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arxiv_dataset-102001808.10854 | Forecasting solar radiation during dust storms using deep learning
physics.ao-ph physics.data-an
Dust storms are common in arid zones on the earth and others planets such as
Mars. The impact of dust storms on solar radiation has significant implications
for solar power plants and autonomous vehicles powered by solar panels. This
paper deals with the analysis of solar radiation and power output of a rooftop
photovoltaic plant during a dust storm and proposes a forecasting methodology
using deep learning network. The increased aerosol content due to dust storms
increases the diffuse component of the solar radiation. This effect persists
for a long duration and can impact the quality of forecasting of solar
radiation. Deep learning networks that capture long range structure can improve
the quality of solar radiation forecasting during dust storms. These results
can help explain the sudden drop in power output of solar plants due to dust
storms originating in another continent. They can shed light on mysterious
cleaning events in autonomous vehicles powered by solar panels to be used in
space missions.
| arxiv topic:physics.ao-ph physics.data-an |
arxiv_dataset-102011809.00084 | Understanding Neural Pathways in Zebrafish through Deep Learning and
High Resolution Electron Microscope Data
cs.CV
The tracing of neural pathways through large volumes of image data is an
incredibly tedious and time-consuming process that significantly encumbers
progress in neuroscience. We are exploring deep learning's potential to
automate segmentation of high-resolution scanning electron microscope (SEM)
image data to remove that barrier. We have started with neural pathway tracing
through 5.1GB of whole-brain serial-section slices from larval zebrafish
collected by the Center for Brain Science at Harvard University. This kind of
manual image segmentation requires years of careful work to properly trace the
neural pathways in an organism as small as a zebrafish larva (approximately 5mm
in total body length). In automating this process, we would vastly improve
productivity, leading to faster data analysis and breakthroughs in
understanding the complexity of the brain. We will build upon prior attempts to
employ deep learning for automatic image segmentation extending methods for
unconventional deep learning data.
| arxiv topic:cs.CV |
arxiv_dataset-102021809.00184 | A Symplectic Interpretation of the Separability of Gaussian Mixed States
quant-ph math-ph math.MP math.OA math.SG
We prove, using symplectic methods and The Wigner formalism, a refinement of
a criterion due to Werner and Wolf for the separability of bipartite Gaussian
mixed states in an arbitrary number of dimensions. We use our result to show
that one can characterize separability by comparing these states with separable
pure Gaussian states.
| arxiv topic:quant-ph math-ph math.MP math.OA math.SG |
arxiv_dataset-102031809.00284 | New Characterizations of Musielak-Orlicz-Sobolev Spaces via Sharp Ball
Averaging Functions
math.CA math.AP math.FA
In this article, the authors establish a new characterization of the
Musielak--Orlicz--Sobolev space on $\mathbb{R}^n$, which includes the classical
Orlicz--Sobolev space, the weighted Sobolev space and the variable exponent
Sobolev space as special cases, in terms of sharp ball averaging functions.
Even in a special case, namely, the variable exponent Sobolev space, the
obtained result in this article improves the corresponding result obtained by
P. H\"ast\"o and A. M. Ribeiro [Commun. Contemp. Math. 19 (2017), 1650022, 13
pp] via weakening the assumption $f\in L^1(\mathbb R^n)$ into $f\in
L_{\mathrm{loc}}^1(\mathbb R^n)$, which was conjectured to be true by H\"ast\"o
and Ribeiro in the aforementioned same article.
| arxiv topic:math.CA math.AP math.FA |
arxiv_dataset-102041809.00384 | Soft anomalous dimension matrices in heavy quark-antiquark
hadroproduction in association with a gluon jet
hep-ph
We compute the soft anomalous dimension (SAD) matrices for production of
massive quarks $Q$ and $\bar{Q}$ in association with a gluon jet, from massless
quarks $q$ and antiquarks $\bar{q}$: $q\bar{q}\rightarrow Q\bar{Q}g$, and in
the gluon scattering $gg\rightarrow Q\bar{Q}g$. To analyze the behaviour of the
eigenvalues of SAD matrices we perform numerical studies of their eigensystems
at two special kinematical configurations.
| arxiv topic:hep-ph |
arxiv_dataset-102051809.00484 | Global search for localised modes in scalar and vector nonlinear
Schr\"odinger-type equations
nlin.PS physics.optics
We present a new approach for search of coexisting classes of localised modes
admitted by the repulsive (defocusing) scalar or vector nonlinear
Schr\"odinger-type equations. The approach is based on the observation that
generic solutions of the corresponding stationary system have singularities at
finite points on the real axis. We start with establishing conditions on the
initial data of the associated Cauchy problem that guarantee the formation of a
singularity. Making use of these sufficient conditions, we identify the
bounded, nonsingular, solutions --- and then classify them according to their
asymptotic behaviour. To determine the bounded solutions, a properly chosen
space of initial data is scanned numerically. Due to asymptotic or symmetry
considerations, we can limit ourselves to a one- or two-dimensional space. For
each set of initial conditions we compute the distances $X^{\pm}$ to the
nearest forward and backward singularities; large $X^+$ or $X^-$ indicate the
proximity to a bounded solution. We illustrate our method with the
Gross-Pitaevskii equation with a $\PT$-symmetric complex potential, a system of
coupled Gross-Pitaevskii equations with real potentials, and the
Lugiato-Lefever equation with normal dispersion.
| arxiv topic:nlin.PS physics.optics |
arxiv_dataset-102061809.00584 | The multidimensional truncated Moment Problem: The Moment Cone
math.FA math.AG math.OC
Let $\mathsf{A}=\{a_1,\dots,a_m\}$, $m\in\mathbb{N}$, be measurable functions
on a measurable space $(\mathcal{X},\mathfrak{A})$. If $\mu$ is a positive
measure on $(\mathcal{X},\mathfrak{A})$ such that $\int a_i d\mu<\infty$ for
all $i$, then the sequence $(\int a_1 d\mu,\dots,\int a_m d\mu)$ is called a
moment sequence. By Richter's Theorem each moment sequence has a $k$-atomic
representing measure with $k\leq m$. The set $\mathcal{S}_\mathsf{A}$ of all
moment sequences is the moment cone.
The aim of this paper is to analyze the various structures of the moment
cone. The main results concern the facial structure (exposed faces, facial
dimensions) and lower and upper bounds of the Carath\'eodory number (that is,
the smallest number of atoms which suffices for all moment sequences) of the
convex cone $\mathcal{S}_{\mathcal{A}}$. In the case when $\mathcal{X}\subseteq
\mathbb{R}^n$ and $a_i\in C^1(\mathcal{X},\mathbb{R})$, the differential
structure of the moment map and regularity/singularity properties of moment
sequences are analyzed. The maximal mass problem is considered and some
applications to other problems are sketched.
| arxiv topic:math.FA math.AG math.OC |
arxiv_dataset-102071809.00684 | Linear structure of functions with maximal Clarke subdifferential
math.FA
It is hereby established that the set of Lipschitz functions
$f:\mathcal{U}\rightarrow \mathbb{R}$ ($\mathcal{U}$ nonempty open subset of
$\ell_{d}^{1}$) with maximal Clarke subdifferential contains a linear subspace
of uncountable dimension (in particular, an isometric copy of
$\ell^{\infty}(\mathbb{N})$). This result goes in the line of a previous result
of Borwein-Wang. However, while the latter was based on Baire category theorem,
our current approach is constructive and is not linked to the uniform
convergence. In particular we establish lineability (and spaceability for the
Lipschitz norm) of the above set inside the set of all Lipschitz continuous
functions.
| arxiv topic:math.FA |
arxiv_dataset-102081809.00784 | Quantum charge pumping through Majorana bound states
cond-mat.mes-hall
We study adiabatic charge pumping through a Majorana bound state tunnel
coupled to multiple normal leads. We show that for most of the parameters such
a pump does not lead to any net pumped charge between the various leads unless
a multiply connected geometry is implemented. We introduce an Aharonov-Bohm
ring geometry at the junction to implement such a multiply connected geometry.
We further show that the Fourier transform of the pumped charge with respect to
flux inserted through the ring shows a clear distinction between the case of an
Andreev bound state and the Majorana bound state. Hence such a Fourier analysis
can serve as a diagnostic for the detection of Majorana bound states in the
proposed geometry.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-102091809.00884 | Absolute parameters and period variation in a semidetached eclipsing
variable V2247 Cyg
astro-ph.SR
We aim to determine the absolute parameters of the components of a poorly
studied Algol-type eclipsing binary V2247 Cyg. The data analysis is based on
our numerous precise UBVRcIc photometric observations and low resolution
spectra. The photometric solution reveals a semi-detached configuration with a
less-massive component filling its Roche lobe. The mass ratio, inclination,
effective temperatures, and fractional radii were determined. Masses and radii
of the components were obtained by a non-direct method. The Eclipse Time
Variation (ETV) diagram revealed the period changes.
| arxiv topic:astro-ph.SR |
arxiv_dataset-102101809.00984 | The materials data ecosystem: materials data science and its role in
data-driven materials discovery
cs.CY
Since its launch in 2011, Materials Genome Initiative (MGI) has drawn the
attention of researchers from across academia, government, and industry
worldwide.As one of the three tools of MGI, the materials data, for the first
time, emerged as an extremely significant approach in materials discovery. Data
science has been applied in different disciplines as an interdisciplinary field
to extract knowledge from the data. The concept of materials data science was
utilized to demonstrate the data application in materials science. To explore
its potential as an active research branch in the big data age, a three-tier
system was put forward to define the infrastructure of data classification,
curation and knowledge extraction of materials data.
| arxiv topic:cs.CY |
arxiv_dataset-102111809.01084 | Energy Efficient Resource Allocation for Mobile-Edge Computation
Networks with NOMA
eess.SP
This paper investigates an uplink non-orthogonal multiple access (NOMA)-based
mobile-edge computing (MEC) network. Our objective is to minimize the total
energy consumption of all users including transmission energy and local
computation energy subject to computation latency and cloud computation
capacity constraints. We first prove that the total energy minimization problem
is a convex problem, and it is optimal to transmit with maximal time. Then, we
accordingly proposed an iterative algorithm with low complexity, where
closed-form solutions are obtained in each step. The proposed algorithm is
successfully shown to be globally optimal. Numerical results show that the
proposed algorithm achieves better performance than the conventional methods.
| arxiv topic:eess.SP |
arxiv_dataset-102121809.01184 | Quantifier-free description of the solutions set of the generalized
interval-quantifier system of linear equations
math.OC
A quantifier-free description of the set of solutions of the generalized
interval-quantifier system of linear equations is obtain.
| arxiv topic:math.OC |
arxiv_dataset-102131809.01284 | Heavy Bernoulli-percolation clusters are indistinguishable
math.PR
We prove that the heavy clusters are indistinguishable for Bernoulli
percolation on quasi-transitive nonunimodular graphs. As an application, we
show that the uniqueness threshold of any quasi-transitive graph is also the
threshold for connectivity decay. This resolves a question of Lyons and Schramm
(1999) in the Bernoulli percolation case and confirms a conjecture of Schonmann
(2001). We also prove that every infinite cluster of Bernoulli percolation on a
nonamenable quasi-transitive graph is transient almost surely.
| arxiv topic:math.PR |
arxiv_dataset-102141809.01384 | Counting Consecutive Pattern Matches in $\mathcal{S}_n(132)$ and
$\mathcal{S}_n(123)$
math.CO
In this paper, we study the distribution of consecutive patterns in the set
of 123-avoiding permutations and the set of 132-avoiding permutations, that is,
in $\mathcal{S}_n(123)$ and $\mathcal{S}_n(132)$. We first study the
distribution of consecutive pattern $\gamma$-matches in $\mathcal{S}_n(123)$
and $\mathcal{S}_n(132)$ for each length 3 consecutive pattern $\gamma$. Then
we extend our methods to study the joint distributions of multiple consecutive
patterns. Some more general cases are discussed in this paper as well.
| arxiv topic:math.CO |
arxiv_dataset-102151809.01484 | Multiple vector bundles: cores, splittings and decompositions
math.DG
This paper introduces $\infty$- and $n$-fold vector bundles as special
functors from the $\infty$- and $n$-cube categories to the category of smooth
manifolds. We study the cores and "n-pullbacks" of $n$-fold vector bundles and
we prove that any $n$-fold vector bundle admits a non-canonical isomorphism to
a decomposed $n$-fold vector bundle. A colimit argument then shows that
$\infty$-fold vector bundles admit as well non-canonical decompositions. For
the convenience of the reader, the case of triple vector bundles is discussed
in detail.
| arxiv topic:math.DG |
arxiv_dataset-102161809.01584 | Calibration of the oscillation amplitude of electrically excited
scanning probe microscopy sensors
physics.app-ph
Atomic force microscopy (AFM) is an analytical surface characterization tool
which can reveal a sample's topography with high spatial resolution while
simultaneously probing tip-sample interactions. Local measurement of chemical
properties with high-resolution has gained much popularity in recent years with
advances in dynamic AFM methodologies. A calibration factor is required to
convert the electrical readout to a mechanical oscillation amplitude in order
to extract quantitative information about the surface. We propose a new
calibration technique for the oscillation amplitude of electrically driven
probes, which is based on measuring the electrical energy input to maintain the
oscillation amplitude constant. We demonstrate the application of the new
technique with quartz tuning fork including the qPlus configuration, while the
same principle can be applied to other piezoelectric resonators such as length
extension resonators, or piezoelectric cantilevers. The calibration factor
obtained by this technique is found to be in agreement with using thermal noise
spectrum method for capsulated, decapsulated tuning forks and tuning forks in
the qPlus configuration.
| arxiv topic:physics.app-ph |
arxiv_dataset-102171809.01684 | On the origin of gas-poor galaxies in galaxy clusters using cosmological
hydrodynamic simulations
astro-ph.GA
The environmental effect is commonly used to explain the excess of gas-poor
galaxies in galaxy clusters. Meanwhile, the presence of gas-poor galaxies at
cluster outskirts, where galaxies have not spent enough time to feel the
cluster environmental effect, hints for the presence of pre-processing. Using
cosmological hydrodynamic simulations on 16 clusters, we investigate the
mechanisms of gas depletion of galaxies found inside clusters. The gas
depletion mechanisms can be categorized into three channels based on where and
when they took place. First, 34$\%$ of our galaxies are gas poor before
entering clusters (`pre-processing'). They are mainly satellites that have
undergone the environmental effect inside group halos. Second, 43$\%$ of the
sample became quickly gas deficient in clusters before the first pericentric
pass (`fast cluster processing'). Some of them were group satellites that are
low in gas at the time of cluster entry compared to the galaxies directly
coming from the field. Even the galaxies with large gas fractions take this
channel if they fall into massive clusters ($> 10^{14.5}\, \rm M_{\odot}$) or
approach cluster centers through radial orbits. Third, 24$\%$ of our sample
retain gas even after their first pericentric pass (`slow cluster processing')
as they fall into the less massive clusters and/or have circular orbits. The
relative importance of each channel varies with a cluster's mass, while the
exact degree of significance is subject to large uncertainties. Group
pre-processing accounts for a third of the total gas depletion; but it also
determines the gas fraction of galaxies at their cluster entry which in turn
determines whether a galaxy should take the fast or the slow cluster
processing.
| arxiv topic:astro-ph.GA |
arxiv_dataset-102181809.01784 | Synthetic direct demodulation method and its applications in
Insight-HXMT data analysis
astro-ph.IM
Aims. A modulation equation relates the observed data to the object where the
observation is approximated by a linear system. Reconstructing the object from
the observed data is therefore is equivalent to solving the modulation
equation. In this work we present the synthetic direct demodulation (synDD)
method to reduce the dimensionality of a general modulation equation and solve
the equation in its sparse representation.
Methods. A principal component analysis is used to reduce the dimensionality
of the kernel matrix and k-means clustering is applied to its sparse
representation in order to decompose the kernel matrix into a weighted sum of a
series of circulant matrices. The matrix- vector and matrix-matrix
multiplication complexities are therefore reduced from polynomial time to
linear-logarithmic time. A general statistical solution of the modulation
equation in sparse representation is derived. Several data-analysis pipelines
are designed for the Hard X-ray modulation Telescope (Insight-HXMT) based on
the synDD method.
Results. In this approach, a large set of data originating from the same
object but sampled irregularly and/or observed with different instruments in
multiple epochs can be reduced simultaneously in a synthetic observation model.
We suggest using the proposed synDD method in Insight-HXMT data analysis
especially for the detection of X-ray transients and monitoring time-varying
objects with scanning observations.
| arxiv topic:astro-ph.IM |
arxiv_dataset-102191809.01884 | Time series photopolarimetry and modelling of the white dwarf pulsar in
AR Scorpii
astro-ph.HE
We present detailed optical photo-polarimetric observations of the
recently-discovered white dwarf pulsar AR Scorpii. Our extensive dataset
reveals that the polarized emission is remarkably stable and repeatable with
spin, beat and orbital modulations. This has enabled us to construct a simple
geometrical model which assumes that all of the optically polarized emission
emanates from two diametrically opposed synchrotron emission regions on the
white dwarf magnetosphere. We suggest that the observed polarimetric
modulations occur as a result of an enhanced injection of relativistic
electrons into the magnetosphere of the white dwarf as it sweeps past the
M-dwarf. This leads to an increase in synchrotron emission as the injected
electrons accelerate towards each magnetic mirror point close to the magnetic
poles of the white dwarf. Whilst this scenario reproduces the detailed
polarimetric modulations, other suggested scenarios involving emission sites
locked in the white dwarf rotating frame are not ruled out. For example,
pulsar-like particle acceleration as a result of either electric potentials
between the white dwarf and the light cylinder or a striped relativistic
magnetohydrodynamic wind, outside the light cylinder. Previous conclusions that
argued that the observed strong optical beat modulations require that the
optical polarization arises predominantly from or near the M-dwarf are
inconsistent with our observations.
| arxiv topic:astro-ph.HE |
arxiv_dataset-102201809.01984 | Training Millions of Personalized Dialogue Agents
cs.CL
Current dialogue systems are not very engaging for users, especially when
trained end-to-end without relying on proactive reengaging scripted strategies.
Zhang et al. (2018) showed that the engagement level of end-to-end dialogue
models increases when conditioning them on text personas providing some
personalized back-story to the model. However, the dataset used in Zhang et al.
(2018) is synthetic and of limited size as it contains around 1k different
personas. In this paper we introduce a new dataset providing 5 million personas
and 700 million persona-based dialogues. Our experiments show that, at this
scale, training using personas still improves the performance of end-to-end
systems. In addition, we show that other tasks benefit from the wide coverage
of our dataset by fine-tuning our model on the data from Zhang et al. (2018)
and achieving state-of-the-art results.
| arxiv topic:cs.CL |
arxiv_dataset-102211809.02084 | Inferring broken detailed balance in the absence of observable currents
cond-mat.stat-mech
Identifying dissipation is essential for understanding the physical
mechanisms underlying nonequilibrium processes. {In living systems, for
example, the dissipation is directly related to the hydrolysis of fuel
molecules such as adenosine triphosphate (ATP)}. Nevertheless, detecting broken
time-reversal symmetry, which is the hallmark of dissipative processes, remains
a challenge in the absence of observable directed motion, flows, or fluxes.
Furthermore, quantifying the entropy production in a complex system requires
detailed information about its dynamics and internal degrees of freedom. Here
we introduce a novel approach to detect time irreversibility and estimate the
entropy production from time-series measurements, even in the absence of
observable currents. We apply our technique to two different physical systems,
namely, a partially hidden network and a molecular motor. Our method does not
require complete information about the system dynamics and thus provides a new
tool for studying nonequilibrium phenomena.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-102221809.02184 | The Albedos, Sizes, Colors and Satellites of Dwarf Planets Compared with
Newly Measured Dwarf Planet 2013 FY27
astro-ph.EP astro-ph.IM astro-ph.SR
2013 FY27 is the ninth intrinsically brightest Trans-Neptunian Object (TNO).
We observed 2013 FY27 at thermal wavelengths with ALMA and in the optical with
Magellan to determine its size and albedo for the first time and compare it to
other dwarf planets. The geometric albedo of 2013 FY27 was found to be 0.17
-0.030+0.045, giving an effective diameter of D = 765 +80-85 km. 2013 FY27 has
a size within the transition region between the largest few TNOs that have
higher albedos and higher densities than smaller TNOs. No significant
short-term optical light curve was found, with variations less than 0.06 mags
over hours and days. The Sloan optical colors of 2013 FY27 are g-r=0.76 +-0.02
and r-i=0.31 +-0.03 mags, which is a moderately red color. This color is
different than the neutral or ultra-red colors found for the ten largest TNOs,
making 2013 FY27 one of the largest known moderately red TNOs, which only start
to be seen, and in abundance, at diameters less than 800 km. This suggests
something physically different might be associated with TNOs larger than 800
km. It could be that moderately red surfaces are older or less ice rich and
TNOs larger than 800 km have fresher surfaces or are able to hold onto more
volatile ices. Its also possible TNOs larger than 800 km are more fully
differentiated, giving them different surface compositions. A satellite at 0.17
arcsec away and 3.0 +-0.2 mags fainter than 2013 FY27 was found through Hubble
Space Telescope observations. Almost all the largest TNOs have satellites, and
the relative small size of 2013 FY27's satellite suggests it was created
through a direct collision, similar to satellites known around the largest
TNOs. Assuming the satellite has a similar albedo as the primary, it is about
190 km in diameter, making the primary D = 740 +85-90 km.
| arxiv topic:astro-ph.EP astro-ph.IM astro-ph.SR |
arxiv_dataset-102231809.02284 | Ergodicity of partially hyperbolic diffeomorphisms in hyperbolic
3-manifolds
math.DS math.GT
We study conservative partially hyperbolic diffeomorphisms in hyperbolic
3-manifolds. We show that they are always accessible and deduce as a result
that every conservative $C^{1+}$ partially hyperbolic in a hyperbolic
3-manifold must be ergodic, giving an afirmative answer to a conjecture of
Hertz-Hertz-Ures in the context of hyperbolic 3-manifolds. Some of the
intermediary steps are also done for general partially hyperbolic
diffeomorphisms homotopic to the identity.
| arxiv topic:math.DS math.GT |
arxiv_dataset-102241809.02384 | Involutive operator algebras
math.OA math-ph math.FA math.MP
Examples of operator algebras with involution include the operator
$*$-algebras occurring in noncommutative differential geometry studied recently
by Mesland, Kaad, Lesch, and others, several classical function algebras,
triangular matrix algebras, (complexifications) of real operator algebras, and
an operator algebraic version of the {\em complex symmetric} operators studied
by Garcia, Putinar, Wogen and others. We investigate the general theory of
involutive operator algebras, and give many applications.
| arxiv topic:math.OA math-ph math.FA math.MP |
arxiv_dataset-102251809.02484 | Presentations of non-commutative deformation rings via
$A_\infty$-algebras and applications to deformations of Galois
representations and pseudorepresentations
math.NT math.AG math.RA math.RT
We introduce an $A_\infty$-algebra structure on the Hochschild cohomology of
the endomorphism bimodule of a finite-dimensional representation of an
associative algebra. We prove that this structure determines a presentation for
non-commutative deformations of the representation. From this, we deduce
presentations of universal deformation rings of Galois representations. In
turn, we apply these presentations in order to deduce universal deformation
rings of Galois pseudorepresentations, supplying a a tangent and obstruction
theory for pseudorepresentations. This generalizes the broadly used tangent and
obstruction theory for Galois representations. We also give applications,
calculating the ranks of certain Hecke algebras.
| arxiv topic:math.NT math.AG math.RA math.RT |
arxiv_dataset-102261809.02584 | Galois representations attached to elliptic curves with complex
multiplication
math.NT
The goal of this article is to give an explicit classification of the
possible $p$-adic Galois representations that are attached to elliptic curves
$E$ with CM defined over $\mathbb{Q}(j(E))$. More precisely, let $K$ be an
imaginary quadratic field, and let $\mathcal{O}_{K,f}$ be an order in $K$ of
conductor $f\geq 1$. Let $E$ be an elliptic curve with CM by
$\mathcal{O}_{K,f}$, such that $E$ is defined by a model over
$\mathbb{Q}(j(E))$. Let $p\geq 2$ be a prime, let $G_{\mathbb{Q}(j(E))}$ be the
absolute Galois group of $\mathbb{Q}(j(E))$, and let $\rho_{E,p^\infty}\colon
G_{\mathbb{Q}(j(E))}\to \operatorname{GL}(2,\mathbb{Z}_p)$ be the Galois
representation associated to the Galois action on the Tate module $T_p(E)$. The
goal is then to describe, explicitly, the groups of
$\operatorname{GL}(2,\mathbb{Z}_p)$ that can occur as images of
$\rho_{E,p^\infty}$, up to conjugation, for an arbitrary order
$\mathcal{O}_{K,f}$.
| arxiv topic:math.NT |
arxiv_dataset-102271809.02684 | Distinct Partial Sums in Cyclic Groups: Polynomial Method and
Constructive Approaches
math.CO
Let $(G,+)$ be an abelian group and consider a subset $A \subseteq G$ with
$|A|=k$. Given an ordering $(a_1, \ldots, a_k)$ of the elements of $A$, define
its {\em partial sums} by $s_0 = 0$ and $s_j = \sum_{i=1}^j a_i$ for $1 \leq j
\leq k$. We consider the following conjecture of Alspach: For any cyclic group
$\Z_n$ and any subset $A \subseteq \Z_n \setminus \{0\}$ with $s_k \neq 0$, it
is possible to find an ordering of the elements of $A$ such that no two of its
partial sums $s_i$ and $s_j$ are equal for $0 \leq i < j \leq k$. We show that
Alspach's Conjecture holds for prime $n$ when $k \geq n-3$ and when $k \leq
10$. The former result is by direct construction, the latter is
non-constructive and uses the polynomial method. We also use the polynomial
method to show that for prime $n$ a sequence of length $k$ having distinct
partial sums exists in any subset of $\Z_n \setminus \{0\}$ of size at least
$2k- \sqrt{8k}$ in all but at most a bounded number of cases.
| arxiv topic:math.CO |
arxiv_dataset-102281809.02784 | On a nonlinear neutral stochastic functional integro-differential
equation driven by fractional Brownian motion
math.PR
In this paper, we study the existence and uniqueness of mild solution for a
stochastic neutral partial functional integro-differential equation with delay
in a Hilbert space driven by a fractional Brownian motion and with
non-deterministic diffusion coefficient. We suppose that the linear part has a
resolvent operator. We also establish a sufficient condition for the existence
of the density of a function of the solution. An example is provided to
illustrate the results of this work
| arxiv topic:math.PR |
arxiv_dataset-102291809.02884 | Probing hotspots of plasmon-enhanced Raman scattering by
nanomanipulation of carbon nanotubes
cond-mat.mes-hall
We present a two-step procedure to probe hotspots of plasmon-enhanced Raman
scattering with carbon nanotubes. Dielectrophoretic deposition places a small
carbon nanotube bundle on top of plasmonic Au nanodimer. After
'pre-characterising' both the nanotubes and dimer structure, we subsequently
use the tip of an AFM to push the bundle into the plasmonic hotspot located in
the 25nm wide dimer gap, characterize its location inside the gap, and observe
the onset of plasmon-enhanced Raman scattering. Evidence for the activation of
the carbon nanotube's double-resonant D-mode by the near-field of the plasmonic
hotspot is discussed.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-102301809.02984 | On zero-sum game formulation of non zero-sum game
math.OC cs.GT
We consider a formulation of a non zero-sum n players game by an n+1 players
zero-sum game. We suppose the existence of the n+1-th player in addition to n
players in the main game, and virtual subsidies to the n players which is
provided by the n+1-th player. Its strategic variable affects only the
subsidies, and does not affect choice of strategies by the n players in the
main game. His objective function is the opposite of the sum of the payoffs of
the n players. We will show 1) The minimax theorem by Sion (Sion(1958)) implies
the existence of Nash equilibrium in the n players non zero-sum game. 2) The
maximin strategy of each player in {1, 2, \dots, n} with the minimax strategy
of the n+1-th player is equivalent to the Nash equilibrium strategy of the n
players non zero-sum game. 3) The existence of Nash equilibrium in the n
players non zero-sum game implies Sion's minimax theorem for pairs of each of
the n players and the n+1-th player.
| arxiv topic:math.OC cs.GT |
arxiv_dataset-102311809.03084 | Efficient Counterfactual Learning from Bandit Feedback
cs.LG cs.AI cs.IR stat.ME stat.ML
What is the most statistically efficient way to do off-policy evaluation and
optimization with batch data from bandit feedback? For log data generated by
contextual bandit algorithms, we consider offline estimators for the expected
reward from a counterfactual policy. Our estimators are shown to have lowest
variance in a wide class of estimators, achieving variance reduction relative
to standard estimators. We then apply our estimators to improve advertisement
design by a major advertisement company. Consistent with the theoretical
result, our estimators allow us to improve on the existing bandit algorithm
with more statistical confidence compared to a state-of-the-art benchmark.
| arxiv topic:cs.LG cs.AI cs.IR stat.ME stat.ML |
arxiv_dataset-102321809.03184 | Minimal 3-generated Majorana algebras
math.GR
Majorana theory was introduced by A. A. Ivanov as the axiomatization of
certain properties of the 2A-axes of the Griess algebra. Since its inception,
Majorana theory has proved to be a remarkable tool with which to study objects
related to the Griess algebra and the Monster simple group. We introduce the
definition of a minimal 3-generated Majorana algebra and begin the first steps
towards classifying such algebras.
In particular, we give a complete classification of finite minimal
3-generated 6-transposition groups. We then use an algorithm developed in GAP
by M. Pfeiffer and M. Whybrow, together with some additional computational
tools, to give an almost complete description of all minimal 3-generated
Majorana algebras arising from this list of groups.
| arxiv topic:math.GR |
arxiv_dataset-102331809.03284 | First Investigation on the Radiation Field of the Gas-Filled Three-Axis
Cylindrical Hohlraum
physics.plasm-ph
A novel ignition hohlraum named three-axis cylindrical hohlraum (TACH) is
designed for indirect-drive inertial confinement fusion. TACH is a kind of 6
laser entrance holes (LEHs) hohlraum, which is orthogonally jointed of three
cylindrical hohlraums. The first experiment on the radiation field of TACH was
performed on Shenguang III laser facility. 24 laser beams were elected and
injected into 6 LEHs quasi-symmetrically. Total laser energy was about 59 kJ,
and the peak radiation temperature reached about 192 eV. Radiation temperature
and pinhole images in gas-filled hohlraum are largely identical but with minor
differences with those in vacuum hohlraum. All laser energy can be totally
delivered into hohlraum in 3 ns duration even without filled gas in the
hohlraum of 1.4 mm diameter. Plasma filling cannot be obviously suppressed even
with 0.5 atm pressure gas in the small hohlraum. Backscattering fractions of
vacuum hohlraum and gas-filled hohlraum are both lower than 2%. Experimental
study of this new kind of hohlraum can provide guidance for future target
design and implosion experiment.
| arxiv topic:physics.plasm-ph |
arxiv_dataset-102341809.03384 | Scaling in necklaces of monopoles and semipoles
astro-ph.CO hep-ph hep-th
Models of symmetry breaking in the early universe can produce networks of
cosmic strings threading 't Hooft-Polyakov monopoles. In certain cases there is
a larger global symmetry group and the monopoles split into so-called
semipoles. These networks are all known as cosmic necklaces. We carry out
large-scale field theory simulations of the simplest model containing these
objects, confirming that the energy density of networks of cosmic necklaces
approaches scaling, i.e. that it remains a constant fraction of the background
energy density. The number of monopoles per unit comoving string length is
constant, meaning that the density fraction of monopoles decreases with time.
Where the necklaces carry semipoles rather than monopoles, we perform the first
simulations large enough to demonstrate that they also maintain a constant
number per unit comoving string length. We also compare our results to a number
of analytical models of cosmic necklaces, finding that none explains our
results. We put forward evidence that annihilation of poles on the strings is
controlled by a diffusive process, a possibility not considered before. The
observational constraints derived in our previous work for necklaces with
monopoles can now be safely applied to those with semipoles as well.
| arxiv topic:astro-ph.CO hep-ph hep-th |
arxiv_dataset-102351809.03484 | Gravitational Wave Decay into Dark Energy
astro-ph.CO gr-qc hep-ph hep-th
We study the decay of gravitational waves into dark energy fluctuations
$\pi$, through the processes $\gamma \to \pi\pi$ and $\gamma \to \gamma \pi$,
made possible by the spontaneous breaking of Lorentz invariance. Within the EFT
of Dark Energy (or Horndeski/beyond Horndeski theories) the first process is
large for the operator $\frac12 \tilde m_4^2(t) \, \delta g^{00}\, \left(
{}^{(3)}\! R + \delta K_\mu^\nu \delta K^\mu_\nu -\delta K^2 \right)$, so that
the recent observations force $\tilde m_4 =0$ (or equivalently $\alpha_{\rm
H}=0$). This constraint, together with the requirement that gravitational waves
travel at the speed of light, rules out all quartic and quintic GLPV theories.
Additionally, we study how the same couplings affect the propagation of
gravitons at loop order. The operator proportional to $\tilde m_4^2$ generates
a calculable, non-Lorentz invariant higher-derivative correction to the
graviton propagation. The modification of the dispersion relation provides a
bound on $\tilde m_4^2$ comparable to the one of the decay. Conversely,
operators up to cubic Horndeski do not generate sizeable higher-derivative
corrections.
| arxiv topic:astro-ph.CO gr-qc hep-ph hep-th |
arxiv_dataset-102361809.03584 | Characteristic-Sorted Portfolios: Estimation and Inference
econ.EM econ.GN q-fin.EC stat.ME
Portfolio sorting is ubiquitous in the empirical finance literature, where it
has been widely used to identify pricing anomalies. Despite its popularity,
little attention has been paid to the statistical properties of the procedure.
We develop a general framework for portfolio sorting by casting it as a
nonparametric estimator. We present valid asymptotic inference methods and a
valid mean square error expansion of the estimator leading to an optimal choice
for the number of portfolios. In practical settings, the optimal choice may be
much larger than the standard choices of 5 or 10. To illustrate the relevance
of our results, we revisit the size and momentum anomalies.
| arxiv topic:econ.EM econ.GN q-fin.EC stat.ME |
arxiv_dataset-102371809.03684 | Visual Attention Model for Cross-sectional Stock Return Prediction and
End-to-End Multimodal Market Representation Learning
cs.CE
Technical and fundamental analysis are traditional tools used to analyze
individual stocks; however, the finance literature has shown that the price
movement of each individual stock correlates heavily with other stocks,
especially those within the same sector. In this paper we propose a general
purpose market representation that incorporates fundamental and technical
indicators and relationships between individual stocks. We treat the daily
stock market as a "market image" where rows (grouped by market sector)
represent individual stocks and columns represent indicators. We apply a
convolutional neural network over this market image to build market features in
a hierarchical way. We use a recurrent neural network, with an attention
mechanism over the market feature maps, to model temporal dynamics in the
market. We show that our proposed model outperforms strong baselines in both
short-term and long-term stock return prediction tasks. We also show another
use for our market image: to construct concise and dense market embeddings
suitable for downstream prediction tasks.
| arxiv topic:cs.CE |
arxiv_dataset-102381809.03784 | Compressive Massive Random Access for Massive Machine-Type
Communications (mMTC)
cs.IT math.IT
In future wireless networks, one fundamental challenge for massive
machine-type communications (mMTC) lies in the reliable support of massive
connectivity with low latency. Against this background, this paper proposes a
compressive sensing (CS)-based massive random access scheme for mMTC by
leveraging the inherent sporadic traffic, where both the active devices and
their channels can be jointly estimated with low overhead. Specifically, we
consider devices in the uplink massive random access adopt pseudo random
pilots, which are designed under the framework of CS theory. Meanwhile, the
massive random access at the base stations (BS) can be formulated as the sparse
signal recovery problem by leveraging the sparse nature of active devices.
Moreover, by exploiting the structured sparsity among different receiver
antennas and subcarriers, we develop a distributed multiple measurement vector
approximate message passing (DMMV-AMP) algorithm for further improved
performance. Additionally, the state evolution (SE) of the proposed DMMV-AMP
algorithm is derived to predict the performance. Simulation results demonstrate
the superiority of the proposed scheme, which exhibits a good tightness with
the theoretical SE.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-102391809.03884 | Perturbations in Quantum Cosmology: The Continuum Limit in Fourier Space
gr-qc
We analyze the passage to a continuum limit of the mode spectrum of
primordial perturbations around flat cosmological spacetimes in Quantum
Cosmology, showing that this limit can be reached even if one starts by
considering a finite fiducial cell as spatial slice. Whereas the resulting
system can be described in an invariant way under changes of the fiducial
volume using appropriate variables, both for the background cosmology and the
perturbations, obtaining in this way a discrete mode spectrum owing to the
compactness of the fiducial cell, we show that the desired continuum limit for
the perturbations can still be established by means of scaling transformations
of the physical volume when this volume grows unboundedly. These
transformations lead to a model with a continuum of modes and independent of
any scale of reference for the physical volume. For the sake of comparison, we
also consider an alternative road to the continuum in Fourier space that has
been employed in geometrodynamics and is based on the use of scaling
transformations of the fiducial volume, together with variables that are
independent of them.
| arxiv topic:gr-qc |
arxiv_dataset-102401809.03984 | C*-algebras of stable rank one and their Cuntz semigroups
math.OA
The uncovering of new structure on the Cuntz semigroup of a C*-algebra of
stable rank one leads to several applications: We answer affirmatively, for the
class of stable rank one C*-algebras, a conjecture by Blackadar and Handelman
on dimension functions, the Global Glimm Halving problem, and the problem of
realizing functions on the cone of 2-quasitraces as ranks of Cuntz semigroup
elements. We also gain new insights into the comparability properties of
positive elements in C*-algebras of stable rank one.
| arxiv topic:math.OA |
arxiv_dataset-102411809.04084 | Rotating Hairy Black Holes in AdS$_5\times$S$^5$
hep-th gr-qc
We present a numerical study of fully non-linear, rotating and charged hairy
black hole solutions in five-dimensional anti-de Sitter space, which originate
from a consistent truncation of $\mathcal{N}=8$ supergravity, and can be
consistently embedded in type IIB supergravity with AdS$_5\times$S$^5$
asymptotics. The hairy black holes have one scalar field charged under a $U(1)$
gauge field, and branch from the near-extremal Cveti\v{c}, L\"{u} and Pope
solutions. We give numerical evidence that the hairy solutions exist
arbitrarily close to the BPS bound for all charges, and saturate it in the
$T\rightarrow 0$ and $T\rightarrow\infty$ limits. We give further evidence for
the conjecture of Markevi\v{c}i\={u}t\.e and Santos, that on the BPS bound, the
rotating hairy black holes form a two-parameter family of solutions with finite
entropy, and can be regarded as a one-parameter extension of the supersymmetric
Gutowski and Reall black hole. We analyse the approach to the supersymmetric
limit and explore the full phase diagram. In the planar horizon limit we find a
two parameter family of rotating hairy black brane solutions which cannot be
obtained via a Lorentz boost. The field theory dual exhibits a spontaneously
generated current. The results of this paper suggest rich and intricate
structure of hairy black hole solutions in AdS$_5\times$S$^5$, and highlight
their importance in understanding the thermodynamics of $\mathcal{N}=4$ SYM.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-102421809.04184 | Searching for Efficient Multi-Scale Architectures for Dense Image
Prediction
cs.CV cs.LG stat.ML
The design of neural network architectures is an important component for
achieving state-of-the-art performance with machine learning systems across a
broad array of tasks. Much work has endeavored to design and build
architectures automatically through clever construction of a search space
paired with simple learning algorithms. Recent progress has demonstrated that
such meta-learning methods may exceed scalable human-invented architectures on
image classification tasks. An open question is the degree to which such
methods may generalize to new domains. In this work we explore the construction
of meta-learning techniques for dense image prediction focused on the tasks of
scene parsing, person-part segmentation, and semantic image segmentation.
Constructing viable search spaces in this domain is challenging because of the
multi-scale representation of visual information and the necessity to operate
on high resolution imagery. Based on a survey of techniques in dense image
prediction, we construct a recursive search space and demonstrate that even
with efficient random search, we can identify architectures that outperform
human-invented architectures and achieve state-of-the-art performance on three
dense prediction tasks including 82.7\% on Cityscapes (street scene parsing),
71.3\% on PASCAL-Person-Part (person-part segmentation), and 87.9\% on PASCAL
VOC 2012 (semantic image segmentation). Additionally, the resulting
architecture is more computationally efficient, requiring half the parameters
and half the computational cost as previous state of the art systems.
| arxiv topic:cs.CV cs.LG stat.ML |
arxiv_dataset-102431809.04284 | An Approach to Handle Big Data Warehouse Evolution
cs.DB
One of the purposes of Big Data systems is to support analysis of data
gathered from heterogeneous data sources. Since data warehouses have been used
for several decades to achieve the same goal, they could be leveraged also to
provide analysis of data stored in Big Data systems. The problem of adapting
data warehouse data and schemata to changes in these requirements as well as
data sources has been studied by many researchers worldwide. However,
innovative methods must be developed also to support evolution of data
warehouses that are used to analyze data stored in Big Data systems. In this
paper, we propose a data warehouse architecture that allows to perform
different kinds of analytical tasks, including OLAP-like analysis, on big data
loaded from multiple heterogeneous data sources with different latency and is
capable of processing changes in data sources as well as evolving analysis
requirements. The operation of the architecture is highly based on the metadata
that are outlined in the paper.
| arxiv topic:cs.DB |
arxiv_dataset-102441809.04384 | Hybrid matrix compression for high-frequency problems
math.NA cs.NA
Boundary element methods for the Helmholtz equation lead to large dense
matrices that can only be handled if efficient compression techniques are used.
Directional compression techniques can reach good compression rates even for
high-frequency problems.
Currently there are two approaches to directional compression: analytic
methods approximate the kernel function, while algebraic methods approximate
submatrices. Analytic methods are quite fast and proven to be robust, while
algebraic methods yield significantly better compression rates.
We present a hybrid method that combines the speed and reliability of
analytic methods with the good compression rates of algebraic methods.
| arxiv topic:math.NA cs.NA |
arxiv_dataset-102451809.04484 | A Study of Pulsation and Fadings in some R Coronae Borealis Stars
astro-ph.SR
We have measured the times of onset of recent fadings in four R CrB stars --
V854 Cen, RY Sgr, R CrB, and S Aps. These times continue to be locked to the
stars' pulsation periods, though with some scatter. In RY Sgr, the onsets of
fading tend to occur at or a few days after pulsation maximum. We have studied
the pulsation properties of RY Sgr through its recent long maximum using (O-C)
analysis and wavelet analysis. The period "wanders" by a few percent. This
wandering can be modelled by random cycle-to-cycle period fluctuations, as in
some other types of pulsating stars. The pulsation amplitude varies between
0.05 and 0.25 in visual light, non-periodically but on a time scale of about 20
pulsation periods.
| arxiv topic:astro-ph.SR |
arxiv_dataset-102461809.04584 | Gate-Based High Fidelity Spin Read-out in a CMOS Device
cond-mat.mes-hall
The engineering of electron spin qubits in a compact unit cell embedding all
quantum functionalities is mandatory for large scale integration. In
particular, the development of a high-fidelity and scalable spin readout method
remains an open challenge. Here we demonstrate high-fidelity and robust spin
readout based on gate reflectometry in a CMOS device comprising one qubit dot
and one ancillary dot coupled to an electron reservoir to perform readout. This
scalable method allows us to read out a spin with a fidelity above 99% for 1 ms
integration time. To achieve such fidelity, we exploit a latched spin blockade
mechanism that requires electron exchange between the ancillary dot and the
reservoir. We show that the demonstrated high read-out fidelity is fully
preserved up to 0.5 K. This results holds particular relevance for the future
co-integration of spin qubits and classical control electronics.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-102471809.04684 | Fair lending needs explainable models for responsible recommendation
cs.LG cs.AI cs.CY stat.AP stat.ML
The financial services industry has unique explainability and fairness
challenges arising from compliance and ethical considerations in credit
decisioning. These challenges complicate the use of model machine learning and
artificial intelligence methods in business decision processes.
| arxiv topic:cs.LG cs.AI cs.CY stat.AP stat.ML |
arxiv_dataset-102481809.04784 | Generalized quasi-statistical structures
math.DG
Given a non-degenerate $(0,2)$-tensor field $h$ on a smooth manifold $M$, we
consider a natural generalized complex and a generalized product structure on
the generalized tangent bundle $TM\oplus T^*M$ of $M$ and we show that they are
$\nabla$-integrable, for $\nabla$ an affine connection on $M$, if and only if
$(M,h,\nabla)$ is a quasi-statistical manifold. We introduce the notion of
generalized quasi-statistical structure and we prove that any quasi-statistical
structure on $M$ induces generalized quasi-statistical structures on $TM\oplus
T^*M$. In this context, dual connections are considered and some of their
properties are established. The results are described in terms of
Patterson-Walker and Sasaki metrics on $T^*M$, horizontal lift and Sasaki
metrics on $TM$ and, when the connection $\nabla$ is flat, we define
prolongation of quasi-statistical structures on manifolds to their cotangent
and tangent bundles via generalized geometry. Moreover, Norden and Para-Norden
structures are defined on $T^*M$ and $TM$.
| arxiv topic:math.DG |
arxiv_dataset-102491809.04884 | Numerical Simulations of Mass Transfer in Binaries with Bipolytropic
Components
astro-ph.SR
We present the first self-consistent, three dimensional study of hydrodynamic
simulations of mass transfer in binary systems with bipolytropic (composite
polytropic) components. In certain systems, such as contact binaries or during
the common envelope phase, the core-envelope structure of the stars plays an
important role in binary interactions. In this paper, we compare mass transfer
simulations of bipolytropic binary systems in order to test the suitability of
our numerical tools for investigating the dynamical behaviour of such systems.
The initial, equilibrium binary models possess a core-envelope structure and
are obtained using the bipolytropic self-consistent field technique. We conduct
mass transfer simulations using two independent, fully three-dimensional,
Eulerian codes - Flow-ER and Octo-tiger. These hydrodynamic codes are compared
across binary systems undergoing unstable as well as stable mass transfer, and
the former at two resolutions. The initial conditions for each simulation and
for each code are chosen to match closely so that the simulations can be used
as benchmarks. Although there are some key differences, the detailed comparison
of the simulations suggests that there is remarkable agreement between the
results obtained using the two codes. This study puts our numerical tools on a
secure footing, and enables us to reliably simulate specific mass transfer
scenarios of binary systems involving components with a core-envelope
structure.
| arxiv topic:astro-ph.SR |
arxiv_dataset-102501809.04984 | Locations of optical and $\gamma$-ray emitting regions in the jet of PMN
J2345-1555
astro-ph.HE
We collect long term $\gamma$-ray, optical and radio $15$ GHz light curves of
quasar object PMN J2345-1555. The correlation analyses between them are
performed via the local cross-correlation function (LCCF). We found that all
the optical $V$, $R$ band and the infrared $J$ band are correlated with the
radio 15 GHz at beyond $3\sigma$ significance level, and the lag times are
$-221.81^{+6.26}_{-6.72}$, $-201.38^{+6.42}_{-6.02}$ and
$-192.27^{+8.26}_{-7.37}$ days, respectively. The $\gamma$-ray is strongly
correlated with optical, but weakly correlated with the radio. We present that
time lags between different frequencies can be used as an alternative parameter
to derive the core-shift measurement. For this target, the magnetic field and
particle density at 1 parsec in jet are derived to be $0.61$ Gauss and
$1533/\gamma_{\rm min}$ cm$^{-3}$, respectively. The black hole mass and the 15
GHz core position in jet are estimated to be $10^{8.44} {\rm M}_{\odot}$ and
$30$ parsec, respectively. The lag times enable us to derive that the optical
and the $\gamma$-ray emitting regions coincide, which are located at
$4.26^{+0.83}_{-0.79}$ pc away from 15 GHz core position in jet and beyond the
broad line region (BLR). We found that a $3\sigma$ correlation between the
color index and the radio light curve, which indicates that opacity may play an
important role in the variation. The $\delta V-\delta R$ behaviors are complex,
while the $R-J$ shows a bluer when brighter trend. As hinted from radio images,
we proposed a positional dependent spectral index model to explain the color
index behaviors, which is complementary for the shock in jet model. The
curvature effects and contribution from accretion disk may also affect
variables of blazars in many aspects.
| arxiv topic:astro-ph.HE |
arxiv_dataset-102511809.05084 | Convolution quadrature methods for time-domain scattering from unbounded
penetrable interfaces
physics.comp-ph math.NA
This paper presents a class of boundary integral equation methods for the
numerical solution of acoustic and electromagnetic time-domain scattering
problems in the presence of unbounded penetrable interfaces in two-spatial
dimensions. The proposed methodology relies on Convolution Quadrature (CQ)
methods in conjunction with the recently introduced Windowed Green Function
(WGF) method. As in standard time-domain scattering from bounded obstacles, a
CQ method of the user's choice is utilized to transform the problem into a
finite number of (complex) frequency-domain problems posed on the domains
involving penetrable unbounded interfaces. Each one of the frequency-domain
transmission problems is then formulated as a second-kind integral equation
that is effectively reduced to a bounded interface by means of the WGF
method---which introduces errors that decrease super-algebraically fast as the
window size increases. The resulting windowed integral equations can then be
solved by means of any (accelerated or unaccelerated) off-the-shelf Helmholtz
boundary integral equation solver capable of handling complex wavenumbers with
a large imaginary part. A high-order Nystr\"om method based on Alpert
quadrature rules is utilized here. A variety of numerical examples including
wave propagation in open waveguides as well as scattering from multiply layered
media demonstrate the capabilities of the proposed approach.
| arxiv topic:physics.comp-ph math.NA |
arxiv_dataset-102521809.05184 | Scalable, "Dip-and-dry" Fabrication of a Wide-Angle Plasmonic Selective
Absorber for High-efficiency Solar-Thermal Energy Conversion
physics.app-ph
A galvanic displacement reaction-based, room-temperature "dip-and-dry"
technique is demonstrated for fabricating selectively solar-absorbing plasmonic
nanostructure-coated foils (PNFs). The technique, which allows for facile
tuning of the PNFs' spectral reflectance to suit different radiative and
thermal environments, yields PNFs which exhibit excellent, wide-angle solar
absorptance (0.96 at 15{\deg}, to 0.97 at 35{\deg}, to 0.79 at 80{\deg}) and
low hemispherical thermal emittance (0.10) without the aid of antireflection
coatings. The thermal emittance is on par with those of notable selective solar
absorbers (SSAs) in the literature, while the wide-angle solar absorptance
surpasses those of previously reported SSAs with comparable optical
selectivities. In addition, the PNFs show promising mechanical and thermal
stabilities at temperatures of up to 200{\deg}C. Along with the performance of
the PNFs, the simplicity, inexpensiveness and environment-friendliness of the
"dip-and-dry" technique makes it an appealing alternative to current methods
for fabricating selective solar absorbers.
| arxiv topic:physics.app-ph |
arxiv_dataset-102531809.05284 | Variational Autoencoder with Implicit Optimal Priors
stat.ML cs.LG
The variational autoencoder (VAE) is a powerful generative model that can
estimate the probability of a data point by using latent variables. In the VAE,
the posterior of the latent variable given the data point is regularized by the
prior of the latent variable using Kullback Leibler (KL) divergence. Although
the standard Gaussian distribution is usually used for the prior, this simple
prior incurs over-regularization. As a sophisticated prior, the aggregated
posterior has been introduced, which is the expectation of the posterior over
the data distribution. This prior is optimal for the VAE in terms of maximizing
the training objective function. However, KL divergence with the aggregated
posterior cannot be calculated in a closed form, which prevents us from using
this optimal prior. With the proposed method, we introduce the density ratio
trick to estimate this KL divergence without modeling the aggregated posterior
explicitly. Since the density ratio trick does not work well in high
dimensions, we rewrite this KL divergence that contains the high-dimensional
density ratio into the sum of the analytically calculable term and the
low-dimensional density ratio term, to which the density ratio trick is
applied. Experiments on various datasets show that the VAE with this implicit
optimal prior achieves high density estimation performance.
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-102541809.05384 | Results and prospects for $K\to\pi\nu\bar{\nu}$ at NA62 and KOTO
hep-ex
The $K\to\pi\nu\bar{\nu}$ ultra-rare decays are precisely computed in the
Standard Model (SM) and are ideal probes for physics beyond the SM. The NA62
experiment at the CERN SPS is designed to measure the charged channel with a
precision of 10\%. The statistics collected in 2016 allows to reach the SM
sensitivity. The KOTO experiment at J-PARC aims at reaching the SM sensitivity
before performing a measurement with $\sim100$ signal events. The NA62
preliminary result for the charged channel is presented, together with the
current experimental status of the neutral channel and their prospects for the
coming years.
| arxiv topic:hep-ex |
arxiv_dataset-102551809.05484 | Conductance of inhomogeneous Luttinger liquids with a finite bandwidth
cond-mat.str-el
The finite-bandwidth conductance of a Luttinger liquid (LL) with a cluster of
impurities is studied and its variation with respect to temperature is shown.
The calculations are done using the correlation functions obtained using the
powerful non-chiral bosonization technique (NCBT) . The results are compared
with those obtained by Matveev, Yue and Glazman [K. Matveev et al., Phys. Rev.
Lett. 71, 3351 (1993)] who deal with a weakly interacting LL. By contrast, NCBT
correctly provides the conductance for all values of the interaction strength
(as well as the sign). In addition to finding perfect agreement with the
results of Matveev et al. for both weakly repulsive and weakly attractive
mutual interactions, we are also able to probe novel physics seen when the
repulsion is strong - in the form of a weakly temperature dependent conductance
when there is a definite relationship between the transmission amplitude of the
non-interacting system and the holon velocity. Secondly, an unusual high
conductance for strongly repulsive mutual interactions is observed for a weak
barrier at low temperatures. Lastly, inclusion of backward scattering leads to
the non-monotonic temperature dependence of conductance when dealing with
fermions with spin. This work is also important as a validation of the NCBT
itself.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-102561809.05584 | Gemini GNIRS near-infrared spectroscopy of 50 quasars at z>~5.7
astro-ph.GA astro-ph.CO
We report initial results from a large Gemini program to observe z>~5.7
quasars with GNIRS near-IR spectroscopy. Our sample includes 50 quasars with
simultaneous ~0.85-2.5 micron spectra covering the rest-frame ultraviolet and
major broad emission lines from Ly-alpha to MgII. We present spectral
measurements for these quasars and compare to their lower-redshift counterparts
at z=1.5-2.3. We find that when quasar luminosity is matched, there are no
significant differences between the rest-UV spectra of z>~5.7 quasars and the
low-z comparison sample. High-z quasars have similar continuum and emission
line properties and occupy the same region in the black hole mass and
luminosity space as the comparison sample, accreting at an average Eddington
ratio of ~0.3. There is no evidence for super-Eddington accretion or
hypermassive (>10^10 Msun) black holes within our sample. We find a mild excess
of quasars with weak CIV lines relative to the control sample. Our results,
corroborating earlier studies but with better statistics, demonstrate that
these high-z quasars are already mature systems of accreting supermassive black
holes operating with the same physical mechanisms as those at lower redshifts.
| arxiv topic:astro-ph.GA astro-ph.CO |
arxiv_dataset-102571809.05684 | Uniform bounds for solutions to elliptic problems on simply connected
planar domains
math.AP
We consider the singular Liouville equation and the Henon-Lane-Emden problem
on simply connected planar domains. We show that any solution to each problem
must satisfy a uniform bound on the mass. The same results applies to some
systems and more general non-linearities. The proofs are based on the Riemann
mapping theorem and a Pohozaev-type identity.
| arxiv topic:math.AP |
arxiv_dataset-102581809.05784 | A High-Order Weighted Compact High Resolution Scheme with Boundary
Closures for Compressible Turbulent Flows with Shocks
physics.comp-ph physics.flu-dyn
We present an improved high-order weighted compact high resolution (WCHR)
scheme that extends the idea of weighted compact nonlinear schemes (WCNS's)
using nonlinear interpolations in conjunction with compact finite difference
schemes for shock-capturing in compressible turbulent flows. The proposed
scheme has better resolution property than previous WCNS's. This is achieved by
using a compact (or spatially implicit) form instead of the traditional fully
explicit form for the nonlinear interpolation. Since compact interpolation
schemes tend to have lower dispersion errors compared to explicit interpolation
schemes, the proposed scheme has the ability to resolve more fine-scale
features while still having the ability to provide sufficiently localized
dissipation to capture shocks and discontinuities robustly. Approximate
dispersion relation characteristics of this scheme are analyzed to show the
superior resolution properties of the scheme compared to other WCNS's of
similar orders of accuracy. Conservative and high-order accurate boundary
schemes are also proposed for non-periodic problems. Further, a new
conservative flux-difference form for compact finite difference schemes is
derived and allows for the use of positivity-preserving limiters for improved
robustness. Different test cases demonstrate the ability of this scheme to
capture discontinuities in a robust and stable manner while also localizing the
required numerical dissipation only to regions containing discontinuities and
very high wavenumber features and hence preserving smooth flow features better
in comparison to WCNS's.
| arxiv topic:physics.comp-ph physics.flu-dyn |
arxiv_dataset-102591809.05884 | Multi-Label Image Classification via Knowledge Distillation from
Weakly-Supervised Detection
cs.CV cs.AI cs.LG cs.MM
Multi-label image classification is a fundamental but challenging task
towards general visual understanding. Existing methods found the region-level
cues (e.g., features from RoIs) can facilitate multi-label classification.
Nevertheless, such methods usually require laborious object-level annotations
(i.e., object labels and bounding boxes) for effective learning of the
object-level visual features. In this paper, we propose a novel and efficient
deep framework to boost multi-label classification by distilling knowledge from
weakly-supervised detection task without bounding box annotations.
Specifically, given the image-level annotations, (1) we first develop a
weakly-supervised detection (WSD) model, and then (2) construct an end-to-end
multi-label image classification framework augmented by a knowledge
distillation module that guides the classification model by the WSD model
according to the class-level predictions for the whole image and the
object-level visual features for object RoIs. The WSD model is the teacher
model and the classification model is the student model. After this cross-task
knowledge distillation, the performance of the classification model is
significantly improved and the efficiency is maintained since the WSD model can
be safely discarded in the test phase. Extensive experiments on two large-scale
datasets (MS-COCO and NUS-WIDE) show that our framework achieves superior
performances over the state-of-the-art methods on both performance and
efficiency.
| arxiv topic:cs.CV cs.AI cs.LG cs.MM |
arxiv_dataset-102601809.05984 | Determining complementary properties using weak-measurement:
uncertainty, predictability, and disturbance
quant-ph
It is often said that measuring a system's position must disturb the
complementary property, momentum, by some minimum amount due to the Heisenberg
uncertainty principle. Using a "weak-measurement", this disturbance can be
reduced. One might expect this comes at the cost of also reducing the
measurement's precision. However, it was recently demonstrated that a sequence
consisting of a weak position measurement followed by a regular momentum
measurement can probe a quantum system at a single point, with zero width, in
position-momentum space. Here, we study this "joint weak-measurement" and
reconcile its compatibility with the uncertainty principle. While a single
trial probes the system with a resolution that can saturate Heisenberg's limit,
we show that averaging over many trials can be used to surpass this limit. The
weak-measurement does not trade-away precision, but rather another type of
uncertainty called "predictability" which quantifies the certainty of
retrodicting the measurement's outcome.
| arxiv topic:quant-ph |
arxiv_dataset-102611809.06084 | Infinite classes of strongly regular graphs derived from $GL(n,F_2)$
math.CO
It is known that the automorphism group of the elementary abelian $2$-group
$Z_2^n$ is isomorphic to the general linear group $GL(n,F_2)$ of degree $n$
over $F_2$. Let $W$ be the collection of permutation matrices of order $n$. It
is clear that $W\le GL(n,F_2)$. In virtue of this, we consider the Cayley graph
$Cay(Z_2^n,S)$, where $S$ is the union of some orbits under the action of $W$.
We call such graphs the orbit Cayley graphs over $Z_2^n$. In this paper, we
give eight infinite families of strongly regular graphs among orbit Cayley
graphs over $Z_2^n$, in which six families are new as we know. By the way, we
formulate the spectra of orbit Cayley graphs as well.
| arxiv topic:math.CO |
arxiv_dataset-102621809.06184 | Constraining the geometry of the nuclear wind in PDS 456 using a novel
emission model
astro-ph.HE
Outflows from active galactic nuclei (AGN) are often invoked to explain the
co-evolution of AGN and their host galaxies, and the scaling relations between
the central black hole mass and the bulge velocity dispersion. Nuclear winds
are often seen in the X-ray spectra through Fe K shell transitions and some of
them are called ultra fast outflows (UFOs) due to their high velocities, up to
some fractions of the speed of light. If they were able to transfer some
percentage of the AGN luminosity to the host galaxy, this might be enough to
trigger an efficient feedback mechanism. We aim to establish new constraints on
the covering fraction and on the kinematic properties of the UFO in the
powerful (L(bol) ~ 10^(47) erg/s) quasar PDS 456, an established Rosetta stone
for studying AGN feedback from disk winds. This will allow us to estimate the
mass outflow rate and the energy transfer rate of the wind, which are key
quantities to understand the potential impact on the host galaxy. We analyze
two sets of simultaneous XMM-Newton and NuSTAR observations taken in September
2013 and reported in Nardini et al. (2015) as having similar broadband spectral
properties. We fit the Fe K features with a P-Cygni profile between 5 and 14
keV, using a novel Monte Carlo model for the WINd Emission (WINE). We find an
outflow velocity ranging from 0.17 to 0.28 c, with a mean value of 0.23 c. We
obtain an opening angle of the wind of 71(+13,-8) deg and a covering fraction
of 0.7(+0.2,-0.3), suggesting a wide-angle outflow. We check the reliability of
the WINE model by performing extensive simulations of joint XMM-Newton and
NuSTAR observations. Furthermore, we test the accuracy of the WINE model in
recovering the geometrical properties of UFOs by simulating observations with
the forthcoming X-ray observatory ATHENA.
| arxiv topic:astro-ph.HE |
arxiv_dataset-102631809.06284 | Style Transfer Through Multilingual and Feedback-Based Back-Translation
cs.CL
Style transfer is the task of transferring an attribute of a sentence (e.g.,
formality) while maintaining its semantic content. The key challenge in style
transfer is to strike a balance between the competing goals, one to preserve
meaning and the other to improve the style transfer accuracy. Prior research
has identified that the task of meaning preservation is generally harder to
attain and evaluate. This paper proposes two extensions of the state-of-the-art
style transfer models aiming at improving the meaning preservation in style
transfer. Our evaluation shows that these extensions help to ground meaning
better while improving the transfer accuracy.
| arxiv topic:cs.CL |
arxiv_dataset-102641809.06384 | Optimally Mapping Large-Scale Structures with Luminous Sources
astro-ph.CO astro-ph.GA
Intensity mapping has emerged as a promising tool to probe the
three-dimensional structure of the universe. The traditional approach of galaxy
redshift surveys is based on individual galaxy detection, typically performed
by thresholding and digitizing large-scale intensity maps. By contrast,
intensity mapping uses the integrated emission from all sources in a 3D pixel
(or voxel) as an analog tracer of large-scale structure. In this work, we
develop a formalism to quantify the performance of both approaches when
measuring large-scale structures. We compute the Fisher information of an
arbitrary observable, derive the optimal estimator, and study its performance
as a function of source luminosity function, survey resolution, instrument
sensitivity, and other survey parameters. We identify regimes where each
approach is advantageous and discuss optimal strategies for different
scenarios. To determine the best strategy for any given survey, we develop a
metric that is easy to compute from the source luminosity function and the
survey sensitivity, and we demonstrate the application with several planned
intensity mapping surveys.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-102651809.06484 | Lagrangian chaos and scalar advection in stochastic fluid mechanics
math.AP math.DS math.PR nlin.CD physics.flu-dyn
We study the Lagrangian flow associated to velocity fields arising from
various models of fluid mechanics subject to white-in-time, $H^s$-in-space
stochastic forcing in a periodic box. We prove that in many circumstances,
these flows are chaotic, that is, the top Lyapunov exponent is strictly
positive. Our main results are for the Navier-Stokes equations on $\mathbb T^2$
and the hyper-viscous regularized Navier-Stokes equations on $\mathbb T^3$ (at
arbitrary Reynolds number and hyper-viscosity parameters), subject to forcing
which is non-degenerate at high frequencies. As an application, we study
statistically stationary solutions to the passive scalar advection-diffusion
equation driven by these velocities and subjected to random sources. The
chaotic Lagrangian dynamics are used to prove a version of anomalous
dissipation in the limit of vanishing diffusivity, which in turn, implies that
the scalar satisfies Yaglom's law of scalar turbulence -- the analogue of the
Kolmogorov 4/5 law. Key features of our study are the use of tools from ergodic
theory and random dynamical systems, namely the Multiplicative Ergodic Theorem
and a version of Furstenberg's Criterion, combined with hypoellipticity via
Malliavin calculus and approximate control arguments.
| arxiv topic:math.AP math.DS math.PR nlin.CD physics.flu-dyn |
arxiv_dataset-102661809.06584 | Long time oscillation of solutions of nonlinear Schr\"odinger equations
near minimal mass ground state
math.AP math-ph math.MP
In this paper, we consider the long time dynamics of radially symmetric
solutions of nonlinear Schr\"odinger equations (NLS) having a minimal mass
ground state. In particular, we show that there exist solutions with initial
data near the minimal mass ground state that oscillate for long time. More
precisely, we introduce a coordinate defined near the minimal mass ground state
which consists of finite and infinite dimensional part associated to the
discrete and continuous part of the linearized operator. Then, we show that the
finite dimensional part, two dimensional, approximately obeys Newton's equation
of motion for a particle in an anharmonic potential well. Showing that the
infinite dimensional part is well separated from the finite dimensional part,
we will have long time oscillation.
| arxiv topic:math.AP math-ph math.MP |
arxiv_dataset-102671809.06684 | Average performance of Orthogonal Matching Pursuit (OMP) for sparse
approximation
cs.IT math.IT
We present a theoretical analysis of the average performance of OMP for
sparse approximation. For signals that are generated from a dictionary with $K$
atoms and coherence $\mu$ and coefficients corresponding to a geometric
sequence with parameter $\alpha<1$, we show that OMP is successful with high
probability as long as the sparsity level $S$ scales as $S\mu^2 \log K \lesssim
1-\alpha $. This improves by an order of magnitude over worst case results and
shows that OMP and its famous competitor Basis Pursuit outperform each other
depending on the setting.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-102681809.06784 | Adversarial Reinforcement Learning for Observer Design in Autonomous
Systems under Cyber Attacks
cs.LG cs.CR math.OC stat.ML
Complex autonomous control systems are subjected to sensor failures,
cyber-attacks, sensor noise, communication channel failures, etc. that
introduce errors in the measurements. The corrupted information, if used for
making decisions, can lead to degraded performance. We develop a framework for
using adversarial deep reinforcement learning to design observer strategies
that are robust to adversarial errors in information channels. We further show
through simulation studies that the learned observation strategies perform
remarkably well when the adversary's injected errors are bounded in some sense.
We use neural network as function approximator in our studies with the
understanding that any other suitable function approximating class can be used
within our framework.
| arxiv topic:cs.LG cs.CR math.OC stat.ML |
arxiv_dataset-102691809.06884 | Green's function coupled cluster formulations utilizing extended inner
excitations
cond-mat.str-el
In this paper we analyze new approximations of the Green's function coupled
cluster (GFCC) method where locations of poles are improved by extending the
excitation level of inner auxiliary operators. These new GFCC approximations
can be categorized as GFCC-i($n,m$) method, where the excitation level of the
inner auxiliary operators ($m$) used to describe the ionization potentials and
electron affinities effects in the $N$$-$1 and $N$+1 particle spaces is higher
than the excitation level ($n$) used to correlate the ground-state coupled
cluster wave function for the $N$-electron system. Furthermore, we reveal the
so-called "$n$+1" rule in this category (or the GFCC-i($n$,$n$+1) method),
which states that in order to maintain size-extensivity of the Green's function
matrix elements, the excitation level of inner auxiliary operators
$X_p(\omega)$ and $Y_q(\omega)$ cannot exceed $n$+1. We also discuss the role
of the moments of coupled cluster equations that in a natural way assures these
properties. Our implementation in the present study is focused on the first
approximation in this GFCC category, i.e. the GFCC-i(2,3) method. As our first
practice, we use the GFCC-i(2,3) method to compute the spectral functions for
the N$_2$ and CO molecules in the inner and outer valence regimes. In
comparison with the GFCCSD results, the computed spectral functions from the
GFCC-i(2,3) method exhibit better agreement with the experimental results and
other theoretical results, particularly in terms of providing higher resolution
of satellite peaks and more accurate relative positions of these satellite
peaks with respect to the main peak positions.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-102701809.06984 | Effective dielectric tensor of deformed-helix ferroelectric liquid
crystals with subwavelength pitch and large tilt angle
physics.optics cond-mat.mtrl-sci cond-mat.soft
Short pitch deformed helix ferroelectric liquid crystals have numerous
applications as active materials in displays, optical telemetry and biomedical
devices. In this paper, we derive convenient analytical formulas to calculate
the effective dielectric tensor of these materials beyond the space average
approximation. By comparison with exact numerical calculations, we show that
our formulas are remarkably accurate in predicting optical properties in
virtually all practical situations, including the important case of large tilt
angles, where the space average approximation breaks down. We also present a
comparison between the two complementary approaches of expanding the mesoscopic
dielectric tensor vs. the mesoscopic transfer matrix, by deriving an expression
for the effective transfer matrix as an infinite expansion and explicitly
calculating the corresponding effective dielectric tensor for the first time.
Our results demonstrate that both methods give accurate predictions when
two-photon scattering terms are taken into account.
| arxiv topic:physics.optics cond-mat.mtrl-sci cond-mat.soft |
arxiv_dataset-102711809.07084 | Numerical Implementation of Harmonic Polylogarithms to Weight w = 8
hep-ph hep-th math-ph math.MP
We present the FORTRAN-code HPOLY.f for the numerical calculation of harmonic
polylogarithms up to w = 8 at an absolute accuracy of $\sim 4.9 \cdot 10^{-15}$
or better. Using algebraic and argument relations the numerical representation
can be limited to the range $x \in [0, \sqrt{2}-1]$. We provide replacement
files to map all harmonic polylogarithms to a basis and the usual range of
arguments $x \in ]-\infty,+\infty[$ to the above interval analytically. We also
briefly comment on a numerical implementation of real valued cyclotomic
harmonic polylogarithms.
| arxiv topic:hep-ph hep-th math-ph math.MP |
arxiv_dataset-102721809.07184 | Weighted Aleksandrov estimates: PDE and stochastic versions
math.AP math.PR
We prove several pointwise estimates for solutions of linear elliptic
(parabolic) equations with measurable coefficients in smooth domains
(cylinders) through the weighted $L_{d}$ ($L_{d+1}$)-norm of the free term. The
weights allow the free term to blow up near the (latteral) boundary. We also
present weighted estimates for occupation times of diffusion processes.
| arxiv topic:math.AP math.PR |
arxiv_dataset-102731809.07284 | A question of Norton-Sullivan in the analytic case
math.DS
In 1996, A. Norton and D. Sullivan asked the following question: If
$f:\mathbb{T}^2\rightarrow\mathbb{T}^2$ is a diffeomorphism,
$h:\mathbb{T}^2\rightarrow\mathbb{T}^2$ is a continuous map homotopic to the
identity, and $h f=T_{\rho} h$ where $\rho\in\mathbb{R}^2$ is a totally
irrational vector and $T_{\rho}:\mathbb{T}^2\rightarrow\mathbb{T}^2,\, z\mapsto
z+\rho$ is a translation, are there natural geometric conditions (e.g.
smoothness) on $f$ that force $h$ to be a homeomorphism? In [ J. Wang and Z.
Zhang, GAFA 2018 ], the first author and Z. Zhang gave a negative answer to the
above question in the $C^{\infty}$ category: In general, not even the infinite
smoothness condition can force $h$ to be a homeomorphism. In this article, we
give a negative answer in the $C^{\omega}$ category: We construct a
real-analytic conservative and minimal totally irrational pseudo-rotation of
$\mathbb{T}^2$ that is semi-conjugate to a translation but not conjugate to a
translation, which simultaneously answers a question raised in [ J. Wang and Z.
Zhang, GAFA 2018 ].
| arxiv topic:math.DS |
arxiv_dataset-102741809.07384 | New insights on the optimality of parameterized wiener filters for
speech enhancement applications
eess.AS cs.SD eess.SP
This work presents a unified framework for defining a family of noise
reduction techniques for speech enhancement applications. The proposed approach
provides a unique theoretical foundation for some widely-applied soft and hard
time-frequency masks, which encompasses the well-known Wiener filter and the
heuristically-designed Binary mask. These techniques can now be considered as
optimal solutions of the same minimization problem. The proposed cost function
is defined by two design parameters that not only establish a desired trade-off
between noise reduction and speech distortion, but also provide an insightful
relationship with the mask morphology. Such characteristic may be useful for
applications that require online adaptation of the suppression function
according to variations of the acoustic scenario. Simulation examples indicate
that the derived conformable suppression mask has approximately the same
quality and intelligibility performance capability of the classical
heuristically-defined parametric Wiener filter. The proposed approach may be of
special interest for real-time embedded speech enhancement applications such as
hearing aids and cochlear implants.
| arxiv topic:eess.AS cs.SD eess.SP |
arxiv_dataset-102751809.07484 | Materials knowledge system for nonlinear composites
cond-mat.mtrl-sci
In this contribution, we present a new Materials Knowledge System framework
for microstructure-sensitive predictions of effective stress--strain responses
in composite materials. The model is developed for composites with a wide range
of combinations of strain hardening laws and topologies of the constituents.
The theoretical foundation of the model is inspired by statistical continuum
theories, leveraged by mean-field approximation of self-consistent models, and
calibrated to data obtained from micromechanical finite element simulations.
The model also relies on newly formulated data-driven linkages between
micromechanical responses (phase-average strain rates and effective strength)
and microstructure as well as strength contrast of the constituents. The paper
describes in detail the theoretical development of the model, its
implementation into an efficient computational plasticity framework,
calibration of the linkages, and demonstration of the model predictions on
two-phase composites with isotropic constituents exhibiting linear and
power-law strain hardening laws. It is shown that the model reproduces finite
element results reasonably well with significant savings of the computational
cost.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-102761809.07584 | Additive Complements for a given Asymptotic Density
math.NT
{The first version of this text was written and submitted to a journal on
April, 12, 2018. This second version was submitted on April, 9, 2019.} We
investigate the existence of subsets $A$ and $B$ of
$\mathbb{N}:=\{0,1,2,\dots\}$ such that the sumset $A+B:=\{a+b~;a\in A,b\in
B\}$ has given asymptotic density. We solve the particular case in which $B$ is
a given finite subset of $\mathbb{N}$ and also the case when $B=A$ ; in the
later case, we generalize our result to $kA:=\{x_1+\cdots+x_k: x_i\in A,
i=1,\dots,k\}$ for an integer $k\geq2.$
| arxiv topic:math.NT |
arxiv_dataset-102771809.07684 | Automatic Parallelization of Sequential Programs
cs.DC
Prior work on Automatically Scalable Computation (ASC) suggests that it is
possible to parallelize sequential computation by building a model of
whole-program execution, using that model to predict future computations, and
then speculatively executing those future computations. Although that prior
work demonstrated scaling, it did not demonstrate speedup, because it ran
entirely in emulation. We took this as a challenge to construct a hardware
prototype that embodies the ideas of ASC, but works on a broader range of
programs and runs natively on hardware. The resulting system is similar in
spirit to the original work, but differs in practically every respect.
We present an implementation of the ASC architecture that runs natively on
x86 hardware and achieves near-linear speedup up to 44-cores (the size of our
test platform) for several classes of programs, such as computational kernels,
map-style programs, and matrix operations. We observe that programs are either
completely predictable, achieving near-perfect predictive accuracy, or totally
unpredictable, and therefore not amenable to scaling via ASC-like techniques.
We also find that in most cases, speedup is limited only by implementation
details: the overhead of our dependency tracking infrastructure and the
manipulation of large state spaces. We are able to automatically parallelize
programs with linked data structures that are not amenable to other forms of
automatic parallelization.
| arxiv topic:cs.DC |
arxiv_dataset-102781809.07784 | IASIS and BigMedilytics: Towards personalized medicine in Europe
cs.CY
One field of application of Big Data and Artificial Intelligence that is
receiving increasing attention is the biomedical domain. The huge volume of
data that is customary generated by hospitals and pharmaceutical companies all
over the world could potentially enable a plethora of new applications. Yet,
due to the complexity of such data, this comes at a high cost. We here review
the activities of the research group composed by people of the Universidad
Polit\'ecnica de Madrid and the Hospital Universitario Puerta de Hierro de
Majadahonda, Spain; discuss their activities within two European projects,
IASIS and BigMedilytics; and present some initial results.
| arxiv topic:cs.CY |
arxiv_dataset-102791809.07884 | Absence of singular continuous spectrum for perturbed discrete
Schr\"odinger operators
math-ph math.MP math.SP
We show that the spectral measure of discrete Schr\"odinger operators $
(Hu)(n)= u({n+1})+u({n-1})+V(n)u(n)$ does not have singular continuous
component if the potential $V(n)=O(n^{-1})$.
| arxiv topic:math-ph math.MP math.SP |
arxiv_dataset-102801809.07984 | A M\"obius invariant discretization of O'Hara's M\"obius energy
math.FA math.GT math.NA
We introduce a new discretization of O'Hara's M\"obius energy. In contrast to
the known discretizations of Simon and Kim and Kusner it is invariant under
M\"obius transformations of the surrounding space. The starting point for this
new discretization is the cosine formula of Doyle and Schramm. We then show
$\Gamma$-convergence of our discretized energies to the M\"obius energy under
very natural assumptions.
| arxiv topic:math.FA math.GT math.NA |
arxiv_dataset-102811809.08084 | Towards Better Understanding Researcher Strategies in Cross-Lingual
Event Analytics
cs.DL
With an increasing amount of information on globally important events, there
is a growing demand for efficient analytics of multilingual event-centric
information. Such analytics is particularly challenging due to the large amount
of content, the event dynamics and the language barrier. Although memory
institutions increasingly collect event-centric Web content in different
languages, very little is known about the strategies of researchers who conduct
analytics of such content. In this paper we present researchers' strategies for
the content, method and feature selection in the context of cross-lingual
event-centric analytics observed in two case studies on multilingual Wikipedia.
We discuss the influence factors for these strategies, the findings enabled by
the adopted methods along with the current limitations and provide
recommendations for services supporting researchers in cross-lingual
event-centric analytics.
| arxiv topic:cs.DL |
arxiv_dataset-102821809.08184 | Higher derivatives of the inverse tangent function and a summation
formula involving binomial coefficients
math.CA
In 2017, O. Deiser and C. Lasser obtained an explicit formula for the $n$-th
derivative of the inverse tangent function. We calculate this derivative by a
different method based on Fa\`a di Bruno's formula. Comparing the two results
leads to the following identity for binomial coefficients:
$$\sum_{i=m}^{[n/2]}\frac{(-1)^i}{4^i}\binom{i}{m}\binom{n-i}{i}=\frac{(-1)^m}{2^n}\binom{n+1}{2m+1},$$
where $n,m\in \mathbb{N}_0$ and $m\leq [n/2]$. As was pointed out to the author
by C. Krattenthaler, this formula is a special case of Gau\ss's formula for the
hypergeometric function $_2F_1$.
| arxiv topic:math.CA |
arxiv_dataset-102831809.08284 | Global well-posedness and scattering for the radial, defocusing, cubic
nonlinear wave equation
math.AP
In this paper we prove global well-posedness and scattering for the
defocusing, cubic, nonlinear wave equation on $\mathbf{R}^{1 + 3}$ with radial
initial data lying in the critical Sobolev space $\dot{H}^{1/2}(\mathbf{R}^{3})
\times \dot{H}^{-1/2}(\mathbf{R}^{3})$.
| arxiv topic:math.AP |
arxiv_dataset-102841809.08384 | Milnor-Hamm sphere fibrations and the equivalence problem
math.AG math.CV
We introduce the sphere fibration for real map germs with radial discriminant
and we address the problem of its equivalence with the Milnor-Hamm tube
fibration. Under natural conditions, we prove the existence of open book
structures with singularities and solve the equivalence problem.
| arxiv topic:math.AG math.CV |
arxiv_dataset-102851809.08484 | Klebanov-Strassler black hole
hep-th
We construct a black hole solution on warped deformed conifold in type IIB
supergravity with fluxes. The black hole has translationary invariant horizon
and is a holographic dual to a thermal homogeneous and isotropic state of a
cascading $SU(K+P)\times SU(K)$ ${\cal N}=1$ supersymmetric gauge theory with
spontaneously broken chiral symmetry. We discuss thermal properties of the new
black hole solutions. We comment on implications of the new black hole
solutions for the landscape of KKLT de Sitter vacua in string theory.
| arxiv topic:hep-th |
arxiv_dataset-102861809.08584 | Nombre de classes de conjugaison d'\'el\'ements d'ordre fini dans les
groupes de Brown-Thompson
math.GR math.DS
We extend a result of Matucci on the number of conjugacy classes of finite
order elements in the Thompson group $T$. According to Liousse, if $
gcd(m-1,q)$ is not a divisor of $r$ then there does not exist element of order
$q$ in the Brown-Thompson group $T_{r,m}$. We show that if $ gcd(m-1,q)$ is a
divisor of $r$ then there are exactly $\varphi(q). gcd(m-1,q)$ conjugacy
classes of elements of order $q$ in $T_{r,m}$, where $\varphi$ is the Euler
function phi. As a corollary, we obtain that the Thompson group $T$ is
isomorphic to none of the groups $T_{r,m}$, for $m\not=2$ and any morphism from
$T$ into $T_{r,m}$, with $m\not=2$ and $r\not= 0$ $mod \ (m-1)$, is trivial.
| arxiv topic:math.GR math.DS |
arxiv_dataset-102871809.08684 | Reduced Order Modeling Framework for Combustor Instabilities Using
Truncated Domain Training
physics.flu-dyn math.NA
A multi-fidelity framework is established and demonstrated for prediction of
combustion instabilities in rocket engines. The major idea is to adapt
appropriate fidelity modeling approaches for different components in a rocket
engine to ensure accurate and efficient predictions. Specifically, the proposed
framework integrates projection-based Reduced Order Models (ROMs) that are
developed using bases generated on truncated domain simulations. The ROM
training is performed on truncated domains, and thus does not require full
order model solutions on the full rocket geometry, thus demonstrating the
potential to greatly reduce training cost. Geometry-specific training is
replaced by the response generated by perturbing the characteristics at the
boundary of the truncated domain. This training method is shown to enhance
predictive capabilities and robustness of the resulting ROMs, including at
conditions outside the training range. Numerical tests are conducted on a
quasi-1D model of a single-element rocket combustor and the present framework
is compared to traditional ROM development approaches.
| arxiv topic:physics.flu-dyn math.NA |
arxiv_dataset-102881809.08784 | Analytical Derivation of the Impulse Response for the Bounded 2-D
Diffusion Channel
cs.ET
This paper focuses on the derivation of the distribution of diffused
particles absorbed by an agent in a bounded environment. In particular, we
analogously consider to derive the impulse response of a molecular
communication channel in 2-D and 3-D environment. In 2-D, the channel involves
a point transmitter that releases molecules to a circular absorbing receiver
that absorbs incoming molecules in an environment surrounded by a circular
reflecting boundary. Considering this setup, the joint distribution of the
molecules on the circular absorbing receiver with respect to time and angle is
derived. Using this distribution, the channel characteristics are examined.
Furthermore, we also extend this channel model to 3-D using a cylindrical
receiver and investigate the channel properties. We also propose how to obtain
an analytical solution for the unbounded 2-D channel from our derived
solutions, as no analytical derivation for this channel is present in the
literature.
| arxiv topic:cs.ET |
arxiv_dataset-102891809.08884 | Taking Informed Action on Student Activity in MOOCs
cs.HC
This paper presents a novel approach to understand specific student behavior
in MOOCs. Instructors currently perceive participants only as one homogeneous
group. In order to improve learning outcomes, they encourage students to get
active in the discussion forum and remind them of approaching deadlines. While
these actions are most likely helpful, their actual impact is often not
measured. Additionally, it is uncertain whether such generic approaches
sometimes cause the opposite effect, as some participants are bothered with
irrelevant information. On the basis of fine granular events emitted by our
learning platform, we derive metrics and enable teachers to employ clustering,
in order to divide the vast field of participants into meaningful subgroups to
be addressed individually.
| arxiv topic:cs.HC |
arxiv_dataset-102901809.08984 | A Bayesian Approach to Multivariate Adaptive Localization in
Ensemble-Based Data Assimilation with Time-Dependent Extensions
cs.NA cs.CE math.OC
Ever since its inception, the Ensemble Kalman Filter has elicited many
heuristic methods that sought to correct it. One such method is
localization---the thought that `nearby' variables should be highly correlated
with `far away' variable not. Recognizing that correlation is a time-dependent
property, adaptive localization is a natural extension to these heuristics. We
propose a Bayesian approach to adaptive Schur-product localization for the
DEnKF, and extend it to support multiple radii of influence. We test both the
empirical validity of (multivariate) adaptive localization, and of our
approach. We test a simple toy problem (Lorenz'96), extending it to a
multivariate model, and a more realistic geophysical problem (1.5 Layer
Quasi-Geostrophic). We show that the multivariate approach has great promise on
the toy problem, and that the univariate approach leads to improved filter
performance for the realistic geophysical problem.
| arxiv topic:cs.NA cs.CE math.OC |
arxiv_dataset-102911809.09084 | Dirac operators on real spinor bundles of complex type
math.DG hep-th
Let $(M,g)$ be a pseudo-Riemannian manifold of signature $(p,q)$. We compute
the obstruction for a vector bundle $S$ over $(M,g)$ to admit a Dirac operator
whose principal symbol induces on $S$ the structure of a bundle of irreducible
real Clifford modules of complex type, that is, a real spinor bundle of
irreducible complex type. In order to do this, we use the theory of Lipschitz
structures in signature $p-q\equiv_8 3,7$ to reformulate the problem as the
obstruction problem for $(M,g)$ to admit a $\mathrm{Spin}^{o}_{\alpha}$
structure with $\alpha = -1$ if $p-q \equiv_{8} 3$ or $\alpha = +1$ if $ p-q
\equiv_{8} 7$, where
$\mathrm{Spin}^o_+(p,q)=\mathrm{Spin}(p,q)\cdot\mathrm{Pin}_{2,0}$ and
$\mathrm{Spin}^o_-(p,q)=\mathrm{Spin}(p,q)\cdot \mathrm{Pin}_{0,2}$. This
allows computing the obstruction in terms of the Karoubi Stiefel-Whitney
classes of $(M,g)$ and the existence of an auxiliary $\mathrm{O}(2)$ bundle
with prescribed characteristic classes. Furthermore, we explicitly show how a
$\mathrm{Spin}^o_{\alpha}$ structure can be used to construct $S$ and we give
geometric characterizations (in terms of associated bundles) of the conditions
under which the structure group of $S$ reduces to certain natural subgroups of
$\mathrm{Spin}^o_{\alpha}$. Finally, we prove that certain codimension two
submanifolds of spin manifolds and certain products of tori with Grassmanians,
which were not known to admit irreducible real spinor bundles, do admit
$\mathrm{Spin}^{o}_{\alpha}$ structures and therefore do admit real spinor
bundles of irreducible complex type.
| arxiv topic:math.DG hep-th |
arxiv_dataset-102921809.09184 | Validation and Uncertainty Quantification for Wall Boiling Closure
Relations in Multiphase-CFD Solver
physics.flu-dyn physics.comp-ph
The two-fluid model based Multiphase Computational Fluid Dynamics (MCFD) has
been considered as one of the most promising tools to investigate two-phase
flow and boiling system for engineering purposes. The MCFD solver requires
closure relations to make the conservation equations solvable. The wall boiling
closure relations, for example, provide predictions on wall superheat and heat
partitioning. The accuracy of these closure relations significantly influences
the predictive capability of the solver. In this paper, a study of validation
and uncertainty quantification (VUQ) for the wall boiling closure relations in
MCFD solver is performed. The work has three purposes: i). identify influential
parameters to the quantities of interest of the boiling system through
sensitivity analysis; ii). evaluate the parameter uncertainty through Bayesian
inference with the support of multiple datasets; iii). quantitatively measure
the agreement between solver predictions and datasets. The widely used
Kurul-Podowski wall boiling closure relation is studied in this paper. Several
statistical methods are used, including Morris screening method for global
sensitivity analysis, Markov Chain Monte Carlo (MCMC) for inverse Bayesian
inference, and confidence interval as the validation metric. The VUQ results
indicated that the current empirical correlations-based wall boiling closure
relations achieved satisfactory agreement on wall superheat predictions.
However, the closure relations also demonstrate intrinsic inconsistency and
fail to give consistently accurate predictions for all quantities of interest
over the well-developed nucleate boiling regime.
| arxiv topic:physics.flu-dyn physics.comp-ph |
arxiv_dataset-102931809.09284 | Tree-Based Optimization: A Meta-Algorithm for Metaheuristic Optimization
cs.NE
Designing search algorithms for finding global optima is one of the most
active research fields, recently. These algorithms consist of two main
categories, i.e., classic mathematical and metaheuristic algorithms. This
article proposes a meta-algorithm, Tree-Based Optimization (TBO), which uses
other heuristic optimizers as its sub-algorithms in order to improve the
performance of search. The proposed algorithm is based on mathematical tree
subject and improves performance and speed of search by iteratively removing
parts of the search space having low fitness, in order to minimize and purify
the search space. The experimental results on several well-known benchmarks
show the outperforming performance of TBO algorithm in finding the global
solution. Experiments on high dimensional search spaces show significantly
better performance when using the TBO algorithm. The proposed algorithm
improves the search algorithms in both accuracy and speed aspects, especially
for high dimensional searching such as in VLSI CAD tools for Integrated Circuit
(IC) design.
| arxiv topic:cs.NE |
arxiv_dataset-102941809.09384 | Relations de Hodge--Riemann et combinatoire des matro\"ides (d'apr\`es
K. Adiprasito, J. Huh et E. Katz)
math.AG
Finite matroids are combinatorial structures that express the concept of
linear independence. In 1964, G.-C. Rota conjectured that the coefficients of
the "characteristic polynomial" of a matroid $M$, polynomial whose coefficients
enumerate its subsets of given rank, form a log-concave sequence. K.
Adiprasito, J. Huh et E. Katz have proved this conjecture using methods which,
although entirely combinatorial, are inspired by algebraic geometry. From the
Bergman fan of the matroid $M$, they define a graded "Chow ring" $A(M)$ for
which they prove analogs of the Poincar\'e duality, the Hard Lefschetz theorem,
and the Hodge--Riemann relations. The sought for log-concavity inequalities are
then analogous to the Khovanskii--Teissier inequalities.
| arxiv topic:math.AG |
arxiv_dataset-102951809.09484 | A simple link of information entropy of quantum and classical systems
with Newtonian $r^{-2}$ dependence of Verlinde's entropic force
quant-ph
It is shown that the entropic force formula $F_e=-\lambda\partial S/\partial
A$ leads to a Newtonian $r^{-2}$ dependence. Here we employ the universal
property of the information entropy $S=a+b\ln N$ ($N$ is the number of
particles of a quantum system and $A$ is the area containing the system). This
property was previously obtained for fermionic systems (atoms, atomic clusters,
nuclei and infinite Fermi systems i.e. electron gas, liquid $^3$He and nuclear
matter) and bosonic ones (correlated boson-atoms in a trap). A similar
dependence of the entropic force has been derived very recently by Plastino et
al with a Bose or Fermi gas entropy, inspired by Verlinde's
conjecture~\cite{Verlide-11} that gravity is an emergent entropic force.
Finally, we point out that our simple argument holds for classical systems as
well.
| arxiv topic:quant-ph |
arxiv_dataset-102961809.09584 | Dynamics of Poles in 2D Hydrodynamics with Free Surface: New Constants
of Motion
nlin.SI nlin.PS physics.flu-dyn
We address a problem of potential motion of ideal incompressible fluid with a
free surface and infinite depth in two dimensional geometry with gravity forces
and surface tension. A time-dependent conformal mapping z(w,t) of the lower
complex half-plane of the variable w into the area filled with fluid is
performed. We study the dynamics of singularities of both z(w,t) and the
complex fluid potential Pi(w,t) in the upper complex half-plane of w. We show
the existence of solutions with an arbitrary finite number N of complex poles
in z_w(w,t) and Pi_w(w,t) which are the derivatives of z(w,t) and Pi(w,t) over
w. The orders of poles can be arbitrary for zero surface tension while all
orders are even for nonzero surface tension. We find that the residues of
z_w(w,t) at these N points are new, previously unknown constants of motion, see
also Ref. V.E. Zakharov and A. I. Dyachenko, arXiv:1206.2046 (2012) for the
preliminary results. All these constants of motion commute with each other in
the sense of underlying Hamiltonian dynamics. In absence of both gravity and
surface tension, the residues of Pi_w(w,t) are also the constants of motion
while nonzero gravity g ensures a trivial linear dependence of these residues
on time. A Laurent series expansion of both z_w(w,t) and Pi_w(w,t) at each
poles position reveals an existence of additional integrals of motion for poles
of the second order. If all poles are simple then the number of independent
real integrals of motion is 4N for zero gravity and 4N-1 for nonzero gravity.
For the second order poles we found 6N motion integral for zero gravity and
6N-1 for nonzero gravity. We suggest that the existence of these nontrivial
constants of motion provides an argument in support of the conjecture of
complete integrability of free surface hydrodynamics in deep water.
| arxiv topic:nlin.SI nlin.PS physics.flu-dyn |
arxiv_dataset-102971809.09684 | LOBO -- Evaluation of Generalization Deficiencies in Twitter Bot
Classifiers
cs.CR cs.SI
Botnets in online social networks are increasingly often affecting the
regular flow of discussion, attacking regular users and their posts, spamming
them with irrelevant or offensive content, and even manipulating the popularity
of messages and accounts. Researchers and cybercriminals are involved in an
arms race, and new and updated botnets designed to defeat current detection
systems are constantly developed, rendering such detection systems obsolete.
In this paper, we motivate the need for a generalized evaluation in Twitter
bot detection and propose a methodology to evaluate bot classifiers by testing
them on unseen bot classes. We show that this methodology is empirically
robust, using bot classes of varying sizes and characteristics and reaching
similar results, and argue that methods trained and tested on single bot
classes or datasets might not able to generalize to new bot classes. We train
one such classifier on over 200,000 data points and show that it achieves over
97% accuracy. The data used to train and test this classifier includes some of
the largest and most varied collections of bots used in literature. We then
test this theoretically sound classifier using our methodology, highlighting
that it does not generalize well to unseen bot classes. Finally, we discuss the
implications of our results, and reasons why some bot classes are easier and
faster to detect than others.
| arxiv topic:cs.CR cs.SI |
arxiv_dataset-102981809.09784 | Exact partition potential for model systems of interacting electrons in
1-D
physics.chem-ph
We find the numerically exact partition potential for 1-D systems of
interacting electrons designed to model diatomic molecules. At integer fragment
occupations, the kinetic contribution to the partition potential develops sharp
features in the internuclear region that nearly cancel corresponding features
of exchange-correlation. They occur at locations that coincide with those of
well-known features of the underlying molecular Kohn-Sham potential. For
non-integer fragment occupations, we demonstrate that the fragment Kohn-Sham
gaps determine the kinetic part of the partition potential. Our results
highlight the importance of non-additive noninteracting kinetic and
exchange-correlation energy approximations in density-embedding methods at
large internuclear separations and the importance of non-additive
noninteracting kinetic energy approximations at all separations.
| arxiv topic:physics.chem-ph |
arxiv_dataset-102991809.09884 | Cavity-induced superconducting and $4k_F$ charge-density-wave states
cond-mat.quant-gas
We propose two experimental setups for fermionic atoms in a high-finesse
optical resonator in which either a superconducting state with s-wave symmetry
of the pairs or a 4k F charge density wave can self-organize. In order to
stabilize the s-wave pairing, a two component attractively in- teracting
fermionic gas is confined to a one dimensional chain structure by an optical
lattice. The tunneling of the atoms along the chains is suppressed initially by
an energy offset between neighbor- ing sites. A Raman transition using the
cavity mode and a transversal pump laser then reintroduces a cavity-assisted
tunneling. The feedback mechanism between the cavity field and the atoms leads
to a spontaneous occupation of the cavity field and of a state of the fermionic
atoms which is dominated by s-wave pairing correlations. Extending the setup to
a quasi-one-dimensional ladder structure where the tunneling of atoms along the
rungs of the ladder is cavity-assisted, the repul- sively interacting fermionic
atoms self-organize into a 4k F charge density wave. We use adiabatic
elimination of the cavity field combined with state-of-the-art density matrix
renormalization group methods in finite systems in order to identify the steady
state phases of the system.
| arxiv topic:cond-mat.quant-gas |
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