, 116
(2005)] where general correlation-consistent basis sets are defined, for any
atom, as solutions of purely atomic functional minimization problems, and which
are shown to work well for chemical bonding in molecules, we take a further
step here and define a new kind of atomic polarization functionals, the
minimization of which yields additional sets of diffuse functions that help to
calculate better molecular electron affinities, polarizabilities, and
intermolecular dispersion interactions. Analytical representations by
generally-contracted Gaussian functions of up to microhartree numerical
accuracy grades are developed for atoms Hydrogen through Nobelium within the
four-component Dirac-Coulomb theory and its scalar-relativistic approximation,
and also for Hydrogen through Krypton in the two-component nonrelativistic
case. The convergence of correlation energy with the basis set size is studied,
and complete-basis-set extrapolation formulas are developed.
| arxiv topic:physics.chem-ph |
arxiv_dataset-101471808.05554 | Control Energy of Lattice Graphs
cs.SY math.CO math.OC
The control of complex networks has generated a lot of interest in a variety
of fields from traffic management to neural systems. A commonly used metric to
compare two particular control strategies that accomplish the same task is the
control energy, the integral of the sum of squares of all control inputs. The
minimum control energy problem determines the control input that lower bounds
all other control inputs with respect to their control energies. Here, we focus
on the infinite lattice graph with linear dynamics and analytically derive the
expression for the minimum control energy in terms of the modified Bessel
function. We then demonstrate that the control energy of the infinite lattice
graph accurately predicts the control energy of finite lattice graphs.
| arxiv topic:cs.SY math.CO math.OC |
arxiv_dataset-101481808.05654 | Motivic characteristic classes in cohomological Hall algebras
math.AG math.RT
The equivariant Chern-Schwartz-MacPherson (CSM) class and the equivariant
Motivic Chern (MC) class are important characteristic classes of singular
varieties in cohomology and K theory---and their theory overlaps with the
theory of Okounkov's stable envelopes. We study CSM and MC classes for the
orbits of Dynkin quiver representations. We show that the problem of computing
the CSM and MC classes of all these orbits can be reduced to some basic classes
$c^o_\beta$, $C^o_\beta$ parameterized by positive roots $\beta$. We prove an
identity in a deformed version of Kontsevich-Soibelman's Cohomological (and
K-theoretic) Hall Algebra (CoHA, KHA), namely, that a product of exponentials
of $c^o_\beta$ (or $C^o_\beta$) classes formally depending on a stability
function Z, does not depend on Z. This identity---which encodes infinitely many
identities among rational functions in growing number of variables---has the
structure of Donaldson-Thomas type quantum dilogarithm identities. Using a
wall-crossing argument we present the $c^o_\beta$, $C^o_\beta$ classes as
certain commutators in the CoHA, KHA.
| arxiv topic:math.AG math.RT |
arxiv_dataset-101491808.05754 | Auto-Classification of Retinal Diseases in the Limit of Sparse Data
Using a Two-Streams Machine Learning Model
cs.CV
Automatic clinical diagnosis of retinal diseases has emerged as a promising
approach to facilitate discovery in areas with limited access to specialists.
Based on the fact that fundus structure and vascular disorders are the main
characteristics of retinal diseases, we propose a novel visual-assisted
diagnosis hybrid model mixing the support vector machine (SVM) and deep neural
networks (DNNs). Furthermore, we present a new clinical retina dataset, called
EyeNet2, for ophthalmology incorporating 52 retina diseases classes. Using
EyeNet2, our model achieves 90.43\% diagnosis accuracy, and the model
performance is comparable to the professional ophthalmologists.
| arxiv topic:cs.CV |
arxiv_dataset-101501808.05854 | Robust Compressive Phase Retrieval via Deep Generative Priors
cs.LG stat.ML
This paper proposes a new framework to regularize the highly ill-posed and
non-linear phase retrieval problem through deep generative priors using simple
gradient descent algorithm. We experimentally show effectiveness of proposed
algorithm for random Gaussian measurements (practically relevant in imaging
through scattering media) and Fourier friendly measurements (relevant in
optical set ups). We demonstrate that proposed approach achieves impressive
results when compared with traditional hand engineered priors including
sparsity and denoising frameworks for number of measurements and robustness
against noise. Finally, we show the effectiveness of the proposed approach on a
real transmission matrix dataset in an actual application of multiple
scattering media imaging.
| arxiv topic:cs.LG stat.ML |
arxiv_dataset-101511808.05954 | Mobility edge and intermediate phase in one-dimensional incommensurate
lattice potentials
cond-mat.dis-nn
We study theoretically the localization properties of two distinct
one-dimensional quasiperiodic lattice models with a single-particle mobility
edge (SPME) separating extended and localized states in the energy spectrum.
The first one is the familiar Soukoulis-Economou trichromatic potential model
with two incommensurate potentials, and the second is a system consisting of
two coupled 1D Aubry-Andre chains each containing one incommensurate potential.
We show that as a function of the Hamiltonian model parameters, both models
have a wide single-particle intermediate phase (SPIP), defined as the regime
where localized and extended single-particle states coexist in the spectrum,
leading to a behavior intermediate between purely extended or purely localized
when the system is dynamically quenched from a generic initial state. Our
results thus suggest that both systems could serve as interesting experimental
platforms for studying the interplay between localized and extended states, and
may provide insight into the role of the coupling of small baths to localized
systems. We also calculate the Lyapunov (or localization) exponent for several
incommensurate 1D models exhibiting SPME, finding that such localization
critical exponents for quasiperiodic potential induced localization are
nonuniversal and depend on the microscopic details of the Hamiltonian.
| arxiv topic:cond-mat.dis-nn |
arxiv_dataset-101521808.06054 | The Goresky-MacPherson formula for toric arrangements
math.AT
A subspace arrangement is a finite collection of affine subspaces in
$\mathbb{R}^n$. One of the main problems associated to arrangements asks up to
what extent the topological invariants of the union of these spaces, and of
their complement are determined by the combinatorics of their intersection. The
most important result in this direction is due to Goresky and MacPherson. As an
application of their stratified Morse theory they showed that the additive
structure of the cohomology of the complement is determined by the underlying
combinatorics.
In this paper we consider toric arrangements; a finite collection of subtori
in $(\mathbb{C}^{\ast})^l$. The aim of this paper is to prove an analogue of
the Goresky-MacPherson's theorem in this context. When all the subtori in the
arrangement are of codimension-$1$ we give an alternate proof of a theorem due
to De Concini and Procesi.
| arxiv topic:math.AT |
arxiv_dataset-101531808.06154 | Emergent quantum criticality from spin-orbital entanglement in $d^8$
Mott insulators: the case of a diamond lattice antiferromagnet
cond-mat.str-el cond-mat.mtrl-sci cond-mat.supr-con
Motivated by the recent activities on the Ni-based diamond lattice
antiferromagnet NiRh$_2$O$_4$, we theoretically explore on a general ground the
unique spin and orbital physics for the Ni$^{2+}$ ions with a $3d^8$ electron
configuration in the tetrahedral crystal field environment and on a diamond
lattice Mott insulator. The superexchange interaction between the local moments
usually favors magnetic orders. Due to the particular electron configuration of
the Ni$^{2+}$ ion with a partially filled upper $t_{2g}$ level and a fully
filled lower $e_g$ level, the atomic spin-orbit coupling becomes active at the
linear order and would favor a spin-orbital-entangled singlet with quenched
local moments in the single-ion limit. Thus, the spin-orbital entanglement
competes with the superexchange and could drive the system to a quantum
critical point that separates the spin-orbital singlet and the magnetic order.
We further explore the effects of magnetic field and uniaxial pressure. The
non-trivial response to the magnetic field is intimately tied to the underlying
spin-orbital structure of the local moments. We discuss the future experiments
such as doping and pressure, and point out the correspondence between different
electron configurations.
| arxiv topic:cond-mat.str-el cond-mat.mtrl-sci cond-mat.supr-con |
arxiv_dataset-101541808.06254 | SABRE: Protecting Bitcoin against Routing Attacks
cs.NI cs.CR
Routing attacks remain practically effective in the Internet today as
existing countermeasures either fail to provide protection guarantees or are
not easily deployable. Blockchain systems are particularly vulnerable to such
attacks as they rely on Internet-wide communication to reach consensus. In
particular, Bitcoin -the most widely-used cryptocurrency- can be split in half
by any AS-level adversary using BGP hijacking. In this paper, we present SABRE,
a secure and scalable Bitcoin relay network which relays blocks worldwide
through a set of connections that are resilient to routing attacks. SABRE runs
alongside the existing peer-to-peer network and is easily deployable. As a
critical system, SABRE design is highly resilient and can efficiently handle
high bandwidth loads, including Denial of Service attacks. We built SABRE
around two key technical insights. First, we leverage fundamental properties of
inter-domain routing (BGP) policies to host relay nodes: (i) in locations that
are inherently protected against routing attacks; and (ii) on paths that are
economically preferred by the majority of Bitcoin clients. These properties are
generic and can be used to protect other Blockchain-based systems. Second, we
leverage the fact that relaying blocks is communication-heavy, not
computation-heavy. This enables us to offload most of the relay operations to
programmable network hardware (using the P4 programming language). Thanks to
this hardware/software co-design, SABRE nodes operate seamlessly under high
load while mitigating the effects of malicious clients. We present a complete
implementation of SABRE together with an extensive evaluation. Our results
demonstrate that SABRE is effective at securing Bitcoin against routing
attacks, even with deployments as small as 6 nodes.
| arxiv topic:cs.NI cs.CR |
arxiv_dataset-101551808.06354 | Signed Graph Convolutional Network
cs.SI physics.soc-ph
Due to the fact much of today's data can be represented as graphs, there has
been a demand for generalizing neural network models for graph data. One recent
direction that has shown fruitful results, and therefore growing interest, is
the usage of graph convolutional neural networks (GCNs). They have been shown
to provide a significant improvement on a wide range of tasks in network
analysis, one of which being node representation learning. The task of learning
low-dimensional node representations has shown to increase performance on a
plethora of other tasks from link prediction and node classification, to
community detection and visualization. Simultaneously, signed networks (or
graphs having both positive and negative links) have become ubiquitous with the
growing popularity of social media. However, since previous GCN models have
primarily focused on unsigned networks (or graphs consisting of only positive
links), it is unclear how they could be applied to signed networks due to the
challenges presented by negative links. The primary challenges are based on
negative links having not only a different semantic meaning as compared to
positive links, but their principles are inherently different and they form
complex relations with positive links. Therefore we propose a dedicated and
principled effort that utilizes balance theory to correctly aggregate and
propagate the information across layers of a signed GCN model. We perform
empirical experiments comparing our proposed signed GCN against
state-of-the-art baselines for learning node representations in signed
networks. More specifically, our experiments are performed on four real-world
datasets for the classical link sign prediction problem that is commonly used
as the benchmark for signed network embeddings algorithms.
| arxiv topic:cs.SI physics.soc-ph |
arxiv_dataset-101561808.06454 | The excluded volume of two-dimensional convex bodies: Shape
reconstruction and non-uniqueness
cond-mat.soft
In the Onsager model of one-component hard-particle systems, the entire phase
behaviour is dictated by a function of relative orientation, which represents
the amount of space excluded to one particle by another at this relative
orientation. We term this function the excluded volume function. Within the
context of two-dimensional convex bodies, we investigate this excluded volume
function for one-component systems addressing two related questions. Firstly,
given a body can we find the excluded volume function?, Secondly, can we
reconstruct a body from its excluded volume function? The former is readily
answered via an explicit Fourier series representation, in terms of the support
function. However we show the latter question is ill-posed in the sense that
solutions are not unique for a large class of bodies. This degeneracy is well
characterised however, with two bodies admitting the same excluded volume
function if and only if the Fourier coefficients of their support functions
differ only in phase. Despite the non-uniqueness issue, we then propose and
analyse a method for reconstructing a convex body given its excluded volume
function, by means of a discretisation procedure where convex bodies are
approximated by zonotopes with a fixed number of sides. It is shown that the
algorithm will always asymptotically produce a best $L^2$ approximation of the
trial function, within the space of excluded volume functions of centrally
symmetric bodies. In particular, if a solution exists, it can be found. Results
from a numerical implementation are presented, showing that with only desktop
computing power, good approximations to solutions can be readily found.
| arxiv topic:cond-mat.soft |
arxiv_dataset-101571808.06554 | Observation and active control of a collective polariton mode and
polaritonic band gap in few-layer WS2 strongly coupled with plasmonic
lattices
physics.optics cond-mat.mtrl-sci
Two-dimensional semiconductors host excitons with very large oscillator
strengths and binding energies due to significantly reduced carrier screening.
Two-dimensional semiconductors integrated with optical cavities are emerging as
a promising platform for studying strong light-matter interactions as a route
to explore a variety of exotic many-body effects. Here, in few-layered WS2
coupled with plasmonic nanoparticle lattices, we observe the formation of a
collective polaritonic mode near the exciton energy and the formation of a
complete polariton band gap with energy scale comparable to the exciton-plasmon
coupling strength. A coupled oscillator model reveals that the collective mode
arises from the cooperative coupling of the excitons to the plasmonic lattice
diffraction orders via exciton-exciton interactions. The emergence of the
collective mode is accompanied by a superlinear increase of the polariton mode
splitting as a function of the square root of the exciton oscillator strength.
The presence of these many body effects, which are enhanced in systems which
lack bulk polarization, not only allows the formation of a collective mode with
periodically varying field profiles, but also further enhances the
exciton-plasmon coupling. By integrating the hybrid WS2-plasmonic lattice
device with a field-effect transistor, we demonstrate active tuning of the
collective mode and the polariton band gap. These systems provide new
opportunities for obtaining a deeper and systematic understanding of many body
cooperative phenomena in periodic photonic systems and for designing more
complex and actively controllable polaritonic devices including switchable
polariton lasers, waveguides, and optical logical elements.
| arxiv topic:physics.optics cond-mat.mtrl-sci |
arxiv_dataset-101581808.06654 | Microscopic phase diagram of LaFeAsO single crystals under pressure
cond-mat.supr-con
We investigated LaFeAsO single crystals by means of synchrotron M\"ossbauer
spectroscopy under pressures up to 7.5 GPa and down to 13 K and provide a
microscopic phase diagram. We found a continuous suppression of the magnetic
hyperfine field with increasing pressure and it completely vanishes at $\sim$
7.5 GPa which is in contrast to the behavior in polycrystalline samples where
the magnetic order vanishes at $\sim$ 20 GPa. The different behavior of the
polycrystalline samples might be due to As-vacancies. Our results are in
qualitative agreement with density functional theory calculations where a
reduction of the magnetic moment with increasing pressure was found. We found
that among different samples at ambient pressure the magnetic phase transition
temperature as well as the low-temperature magnetic hyperfine field decrease
with increasing unit cell volume.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-101591808.06754 | Dominant Channel Estimation via MIPS for Large-Scale Antenna Systems
with One-Bit ADCs
cs.IT eess.SP math.IT
In large-scale antenna systems, using one-bit analog-to-digital converters
(ADCs) has recently become important since they offer significant reductions in
both power and cost. However, in contrast to high-resolution ADCs, the coarse
quantization of one-bit ADCs results in an irreversible loss of information. In
the context of channel estimation, studies have been developed extensively to
combat the performance loss incurred by one-bit ADCs. Furthermore, in the field
of array signal processing, direction-of-arrival (DOA) estimation combined with
one-bit ADCs has gained growing interests recently to minimize the estimation
error. In this paper, a channel estimator is proposed for one-bit ADCs where
the channels are characterized by their angular geometries, e.g., uniform
linear arrays (ULAs). The goal is to estimate the dominant channel among
multiple paths. The proposed channel estimator first finds the DOA estimate
using the maximum inner product search (MIPS). Then, the channel fading
coefficient is estimated using the concavity of the log-likelihood function.
The limit inherent in one-bit ADCs is also investigated, which results from the
loss of magnitude information.
| arxiv topic:cs.IT eess.SP math.IT |
arxiv_dataset-101601808.06854 | A linearly implicit and local energy-preserving scheme for the
sine-Gordon equation based on the invariant energy quadratization approach
math.NA cs.NA
In this paper, we develop a novel, linearly implicit and local
energy-preserving scheme for the sine-Gordon equation. The basic idea is from
the invariant energy quadratization approach to construct energy stable schemes
for gradient systems, which are energy dispassion. We here take the sine-Gordon
equation as an example to show that the invariant energy quadratization
approach is also an efficient way to construct linearly implicit and local
energy-conserving schemes for energy-conserving systems. Utilizing the
invariant energy quadratization approach, the sine-Gordon equation is first
reformulated into an equivalent system, which inherits a modified local energy
conservation law. The new system are then discretized by the conventional
finite difference method and a semi-discretized system is obtained, which can
conserve the semi-discretized local energy conservation law. Subsequently, the
linearly implicit structure-preserving method is applied for the resulting
semi-discrete system to arrive at a fully discretized scheme. We prove that the
resulting scheme can exactly preserve the discrete local energy conservation
law. Moveover, with the aid of the classical energy method, an unconditional
and optimal error estimate for the scheme is established in discrete
$H_h^1$-norm. Finally, various numerical examples are addressed to confirm our
theoretical analysis and demonstrate the advantage of the new scheme over some
existing local structure-preserving schemes.
| arxiv topic:math.NA cs.NA |
arxiv_dataset-101611808.06954 | Group Activity Selection with Few Agent Types
cs.DS
The Group Activity Selection Problem (GASP) models situations where a group
of agents needs to be distributed to a set of activities while taking into
account preferences of the agents w.r.t. individual activities and activity
sizes. The problem, along with its two previously proposed variants sGASP and
gGASP, has been studied in the parameterized complexity setting with various
parameterizations, such as number of agents, number of activities and solution
size. However, the complexity of the problem parameterized by the number of
types of agents, a parameter motivated and proposed already in the paper that
introduced GASP, has so far remained open.
In this paper we establish the complexity map for GASP, sGASP and gGASP when
the number of types of agents is the parameter. Our positive results,
consisting of one fixed-parameter algorithm and one XP algorithm, rely on a
combination of novel Subset Sum machinery (which may be of general interest)
and identifying certain compression steps which allow us to focus on solutions
which are "acyclic". These algorithms are complemented by matching lower
bounds, which among others answer an open question of Gupta, Roy, Saurabh and
Zehavi (2017). In this direction, the techniques used to establish
W[1]-hardness of sGASP are of particular interest: as an intermediate step, we
use Sidon sequences to show the W[1]-hardness of a highly restricted variant of
multi-dimensional Subset Sum, which may find applications in other settings as
well.
| arxiv topic:cs.DS |
arxiv_dataset-101621808.07054 | Characteristic numbers of elliptic fibrations with non-trivial
Mordell-Weil groups
hep-th math-ph math.AG math.MP
We compute characteristic numbers of elliptically fibered fourfolds with
multisections or non-trivial Mordell-Weil groups. We first consider the models
of type E$_{9-d}$ with $d=1,2,3,4$ whose generic fibers are normal elliptic
curves of degree $d$. We then analyze the characteristic numbers of the
$Q_7$-model, which provides a smooth model for elliptic fibrations of rank one
and generalizes the E$_5$, E$_6$, and E$_7$-models. Finally, we examine the
characteristic numbers of $G$-models with $G=\text{SO}(n)$ with $n=3,4,5,6$ and
$G=\text{PSU}(3)$ whose Mordell-Weil groups are respectively
$\mathbb{Z}/2\mathbb{Z}$ and $\mathbb{Z}/3 \mathbb{Z}$. In each case, we
compute the Chern and Pontryagin numbers, the Euler characteristic, the
holomorphic genera, the Todd-genus, the L-genus, the A-genus, and the
eight-form curvature invariant from M-theory.
| arxiv topic:hep-th math-ph math.AG math.MP |
arxiv_dataset-101631808.07154 | Assessing sources of uncertainty in length-based estimates of body
growth in populations of fishes and macroinvertebrates with bootstrapped
ELEFAN
q-bio.PE
The determination of rates of body growth is the first step in many aquatic
population studies and fisheries stock assessments. ELEFAN (Electronic LEngth
Frequency ANalysis) is a widely used method to fit a growth curve to
length-frequency distribution (LFD) data. However, up to now, it was not
possible to assess its accuracy or the uncertainty inherent of this method, or
to obtain confidence intervals for growth parameters within an unconstrained
search space. In this study, experiments were conducted to assess the precision
and accuracy of bootstrapped and single-fit ELEFAN-based curve fitting methods,
using synthetic LFDs with known input parameters and a real data set of Abra
alba shell lengths. The comparison of several types of bootstrap experiments
and their outputs (95% confidence intervals and confidence contour plots)
provided a first glimpse into the accuracy of modern ELEFAN-based fit methods.
The main components of uncertainty (precision and reproducibility of fit
algorithms, seed effects, sample size and matrix information content) could be
assessed from partial bootstraps. Uncertainty was mainly determined by LFD
matrix size, total number of non-zero bins and the sampling of large-sized
individuals. A new pseudo-Rsquared index for the goodness-of-fit of VBGF models
to LFD data is proposed. For a large, perfect synthetic data set,
pseudo-RsquaredPhi was very high (88 to 100%), indicating an excellent fit of
the VBGF model. The small Abra alba data set showed a low pseudo-RsquaredPhi,
from to 54% to 68%, indicating the need for more samples and a larger LFD data
matrix. New, robust, bootstrap-based methods for curve fitting are presented
and discussed. This study demonstrates a promising new path for length-based
analyses of growth and mortality in natural populations, which are the basis
for a new suite of methods that are included in the new fishboot package.
| arxiv topic:q-bio.PE |
arxiv_dataset-101641808.07254 | Checkerboard incircular nets. Laguerre geometry and parametrisation
math.DG nlin.SI
We present a procedure which allows one to integrate explicitly the class of
checkerboard IC-nets which has recently been introduced as a generalisation of
incircular (IC) nets. The latter class of privileged congruences of lines in
the plane is known to admit a great variety of geometric properties which are
also present in the case of checkerboard IC-nets. The parametrisation obtained
in this manner is reminiscent of that associated with elliptic billiards.
Connections with discrete confocal coordinate systems and the fundamental QRT
maps of integrable systems theory are made. The formalism developed in this
paper is based on the existence of underlying pencils of conics and quadrics
which is exploited in a Laguerre geometric setting.
| arxiv topic:math.DG nlin.SI |
arxiv_dataset-101651808.07354 | Implementation of Uplink Network Coded Modulation for Two-Hop Networks
cs.NI
With the fast growing number of wireless devices and demand of user data, the
backhaul load becomes a bottleneck in wireless networks. Physical layer network
coding (PNC) allows Access Points (APs) to relay compressed, network coded user
data, therefore reducing the backhaul traffic. In this paper, an implementation
of uplink Network Coded Modulation (NetCoM) with PNC is presented. A 5-node
prototype NetCoM system is established using Universal Software Radio
Peripherals (USRPs) and a practical PNC scheme designed for binary systems is
utilised. An orthogonal frequency division multiplexing (OFDM) waveform
implementation and the practical challenges (e.g. device synchronisation and
clock drift) of applying OFDM to NetCoM are discussed. To the best of our
knowledge this is the first PNC implementation in an uplink scenario in radio
access networks and our prototype provides an industrially-applicable
implementation of the proposed NetCoM with PNC approach.
| arxiv topic:cs.NI |
arxiv_dataset-101661808.07454 | Strain localization and dynamic recrystallization in polycrystalline
metals: thermodynamic theory and simulation framework
cond-mat.mtrl-sci cond-mat.stat-mech
We describe a theoretical and computational framework for adiabatic shear
banding (ASB) and dynamic recrystallization (DRX) in polycrystalline materials.
The Langer-Bouchbinder-Lookman (LBL) thermodynamic theory of polycrystalline
plasticity, which we recently reformulated to describe DRX via the inclusion of
the grain boundary density or the grain size as an internal state variable,
provides a convenient and self-consistent way to represent the viscoplastic and
thermal behavior of the material, with minimal ad-hoc assumptions regarding the
initiation of yielding or onset of shear banding. We implement the LBL-DRX
theory in conjunction with a finite-element computational framework. Favorable
comparison to experimental measurements on a top-hat AISI 316L stainless steel
sample compressed with a split-Hopkinson pressure bar suggests the accuracy and
usefulness of the LBL-DRX framework, and demonstrates the crucial role of DRX
in strain localization.
| arxiv topic:cond-mat.mtrl-sci cond-mat.stat-mech |
arxiv_dataset-101671808.07554 | A lattice Boltzmann model for two-phase flow in porous media
physics.comp-ph
In this paper, a lattice Boltzmann (LB) model with double distribution
functions is proposed for two-phase flow in porous media where one distribution
function is used for pressure governed by the Poisson equation, and the other
is applied for saturation evolution described by the convection-diffusion
equation with a source term. We first performed a Chapman-Enskog analysis, and
show that the macroscopic nonlinear equations for pressure and saturation can
be recovered correctly from present LB model. Then in the framework of LB
method, we develop a local scheme for pressure gradient or equivalently
velocity, which may be more efficient than the nonlocal second-order
finite-difference schemes. We also perform some numerical simulations, and the
results show that the developed LB model and local scheme for velocity are
accurate and also have a second-order convergence rate in space. Finally,
compared to the available pore-scale LB models for two-phase flow in porous
media, the present LB model has more potential in the study of the large-scale
problems.
| arxiv topic:physics.comp-ph |
arxiv_dataset-101681808.07654 | Stokes phenomenon and Yang-Baxter equations
math-ph math.CA math.MP math.QA math.RT
We describe the monodromy of dynamical Knizhnik-Zamolodchikov equations via
Stokes phenomenon. It defines a family of braid groups representations by
certain Stokes matrices. In particular, these Stokes matrices satisfy the
Yang-Baxter equation.
| arxiv topic:math-ph math.CA math.MP math.QA math.RT |
arxiv_dataset-101691808.07754 | New formulation of the finite depth free surface Green function
physics.flu-dyn math-ph math.MP
For a pulsating free surface source in a three-dimensional finite depth fluid
domain, the Green function of the source presented by John [F. John, On the
motion of floating bodies II. Simple harmonic motions, Communs. Pure Appl.
Math. 3 (1950) 45-101] is superposed as the Rankine source potential, an image
source potential and a wave integral in the infinite domain $(0, \infty)$. When
the source point together with a field point is on the free surface, John's
integral and its gradient are not convergent since the integration
$\int^\infty_\kappa$ of the corresponding integrands does not tend to zero in a
uniform manner as $\kappa$ tends to $\infty$. Thus evaluation of the Green
function is not based on direct integration of the wave integral but is
obtained by approximation expansions in earlier investigations. In the present
study, five images of the source with respect to the free surface mirror and
the water bed mirror in relation to the image method are employed to
reformulate the wave integral. Therefore the free surface Green function of the
source is decomposed into the Rankine potential, the five image source
potentials and a new wave integral, of which the integrand is approximated by a
smooth and rapidly decaying function. The gradient of the Green function is
further formulated so that the same integration stability with the wave
integral is demonstrated. The significance of the present research is that the
improved wave integration of the Green function and its gradient becomes
convergent. Therefore evaluation of the Green function is obtained through the
integration of the integrand in a straightforward manner. The application of
the scheme to a floating body or a submerged body motion in regular waves shows
that the approximation is sufficiently accurate to compute linear wave loads in
practice.
| arxiv topic:physics.flu-dyn math-ph math.MP |
arxiv_dataset-101701808.07854 | Voting power of political parties in the Senate of Chile during the
whole binomial system period: 1990-2017
econ.GN physics.soc-ph q-fin.EC
The binomial system is an electoral system unique in the world. It was used
to elect the senators and deputies of Chile during 27 years, from the return of
democracy in 1990 until 2017. In this paper we study the real voting power of
the different political parties in the Senate of Chile during the whole
binomial period. We not only consider the different legislative periods, but
also any party changes between one period and the next. The real voting power
is measured by considering power indices from cooperative game theory, which
are based on the capability of the political parties to form winning
coalitions. With this approach, we can do an analysis that goes beyond the
simple count of parliamentary seats.
| arxiv topic:econ.GN physics.soc-ph q-fin.EC |
arxiv_dataset-101711808.07954 | From Hand-Crafted to Deep Learning-based Cancer Radiomics: Challenges
and Opportunities
cs.CV
Recent advancements in signal processing and machine learning coupled with
developments of electronic medical record keeping in hospitals and the
availability of extensive set of medical images through internal/external
communication systems, have resulted in a recent surge of significant interest
in "Radiomics". Radiomics is an emerging and relatively new research field,
which refers to extracting semi-quantitative and/or quantitative features from
medical images with the goal of developing predictive and/or prognostic models,
and is expected to become a critical component for integration of image-derived
information for personalized treatment in the near future. The conventional
Radiomics workflow is typically based on extracting pre-designed features (also
referred to as hand-crafted or engineered features) from a segmented region of
interest. Nevertheless, recent advancements in deep learning have caused trends
towards deep learning-based Radiomics (also referred to as discovery
Radiomics). Considering the advantages of these two approaches, there are also
hybrid solutions developed to exploit the potentials of multiple data sources.
Considering the variety of approaches to Radiomics, further improvements
require a comprehensive and integrated sketch, which is the goal of this
article. This manuscript provides a unique interdisciplinary perspective on
Radiomics by discussing state-of-the-art signal processing solutions in the
context of Radiomics.
| arxiv topic:cs.CV |
arxiv_dataset-101721808.08054 | The Co-Terminal Swap Market Model with Bergomi Stochastic Volatility
q-fin.CP q-fin.PR
In this article, we apply the forward variance modeling approach by L.Bergomi
to the co-terminal swap market model. We build an interest rate model for which
all the market price changes of hedging instruments, interest rate swaps and
European swaptions, are interpreted as the state variable variations, and no
diffusion parameter calibration procedure is required. The model provides quite
simple profit and loss (PnL) formula, with which we can easily understand where
a material PnL trend comes from when it appears, and consider how we should
modify the model parameters. The model has high flexibility to control the
model dynamics because parameter calibration is unnecessary and the model
parameters can be used solely for the purpose of the model dynamics control.
With the model, the position management of the exotic interest rate products,
e.g. Bermudan swaptions, can be carried out in a more sophisticated and
systematic manner. A numerical experiment is performed to show the
effectiveness of the approach for a Canary swaption, which is a special form of
a Bermudan swaption.
| arxiv topic:q-fin.CP q-fin.PR |
arxiv_dataset-101731808.08154 | On the equivalence of Jordan and Einstein frames in scale-invariant
gravity
gr-qc hep-th
In this note we consider the issue of the classical equivalence of
scale-invariant gravity in the Einstein and in the Jordan frames. We first
consider the simplest example $f(R)=R^{2}$ and show explicitly that the
equivalence breaks down when dealing with Ricci-flat solutions. We discuss the
link with the fact that flat solutions in quadratic gravity have zero energy.
We also consider the case of scale-invariant tensor-scalar gravity and general
$f(R)$ theories. We argue that all scale-invariant gravity models have Ricci
flat solutions in the Jordan frame that cannot be mapped into the Einstein
frame. In particular, the Minkowski metric exists only in the Jordan frame. In
this sense, the two frames are not equivalent.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-101741808.08254 | Gravitational back-reaction near cosmic string kinks and cusps
gr-qc astro-ph.CO
We find the leading-order effect of gravitational back-reaction on cosmic
strings for points near kinks and cusps. Near a kink, the effect diverges as
the inverse cube root of the distance to the kink, and acts in a direction
transverse to the worldsheet. Over time the kink is rounded off, but only
regions fairly close to the kink are significantly affected. Near cusps, the
effect diverges inverse linearly with the distance to the cusp, and acts
against the direction of the cusp motion. This results in a fractional loss of
string energy that diverges logarithmically with the distance of closest
approach to the cusp.
| arxiv topic:gr-qc astro-ph.CO |
arxiv_dataset-101751808.08354 | Intraband divergences in third order optical response of 2D systems
cond-mat.mtrl-sci cond-mat.mes-hall physics.optics
The existence of large nonlinear optical coefficients is one of the
preconditions for using nonlinear optical materials in nonlinear optical
devices. For a crystal, such large coefficients can be achieved by matching
photon energies with resonant energies between different bands, and so the
details of the crystal band structure play an important role. Here we
demonstrate that large third-order nonlinearities can also be generally
obtained by a different strategy: As any of the incident frequencies or the sum
of any two or three frequencies approaches zero, the doped or excited
populations of electronic states lead to divergent contributions in the induced
current density. We refer to these as intraband divergences, by analogy with
the behavior of Drude conductivity in linear response. Physically, such
resonant processes can be associated with a combination of inraband and
interband optical transitions. Current-induced second order nonlinearity,
coherent current injection, and jerk currents are all related to such
divergences, and we find similar divergences in degenerate four wave mixing and
cross-phase modulation under certain conditions. These divergences are limited
by intraband relaxation parameters, and lead to a large optical response from a
high quality sample; we find they are very robust with respect to variations in
the details of the band structure. To clearly track all of these effects, we
analyze gapped graphene, describing the electrons as massive Dirac fermions;
under the relaxation time approximation, we derive analytic expressions for the
third order conductivities, and identify the divergences that arise in
describing the associated nonlinear phenomena.
| arxiv topic:cond-mat.mtrl-sci cond-mat.mes-hall physics.optics |
arxiv_dataset-101761808.08454 | On centro-affine curves and Backlund transformations of the KdV equation
math.DS
We continue the study of the Korteweg-de Vries equation in terms of
cento-affine curves, initiated by U. Pinkall. A centro-affine curve is a closed
parametric curve in the affine plane such that the determinant made by the
position and the velocity vectors is identically 1. The space of centro-affine
curves is acted upon by the special linear group, and the quotient is
identified with the space of Hill's equations with periodic solutions. It is
known that the space of centro-affine curves carries two pre-symplectic
structures, and the KdV flow is identified with is a bi-Hamiltonian dynamical
system therein. We introduce a 1-parameter family of transformations on
centro-affine curves, prove that they preserve both presymplectic structures,
commute with the KdV flow, and share the integrals with it. Furthermore, the
transformation commute with each other (Bianchi permutability). We also
describe integrals of the KdV equation as arising from the monodromy of Riccati
equations associated with centro-affine curves. We are motivated by our work in
progress (joint with M. Arnold, D. Fuchs, and I. Izmenstiev), concerning the
cross-ratio dynamics on ideal polygons in the hyperbolic plane and hyperbolic
space, whose continuous version is studied in the present note.
| arxiv topic:math.DS |
arxiv_dataset-101771808.08554 | On the joint distribution of the marginals of multipartite random
quantum states
math.PR math-ph math.CO math.MP quant-ph
We study the joint distribution of the set of all marginals of a random
Wishart matrix acting on a tensor product Hilbert space. We compute the
limiting free mixed cumulants of the marginals, and we show that in the
balanced asymptotical regime, the marginals are asymptotically free. We connect
the matrix integrals relevant to the study of operators on tensor product
spaces with the corresponding classes of combinatorial maps, for which we
develop the combinatorial machinery necessary for the asymptotic study.
Finally, we present some applications to the theory of random quantum states in
quantum information theory.
| arxiv topic:math.PR math-ph math.CO math.MP quant-ph |
arxiv_dataset-101781808.08654 | A fractional notion of length and an associated nonlocal curvature
math.DG
Here a new notion of fractional length of a smooth curve, which depends on a
parameter $\sigma$, is introduced that is analogous to the fractional perimeter
functional of sets that has been studied in recent years. It is shown that in
an appropriate limit the fractional length converges to the traditional notion
of length up to a multiplicative constant. Since a curve that connects two
points of minimal length must have zero curvature, the Euler--Lagrange equation
associated with the fractional length is used to motivate a nonlocal notion of
curvature for a curve. This is analogous to how the fractional perimeter has
been used to define a nonlocal mean curvature.
| arxiv topic:math.DG |
arxiv_dataset-101791808.08754 | What Makes Natural Scene Memorable?
cs.CV cs.AI
Recent studies on image memorability have shed light on the visual features
that make generic images, object images or face photographs memorable. However,
a clear understanding and reliable estimation of natural scene memorability
remain elusive. In this paper, we provide an attempt to answer: "what exactly
makes natural scene memorable". Specifically, we first build LNSIM, a
large-scale natural scene image memorability database (containing 2,632 images
and memorability annotations). Then, we mine our database to investigate how
low-, middle- and high-level handcrafted features affect the memorability of
natural scene. In particular, we find that high-level feature of scene category
is rather correlated with natural scene memorability. Thus, we propose a deep
neural network based natural scene memorability (DeepNSM) predictor, which
takes advantage of scene category. Finally, the experimental results validate
the effectiveness of DeepNSM.
| arxiv topic:cs.CV cs.AI |
arxiv_dataset-101801808.08854 | Binary additive MRD codes with minimum distance n-1 must contain a
semifield spread set
math.CO
In this paper we prove a result on the structure of the elements of an
additive {\it maximum rank distance (MRD) code} over the field of order two,
namely that in some cases such codes must contain a semifield spread set. We
use this result to classify additive MRD codes in $M_n(\mathbb{F}_2)$ with
minimum distance $n-1$ for $n\leq 6$. Furthermore we present a computational
classification of additive MRD codes in $M_4(\mathbb{F}_3)$. The computational
evidence indicates that MRD codes of minimum distance $n-1$ are much more rare
than MRD codes of minimum distance $n$, i.e. semifield spread sets. In all
considered cases, each equivalence class has a known algebraic construction.
| arxiv topic:math.CO |
arxiv_dataset-101811808.08954 | Behavior Trees as a Representation for Medical Procedures
cs.HC cs.AI
Objective: Effective collaboration between machines and clinicians requires
flexible data structures to represent medical processes and clinical practice
guidelines. Such a data structure could enable effective turn-taking between
human and automated components of a complex treatment, accurate on-line
monitoring of clinical treatments (for example to detect medical errors), or
automated treatment systems (such as future medical robots) whose overall
treatment plan is understandable and auditable by human experts.
Materials and Methods: Behavior trees (BTs) emerged from video game
development as a graphical language for modeling intelligent agent behavior.
BTs have several properties which are attractive for modeling medical
procedures including human-readability, authoring tools, and composability.
Results: This paper will illustrate construction of BTs for exemplary medical
procedures and clinical protocols.
Discussion and Conclusion: Behavior Trees thus form a useful, and human
authorable/readable bridge between clinical practice guidelines and AI systems.
| arxiv topic:cs.HC cs.AI |
arxiv_dataset-101821808.09054 | Measurements of gluon-gluon fusion and vector-boson fusion Higgs boson
production cross-sections in the $H \to WW^{\ast} \to e\nu\mu\nu$ decay
channel in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector
hep-ex
Higgs boson production cross-sections in proton-proton collisions are
measured in the $H \to WW^{\ast} \to e\nu\mu\nu$ decay channel. The
proton-proton collision data were produced at the Large Hadron Collider at a
centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and
2016, corresponding to an integrated luminosity of 36.1 fb$^{-1}$. The product
of the $H \to WW^{\ast}$ branching fraction times the gluon-gluon fusion and
vector-boson fusion cross-sections are measured to be $11.4 ^{+1.2}_{-1.1}
(\mathrm{stat.}) ^{+1.8}_{-1.7}(\mathrm{syst.})$ $\mathrm{pb}$ and $0.50
^{+0.24}_{-0.22} (\mathrm{stat.}) \pm 0.17(\mathrm{syst.})$ $\mathrm{pb}$,
respectively, in agreement with the Standard Model predictions.
| arxiv topic:hep-ex |
arxiv_dataset-101831808.09154 | MIMO-OFDM Scheme design for Medium Voltage Underground Cables based
Power Line Communication
cs.IT math.IT
Power line communication (PLC) provides intelligent electrical functions such
as power quality measurement, fault surveys, and remote control of electrical
network. However, most of research works have been done in low voltage (LV)
scenario due to the fast development of in-home PLC. The aim of this paper is
to design a MIMO-OFDM based transmission link under medium voltage (MV)
underground power line channel and evaluate the performance. The MIMO channel
is modeled as a modified multipath model in the presence of impulsive noise and
background noise. Unlike most literatures on MIMO power line transmission, we
adopt spatial multiplexing instead of diversity to increase the transmission
rate in this paper. The turbo coding method originally designed for LV power
line communication is used in the proposed transmission system. By comparing
the BER performance of MIMO-OFDM system with and without the turbo coding, we
evaluate its applicability in MV power line communication. The effect of
frequency band varying on the PLC system's performance is also investigated.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-101841808.09254 | Estimating seal pup production in the Greenland Sea using Bayesian
hierarchical modeling
stat.AP
The Greenland Sea is an important breeding ground for harp and hooded seals.
Estimates of the annual seal pup production are critical factors in the
abundance estimation needed for management of the species. These estimates are
usually based on counts from aerial photographic surveys. However, only a minor
part of the whelping region can be photographed, due to its large extent. To
estimate the total seal pup production, we propose a Bayesian hierarchical
modeling approach motivated by viewing the seal pup appearances as a
realization of a log-Gaussian Cox process using covariate information from
satellite imagery as a proxy for ice thickness. For inference, we utilize the
stochastic partial differential equation (SPDE) module of the integrated nested
Laplace approximation (INLA) framework. In a case study using survey data from
2012, we compare our results with existing methodology in a comprehensive
cross-validation study. The results of the study indicate that our method
improves local estimation performance, and that the increased prediction
uncertainty of our method is required to obtain calibrated count predictions.
This suggests that the sampling density of the survey design may not be
sufficient to obtain reliable estimates of the seal pup production.
| arxiv topic:stat.AP |
arxiv_dataset-101851808.09354 | Universal Dependency Parsing with a General Transition-Based DAG Parser
cs.CL
This paper presents our experiments with applying TUPA to the CoNLL 2018 UD
shared task. TUPA is a general neural transition-based DAG parser, which we use
to present the first experiments on recovering enhanced dependencies as part of
the general parsing task. TUPA was designed for parsing UCCA, a
cross-linguistic semantic annotation scheme, exhibiting reentrancy,
discontinuity and non-terminal nodes. By converting UD trees and graphs to a
UCCA-like DAG format, we train TUPA almost without modification on the UD
parsing task. The generic nature of our approach lends itself naturally to
multitask learning. Our code is available at
https://github.com/CoNLL-UD-2018/HUJI
| arxiv topic:cs.CL |
arxiv_dataset-101861808.09454 | Relating the HI Gas Structure of Spiral Disks to Passing Satellites
astro-ph.GA
We extend the work of Chang & Chakrabarti (2011) to find simple scaling
relations between the density response of the gas disk of a spiral galaxy and
the pericenter distance and mass ratio of a perturbing satellite. From the
analysis of results from a test particle code, we obtained a simple scaling
relation for the density response due to a single satellite interacting with a
galactic disk, over a wide range of satellite masses and pericenter distances.
We have also explored the effects of multiple satellites on the galactic disk,
focusing on cases that are commonly found in cosmological simulations. Here, we
use orbits for the satellites that are drawn from cosmological simulations. For
these cases, we compare our approximate scaling relations to the density
response generated by satellites, and find that for two satellite interactions,
our scaling relations approximately recover the response of the galactic disk.
We have also examined the observed HI data in the outskirts of several spiral
galaxies from the THINGS sample and compared the observed perturbations to that
of cosmological simulations and our own scaling relations. While small
perturbations can be excited by satellites drawn from cosmological simulations,
we find that large perturbations (such as those that are seen in some THINGS
galaxies like M51) are not recovered by satellites drawn from cosmological
simulations that are similar to Milky Way galaxies.
| arxiv topic:astro-ph.GA |
arxiv_dataset-101871808.09554 | Investigating the possibility of reversing giant planet migration via
gap edge illumination
astro-ph.EP
A massive planet in a protoplanetary disc will open a gap in the disc
material which acts as a transition between Type I and Type II planetary
migration. Type II migration is slower than Type I migration, however it is
still desirable to slow down Type II migration to allow gas giant planets with
semi-major axis in the range 5 to 10AU to exist, similarly to our Solar system.
We investigate a method of slowing down and reversing Type II migration by
heating the outer gap edge due to incident radiation from the central star.
Using an approximate vertically averaged heating method we find that Type II
migration can be slowed or in extreme cases reversed if we assume near maximum
allowed irradiation from the central star. Therefore, we believe this is a very
interesting phenomenon that should be investigated in greater detail using
three dimensional hydrodynamic and radiative transfer simulations.
| arxiv topic:astro-ph.EP |
arxiv_dataset-101881808.09654 | Generalized Solitary Waves in a Finite-Difference Korteweg-de Vries
Equation
math-ph math.MP
Generalized solitary waves with exponentially small non-decaying far field
oscillations have been studied in a range of singularly-perturbed differential
equations, including higher-order Korteweg-de Vries (KdV) equations. Many of
these studies used exponential asymptotics to compute the behaviour of the
oscillations, revealing that they appear in the solution as special curves
known as Stokes lines are crossed. Recent studies have identified similar
behaviour in solutions to difference equations. Motivated by these studies, the
seventh-order KdV and a hierarchy of higher-order KdV equations are
investigated, identifying conditions which produce generalized solitary wave
solutions. These results form a foundation for the study of infinite-order
differential equations, which are used as a model for studying lattice
equations. Finally, a lattice KdV equation is generated using finite-difference
discretization, in which a lattice generalized solitary wave solution is found.
| arxiv topic:math-ph math.MP |
arxiv_dataset-101891808.09754 | Singular Support of Minimizers of the Causal Variational Principle on
the Sphere
math.CA math-ph math.FA math.MP
The support of minimizing measures of the causal variational principle on the
sphere is analyzed. It is proven that in the case $\tau>\sqrt{3}$, the support
of every minimizing measure is contained in a finite number of real analytic
curves which intersect at a finite number of points. In the case
$\tau>\sqrt{6}$, the support is proven to have Hausdorff dimension at most
$6/7$.
| arxiv topic:math.CA math-ph math.FA math.MP |
arxiv_dataset-101901808.09854 | Quantization of Poisson CGL extensions
math.QA
CGL extensions, named after G. Cauchon, K. Goodearl, and E. Letzter, are a
special class of noncommutative algebras that are iterated Ore extensions of
associative algebras with compatible torus actions. Examples of CGL extensions
include quantum Schubert cells and quantized coordinate rings of double Bruhat
cells. CGL extensions have been studied extensively in connection with quantum
groups and quantum cluster algebras. For a field $\mathbf{k}$ of characteristic
$0$, let $L=\mathbf{k}[q^{\pm 1}]$ be the $\mathbf{k}$-algebra of Laurent
polynomials in the single variable $q$ and let $\mathbb{K}=\mathbf{k}(q)$ be
the fraction field of $L$. We introduce quantum-CGL extensions as certain
$L$-forms of CGL extensions over $\mathbb{K}$, which have Poisson-CGL
extensions as their semiclassical limits. Poisson-CGL extensions, recently
introduced and systematically studied by K. Goodearl and M. Yakimov, are
certain Poisson polynomial algebras which admit presentations as iterated
Poisson-Ore extensions with compatible torus actions. Examples of Poisson-CGL
extensions include the coordinate rings of matrix affine Poisson spaces and
more generally those of Schubert cells. We describe an explicit procedure for
constructing a symmetric quantum-CGL extension from a symmetric integral
Poisson-CGL extension and establish the uniqueness of such a quantization in a
proper sense.
| arxiv topic:math.QA |
arxiv_dataset-101911808.09954 | The Star-Planet Activity Research CubeSat (SPARCS): A Mission to
Understand the Impact of Stars in Exoplanets
astro-ph.IM astro-ph.EP astro-ph.SR
The Star-Planet Activity Research CubeSat (SPARCS) is a NASA-funded
astrophysics mission, devoted to the study of the ultraviolet (UV) time-domain
behavior in low-mass stars. Given their abundance and size, low-mass stars are
important targets in the search for habitable-zone, exoplanets. However, not
enough is known about the stars flare and quiescent emission, which powers
photochemical reactions on the atmospheres of possible planets. Over its
initial 1-year mission, SPARCS will stare at ~10 stars in order to measure
short- (minutes) and long- (months) term variability simultaneously in the
near-UV (NUV - lam = 280 nm) and far-UV (FUV - lam = 162 nm). The SPARCS
payload consists of a 9-cm reflector telescope paired with two high-sensitivity
2D-doped CCDs. The detectors are kept passively cooled at 238K, in order to
reduce dark-current contribution. The filters have been selected to provide
strong rejection of longer wavelengths, where most of the starlight is emitted.
The payload will be integrated within a 6U CubeSat to be placed on a
Sun-synchronous terminator orbit, allowing for long observing stares for all
targets. Launch is expected to occur not earlier than October 2021.
| arxiv topic:astro-ph.IM astro-ph.EP astro-ph.SR |
arxiv_dataset-101921808.10054 | Frequency comb up- and down-conversion in a synchronously-driven
$\chi^{(2)}$ optical microresonator
physics.optics
Optical frequency combs are key to optical precision measurements. While most
frequency combs operate in the near-infrared regime, many applications require
combs at mid-infrared, visible or even ultra-violet wavelengths. Frequency
combs can be transferred to other wavelengths via nonlinear optical processes,
however, this becomes exceedingly challenging for high-repetition rate
frequency combs. Here, it is demonstrated that a synchronously driven high-Q
microresonator with a second-order optical nonlinearity can efficiently convert
high-repetition rate near-infrared frequency combs to visible, ultra-violet and
mid-infrared wavelengths providing new opportunities for microresonator and
electro-optic combs in applications including molecular sensing, astronomy, and
quantum optics.
| arxiv topic:physics.optics |
arxiv_dataset-101931808.10154 | Convergence of dynamic programming principles for the $p$-Laplacian
math.AP cs.NA math.NA
We provide a unified strategy to show that solutions of dynamic programming
principles associated to the $p$-Laplacian converge to the solution of the
corresponding Dirichlet problem. Our approach includes all previously known
cases for continuous and discrete dynamic programming principles, provides new
results, and gives a convergence proof free of probability arguments.
| arxiv topic:math.AP cs.NA math.NA |
arxiv_dataset-101941808.10254 | Short-term variability and mass loss in Be stars IV. Two groups of
closely spaced, approximately equidistant frequencies in three decades of
space photometry of $\nu$ Puppis (B7-8 IIIe)
astro-ph.SR
In early-type Be stars, groups of nonradial pulsation (NRP) modes with
numerically related frequencies may be instrumental for the release of excess
angular momentum through mass-ejection events. Difference and sum/harmonic
frequencies often form additional groups. The goal of this study is to find out
whether a similar frequency pattern occurs in the cooler third-magnitude
B7-8\,IIIe shell star $\nu$ Pup. Time-series analyses are performed of space
photometry with BRITE-Constellation (2015, 2016/17, and 2017/18), SMEI
(2003--011), and Hipparcos (1989-1993). Two IUE SWP and 27 optical echelle
spectra spanning 20 years were retrieved from various archives. The optical
spectra exhibit no anomalies or well-defined variabilities. A magnetic field
was not detected. All three photometry satellites recorded variability near
0.656 c/d which is resolved into three features separated by ~0.0021 c/d. First
harmonics form a second frequency group, also spaced by ~0.0021 c/d. The
frequency spacing is very nearly but not exactly equidistant. Variability near
0.0021 c/d was not detected. The long-term frequency stability could be used to
derive meaningful constraints on the properties of a putative companion star.
The IUE spectra do not reveal the presence of a hot subluminous secondary.
$\nu$\,Pup is another Be star exhibiting an NRP variability pattern with
long-term constancy and underlining the importance of combination frequencies
and frequency groups. The star is a good target for efforts to identify an
effectively single Be star.
| arxiv topic:astro-ph.SR |
arxiv_dataset-101951808.10354 | Valence Quark Transversity at Small $x$
hep-ph nucl-th
In our previous work we established a formalism which allows one to determine
the small-$x$ asymptotics of any transverse momentum-dependent parton
distribution function (TMD PDF) of the proton at small values of strong
coupling. In this paper we apply this formalism to the valence quark
transversity TMD. We relate the valence quark transversity to the transversely
polarized dipole scattering amplitude, written in terms of the fundamental
transversely-polarized "Wilson line" operator, an expression for which we
derive explicitly as well. We then write down the evolution equation for the
transversely polarized dipole amplitude. Solving that equation we arrive at the
following small-$x$ asymptotics of the valence quark transversity in the
large-$N_c$ limit: \begin{align} h_{1T}^v (x, k_T^2) \sim h_{1T}^{\perp \, v}
(x, k_T^2) \sim \left( \frac{1}{x} \right)^{-1 + 2 \, \sqrt{\frac{\alpha_s \,
N_c}{2 \, \pi}} } . \notag \end{align} This result is in agreement with one of
the two possible small-$x$ asymptotics for the transverse structure function
found previously by Kirschner, Mankiewicz, Sch\"{a}fer, and Szymanowski.
| arxiv topic:hep-ph nucl-th |
arxiv_dataset-101961808.10454 | The Outer Stellar Halos of Galaxies: how Radial Merger Mass Deposition,
Shells and Streams depend on Infall-Orbit Configurations
astro-ph.GA
Galaxy mergers are a fundamental part of galaxy evolution. To study the
resulting mass distributions of different kinds of galaxy mergers, we present a
simulation suite of 36 high-resolution isolated merger simulations, exploring a
wide range of parameter space in terms of mass ratios (mu = 1:5, 1:10, 1:50,
1:100) and orbital parameters. We find that mini mergers deposit a higher
fraction of their mass in the outer halo compared to minor mergers, while their
contribution to the central mass distribution is highly dependent on the
orbital impact parameter: for larger pericentric distances we find that the
centre of the host galaxy is almost not contaminated by merger particles. We
also find that the median of the resulting radial mass distribution for mini
mergers differs significantly from the predictions of simple theoretical
tidal-force models. Furthermore, we find that mini mergers can increase the
size of the host disc significantly without changing the global shape of the
galaxy, if the impact occurs in the disc plane, thus providing a possible
explanation for extended low-surface brightness disks reported in observations.
Finally, we find clear evidence that streams are a strong indication of nearly
circular infall of a satellite (with large angular momentum), whereas the
appearance of shells clearly points to (nearly) radial satellite infall.
| arxiv topic:astro-ph.GA |
arxiv_dataset-101971808.10554 | Absence of $D^4 R^4$ in M-Theory From ABJM
hep-th
Supersymmetry allows a $D^4 R^4$ interaction in M-theory, but such an
interaction is inconsistent with string theory dualities and so is known to be
absent. We provide a novel proof of the absence of the $D^4 R^4$ M-theory
interaction by calculating 4-point scattering amplitudes of 11d supergravitons
from ABJM theory. This calculation extends a previous calculation performed to
the order corresponding to the $R^4$ interaction. The new ingredient in this
extension is the interpretation of the fourth derivative of the mass deformed
$S^3$ partition function of ABJM theory, which can be determined using
supersymmetric localization, as a constraint on the Mellin amplitude associated
with the stress tensor multiplet 4-point function. As part of this computation,
we relate the 4-point function of the superconformal primary of the stress
tensor multiplet of any 3d ${\cal N} = 8$ SCFT to some of the 4-point functions
of its superconformal descendants. We also provide a concise formula for a
general integrated 4-point function on $S^d$ for any $d$.
| arxiv topic:hep-th |
arxiv_dataset-101981808.10654 | Gibson Env: Real-World Perception for Embodied Agents
cs.AI cs.CV cs.GR cs.LG cs.RO
Developing visual perception models for active agents and sensorimotor
control are cumbersome to be done in the physical world, as existing algorithms
are too slow to efficiently learn in real-time and robots are fragile and
costly. This has given rise to learning-in-simulation which consequently casts
a question on whether the results transfer to real-world. In this paper, we are
concerned with the problem of developing real-world perception for active
agents, propose Gibson Virtual Environment for this purpose, and showcase
sample perceptual tasks learned therein. Gibson is based on virtualizing real
spaces, rather than using artificially designed ones, and currently includes
over 1400 floor spaces from 572 full buildings. The main characteristics of
Gibson are: I. being from the real-world and reflecting its semantic
complexity, II. having an internal synthesis mechanism, "Goggles", enabling
deploying the trained models in real-world without needing further domain
adaptation, III. embodiment of agents and making them subject to constraints of
physics and space.
| arxiv topic:cs.AI cs.CV cs.GR cs.LG cs.RO |
arxiv_dataset-101991808.10754 | Deep Reinforcement Learning achieves flow control of the 2D Karman
Vortex Street
physics.flu-dyn
The Karman Vortex Street has been investigated for over a century and offers
a reference case for investigation of flow stability and control of high
dimensionality, non-linear systems. Active flow control, while of considerable
interest from a theoretical point of view and for industrial applications, has
remained inaccessible due to the difficulty in finding successful control
strategies. Here we show that Deep Reinforcement Learning can achieve a stable
active control of the Karman vortex street behind a two-dimensional cylinder.
Our results show that Deep Reinforcement Learning can be used to design active
flow controls and is a promising tool to study high dimensionality, non-linear,
time dependent dynamic systems present in a wide range of scientific problems.
| arxiv topic:physics.flu-dyn |
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