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arxiv_dataset-80001612.04191 | DEMoS Manifesto
cs.OH
This is a manifesto for DEMoS, which is a Distributed Embedded Modular
System, but also a manifesto addressing the need for more
inter-/cross-disciplinary mastery of working knowledge related to installing
this class of systems in the real world. There is somehow room for yet another
class of systems - complementary to existing embedded systems - complementing
distributed operating systems - which takes on an interdisciplinary
cyber-physical-materiality approach, a dedicated holistic perspective that
recognizes the true value of interdisciplinary mastery vs. the implicit and
overlooked expense of narrow intra-disciplinary focus dominating much of
systems development (e.g. EE, CE, CS, SE, and IS). Interdisciplinary mastery
yields its accumulated value across the development, deployment, use, re-use,
and decommission phases for this class of systems: DEMoS is a system
architected to be locally distributed, embedded, and modular as outlined herein
and with the additional goals of human interdisciplinary mastery in this
context: A potential set of goals for developing and applying DEMoS can be
found in UN Resolution 70/1.
| arxiv topic:cs.OH |
arxiv_dataset-80011612.04291 | A local fermion update algorithm for SYM quantum mechanics
hep-lat
We present a local fermion update algorithm for N=4 supersymmetric Yang-Mills
quantum mechanics which allows simulations in fixed canonical sectors. We
discuss some aspects of the physics of this theory, including the appearance of
flat directions in the bosonic potential and the metastabilities related to
those. In particular, we show that the modulus of the bosonic fields diverges
in some of the fermion sectors and for thermal boundary conditions.
| arxiv topic:hep-lat |
arxiv_dataset-80021612.04391 | A Robotic Prosthesis for an Amputee Drummer
cs.RO cs.HC
The design and evaluation of a robotic prosthesis for a drummer with a
transradial amputation is presented. The principal objective of the prosthesis
is to simulate the role fingers play in drumming. This primarily includes
controlling the manner in which the drum stick rebounds after initial impact.
This is achieved using a DC motor driven by a variable impedance control
framework in a shared control system. The user's ability to perform with and
control the prosthesis is evaluated using a musical synchronization study. A
secondary objective of the prosthesis is to explore the implications of musical
expression and human-robotic interaction when a second, completely autonomous,
stick is added to the prosthesis. This wearable robotic musician interacts with
the user by listening to the music and responding with different rhythms and
behaviors. We recount some empirical findings based on the user's experience of
performing under such a paradigm.
| arxiv topic:cs.RO cs.HC |
arxiv_dataset-80031612.04491 | Broadband reconfigurable logic gates in phonon waveguides
cond-mat.mes-hall
The high-quality-factor mechanical resonator in electromechanical systems has
facilitated dynamic control of phonons via parametric nonlinear processes and
paved the development of mechanical logic-elements. However the resonating
element with a narrow bandwidth limits the resultant operation speeds as well
as constraining the availability of nonlinear phenomena to a narrow spectral
range. To overcome these drawbacks we have developed phonon waveguides in which
the mechanical analogue of four-wave-mixing is demonstrated that enables the
frequency of phonon waves to be converted over 1 MHz. We harness this platform
to execute multiple binary mechanical logic gates in parallel, via frequency
division multiplexing in a two-octave-wide phonon transmission band, where each
gate can be independently reconfigured. The fidelity of the binary gates is
verified via temporal measurements yielding eye diagrams which confirm the
availability of high speed logic operations. The phonon waveguide architecture
thus offers the broadband functionality that is essential to realising
mechanical signal processors.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-80041612.04591 | The beta Pictoris association: Catalog of photometric rotational periods
of low-mass members and candidate members
astro-ph.SR astro-ph.EP
We intended to compile the most complete catalog of bona fide members and
candidate members of the beta Pictoris association, and to measure their
rotation periods and basic properties from our own observations, public
archives, and exploring the literature. We carried out a multi-observatories
campaign to get our own photometric time series and collected all archived
public photometric data time series for the stars in our catalog. Each time
series was analyzed with the Lomb-Scargle and CLEAN periodograms to search for
the stellar rotation periods. We complemented the measured rotational
properties with detailed information on multiplicity, membership, and projected
rotational velocity available in the literature and discussed star by star. We
measured the rotation periods of 112 out of 117 among bona fide members and
candidate members of the beta Pictoris association and, whenever possible, we
also measured the luminosity, radius, and inclination of the stellar rotation
axis. This represents to date the largest catalog of rotation periods of any
young loose stellar association. We provided an extensive catalog of rotation
periods together with other relevant basic properties useful to explore a
number of open issues, such as the causes of spread of rotation periods among
coeval stars, evolution of angular momentum, and lithium-rotation connection.
| arxiv topic:astro-ph.SR astro-ph.EP |
arxiv_dataset-80051612.04691 | On the role of moisture in triggering out-of-plane displacement in
paper: from the network level to the macroscopic scale
cond-mat.mtrl-sci
The response of paper to humidity variations is a complex multi-scale
problem. The hygroscopic swelling of individual fibres and their interactions
within the fibrous network govern the macroscopic response. At this scale,
moisture induced instabilities and out-of-plane deformations may occur. This
work focuses on several aspects of this issue. A macroscopic phenomenological
hygro-mechanical model is first proposed, which aims at predicting moisture
induced out-of-plane deformations in paper sheets. The constitutive model is
based on the relation between these deformations and typical irreversible
phenomena associated to the history of paper manufacturing, i.e. the release of
dried-in strains. The model is used to describe bending induced by moisture
gradients through the thickness of the sheet as well as buckling due to
moisture variation in the presence of mechanical constraints. The results of
the model show that the anisotropic sheet-level hygro-expansion has a strong
influence on the instability phenomena. Moreover, a comparison with experiments
provides adequate semi-quantitative estimates. An additional step is made
towards the multi-scale understanding of paper hygro-mechanics. The fundamental
mechanisms governing the macroscopic moisture induced response are investigated
on the basis of the underlying fibrous network. To this aim, a meso-structural
model is developed which consists of a network of fibres randomly positioned in
a planar region according to an orientation probability density function. A
series of network simulations reveals that upon moisture content variations the
expansion of the inter-fibre bonding regions drives the overall deformation.
Particularly in the case of anisotropic fibre orientation, this explains the
origin of the macro-scale anisotropic hygro-expansion, which is essential for
the observed sheet-level instability phenomena.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-80061612.04791 | Scalable Computation of Optimized Queries for Sequential Diagnosis
cs.AI
In many model-based diagnosis applications it is impossible to provide such a
set of observations and/or measurements that allow to identify the real cause
of a fault. Therefore, diagnosis systems often return many possible candidates,
leaving the burden of selecting the correct diagnosis to a user. Sequential
diagnosis techniques solve this problem by automatically generating a sequence
of queries to some oracle. The answers to these queries provide additional
information necessary to gradually restrict the search space by removing
diagnosis candidates inconsistent with the answers.
During query computation, existing sequential diagnosis methods often require
the generation of many unnecessary query candidates and strongly rely on
expensive logical reasoners. We tackle this issue by devising efficient
heuristic query search methods. The proposed methods enable for the first time
a completely reasoner-free query generation while at the same time guaranteeing
optimality conditions, e.g. minimal cardinality or best understandability, of
the returned query that existing methods cannot realize. Hence, the performance
of this approach is independent of the (complexity of the) diagnosed system.
Experiments conducted using real-world problems show that the new approach is
highly scalable and outperforms existing methods by orders of magnitude.
| arxiv topic:cs.AI |
arxiv_dataset-80071612.04891 | Deep learning is effective for the classification of OCT images of
normal versus Age-related Macular Degeneration
stat.ML cs.CV cs.LG
Objective: The advent of Electronic Medical Records (EMR) with large
electronic imaging databases along with advances in deep neural networks with
machine learning has provided a unique opportunity to achieve milestones in
automated image analysis. Optical coherence tomography (OCT) is the most
commonly obtained imaging modality in ophthalmology and represents a dense and
rich dataset when combined with labels derived from the EMR. We sought to
determine if deep learning could be utilized to distinguish normal OCT images
from images from patients with Age-related Macular Degeneration (AMD). Methods:
Automated extraction of an OCT imaging database was performed and linked to
clinical endpoints from the EMR. OCT macula scans were obtained by Heidelberg
Spectralis, and each OCT scan was linked to EMR clinical endpoints extracted
from EPIC. The central 11 images were selected from each OCT scan of two
cohorts of patients: normal and AMD. Cross-validation was performed using a
random subset of patients. Area under receiver operator curves (auROC) were
constructed at an independent image level, macular OCT level, and patient
level. Results: Of an extraction of 2.6 million OCT images linked to clinical
datapoints from the EMR, 52,690 normal and 48,312 AMD macular OCT images were
selected. A deep neural network was trained to categorize images as either
normal or AMD. At the image level, we achieved an auROC of 92.78% with an
accuracy of 87.63%. At the macula level, we achieved an auROC of 93.83% with an
accuracy of 88.98%. At a patient level, we achieved an auROC of 97.45% with an
accuracy of 93.45%. Peak sensitivity and specificity with optimal cutoffs were
92.64% and 93.69% respectively. Conclusions: Deep learning techniques are
effective for classifying OCT images. These findings have important
implications in utilizing OCT in automated screening and computer aided
diagnosis tools.
| arxiv topic:stat.ML cs.CV cs.LG |
arxiv_dataset-80081612.04991 | Enhancing the charging power of quantum batteries
quant-ph cond-mat.stat-mech
Can collective quantum effects make a difference in a meaningful
thermodynamic operation? Focusing on energy storage and batteries, we
demonstrate that quantum mechanics can lead to an enhancement in the amount of
work deposited per unit time, i.e., the charging power, when $N$ batteries are
charged collectively. We first derive analytic upper bounds for the collective
\emph{quantum advantage} in charging power for two choices of constraints on
the charging Hamiltonian. We then highlight the importance of entanglement by
proving that the quantum advantage vanishes when the collective state of the
batteries is restricted to be in the separable ball. Finally, we provide an
upper bound to the achievable quantum advantage when the interaction order is
restricted, i.e., at most $k$ batteries are interacting. Our result is a
fundamental limit on the advantage offered by quantum technologies over their
classical counterparts as far as energy deposition is concerned.
| arxiv topic:quant-ph cond-mat.stat-mech |
arxiv_dataset-80091612.05091 | Time evolution of Hanle and Zeeman polarization in MHD models
astro-ph.SR
Exposing the polarization signatures of the solar chromosphere requires
studying its temporal variations, which is rarely done when modelling and
interpreting scattering and Hanle signals. The present contribution sketches
the scientific problem of solar polarization diagnosis from the point of view
of the temporal dimension, remarking some key aspects for solving it. Our
time-dependent calculations expose the need of considering dynamics explicitly
when modelling and observing scattering polarization in order to achieve
effective diagnosis techniques as well as a deeper knowledge of the second
solar spectrum.
| arxiv topic:astro-ph.SR |
arxiv_dataset-80101612.05191 | Nash Social Welfare for Indivisible Items under Separable,
Piecewise-Linear Concave Utilities
cs.GT cs.DM cs.DS math.CO
Recently Cole and Gkatzelis gave the first constant factor approximation
algorithm for the problem of allocating indivisible items to agents, under
additive valuations, so as to maximize the Nash Social Welfare. We give
constant factor algorithms for a substantial generalization of their problem --
to the case of separable, piecewise-linear concave utility functions. We give
two such algorithms, the first using market equilibria and the second using the
theory of stable polynomials.
In AGT, there is a paucity of methods for the design of mechanisms for the
allocation of indivisible goods and the result of Cole and Gkatzelis seemed to
be taking a major step towards filling this gap. Our result can be seen as
another step in this direction.
| arxiv topic:cs.GT cs.DM cs.DS math.CO |
arxiv_dataset-80111612.05291 | Catalyzing Cloud-Fog Interoperation in 5G Wireless Networks: An SDN
Approach
cs.NI
The piling up storage and compute stacks in cloud data center are expected to
accommodate the majority of internet traffic in the future. However, as the
number of mobile devices significantly increases, getting massive data into and
out of the cloud wirelessly inflicts high pressure on the bandwidth, and
meanwhile induces unpredictable latency. Fog computing, which advocates
extending clouds to network edge, guarantees low latency and location-aware
service provisioning. In this article, we consider fog computing as an ideal
complement rather than a substitute of cloud computing, and we propose a
software defined networking (SDN) enabled framework for cloud-fog
interoperation, aiming at improving quality of experience and optimizing
network resource usage. Two case studies are provided to illuminate the
feasibility and advantage of the proposed framework. At last, potential
research issues are presented for further investigation.
| arxiv topic:cs.NI |
arxiv_dataset-80121612.05391 | Simultaneous microscopic description of nuclear level density and
radiative strength function
nucl-th
Nuclear level density (NLD) and radiative strength function (RSF) are
described simultaneously within a microscopic approach, which takes into
account the thermal effects of the exact pairing as well as the giant
resonances within the phonon-damping model. The good agreement between the
results of calculations and experimental data extracted by the Oslo group for
$^{170, 171, 172}$Yb isotopes shows the importance of exact thermal pairing in
the description of NLD at low and intermediate excitation energies and
invalidates the assumption based on the Brink-Axel hypothesis in the
description of the RSF.
| arxiv topic:nucl-th |
arxiv_dataset-80131612.05491 | Strong Federations: An Interoperable Blockchain Solution to Centralized
Third-Party Risks
cs.CR cs.CY
Bitcoin, the first peer-to-peer electronic cash system, opened the door to
permissionless, private, and trustless transactions. Attempts to repurpose
Bitcoin's underlying blockchain technology have run up against fundamental
limitations to privacy, faithful execution, and transaction finality. We
introduce \emph{Strong Federations}: publicly verifiable, Byzantine-robust
transaction networks that facilitate movement of any asset between disparate
markets, without requiring third-party trust. \emph{Strong Federations} enable
commercial privacy, with support for transactions where asset types and amounts
are opaque, while remaining publicly verifiable. As in Bitcoin, execution
fidelity is cryptographically enforced; however, \emph{Strong Federations}
significantly lower capital requirements for market participants by reducing
transaction latency and improving interoperability. To show how this innovative
solution can be applied today, we describe \emph{\liquid}: the first
implementation of \emph{Strong Federations} deployed in a Financial Market.
| arxiv topic:cs.CR cs.CY |
arxiv_dataset-80141612.05591 | On the rotationally driven pevatron in the centre of the Milky Way
astro-ph.HE
Based on the collective linear and nonlinear processes in a magnetized plasma
surrounding the black hole at the galactic center (GC), an acceleration
mechanism is proposed to explain the recent detection/discovery of PeV protons.
In a two stage process, the gravitation energy is first converted to the
electrical energy in fast growing Langmuir waves, and then the electrical
energy is transformed to the particle kinetic energy through Landau damping of
waves. It is shown that, for the characteristics parameters of GC plasma,
proton energy can be boosted upto 5PeV.
| arxiv topic:astro-ph.HE |
arxiv_dataset-80151612.05691 | Magnetar central engine and possible gravitational wave emission of
nearby short GRB 160821B
astro-ph.HE hep-ph
GRB 160821B is a short gamma-ray burst (GRB) at redshift $z=0.16$, with a
duration less than 1 second and without detection of any "extended emission" up
to more than 100 seconds in both {\em Swift}/BAT and {\em Fermi}/GBM bands. An
X-ray plateau with a sharp drop 180 seconds after the BAT trigger was observed
with {\em Swift}/XRT. No supernova or kilo-nova signature was detected.
Assuming the central engine of this SGRB is a recently born supra-massive
magnetar, we can explain the SGRB as jet radiation and its X-ray plateau as the
internal energy dissipation of the pulsar wind as it spins down. We constrain
its surface magnetic field as $B_{\rm p}<3.12\times 10^{16}$ G and initial spin
period as $P_0< 8.5\times 10^{-3}$ seconds. Its equation of state is consistent
with the GM1 model with $M_{\rm TOV} \sim 2.37 M_\odot$ and ellipticity
$\epsilon<0.07$. Its gravitational wave (GW) radiation may be detectable with
the future Einstein Telescope, but is much weaker than the current
detectability limit of advanced-LIGO. The GW radiation of such an event would
be detectable by advanced-LIGO if it occurred at a distance of 100 Mpc
($z=0.023$).
| arxiv topic:astro-ph.HE hep-ph |
arxiv_dataset-80161612.05791 | Electrons and polarons at oxide interfaces explored by soft-X-ray ARPES
cond-mat.mes-hall cond-mat.mtrl-sci
Soft-X-ray ARPES (SX-ARPES) with its enhanced probing depth and chemical
specificity allows access to fundamental electronic structure characteristics -
momentum-resolved spectral function, band structure, Fermi surface - of systems
difficult and even impossible for the conventional ARPES such as
three-dimensional materials, buried interfaces and impurities. After a recap of
the spectroscopic abilities of SX-ARPES, we review its applications to oxide
interfaces, focusing on the paradigm LaAlO3-SrTiO3 interface. Resonant SX-ARPES
at the Ti L-edge accentuates photoemission response of the mobile interface
electrons and exposes their dxy-, dyz- and dxz-derived subbands forming the
Fermi surface in the interface quantum well. After a recap of the
electron-phonon interaction physics, we demonstrate that peak-dip-hump
structure of the experimental spectral function manifests the Holstein-type
large polaron nature of the interface charge carriers, explaining their
fundamentally reduced mobility. Coupling of the charge carriers to polar soft
phonon modes defines dramatic drop of mobility with temperature. Oxygen
deficiency adds another dimension to the rich physics of LaAlO3-SrTiO3
resulting from co-existence of mobile and localized electrons introduced by
oxygen vacancies. Oxygen deficiency allows tuning of the polaronic coupling and
thus mobility of the charge carriers, as well as of interfacial ferromagnetism
connected with various atomic configurations of the vacancies. Finally, we
discuss spectroscopic evidence of phase separation at the LaAlO3-SrTiO3
interface. Concluding, we put prospects of SX-ARPES for complex
heterostructures, spin-resolving experiments opening the totally unexplored
field of interfacial spin structure, and in-operando field-effect experiments
paving the way towards device applications of the reach physics of oxide
interfaces.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-80171612.05891 | Various semiclassical limits of torus conformal blocks
hep-th
We study four types of one-point torus blocks arising in the large central
charge regime. According to different limits of conformal dimensions we
distinguish between the global block, the light block, the heavy-light block,
and the linearized classical block. We show that they are not independent and
connected to each other by various links. We find that the global, light, and
heavy-light blocks correspond to three different contractions of the Virasoro
algebra. Also, we formulate the c-recursive representation of the one-point
torus blocks which is relevant in the semiclassical approximation.
| arxiv topic:hep-th |
arxiv_dataset-80181612.05991 | Tensor Galileons and Gravity
hep-th
The particular structure of Galileon interactions allows for
higher-derivative terms while retaining second order field equations for scalar
fields and Abelian $p$-forms. In this work we introduce an index-free
formulation of these interactions in terms of two sets of Grassmannian
variables. We employ this to construct Galileon interactions for mixed-symmetry
tensor fields and coupled systems thereof. We argue that these tensors are the
natural generalization of scalars with Galileon symmetry, similar to $p$-forms
and scalars with a shift-symmetry. The simplest case corresponds to linearised
gravity with Lovelock invariants, relating the Galileon symmetry to
diffeomorphisms. Finally, we examine the coupling of a mixed-symmetry tensor to
gravity, and demonstrate in an explicit example that the inclusion of
appropriate counterterms retains second order field equations.
| arxiv topic:hep-th |
arxiv_dataset-80191612.06091 | On the homotopy analysis method for backward/forward-backward stochastic
differential equations
math.NA
In this paper, an analytic approximation method for highly nonlinear
equations, namely the homotopy analysis method (HAM), is employed to solve some
backward stochastic differential equations (BSDEs) and forward-backward
stochastic differential equations (FBSDEs), including one with high
dimensionality (up to 12 dimensions). By means of the HAM, convergent series
solutions can be quickly obtained with high accuracy for a FBSDE in a 6
dimensional case, within less than $1\%$ CPU time used by a currently reported
numerical method for the same case [34]. Especially, as dimensionality
enlarges, the increase of computational complexity for the HAM is not as
dramatic as this numerical method. All of these demonstrate the validity and
high efficiency of the HAM for the backward/forward-backward stochastic
differential equations in science, engineering and finance.
| arxiv topic:math.NA |
arxiv_dataset-80201612.06191 | The Authorization Policy Existence Problem
cs.CR cs.DS
Constraints such as separation-of-duty are widely used to specify
requirements that supplement basic authorization policies. However, the
existence of constraints (and authorization policies) may mean that a user is
unable to fulfill her/his organizational duties because access to resources has
been denied. In short, there is a tension between the need to protect resources
(using policies and constraints) and the availability of resources. Recent work
on workflow satisfiability and resiliency in access control asks whether this
tension compromises the ability of an organization to achieve its objectives.
In this paper, we develop a new method of specifying constraints which subsumes
much related work and allows a wider range of constraints to be specified. The
use of such constraints leads naturally to a range of questions related to
"policy existence", where a positive answer means that an organization's
objectives can be realized. We analyze the complexity of these policy existence
questions and, for particular sub-classes of constraints defined by our
language, develop fixed-parameter tractable algorithms to solve them.
| arxiv topic:cs.CR cs.DS |
arxiv_dataset-80211612.06291 | The Topology of Inter-industry Relations from the Portuguese National
Accounts
q-fin.EC
In last years, the Portuguese economy has gone through a severe adjustment
process, affecting almost all industrial sectors, the building blocks of
economic structures. Research on economic structural changes has made use of
input/output tables to define networks of industrial relations. Here, these
networks are induced from output tables of the Portuguese national accounting
system, being each inter-industry relation defined by the output made by any
two industries for the products that they both produce. The topological
analysis of these networks allows to uncover a particular structure that comes
out during the Portuguese adjustment program. The evolution of the industrial
networks shows an important structural change in 2011-2014, confirming the
usefulness of inducting similarity networks from output tables and the
consequent promising power of the graph formulation for the analysis of
inter-industry relations.
| arxiv topic:q-fin.EC |
arxiv_dataset-80221612.06391 | Talk it up or play it down? (Un)expected correlations between
(de-)emphasis and recurrence of discussion points in consequential U.S.
economic policy meetings
cs.SI cs.CL physics.soc-ph
In meetings where important decisions get made, what items receive more
attention may influence the outcome. We examine how different types of
rhetorical (de-)emphasis -- including hedges, superlatives, and contrastive
conjunctions -- correlate with what gets revisited later, controlling for item
frequency and speaker. Our data consists of transcripts of recurring meetings
of the Federal Reserve's Open Market Committee (FOMC), where important aspects
of U.S. monetary policy are decided on. Surprisingly, we find that words
appearing in the context of hedging, which is usually considered a way to
express uncertainty, are more likely to be repeated in subsequent meetings,
while strong emphasis indicated by superlatives has a slightly negative effect
on word recurrence in subsequent meetings. We also observe interesting patterns
in how these effects vary depending on social factors such as status and gender
of the speaker. For instance, the positive effects of hedging are more
pronounced for female speakers than for male speakers.
| arxiv topic:cs.SI cs.CL physics.soc-ph |
arxiv_dataset-80231612.06491 | Tripartite-to-bipartite Entanglement Transformation by Stochastic Local
Operations and Classical Communication and the Structure of Matrix Spaces
quant-ph
We study the problem of transforming a tripartite pure state to a bipartite
one using stochastic local operations and classical communication (SLOCC). It
is known that the tripartite-to-bipartite SLOCC convertibility is characterized
by the maximal Schmidt rank of the given tripartite state, i.e. the largest
Schmidt rank over those bipartite states lying in the support of the reduced
density operator. In this paper, we further study this problem and exhibit
novel results in both multi-copy and asymptotic settings. In the multi-copy
regime, we observe that the maximal Schmidt rank is strictly
super-multiplicative, i.e. the maximal Schmidt rank of the tensor product of
two tripartite pure states can be strictly larger than the product of their
maximal Schmidt ranks. We then provide a full characterization of those
tripartite states whose maximal Schmidt rank is strictly super-multiplicative
when taking tensor product with itself. In the asymptotic setting, we focus on
determining the tripartite-to-bipartite SLOCC entanglement transformation rate,
which turns out to be equivalent to computing the asymptotic maximal Schmidt
rank of the tripartite state, defined as the regularization of its maximal
Schmidt rank. Despite the difficulty caused by the super-multiplicative
property, we provide explicit formulas for evaluating the asymptotic maximal
Schmidt ranks of two important families of tripartite pure states, by resorting
to certain results of the structure of matrix spaces, including the study of
matrix semi-invariants. These formulas give a sufficient and necessary
condition to determine whether a given tripartite pure state can be transformed
to the bipartite maximally entangled state under SLOCC, in the asymptotic
setting. Applying the recent progress on the non-commutative rank problem, we
can verify this condition in deterministic polynomial time.
| arxiv topic:quant-ph |
arxiv_dataset-80241612.06591 | Lower bounds on the moduli of three-dimensional Coulomb-Dirac operators
via fractional Laplacians with applications
math-ph math.MP
For $\nu\in[0, 1]$ let $D^\nu$ be the distinguished self-adjoint realisation
of the three-dimensional Coulomb-Dirac operator $-\mathrm
i\boldsymbol\alpha\cdot\nabla -\nu|\cdot|^{-1}$. For $\nu\in[0, 1)$ we prove
the lower bound of the form $|D^\nu| \geqslant C_\nu\sqrt{-\Delta}$, where
$C_\nu$ is found explicitly and is better then in all previous works on the
topic. In the critical case $\nu =1$ we prove that for every $\lambda\in [0,
1)$ there exists $K_\lambda >0$ such that the estimate $|D^{1}| \geqslant
K_\lambda a^{\lambda -1}(-\Delta)^{\lambda/2} -a^{-1}$ holds for all $a >0$. As
applications we extend the range of coupling constants in the proof of the
stability of the relativistic electron-positron field and obtain
Cwickel-Lieb-Rozenblum and Lieb-Thirring type estimates on the negative
eigenvalues of perturbed projected massless Coulomb-Dirac operators in the
Furry picture. We also study the existence of a virtual level at zero for such
projected operators.
| arxiv topic:math-ph math.MP |
arxiv_dataset-80251612.06691 | $\Upsilon$ production in p-Pb and Pb-Pb collisions with ALICE at the LHC
hep-ex nucl-ex
ALICE (A Large Ion Collider Experiment) is devoted to the study of heavy-ion
collisions at LHC energies. In such collisions a deconfined state of nuclear
matter, the Quark-Gluon Plasma (QGP), is formed. Due to their early production,
quarkonium states are good probes to study the QGP evolution. Such states are
affected by suppression mechanisms which lead to reduced yields with respect to
pp and p-Pb collisions, while regeneration phenomena might lead to an
enhancement of their production. The latter effects are expected to be
negligible at LHC for bottomonium states. The recent ALICE results on
$\Upsilon$ production in Pb-Pb collisions at $\sqrt{s_{\rm
NN}}=5.02\;\rm{T}e\rm{V}$ will be presented and compared with previous
measurements at $\sqrt{s_{\rm NN}}=2.76\;\rm{T}e\rm{V}$. A comparison with
theoretical calculations will be performed as well. Results obtained in p-Pb
collisions at $\sqrt{s_{\rm NN}}=5.02\;\rm{T}e\rm{V}$ will also be discussed.
| arxiv topic:hep-ex nucl-ex |
arxiv_dataset-80261612.06791 | Systems of Dilated Functions: completeness, minimality, basisness
math.CA
We discuss completeness, minimality, and basisness, in $L^2[0, \pi]$ and
$L^p[0, \pi]$, $p \neq 2$, of dilated systems $u_n(x) = S(nx)$, $n \in
\mathbb{N}$, where $S$ is a trigonometric polynomial
$S(x) = \sum_{k = 0}^m a_k \sin(kx), \quad a_0 a_m \neq 0.$
We will present some results and mention a few unsolved questions.
| arxiv topic:math.CA |
arxiv_dataset-80271612.06891 | Theoretical Challenges in Galaxy Formation
astro-ph.GA
Numerical simulations have become a major tool for understanding galaxy
formation and evolution. Over the decades the field has made significant
progress. It is now possible to simulate the formation of individual galaxies
and galaxy populations from well defined initial conditions with realistic
abundances and global properties. An essential component of the calculation is
to correctly estimate the inflow to and outflow from forming galaxies since
observations indicating low formation efficiency and strong circum-glactic
presence of gas are persuasive. Energetic 'feedback' from massive stars and
accreting super-massive black holes - generally unresolved in cosmological
simulations - plays a major role for driving galactic outflows, which have been
shown to regulate many aspects of galaxy evolution. A surprisingly large
variety of plausible sub-resolution models succeeds in this exercise. They
capture the essential characteristics of the problem, i.e. outflows regulating
galactic gas flows, but their predictive power is limited. In this review we
focus on one major challenge for galaxy formation theory: to understand the
underlying physical processes that regulate the structure of the interstellar
medium, star formation and the driving of galactic outflows. This requires
accurate physical models and numerical simulations, which can precisely
describe the multi-phase structure of the interstellar medium on the currently
unresolved few hundred parsecs scales of large scale cosmological simulations.
Such models ultimately require the full accounting for the dominant cooling and
heating processes, the radiation and winds from massive stars and accreting
black holes, an accurate treatment of supernova explosions as well as the
non-thermal components of the interstellar medium like magnetic fields and
cosmic rays.
| arxiv topic:astro-ph.GA |
arxiv_dataset-80281612.06991 | Twisted Heisenberg-Virasoro vertex operator algebra
math.QA
In this paper, we study a new kind of vertex operator algebra related to the
twisted Heisenberg-Virasoro algebra, which we call the twisted
Heisenberg-Virasoro vertex operator algebra, and its modules. Specifically, we
present some results concerning the relationship between the restricted module
categories of twisted Heisenberg-Virasoro algebras of rank one and rank two and
several different kinds of module categories of their corresponding vertex
algebras. We also study fully the structures of the twisted Heisenberg-Virasoro
vertex operator algebra, give a characterization of it as a tensor product of
two well-known vertex operator algebras, and solve the commutant problem.
| arxiv topic:math.QA |
arxiv_dataset-80291612.07091 | Thermal shifts, fluctuations, and missing states
hep-ph hep-lat nucl-th
Thermal shifts and fluctuations at finite temperature below the deconfinement
crossover from hadronic matter to the quark-gluon plasma provide a viable way
to search for missing states with given quantum numbers in the hadronic
spectrum. We analyze three realizations of the hadron resonance gas model in
the light quark (uds) sector: the states from the Particle Data Group tables
with or without width and from the Relativized Quark Model. We elaborate on the
meaning of hadronic completeness and thermodynamical equivalence on the light
of lattice QCD trace anomaly, heavy quark entropy shift and baryon,charge and
strangeness susceptibilities.
| arxiv topic:hep-ph hep-lat nucl-th |
arxiv_dataset-80301612.07191 | Breakdown of optical phonons' splitting in two-dimensional materials
cond-mat.mtrl-sci
We investigate the long-wavelength dispersion of longitudinal and transverse
optical phonon modes in polar two-dimensional materials, multilayers, and their
heterostructures. Using analytical models and density-functional perturbation
theory in a two-dimensional framework, we show that, at variance with the
three-dimensional case, these modes are degenerate at the zone center but the
macroscopic electric field associated with the longitudinal-optical modes gives
rise to a finite slope at the zone center in their corresponding phonon
dispersions. This slope increases linearly with the number of layers and it is
determined solely by the Born effective charges of the material and the
dielectric properties of the surrounding media. Screening from the environment
can greatly reduce the slope splitting between the longitudinal and transverse
optical modes and can be seen in the experimentally relevant case of boron
nitride-graphene heterostructures. As the phonon momentum increases, the
intrinsic screening properties of the two-dimensional material dictate the
transition to a momentum-independent splitting similar to that of
three-dimensional materials. These considerations are essential to understand
electrical transport and optical coupling in two-dimensional systems.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-80311612.07291 | Initial performance studies of a general-purpose detector for multi-TeV
physics at a 100 TeV pp collider
hep-ex physics.ins-det
This paper describes simulations of detector response to multi-TeV physics at
the Future Circular Collider (FCC-hh) or Super proton-proton Collider (SppC)
which aim to collide proton beams with a centre-of-mass energy of 100 TeV. The
unprecedented energy regime of these future experiments imposes new
requirements on detector technologies which can be studied using the detailed
GEANT4 simulations presented in this paper. The initial performance of a
detector designed for physics studies at the FCC-hh or SppC experiments is
described with an emphasis on measurements of single particles up to 33 TeV in
transverse momentum. The reconstruction of hadronic jets has also been studied
in the transverse momentum range from 50 GeV to 26 TeV. The granularity
requirements for calorimetry are investigated using the two-particle spatial
resolution achieved for hadron showers.
| arxiv topic:hep-ex physics.ins-det |
arxiv_dataset-80321612.07391 | Stirling permutations, marked permutations and Stirling derangements
math.CO
In this paper we introduce the definition of marked permutations. We first
present a bijection between Stirling permutations and marked permutations. We
then present an involution on Stirling derangements. Furthermore, we present a
symmetric bivariate enumerative polynomials on $r$-colored marked permutations.
Finally, we give an explanation of $r$-colored marked permutations by using the
language of combinatorial objects.
| arxiv topic:math.CO |
arxiv_dataset-80331612.07491 | Cube vs. Cube Low Degree Test
cs.CC
We revisit the Raz-Safra plane-vs.-plane test and study the closely related
cube vs. cube test. In this test the tester has access to a "cubes table" which
assigns to every cube a low degree polynomial. The tester randomly selects two
cubes (affine sub-spaces of dimension $3$) that intersect on a point $x\in
\mathbf{F}^m$, and checks that the assignments to the cubes agree with each
other on the point $x$.
Our main result is a new combinatorial proof for a low degree test that comes
closer to the soundness limit, as it works for all $\epsilon \ge
poly(d)/{\mathbf{F}}^{1/2}$, where $d$ is the degree. This should be compared
to the previously best soundness value of $\epsilon \ge poly(m,
d)/\mathbf{F}^{1/8}$. Our soundness limit improves upon the dependence on the
field size and does not depend on the dimension of the ambient space.
Our proof is combinatorial and direct: unlike the Raz-Safra proof, it
proceeds in one shot and does not require induction on the dimension of the
ambient space. The ideas in our proof come from works on direct product testing
which are even simpler in the current setting thanks to the low degree.
Along the way we also prove a somewhat surprising fact about connection
between different agreement tests: it does not matter if the tester chooses the
cubes to intersect on points or on lines: for every given table, its success
probability in either test is nearly the same.
| arxiv topic:cs.CC |
arxiv_dataset-80341612.07591 | Length enumeration of fully commutative elements in finite and affine
Coxeter groups
math.CO
An element w of a Coxeter group W is said to be fully commutative, if any
reduced expression of w can be obtained from any other by transposing adjacent
pairs of generators. These elements were described in 1996 by Stembridge in the
case of finite irreducible groups, and more recently by Biagioli, Jouhet and
Nadeau (BJN) in the affine cases. We focus here on the length enumeration of
these elements. Using a recursive description, BJN established for the
associated generating functions systems of non-linear q-equations. Here, we
show that an alternative recursive description leads to explicit expressions
for these generating functions.
| arxiv topic:math.CO |
arxiv_dataset-80351612.07691 | Collapse in ultracold Bose Josephson junctions
quant-ph cond-mat.quant-gas
We investigate how ultracold atoms in double well potentials can be used to
study and put bounds on models describing wave function collapse. We refer in
particular to the continuous spontaneous localization (CSL) model, which is the
most well studied among dynamical reduction models. It modifies the Schrodinger
equation in order to include the collapse of the wave function in its dynamics.
We consider Bose Josephson junctions, where ultracold bosons are trapped in a
double well potential,since they can be experimentally controlled with high
accuracy and are suited and used to study macroscopic quantum phenomena on
scale of microns with a number of particles typically ranging from $\sim
10^2-10^3$ to $\sim 10^5-10^6$. We study the CSL dynamics of three atomic
states showing macroscopic quantum coherence: the atomic coherent state, the
superposition of two atomic coherent states, and the NOON state. We show that
for the last two states the suppression of quantum coherence induced by CSL
model increases exponentially with the number of atoms. We observe that, in the
case of optically trapped atoms, the spontaneous photon emission of the atoms
induce a dynamics similar to the CSL one and we conclude that magnetically
trapped atoms may be more convenient to experimentally test the CSL model. We
finally discuss decoherence effects in order to provide reasonable estimates on
the bounds that it is (or it will) possible to obtain for the parameters of the
CSL model in such class of experiments: as an example, we show that a NOON
state with $N \sim 10^3$ with a coherence time of $\sim 1$ s can constrain the
CSL parameters in a region where the other systems presently cannot.
| arxiv topic:quant-ph cond-mat.quant-gas |
arxiv_dataset-80361612.07791 | Infinite loop spaces from operads with homological stability
math.AT
Motivated by the operad built from moduli spaces of Riemann surfaces, we
consider a general class of operads in the category of spaces that satisfy
certain homological stability conditions. We prove that such operads are
infinite loop space operads in the sense that the group completions of their
algebras are infinite loop spaces.
The recent, strong homological stability results of Galatius and
Randal-Williams for moduli spaces of even dimensional manifolds can be used to
construct examples of operads with homological stability. As a consequence the
map to $K$-theory defined by the action of the diffeomorphisms on the middle
dimensional homology can be shown to be a map of infinite loop spaces.
| arxiv topic:math.AT |
arxiv_dataset-80371612.07891 | Radio Emission of Air Showers with Energy E$_0$ $\geq$ 10$^{19}$ eV by
Yakutsk Array Data
astro-ph.HE
In this paper, we present results obtained from the measurements of radio
emission at frequency of 32 MHz with energy more than 10$^{19}$ eV. Generalized
formula that describe lateral distribution and depends on main characteristic
of the air showers: energy E$_0$ and depth of maximum X$_{max}$ was derived.
The formula has a good agreement with data at average and large distances from
shower axis. Employing the ratio of radio emission amplitude at distances 175 m
and 725 m we determined the depth of maximum X$_{max}$ for air shower with
energy 3.7$\cdot$10$^{19}$ eV, which in our case is equal to X$_{max}$ =
769$\pm$34g$\cdot$cm$^{-2}$.
| arxiv topic:astro-ph.HE |
arxiv_dataset-80381612.07991 | Circular Wilson loops in defect Conformal Field Theory
hep-th
We study a D3-D5 system dual to a conformal field theory with a
codimension-one defect that separates regions where the ranks of the gauge
groups differ by $k$. With the help of this additional parameter, as observed
by Nagasaki, Tanida and Yamaguchi, one can define a double scaling limit in
which the quantum corrections are organized in powers of $\lambda/k^2$, which
should allow to extrapolate results between weak and strong coupling regimes.
In particular we consider a radius $R$ circular Wilson loop placed at a
distance $L$, whose internal space orientation is given by an angle $\chi$. We
compute its vacuum expectation value and show that, in the double scaling limit
and for small $\chi$ and small $L/R$, weak coupling results can be extrapolated
to the strong coupling limit.
| arxiv topic:hep-th |
arxiv_dataset-80391612.08091 | ProjectQ: An Open Source Software Framework for Quantum Computing
quant-ph cs.ET cs.PL
We introduce ProjectQ, an open source software effort for quantum computing.
The first release features a compiler framework capable of targeting various
types of hardware, a high-performance simulator with emulation capabilities,
and compiler plug-ins for circuit drawing and resource estimation. We introduce
our Python-embedded domain-specific language, present the features, and provide
example implementations for quantum algorithms. The framework allows testing of
quantum algorithms through simulation and enables running them on actual
quantum hardware using a back-end connecting to the IBM Quantum Experience
cloud service. Through extension mechanisms, users can provide back-ends to
further quantum hardware, and scientists working on quantum compilation can
provide plug-ins for additional compilation, optimization, gate synthesis, and
layout strategies.
| arxiv topic:quant-ph cs.ET cs.PL |
arxiv_dataset-80401612.08191 | On a minimax theorem: an improvement, a new proof and an overview of its
applications
math.FA math.AP
Theorem 1 of [14], a minimax result for functions $f:X\times Y\to {\bf R}$,
where $Y$ is a real interval, was partially extended to the case where $Y$ is a
convex set in a Hausdorff topological vector space ([15], Theorem 3.2). In
doing that, a key tool was a partial extension of the same result to the case
where $Y$ is a convex set in ${\bf R}^n$ ([7], Theorem 4.2). In the present
paper, we first obtain a full extension of the result in [14] by means of a new
proof fully based on the use of the result itself via an inductive argument.
Then, we present an overview of the various and numerous applications of these
results.
| arxiv topic:math.FA math.AP |
arxiv_dataset-80411612.08291 | Effects of Interstitial Oxygen and Carbon on Niobium Superconducting
Cavities
physics.acc-ph
We present results on the effects of interstitial oxygen and carbon on a
bulk-niobium superconducting radio-frequency cavity. Previous experiments have
shown that high-temperature (~800 $^\circ\text{C}$) nitrogen-doping plays the
dominant role in the reduction of the electron mean free path in the RF
penetration layer of niobium that leads to a decrease in microwave surface
resistance and a suppression the temperature-dependent component of the surface
resistance with increasing accelerating gradient. In this work, we show that
oxygen and carbon-doping has very similar effects on cavity performance,
demonstrating that these effects are not unique to nitrogen. The preparation
method used in the introduction of interstitial oxygen and carbon has the
advantage that it is done at lower temperatures than that of high-temperature
nitrogen-doping and does not require post-treatment electro-polishing.
| arxiv topic:physics.acc-ph |
arxiv_dataset-80421612.08391 | Audio-based Distributional Semantic Models for Music Auto-tagging and
Similarity Measurement
cs.IR
The recent development of Audio-based Distributional Semantic Models (ADSMs)
enables the computation of audio and lexical vector representations in a joint
acoustic-semantic space. In this work, these joint representations are applied
to the problem of automatic tag generation. The predicted tags together with
their corresponding acoustic representation are exploited for the construction
of acoustic-semantic clip embeddings. The proposed algorithms are evaluated on
the task of similarity measurement between music clips. Acoustic-semantic
models are shown to outperform the state-of-the-art for this task and produce
high quality tags for audio/music clips.
| arxiv topic:cs.IR |
arxiv_dataset-80431612.08491 | Impact of a locally measured H_0 on the interpretation of cosmic
chronometer data
astro-ph.CO astro-ph.GA
Whereas many measurements in cosmology depend on the use of integrated
distances or time, galaxies evolving passively on a time scale much longer than
their age difference allow us to determine the expansion rate H(z) solely as a
function of the redshift-time derivative dz/dt. These model-independent `cosmic
chronometers' can therefore be powerful discriminators for testing different
cosmologies. In previous applications, the available sources strongly
disfavoured models (such as LambdaCDM) predicting a variable acceleration,
preferring instead a steady expansion rate over the redshift range 0 < z < 2. A
more recent catalog of 30 objects appears to suggest non-steady expansion. In
this paper, we show that such a result is entirely due to the inclusion of a
high, locally-inferred value of the Hubble constant H_0 as an additional datum
in a set of otherwise pure cosmic-chronometer measurements. This H_0, however,
is not the same as the background Hubble constant if the local expansion rate
is influenced by a Hubble Bubble. Used on their own, the cosmic chronometers
completely reverse this conclusion, favouring instead a constant expansion rate
out to z ~ 2.
| arxiv topic:astro-ph.CO astro-ph.GA |
arxiv_dataset-80441612.08591 | A new approach to predict changes in physical condition: A new extension
of the classical Banister model
math.CA
In this article, a new model based on techniques of differential equations is
introduced to predict the athletic performance based training load and a data
sample of the physical form of athletes arises. This model is an extension of
the classical model of Banister but, in this case, unlike the classical
Banister model, the variation produced in the athletic performance depends, not
only on the current training load, but also on the training performed the
previous day. The model has been validated with the training data of a cyclist
taken from the reference \cite{Clarke}, obtaining an excellent fit of the
predicted data with respect to the experimental data.
| arxiv topic:math.CA |
arxiv_dataset-80451612.08691 | Free boundary minimal surfaces of unbounded genus
math.DG math.AP
For each integer $g\geq 1$ we use variational methods to construct in the
unit $3$-ball $B$ a free boundary minimal surface $\Sigma_g$ of symmetry group
$\mathbb{D}_{g+1}$. For $g$ large, $\Sigma_g$ has three boundary components and
genus $g$. As $g\rightarrow\infty$ the surfaces $\Sigma_g$ converge as
varifolds to the union of the disk and critical catenoid. These examples are
the first with genus greater than $1$ and were conjectured to exist by
Fraser-Schoen. We also construct several new free boundary minimal surfaces in
$B$ with the symmetry groups of the cube, tetrahedron and dodecahedron.
Finally, we prove that free boundary minimal surfaces isotopic to those of
Fraser-Schoen can be constructed variationally using an equivariant min-max
procedure. We also prove an $\epsilon$-regularity theorem for free boundary
minimal surfaces in $B$.
| arxiv topic:math.DG math.AP |
arxiv_dataset-80461612.08791 | Quantum coherence of two-qubit over quantum channels with memory
quant-ph
Using the axiomatic definition of the coherence measure, such as the $l_{1}$
norm and the relative entropy, we study the phenomena of two-qubit system
quantum coherence through quantum channels where successive uses of the
channels are memory. Different types of noisy channels with memory, such as
amplitude damping, phase-damping, and depolarizing channels effect on quantum
coherence have been discussed in detail. The results show that, quantum
channels with memory can efficiently protect coherence from noisy channels.
Particularly, as channels with perfect memory, quantum coherence is unaffected
by the phase damping as well as depolarizing channels. Besides, we also
investigate the cohering and decohering power of quantum channels with memory.
| arxiv topic:quant-ph |
arxiv_dataset-80471612.08891 | Conformal Galilei algebras, symmetric polynomials and singular vectors
math.RT math-ph math.AP math.DG math.FA math.MP
We classify and explicitly describe homomorphisms of Verma modules for
conformal Galilei algebras $\mathfrak{cga}_\ell(d,{\mathbb C})$ with $d=1$ for
any integer value $\ell \in \mathbb{N}$. The homomorphisms are uniquely
determined by singular vectors as solutions of certain differential operators
of flag type, and identified with specific polynomials arising as coefficients
in the expansion of a parametric family of symmetric polynomials into power sum
symmetric polynomials.
| arxiv topic:math.RT math-ph math.AP math.DG math.FA math.MP |
arxiv_dataset-80481612.08991 | The amplitude of the cross-covariance function of solar oscillations as
a diagnostic tool for wave attenuation and geometrical spreading
astro-ph.SR
Context. In time-distance helioseismology, wave travel times are measured
from the two-point cross-covariance function of solar oscillations and are used
to image the solar convection zone in three dimensions. There is, however, also
information in the amplitude of the cross-covariance function, for example
about seismic wave attenuation. Aims. Here we develop a convenient procedure to
measure the amplitude of the cross-covariance function of solar oscillations.
Methods. In this procedure, the amplitude of the cross-covariance function is
linearly related to the cross-covariance function and can be measured even for
high levels of noise. Results. As an example application, we measure the
amplitude perturbations of the seismic waves that propagate through the sunspot
in active region NOAA 9787. We can recover the amplitude variations due to the
scattering and attenuation of the waves by the sunspot and associated
finite-wavelength effects. Conclusions. The proposed definition of
cross-covariance amplitude is robust to noise, can be used to relate measured
amplitudes to 3D perturbations in the solar interior under the Born
approximation, and will provide independent information from the travel times.
| arxiv topic:astro-ph.SR |
arxiv_dataset-80491612.09091 | Impact of Lattice QCD on CKM Phenomenology
hep-lat hep-ph
Precise lattice QCD results for hadronic matrix elements, decay constants and
form factors play a crucial role in the determination of CKM matrix elements
and in the identification of possible new physics contributions to flavour
violating observables. This article reviews the implications of recent lattice
QCD results on the phenomenology of flavour and CP violating meson decays, and
highlights some future directions for lattice QCD calculations which would have
a major impact on flavour phenomenology.
| arxiv topic:hep-lat hep-ph |
arxiv_dataset-80501612.09191 | Open Gauged Sigma Models, Equivariant Branes, and Equivariant
Homological Mirror Symmetry
hep-th math.AG math.SG
We describe supersymmetric A-branes and B-branes in open N=(2,2) dynamically
gauged nonlinear sigma models (GNLSM), placing emphasis on toric manifold
target spaces. For a subset of toric manifolds, these equivariant branes have a
mirror description as branes in gauged Landau-Ginzburg models with neutral
matter. We then study correlation functions in the topological A-twisted
version of the GNLSM, and identify their values with open Hamiltonian
Gromov-Witten invariants. Supersymmetry breaking can occur in the A-twisted
GNLSM due to nonperturbative open symplectic vortices, and we canonically BRST
quantize the mirror theory to analyze this phenomenon.
| arxiv topic:hep-th math.AG math.SG |
arxiv_dataset-80511612.09291 | Quantum computational representation of gauge field theory
quant-ph hep-th
Presented is a quantum computing model of a quantum field theory for a system
of fermions interacting via a massive gauge field. The model describes a
relativistic superconducting fluid and uses a metric tensor field to both
encode the fermion's intrinsic spin in the torsion of curved space and encode
the coupling of fermions via a massive 4-potential field. The quantum computing
model is a lattice model whose cell size is a deformation parameter: the
equivalent lattice and curved-space gauge field theory models both reduce to
quantum field theory in flat Minkowski space at zero cell size. The low-energy
expansions of the lattice model and Euler-Lagrange equations of the
curved-space gauge field theory are the same equations of motion. The fermion
and gauge fields obey the Dirac and Proca equations, and the gauge field
strength is determined by the fermion field.
| arxiv topic:quant-ph hep-th |
arxiv_dataset-80521612.09391 | Indecomposable generalized weight modules over the algebra of polynomial
integro-differential operators
math.RT
For the algebra L= K <x, d/dx, \int> of polynomial integro-differential
operators over a field K of characteristic zero, a classification of
indecomposable, generalized weight L-modules of finite length is given. Each
such module is an infinite dimensional uniserial module. Ext-groups are found
between indecomposable generalized weight modules, it is proven that they are
finite dimensional vector spaces.
| arxiv topic:math.RT |
arxiv_dataset-80531612.09491 | Massively Parallel Computation of Accurate Densities for N-body Dark
Matter Simulations using the Phase-Space-Element Method
physics.comp-ph astro-ph.IM
This paper presents an accurate density computation approach for large dark
matter simulations, based on a recently introduced phase-space tessellation
technique and designed for massively parallel, heterogeneous cluster
architectures. We discuss a memory efficient construction of an oct-tree
structure to sample the mass densities with locally adaptive resolution,
according to the features of the underlying tetrahedral tessellation. We
propose an efficient GPU implementation for the computationally intensive
operation of intersecting the tetrahedra with the cubical cells of the deposit
grid, that achieves a speedup of almost an order of magnitude compared to an
optimized CPU version. We discuss two dynamic load balancing schemes - the
first exchanges particle data between cluster nodes and deposits all tetrahedra
for each block of the grid structure on single nodes, whereas the second
approach uses global reduction operations to obtain the total masses. We
demonstrate the scalability of our algorithms for up to 256 GPUs and TB-sized
simulation snapshots, resulting in tessellations with over 400 billion
tetrahedra.
| arxiv topic:physics.comp-ph astro-ph.IM |
arxiv_dataset-80541612.09591 | PrASP Report
cs.AI
This technical report describes the usage, syntax, semantics and core
algorithms of the probabilistic inductive logic programming framework PrASP.
PrASP is a research software which integrates non-monotonic reasoning based on
Answer Set Programming (ASP), probabilistic inference and parameter learning.
In contrast to traditional approaches to Probabilistic (Inductive) Logic
Programming, our framework imposes only little restrictions on probabilistic
logic programs. In particular, PrASP allows for ASP as well as First-Order
Logic syntax, and for the annotation of formulas with point probabilities as
well as interval probabilities. A range of widely configurable inference
algorithms can be combined in a pipeline-like fashion, in order to cover a
variety of use cases.
| arxiv topic:cs.AI |
arxiv_dataset-80551701.00092 | Hermite-Hadamard, Hermite-Hadamard-Fejer, Dragomir-Agarwal and Pachpatte
Type Inequalities for Convex Functions via Fractional Integrals
math.FA
The aim of this paper is to establish Hermite-Hadamard,
Hermite-Hadamard-Fej\'er, Dragomir-Agarwal and Pachpatte type inequalities for
new fractional integral operators with exponential kernel. These results allow
us to obtain a new class of functional inequalities which generalizes known
inequalities involving convex functions. Furthermore, the obtained results may
act as a useful source of inspiration for future research in convex analysis
and related optimization fields.
| arxiv topic:math.FA |
arxiv_dataset-80561701.00192 | Iron K$\alpha$ line of Proca stars
gr-qc astro-ph.HE
X-ray reflection spectroscopy can be a powerful tool to test the nature of
astrophysical black holes. Extending previous work on Kerr black holes with
scalar hair [1] and on boson stars [2], here we study whether astrophysical
black hole candidates may be horizonless, self-gravitating, vector
Bose-Einstein condensates, known as Proca stars [3]. We find that observations
with current X-ray missions can only provide weak constraints and rule out
solely Proca stars with low compactness. There are two reasons. First, at the
moment we do not know the geometry of the corona, and therefore the uncertainty
in the emissivity profile limits the ability to constrain the background
metric. Second, the photon number count is low even in the case of a bright
black hole binary, and we cannot have a precise measurement of the spectrum.
| arxiv topic:gr-qc astro-ph.HE |
arxiv_dataset-80571701.00292 | Gaia Data Release 1: Catalogue validation
astro-ph.IM astro-ph.GA astro-ph.SR
Before the publication of the Gaia Catalogue, the contents of the first data
release have undergone multiple dedicated validation tests. These tests aim at
analysing in-depth the Catalogue content to detect anomalies, individual
problems in specific objects or in overall statistical properties, either to
filter them before the public release, or to describe the different caveats of
the release for an optimal exploitation of the data. Dedicated methods using
either Gaia internal data, external catalogues or models have been developed
for the validation processes. They are testing normal stars as well as various
populations like open or globular clusters, double stars, variable stars,
quasars. Properties of coverage, accuracy and precision of the data are
provided by the numerous tests presented here and jointly analysed to assess
the data release content. This independent validation confirms the quality of
the published data, Gaia DR1 being the most precise all-sky astrometric and
photometric catalogue to-date. However, several limitations in terms of
completeness, astrometric and photometric quality are identified and described.
Figures describing the relevant properties of the release are shown and the
testing activities carried out validating the user interfaces are also
described. A particular emphasis is made on the statistical use of the data in
scientific exploitation.
| arxiv topic:astro-ph.IM astro-ph.GA astro-ph.SR |
arxiv_dataset-80581701.00392 | On the Computation of Complex-valued Gradients with Application to
Statistically Optimum Beamforming
cs.NA cs.CE
This report describes the computation of gradients by algorithmic
differentiation for statistically optimum beamforming operations. Especially
the derivation of complex-valued functions is a key component of this approach.
Therefore the real-valued algorithmic differentiation is extended via the
complex-valued chain rule. In addition to the basic mathematic operations the
derivative of the eigenvalue problem with complex-valued eigenvectors is one of
the key results of this report. The potential of this approach is shown with
experimental results on the CHiME-3 challenge database. There, the beamforming
task is used as a front-end for an ASR system. With the developed derivatives a
joint optimization of a speech enhancement and speech recognition system w.r.t.
the recognition optimization criterion is possible.
| arxiv topic:cs.NA cs.CE |
arxiv_dataset-80591701.00492 | A lower bound on the Bekenstein-Hawking temperature of black holes
gr-qc astro-ph.HE hep-th
We present evidence for the existence of a quantum lower bound on the
Bekenstein-Hawking temperature of black holes. The suggested bound is supported
by a gedanken experiment in which a charged particle is dropped into a Kerr
black hole. It is proved that the temperature of the final Kerr-Newman
black-hole configuration is bounded from below by the relation
$T_{\text{BH}}\times r_{\text{H}}>(\hbar/r_{\text{H}})^2$, where $r_{\text{H}}$
is the horizon radius of the black hole.
| arxiv topic:gr-qc astro-ph.HE hep-th |
arxiv_dataset-80601701.00592 | Comment on Jackson's analysis of electric charge quantization due to
interaction with Dirac's magnetic monopole
physics.class-ph
In J.D. Jackson's Classical Electrodynamics textbook, the analysis of Dirac's
charge quantization condition in the presence of a magnetic monopole has a
mathematical omission and an all too brief physical argument that might mislead
some students. This paper presents a detailed derivation of Jackson's main
result, explains the significance of the missing term, and highlights the close
connection between Jackson's findings and Dirac's original argument.
| arxiv topic:physics.class-ph |
arxiv_dataset-80611701.00692 | How Large is the Contribution of Excited Mesons in Coupled-Channel
Effects?
hep-ph
We study the excited $B$ mesons' contributions to the coupled-channel effects
under the framework of ${}^3P_0$ model for the bottomonium. Contrary to what
has been widely accepted, the contributions of $P$ wave $B$ mesons are
generally the largest and this result is independent of the potential
parameters to some extent. We also push the calculation beyond $B(1P)$ and
carefully analyze the contributions of $B(2S)$. A form factor is a key
ingredient to suppress the contributions of $B(2S)$ for low lying bottomonia.
However, this suppression mechanism is not efficient for highly excited
bottomonia such as $\Upsilon(5S)$ and $\Upsilon(6S)$. We give explanations why
this difficulty happens to ${}^3P_0$ model and suggest analyzing flux-tube
breaking model for the full calculation of coupled-channel effects.
| arxiv topic:hep-ph |
arxiv_dataset-80621701.00792 | Exploring impulsive solar magnetic energy release and particle
acceleration with focused hard X-ray imaging spectroscopy
astro-ph.SR
How impulsive magnetic energy release leads to solar eruptions and how those
eruptions are energized and evolve are vital unsolved problems in Heliophysics.
The standard model for solar eruptions summarizes our current understanding of
these events. Magnetic energy in the corona is released through drastic
restructuring of the magnetic field via reconnection. Electrons and ions are
then accelerated by poorly understood processes. Theories include contracting
loops, merging magnetic islands, stochastic acceleration, and turbulence at
shocks, among others. Although this basic model is well established, the
fundamental physics is poorly understood. HXR observations using
grazing-incidence focusing optics can now probe all of the key regions of the
standard model. These include two above-the-looptop (ALT) sources which bookend
the reconnection region and are likely the sites of particle acceleration and
direct heating. The science achievable by a direct HXR imaging instrument can
be summarized by the following science questions and objectives which are some
of the most outstanding issues in solar physics (1) How are particles
accelerated at the Sun? (1a) Where are electrons accelerated and on what time
scales? (1b) What fraction of electrons is accelerated out of the ambient
medium? (2) How does magnetic energy release on the Sun lead to flares and
eruptions? A Focusing Optics X-ray Solar Imager (FOXSI) instrument, which can
be built now using proven technology and at modest cost, would enable
revolutionary advancements in our understanding of impulsive magnetic energy
release and particle acceleration, a process which is known to occur at the Sun
but also throughout the Universe.
| arxiv topic:astro-ph.SR |
arxiv_dataset-80631701.00892 | A Hierarchical Image Matting Model for Blood Vessel Segmentation in
Fundus images
cs.CV
In this paper, a hierarchical image matting model is proposed to extract
blood vessels from fundus images. More specifically, a hierarchical strategy
utilizing the continuity and extendibility of retinal blood vessels is
integrated into the image matting model for blood vessel segmentation. Normally
the matting models require the user specified trimap, which separates the input
image into three regions manually: the foreground, background and unknown
regions. However, since creating a user specified trimap is a tedious and
time-consuming task, region features of blood vessels are used to generate the
trimap automatically in this paper. The proposed model has low computational
complexity and outperforms many other state-ofart supervised and unsupervised
methods in terms of accuracy, which achieves a vessel segmentation accuracy of
96:0%, 95:7% and 95:1% in an average time of 10:72s, 15:74s and 50:71s on
images from three publicly available fundus image datasets DRIVE, STARE, and
CHASE DB1, respectively.
| arxiv topic:cs.CV |
arxiv_dataset-80641701.00992 | Viscous displacement in porous media: the Muskat problem in 2D
math.AP
We consider the Muskat problem describing the viscous displacement in a
two-phase fluid system located in an unbounded two-dimensional porous medium or
Hele-Shaw cell. After formulating the mathematical model as an evolution
problem for the sharp interface between the fluids, we show that Muskat problem
with surface tension is a quasilinear parabolic problem, whereas, in the
absence of surface tension effects, the Rayleigh-Taylor condition identifies a
domain of parabolicity for the fully nonlinear problem. Based upon these
aspects, we then establish the local well-posedness for arbitrary large initial
data in $H^s$, $s>2$, if surface tension is taken into account, respectively
for arbitrary large initial data in $H^2$ that additionally satisfy the
Rayleigh-Taylor condition if surface tension effects are neglected. We also
show that the problem exhibits the parabolic smoothing effect and we provide
criteria for the global existence of solutions.
| arxiv topic:math.AP |
arxiv_dataset-80651701.01092 | Inverting the coupling of the signed Gausssian free field with a loop
soup
math.PR
Lupu introduced a coupling between a random walk loop-soup and a Gaussian
free field, where the sign of the field is constant on each cluster of loops.
This coupling is a signed version of isomorphism theorems relating the square
of the GFF to the occupation field of Markovian trajectories. His construction
starts with a loop-soup, and by adding additional randomness samples a GFF out
of it. In this article we provide the inverse construction: starting from a
signed free field and using a self-interacting random walk related to this
field, we construct a random walk loop-soup. Our construction relies on the
previous work by Sabot and Tarr\`es, which inverts the coupling from the square
of the GFF rather than the signed GFF itself. As a consequence, we also deduce
an inversion of the coupling between the random current and the FK-Ising random
cluster models introduced by Lupu and Werner.
| arxiv topic:math.PR |
arxiv_dataset-80661701.01192 | Liquid-like thermal conduction in a crystalline solid
cond-mat.mtrl-sci cond-mat.dis-nn
A solid conducts heat through both transverse and longitudinal acoustic
phonons, but a liquid employs only longitudinal vibrations. Here, we report
that the crystalline solid AgCrSe2 has liquid-like thermal conduction. In this
compound, Ag atoms exhibit a dynamic duality that they are exclusively involved
in intense low-lying transverse acoustic phonons while they also undergo local
fluctuations inherent in an order-to-disorder transition occurring at 450 K. As
a consequence of this extreme disorder-phonon coupling, transverse acoustic
phonons become damped as approaching the transition temperature, above which
they are not defined anymore because their lifetime is shorter than the
relaxation time of local fluctuations. Nevertheless, the damped longitudinal
acoustic phonon survives for thermal transport. This microscopic insight might
reshape the fundamental idea on thermal transport properties of matter and
facilitates the optimization of thermoelectrics.
| arxiv topic:cond-mat.mtrl-sci cond-mat.dis-nn |
arxiv_dataset-80671701.01292 | Eternal non-Markovianity is generic for the spin-boson model
quant-ph
The spin-boson model describes a qubit coupled to a bosonic bath in thermal
equilibrium, and is applicable to a wide range of physical contexts. We show
that two weak conditions for the qubit evolution to be Markovian (decreasing
system distinguishability and divisibility) are violated at all times t>0,
except for a measure-zero set of model parameters. Thus, the recently
identified phenomenon of `eternal non-Markovianity' is generic for the
spin-boson model. Moreover, there can never be more than one strictly positive
decoherence rate, even in the Markovian regime. The main result relies on a
recent derivation of the exact form of the master equation. We also show that
approximations of the spin-boson model in the literature need not exhibit
generic eternal non-Markovianity, indicating the presence of corresponding
inherent `Markovian' assumptions.
| arxiv topic:quant-ph |
arxiv_dataset-80681701.01392 | Price-based Controller for Quality-Fair HTTP Adaptive Streaming
(Extended Version)
cs.NI cs.MM
HTTP adaptive streaming (HAS) has become the universal technology for video
streaming over the Internet. Many HAS system designs aim at sharing the network
bandwidth in a rate-fair manner. However, rate fairness is in general not
equivalent to quality fairness as different video sequences might have
different characteristics and resource requirements. In this work, we focus on
this limitation and propose a novel controller for HAS clients that is able to
reach quality fairness while preserving the main characteristics of HAS systems
and with a limited support from the network devices. In particular, we adopt a
price-based mechanism in order to build a controller that maximizes the
aggregate video quality for a set of HAS clients that share a common
bottleneck. When network resources are scarce, the clients with simple video
sequences reduce the requested bitrate in favor of users that subscribe to more
complex video sequences, leading to a more efficient network usage. The
proposed controller has been implemented in a network simulator, and the
simulation results demonstrate its ability to share the available bandwidth
among the HAS users in a quality-fair manner.
| arxiv topic:cs.NI cs.MM |
arxiv_dataset-80691701.01492 | Stochastic Least-Squares Petrov-Galerkin Method for Parameterized Linear
Systems
math.NA
We consider the numerical solution of parameterized linear systems where the
system matrix, the solution, and the right-hand side are parameterized by a set
of uncertain input parameters. We explore spectral methods in which the
solutions are approximated in a chosen finite-dimensional subspace. It has been
shown that the stochastic Galerkin projection technique fails to minimize any
measure of the solution error [20]. As a remedy for this, we propose a novel
stochastic least-squares Petrov--Galerkin (LSPG) method. The proposed method is
optimal in the sense that it produces the solution that minimizes a weighted
l2-norm of the residual over all solutions in a given finite-dimensional
subspace. Moreover, the method can be adapted to minimize the solution error in
different weighted l2-norms by simply applying a weighting function within the
least-squares formulation. In addition, a goal-oriented semi-norm induced by an
output quantity of interest can be minimized by defining a weighting function
as a linear functional of the solution. We establish optimality and error
bounds for the proposed method, and extensive numerical experiments show that
the weighted LSPG methods outperforms other spectral methods in minimizing
corresponding target weighted norms.
| arxiv topic:math.NA |
arxiv_dataset-80701701.01592 | Geometric formulation of the Cauchy invariants for incompressible Euler
flow in flat and curved spaces
physics.flu-dyn math.AP math.DG
Cauchy invariants are now viewed as a powerful tool for investigating the
Lagrangian structure of three-dimensional (3D) ideal flow (Frisch &
Zheligovsky, Commun. Math. Phys., vol. 326, 2014, pp. 499-505, Podvigina et
al., J. Comput. Phys., vol. 306, 2016, pp. 320-342). Looking at such invariants
with the modern tools of differential geometry and of geodesic flow on the
space SDiff of volume-preserving transformations (Arnold, Ann. Inst. Fourier,
vol. 16, 1966, pp. 319-361), all manners of generalisations are here derived.
The Cauchy invariants equation and the Cauchy formula, relating the vorticity
and the Jacobian of the Lagrangian map, are shown to be two expressions of this
Lie-advection invariance, which are duals of each other (specifically, Hodge
dual). Actually, this is shown to be an instance of a general result, which
holds for flow both in flat (Euclidean) space and in a curved Riemannian space:
any Lie-advection invariant p-form which is exact (i.e. is a differential of a
(p-1)-form) has an associated Cauchy invariants equation and a Cauchy formula.
This constitutes a new fundamental result in linear transport theory, providing
a Lagrangian formulation of Lie advection for some classes of differential
forms. The result has a broad applicability: examples include the
magnetohydrodynamics (MHD) equations and various extensions thereof, discussed
by Lingam et al. (Phys. Lett. A, vol. 380, 2016, pp. 2400-2406), and include
also the equations of Tao (2016, arXiv:1606.08481 [math.AP]), Euler equations
with modified Biot-Savart law, displaying finite-time blow-up. Our main result
is also used for new derivations, and several new results, concerning local
helicity-type invariants for fluids and MHD flow in flat or curved spaces of
arbitrary dimension.
| arxiv topic:physics.flu-dyn math.AP math.DG |
arxiv_dataset-80711701.01692 | To Boost or Not to Boost? On the Limits of Boosted Trees for Object
Detection
cs.CV
We aim to study the modeling limitations of the commonly employed boosted
decision trees classifier. Inspired by the success of large, data-hungry visual
recognition models (e.g. deep convolutional neural networks), this paper
focuses on the relationship between modeling capacity of the weak learners,
dataset size, and dataset properties. A set of novel experiments on the Caltech
Pedestrian Detection benchmark results in the best known performance among
non-CNN techniques while operating at fast run-time speed. Furthermore, the
performance is on par with deep architectures (9.71% log-average miss rate),
while using only HOG+LUV channels as features. The conclusions from this study
are shown to generalize over different object detection domains as demonstrated
on the FDDB face detection benchmark (93.37% accuracy). Despite the impressive
performance, this study reveals the limited modeling capacity of the common
boosted trees model, motivating a need for architectural changes in order to
compete with multi-level and very deep architectures.
| arxiv topic:cs.CV |
arxiv_dataset-80721701.01792 | Instantaneous GNSS attitude determination: A Monte Carlo sampling
approach
astro-ph.IM
A novel instantaneous GNSS ambiguity resolution approach which makes use of
only single-frequency carrier phase measurements for ultra-short baseline
attitude determination is proposed. The Monte Carlo sampling method is employed
to obtain the probability density function of ambiguities from a
quaternion-based GNSS-attitude model and the LAMBDA method strengthened with a
screening mechanism is then utilized to fix the integer values. Experimental
results show that 100% success rate could be achieved for ultra-short
baselines.
| arxiv topic:astro-ph.IM |
arxiv_dataset-80731701.01892 | Urban Scene Segmentation with Laser-Constrained CRFs
cs.CV
Robots typically possess sensors of different modalities, such as colour
cameras, inertial measurement units, and 3D laser scanners. Often, solving a
particular problem becomes easier when more than one modality is used. However,
while there are undeniable benefits to combine sensors of different modalities
the process tends to be complicated. Segmenting scenes observed by the robot
into a discrete set of classes is a central requirement for autonomy as
understanding the scene is the first step to reason about future situations.
Scene segmentation is commonly performed using either image data or 3D point
cloud data. In computer vision many successful methods for scene segmentation
are based on conditional random fields (CRF) where the maximum a posteriori
(MAP) solution to the segmentation can be obtained by inference. In this paper
we devise a new CRF inference method for scene segmentation that incorporates
global constraints, enforcing the sets of nodes are assigned the same class
label. To do this efficiently, the CRF is formulated as a relaxed quadratic
program whose MAP solution is found using a gradient-based optimisation
approach. The proposed method is evaluated on images and 3D point cloud data
gathered in urban environments where image data provides the appearance
features needed by the CRF, while the 3D point cloud data provides global
spatial constraints over sets of nodes. Comparisons with belief propagation,
conventional quadratic programming relaxation, and higher order potential CRF
show the benefits of the proposed method.
| arxiv topic:cs.CV |
arxiv_dataset-80741701.01992 | From semimetal to chiral Fulde-Ferrell superfluids
cond-mat.supr-con cond-mat.mes-hall quant-ph
The recent realization of two-dimensional (2D) synthetic spin-orbit (SO)
coupling opens a broad avenue to study novel topological states for ultracold
atoms. Here, we propose a new scheme to realize exotic chiral Fulde-Ferrell
superfluid for ultracold fermions, with a generic theory being shown that the
topology of superfluid pairing phases can be determined from the normal states.
The main findings are two fold. First, a semimetal is driven by a new type of
2D SO coupling whose realization is even simpler than the recent experiment,
and can be tuned into massive Dirac fermion phases with or without inversion
symmetry. Without inversion symmetry the superfluid phase with nonzero pairing
momentum is favored under an attractive interaction. Furthermore, we show a
fundamental theorem that the topology of a 2D chiral superfluid can be uniquely
determined from the unpaired normal states, with which the topological chiral
Fulde-Ferrell superfluid with a broad topological region is predicted for the
present system. This generic theorem is also useful for condensed matter
physics and material science in search for new topological superconductors.
| arxiv topic:cond-mat.supr-con cond-mat.mes-hall quant-ph |
arxiv_dataset-80751701.02092 | Exact Energy Levels and Eigenfunctions of an Electron on a Nanosphere
Under the Radial Magnetic Field
quant-ph cond-mat.mes-hall
The exact energy levels and wave functions of an electron free to move on a
sphere under the radial magnetic field is found. Wave functions are expressed
in terms of Jacobi polynomials which were well-defined and have orthogonality
relation, recurrence relations, series expansions etc. We have also discussed
the the wave functions and energy levels in case of very large magnetic field.
Landau energy levels are shown for strong constant magnetic field occurring on
two-dimensional surfaces, if the radius is very large. The results compared
with those previously found in the literature.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-80761701.02192 | Quadratic Programming Approach to Fit Protein Complexes into Electron
Density Maps
math.OC q-bio.QM
The paper investigates the problem of fitting protein complexes into electron
density maps. They are represented by high-resolution cryoEM density maps
converted into overlapping matrices and partly show a structure of a complex.
The general purpose is to define positions of all proteins inside it. This
problem is known to be NP-hard, since it lays in the field of combinatorial
optimization over a set of discrete states of the complex. We introduce
quadratic programming approaches to the problem. To find an approximate
solution, we convert a density map into an overlapping matrix, which is
generally indefinite. Since the matrix is indefinite, the optimization problem
for the corresponding quadratic form is non-convex. To treat non-convexity of
the optimization problem, we use different convex relaxations to find which set
of proteins minimizes the quadratic form best.
| arxiv topic:math.OC q-bio.QM |
arxiv_dataset-80771701.02292 | On short cycle enumeration in biregular bipartite graphs
cs.IT math.CO math.IT
A number of recent works have used a variety of combinatorial constructions
to derive Tanner graphs for LDPC codes and some of these have been shown to
perform well in terms of their probability of error curves and error floors.
Such graphs are bipartite and many of these constructions yield biregular
graphs where the degree of left vertices is a constant $c+1$ and that of the
right vertices is a constant $d+1$. Such graphs are termed $(c+1,d+1)$
biregular bipartite graphs here. One property of interest in such work is the
girth of the graph and the number of short cycles in the graph, cycles of
length either the girth or slightly larger. Such numbers have been shown to be
related to the error floor of the probability of error curve of the related
LDPC code. Using known results of graph theory, it is shown how the girth and
the number of cycles of length equal to the girth may be computed for these
$(c+1,d+1)$ biregular bipartite graphs knowing only the parameters $c$ and $d$
and the numbers of left and right vertices. While numerous algorithms to
determine the number of short cycles in arbitrary graphs exist, the reduction
of the problem from an algorithm to a computation for these biregular bipartite
graphs is of interest.
| arxiv topic:cs.IT math.CO math.IT |
arxiv_dataset-80781701.02392 | Reinforcement Learning via Recurrent Convolutional Neural Networks
cs.LG cs.AI
Deep Reinforcement Learning has enabled the learning of policies for complex
tasks in partially observable environments, without explicitly learning the
underlying model of the tasks. While such model-free methods achieve
considerable performance, they often ignore the structure of task. We present a
natural representation of to Reinforcement Learning (RL) problems using
Recurrent Convolutional Neural Networks (RCNNs), to better exploit this
inherent structure. We define 3 such RCNNs, whose forward passes execute an
efficient Value Iteration, propagate beliefs of state in partially observable
environments, and choose optimal actions respectively. Backpropagating
gradients through these RCNNs allows the system to explicitly learn the
Transition Model and Reward Function associated with the underlying MDP,
serving as an elegant alternative to classical model-based RL. We evaluate the
proposed algorithms in simulation, considering a robot planning problem. We
demonstrate the capability of our framework to reduce the cost of replanning,
learn accurate MDP models, and finally re-plan with learnt models to achieve
near-optimal policies.
| arxiv topic:cs.LG cs.AI |
arxiv_dataset-80791701.02492 | Recurrent fast radio bursts from collisions of neutron stars in the
evolved stellar clusters
astro-ph.HE
We propose the model describing the observed multiple fast radio bursts due
to the close encounters and collisions of neutron stars in the central clusters
of the evolved galactic nuclei. The subsystem of neutron star cluster may
originate in the dense galactic nucleus evolutionary in the combined processes
of stellar and dynamical evolution. The neutron stars in the compact cluster
can produce the short living binaries with the highly eccentric orbits, and
finally collide after several orbital revolutions. Fast radio bursts may be
produced during the close periastron approach and at the process of the final
binary merging. In the sufficiently dense star cluster the neutron stars
collisions can be very frequent. Therefore, this model can explain in principle
the observed recurrent (multiple) fast radio bursts, analogous to the observed
ones from the source FRB 121102. Among the possible observational signatures of
the proposed model may be the registration of the gravitational wave bursts by
the laser interferometers LIGO/VIRGO or by the next generation of gravitational
wave detectors.
| arxiv topic:astro-ph.HE |
arxiv_dataset-80801701.02592 | Order parameter analysis of synchronization transitions on star networks
nlin.AO
Collective behaviors of populations of coupled oscillators have attracted
much attention in recent years. In this paper, an order parameter approach is
proposed to study the low-dimensional dynam- ical mechanism of collective
synchronizations by adopting the star-topology of coupled oscillators as a
prototype system. The order parameter equation of star-linked phase oscillators
can be obtained in terms of the Watanabe-Strogatz transformation, Ott-Antonsen
ansatz, and the ensemble order parameter approach. Different solutions of the
order parameter equation correspond to diverse col- lective states, and
different bifurcations reveal various transitions among these collective
states. The properties of various transitions are revealed in the star-network
model by using tools of nonlinear dynamics such as time reversibility analysis
and linear stability analysis.
| arxiv topic:nlin.AO |
arxiv_dataset-80811701.02692 | Von Neumann Regular Cellular Automata
math.GR cs.DM cs.FL
For any group $G$ and any set $A$, a cellular automaton (CA) is a
transformation of the configuration space $A^G$ defined via a finite memory set
and a local function. Let $\text{CA}(G;A)$ be the monoid of all CA over $A^G$.
In this paper, we investigate a generalisation of the inverse of a CA from the
semigroup-theoretic perspective. An element $\tau \in \text{CA}(G;A)$ is von
Neumann regular (or simply regular) if there exists $\sigma \in \text{CA}(G;A)$
such that $\tau \circ \sigma \circ \tau = \tau$ and $\sigma \circ \tau \circ
\sigma = \sigma$, where $\circ$ is the composition of functions. Such an
element $\sigma$ is called a generalised inverse of $\tau$. The monoid
$\text{CA}(G;A)$ itself is regular if all its elements are regular. We
establish that $\text{CA}(G;A)$ is regular if and only if $\vert G \vert = 1$
or $\vert A \vert = 1$, and we characterise all regular elements in
$\text{CA}(G;A)$ when $G$ and $A$ are both finite. Furthermore, we study
regular linear CA when $A= V$ is a vector space over a field $\mathbb{F}$; in
particular, we show that every regular linear CA is invertible when $G$ is
torsion-free elementary amenable (e.g. when $G=\mathbb{Z}^d, \ d \in
\mathbb{N}$) and $V=\mathbb{F}$, and that every linear CA is regular when $V$
is finite-dimensional and $G$ is locally finite with $\text{Char}(\mathbb{F})
\nmid o(g)$ for all $g \in G$.
| arxiv topic:math.GR cs.DM cs.FL |
arxiv_dataset-80821701.02792 | Flexible Bacterial Cellulose Permalloy nanocomposite xerogel sheets size
scalable magnetic actuator cum electrical conductor
cond-mat.mtrl-sci physics.class-ph
Permalloy nanoparticles containing bacterial cellulose hydrogel obtained
after reduction was compressed into a xerogel flexible sheet by hot pressing at
60 C at different pressures. The permalloy nanoparticles with an ordered
structure have a bimodal size distribution centered around 25 nm and 190 nm.
The smaller nanoparticles are superparamagnetic while the larger particles are
ferromagnetic at room temperature. The sheets have a room temperature
magnetisation of 20 emu/g and a coercivity of 32 Oe. The electrical
conductivity of the flexible sheets increases with hot pressing pressure from 7
S/cm to 40 S/cm at room temperature.
| arxiv topic:cond-mat.mtrl-sci physics.class-ph |
arxiv_dataset-80831701.02892 | Multivariate Regression with Grossly Corrupted Observations: A Robust
Approach and its Applications
stat.ML cs.CV cs.LG
This paper studies the problem of multivariate linear regression where a
portion of the observations is grossly corrupted or is missing, and the
magnitudes and locations of such occurrences are unknown in priori. To deal
with this problem, we propose a new approach by explicitly consider the error
source as well as its sparseness nature. An interesting property of our
approach lies in its ability of allowing individual regression output elements
or tasks to possess their unique noise levels. Moreover, despite working with a
non-smooth optimization problem, our approach still guarantees to converge to
its optimal solution. Experiments on synthetic data demonstrate the
competitiveness of our approach compared with existing multivariate regression
models. In addition, empirically our approach has been validated with very
promising results on two exemplar real-world applications: The first concerns
the prediction of \textit{Big-Five} personality based on user behaviors at
social network sites (SNSs), while the second is 3D human hand pose estimation
from depth images. The implementation of our approach and comparison methods as
well as the involved datasets are made publicly available in support of the
open-source and reproducible research initiatives.
| arxiv topic:stat.ML cs.CV cs.LG |
arxiv_dataset-80841701.02992 | Bingham flow in porous media with obstacles of different size
math.AP math-ph math.MP
By using the unfolding operators for periodic homogenization, we give a
general compactness result for a class of functions defined on bounded domains
presenting perforations of two different size. Then we apply this result to the
homogenization of the flow of a Bingham fluid in a porous medium with solid
obstacles of different size. Next we give the interpretation of the limit
problem in term of a non linear Darcy law.
| arxiv topic:math.AP math-ph math.MP |
arxiv_dataset-80851701.03092 | Job Detection in Twitter
cs.CL
In this report, we propose a new application for twitter data called
\textit{job detection}. We identify people's job category based on their
tweets. As a preliminary work, we limited our task to identify only IT workers
from other job holders. We have used and compared both simple bag of words
model and a document representation based on Skip-gram model. Our results show
that the model based on Skip-gram, achieves a 76\% precision and 82\% recall.
| arxiv topic:cs.CL |
arxiv_dataset-80861701.03192 | Gauge Choice in Conformal Gravity
gr-qc astro-ph.GA
In a recent paper (MNRAS 458, 4122 (2016)) K. Horne examined the effect of a
conformally coupled scalar field (referred to as Higgs field) on the
Mannheim-Kazanas metric $g_{\mu\nu}$, i.e. the static spherically symmetric
metric within the context of conformal gravity (CG), and studied its effect on
the rotation curves of galaxies. He showed that for a Higgs field of the form
$S(r) = S_0 a/(r + a)$, where $a$ is a radial length scale, the equivalent
Higgs-frame Mannheim-Kazanas metric $\tilde{g}_{\mu\nu} = \Omega^2 g_{\mu\nu}$,
with $\Omega = S(r)/S_{0}$, lacks the linear $\gamma r$ term, which has been
employed in the fitting of the galactic rotation curves without the need to
invoke dark matter. In this brief note we point out that the representation of
the Mannheim-Kazanas metric in a gauge where it lacks the linear term has
already been presented by others, including Mannheim and Kazanas themselves,
without the need to introduce a conformally coupled Higgs field. Furthermore,
Horne argues that the absence of the linear term resolves the issue of light
bending in the wrong direction, i.e. away from the gravitating mass, if $\gamma
r > 0$ in the Mannheim-Kazanas metric, a condition necessary to resolve the
galactic dynamics in the absence of dark matter. In this case we also point out
that the elimination of the linear term is not even required because the sign
of the $\gamma r$ term in the metric can be easily reversed by a simple gauge
transformation, and also that the effects of this term are indeed too small to
be observed.
| arxiv topic:gr-qc astro-ph.GA |
arxiv_dataset-80871701.03292 | Structural instability of large-scale functional networks
physics.soc-ph nlin.AO
We study how large functional networks can grow stably under possible
cascading overload failures and evaluated the maximum stable network size above
which even a small-scale failure would cause a fatal breakdown of the network.
Employing a model of cascading failures induced by temporally fluctuating
loads, the maximum stable size $n_{\text{max}}$ has been calculated as a
function of the load reduction parameter $r$ that characterizes how quickly the
total load is reduced during the cascade. If we reduce the total load
sufficiently fast ($r\ge r_{\text{c}}$), the network can grow infinitely.
Otherwise, $n_{\text{max}}$ is finite and increases with $r$. For a fixed
$r\,(<r_{\text{c}})$, $n_{\text{max}}$ for a scale-free network is larger than
that for an exponential network with the same average degree. We also discuss
how one detects and avoids the crisis of a fatal breakdown of the network from
the relation between the sizes of the initial network and the largest component
after an ordinarily occurring cascading failure.
| arxiv topic:physics.soc-ph nlin.AO |
arxiv_dataset-80881701.03392 | Fully quantum description of the Zundel ion: combining variational
quantum Monte Carlo with path integral Langevin dynamics
physics.chem-ph cond-mat.mtrl-sci quant-ph
We introduce a novel approach for a fully quantum description of coupled
electron-ion systems from first principles. It combines the variational quantum
Monte Carlo (QMC) solution of the electronic part with the path integral (PI)
formalism for the quantum nuclear dynamics. On the one hand, the PI molecular
dynamics includes nuclear quantum effects by adding a set of fictitious
classical particles (beads) aimed at reproducing nuclear quantum fluctuations
via a harmonic kinetic term. On the other hand, variational QMC can provide
Born-Oppenheimer (BO) potential energy surfaces with a precision comparable to
the most advanced post Hartree-Fock approaches, and with a favorable scaling
with the system size. To deal with the intrinsic QMC noise, we generalize the
PI molecular dynamics using a Langevin thermostat correlated according to the
covariance matrix of QMC nuclear forces. The variational parameters of the QMC
wave function are evolved during the nuclear dynamics, such that the BO
potential energy surface is unbiased. Statistical errors on the wave function
parameters are reduced by resorting to bead grouping average, which we show to
be accurate and well controlled. Our general algorithm relies on a Trotter
breakup between the dynamics driven by ionic forces and the one set by the
harmonic interbead couplings. The latter is exactly integrated even in presence
of the Langevin thermostat, thanks to the mapping onto an Ornstein-Uhlenbeck
process. This framework turns out to be very efficient also in the case of
deterministic ionic forces. The new implementation is validated on the Zundel
ion by direct comparison with standard PI Langevin dynamics calculations made
with a coupled cluster potential energy surface. Nuclear quantum effects are
confirmed to be dominant over thermal effects well beyond room temperature
giving the excess proton an increased mobility by quantum tunneling.
| arxiv topic:physics.chem-ph cond-mat.mtrl-sci quant-ph |
arxiv_dataset-80891701.03492 | Scalable, Trie-based Approximate Entity Extraction for Real-Time
Financial Transaction Screening
cs.CL cs.IR
Financial institutions have to screen their transactions to ensure that they
are not affiliated with terrorism entities. Developing appropriate solutions to
detect such affiliations precisely while avoiding any kind of interruption to
large amount of legitimate transactions is essential. In this paper, we present
building blocks of a scalable solution that may help financial institutions to
build their own software to extract terrorism entities out of both structured
and unstructured financial messages in real time and with approximate
similarity matching approach.
| arxiv topic:cs.CL cs.IR |
arxiv_dataset-80901701.03592 | Angpow: a software for the fast computation of accurate tomographic
power spectra
astro-ph.CO
The statistical distribution of galaxies is a powerful probe to constrain
cosmological models and gravity. In particular the matter power spectrum $P(k)$
brings information about the cosmological distance evolution and the galaxy
clustering together. However the building of $P(k)$ from galaxy catalogues
needs a cosmological model to convert angles on the sky and redshifts into
distances, which leads to difficulties when comparing data with predicted
$P(k)$ from other cosmological models, and for photometric surveys like LSST.
The angular power spectrum $C_\ell(z_1,z_2)$ between two bins located at
redshift $z_1$ and $z_2$ contains the same information than the matter power
spectrum, is free from any cosmological assumption, but the prediction of
$C_\ell(z_1,z_2)$ from $P(k)$ is a costly computation when performed exactly.
The Angpow software aims at computing quickly and accurately the auto
($z_1=z_2$) and cross ($z_1 \neq z_2$) angular power spectra between redshift
bins. We describe the developed algorithm, based on developments on the
Chebyshev polynomial basis and on the Clenshaw-Curtis quadrature method. We
validate the results with other codes, and benchmark the performance. Angpow is
flexible and can handle any user defined power spectra, transfer functions, and
redshift selection windows. The code is fast enough to be embedded inside
programs exploring large cosmological parameter spaces through the
$C_\ell(z_1,z_2)$ comparison with data. We emphasize that the Limber's
approximation, often used to fasten the computation, gives wrong $C_\ell$
values for cross-correlations.
| arxiv topic:astro-ph.CO |
arxiv_dataset-80911701.03692 | Volkov States and Non-linear Compton Scattering in Short and Intense
Laser Pulses
physics.plasm-ph hep-ph
The collision of ultra-relativistic electron beams with intense short laser
pulses makes possible to study QED in the high-intensity regime. Present day
high-intensity lasers mostly operate with short pulse durations of several tens
of femtoseconds, i.e. only a few optical cycles. A profound theoretical
understanding of short pulse effects is important not only for studying
fundamental aspects of high-intensity laser matter interaction, but also for
applications as novel X- and gamma-ray radiation sources. In this article we
give a brief overview of the theory of high-intensity QED with focus on effects
due to the short pulse duration. The non-linear spectral broadening in
non-linear Compton scattering due to the short pulse duration and its
compensation is discussed.
| arxiv topic:physics.plasm-ph hep-ph |
arxiv_dataset-80921701.03792 | Not so lumpy after all: modeling the depletion of dark matter subhalos
by Milky Way-like galaxies
astro-ph.GA
Among the most important goals in cosmology is detecting and quantifying
small ($M_{\rm halo}\simeq10^{6-9}~\mathrm{M}_\odot$) dark matter (DM)
subhalos. Current probes around the Milky Way (MW) are most sensitive to such
substructure within $\sim20$ kpc of the halo center, where the galaxy
contributes significantly to the potential. We explore the effects of baryons
on subhalo populations in $\Lambda$CDM using cosmological zoom-in baryonic
simulations of MW-mass halos from the Latte simulation suite, part of the
Feedback In Realistic Environments (FIRE) project. Specifically, we compare
simulations of the same two halos run using (1) DM-only (DMO), (2) full
baryonic physics, and (3) DM with an embedded disk potential grown to match the
FIRE simulation. Relative to baryonic simulations, DMO simulations contain
$\sim2\times$ as many subhalos within 100 kpc of the halo center; this excess
is $\gtrsim5\times$ within 25 kpc. At $z=0$, the baryonic simulations are
completely devoid of subhalos down to $3\times10^6~\mathrm{M}_\odot$ within
$15$ kpc of the MW-mass galaxy, and fewer than 20 surviving subhalos have
orbital pericenters <20 kpc. Despite the complexities of baryonic physics, the
simple addition of an embedded central disk potential to DMO simulations
reproduces this subhalo depletion, including trends with radius, remarkably
well. Thus, the additional tidal field from the central galaxy is the primary
cause of subhalo depletion. Subhalos on radial orbits that pass close to the
central galaxy are preferentially destroyed, causing the surviving subhalo
population to have tangentially biased orbits compared to DMO predictions. Our
method of embedding a disk potential in DMO simulations provides a fast and
accurate alternative to full baryonic simulations, thus enabling suites of
cosmological simulations that can provide accurate and statistical predictions
of substructure populations.
| arxiv topic:astro-ph.GA |
arxiv_dataset-80931701.03892 | A characterization of signed discrete infinitely divisible distributions
math.ST math.PR stat.TH
In this article, we give some reviews concerning negative probabilities model
and quasi-infinitely divisible at the beginning. We next extend Feller's
characterization of discrete infinitely divisible distributions to signed
discrete infinitely divisible distributions, which are discrete pseudo compound
Poisson (DPCP) distributions with connections to the L\'evy-Wiener theorem.
This is a special case of an open problem which is proposed by Sato(2014),
Chaumont and Yor(2012). An analogous result involving characteristic functions
is shown for signed integer-valued infinitely divisible distributions. We show
that many distributions are DPCP by the non-zero p.g.f. property, such as the
mixed Poisson distribution and fractional Poisson process. DPCP has some
bizarre properties, and one is that the parameter $\lambda $ in the DPCP class
cannot be arbitrarily small.
| arxiv topic:math.ST math.PR stat.TH |
arxiv_dataset-80941701.03992 | The Hiemstra-Jones Test Revisited
stat.ME
The famous Hiemstra-Jones (HJ) test developed by Hiemstra and Jones (1994)
plays a significant role in studying nonlinear causality. Over the last two
decades, there have been numerous applications and theoretical extensions based
on this pioneering work. However, several works note that counterintuitive
results are obtained from the HJ test, and some researchers find that the HJ
test is seriously over-rejecting in simulation studies. In this paper, we
reinvestigate HJ's creative 1994 work and find that their proposed estimators
of the probabilities over different time intervals were not consistent with the
target ones proposed in their criterion. To test HJ's novel hypothesis on
Granger causality, we propose new estimators of the probabilities defined in
their paper and reestablish the asymptotic properties to induce new tests
similar to those of HJ. Some simulations will also be presented to support our
findings.
| arxiv topic:stat.ME |
arxiv_dataset-80951701.04092 | Correlations of sums of two squares and other arithmetic functions in
function fields
math.NT math.AC math.GR
We investigate a function field analogue of a recent conjecture on
autocorrelations of sums of two squares by Freiberg, Kurlberg and Rosenzweig,
which generalizes an older conjecture by Connors and Keating. In particular, we
provide extensive numerical evidence and prove it in the large finite field
limit. Our method can also handle correlations of other arithmetic functions
and we give applications to (function field analogues of) the average of sums
of two squares on shifted primes, and to autocorrelations of higher divisor
functions twisted by a quadratic character.
| arxiv topic:math.NT math.AC math.GR |
arxiv_dataset-80961701.04192 | Pivotal decomposition schemes inducing clones of operations
math.RA math.LO
We study pivotal decomposition schemes and investigate classes of pivotally
decomposable operations. We provide sufficient conditions on pivotal operations
that guarantee that the corresponding classes of pivotally decomposable
operations are clones, and show that under certain assumptions these conditions
are also necessary. In the latter case, the pivotal operation together with the
constant operations generate the corresponding clone.
| arxiv topic:math.RA math.LO |
arxiv_dataset-80971701.04292 | Semantic classifier approach to document classification
cs.IR cs.CL
In this paper we propose a new document classification method, bridging
discrepancies (so-called semantic gap) between the training set and the
application sets of textual data. We demonstrate its superiority over classical
text classification approaches, including traditional classifier ensembles. The
method consists in combining a document categorization technique with a single
classifier or a classifier ensemble (SEMCOM algorithm - Committee with Semantic
Categorizer).
| arxiv topic:cs.IR cs.CL |
arxiv_dataset-80981701.04392 | Optimal quantum spatial search on random temporal networks
quant-ph
To investigate the performance of quantum information tasks on networks whose
topology changes in time, we study the spatial search algorithm by continuous
time quantum walk to find a marked node on a random temporal network. We
consider a network of $n$ nodes constituted by a time-ordered sequence of
Erd\"os-R\'enyi random graphs $G(n,p)$, where $p$ is the probability that any
two given nodes are connected: after every time interval $\tau$, a new graph
$G(n,p)$ replaces the previous one. We prove analytically that for any given
$p$, there is always a range of values of $\tau$ for which the running time of
the algorithm is optimal, i.e.\ $\mathcal{O}(\sqrt{n})$, even when search on
the individual static graphs constituting the temporal network is sub-optimal.
On the other hand, there are regimes of $\tau$ where the algorithm is
sub-optimal even when each of the underlying static graphs are sufficiently
connected to perform optimal search on them. From this first study of quantum
spatial search on a time-dependent network, it emerges that the non-trivial
interplay between temporality and connectivity is key to the algorithmic
performance. Moreover, our work can be extended to establish high-fidelity
qubit transfer between any two nodes of the network. Overall, our findings show
that one can exploit temporality to achieve optimal quantum information tasks
on dynamical random networks.
| arxiv topic:quant-ph |
arxiv_dataset-80991701.04492 | A nonuniform fast Fourier transform based on low rank approximation
math.NA
By viewing the nonuniform discrete Fourier transform (NUDFT) as a perturbed
version of a uniform discrete Fourier transform, we propose a fast, stable, and
simple algorithm for computing the NUDFT that costs $\mathcal{O}(N\log
N\log(1/\epsilon)/\log\!\log(1/\epsilon))$ operations based on the fast Fourier
transform, where $N$ is the size of the transform and $0<\epsilon <1$ is a
working precision. Our key observation is that a NUDFT and DFT matrix divided
entry-by-entry is often well-approximated by a low rank matrix, allowing us to
express a NUDFT matrix as a sum of diagonally-scaled DFT matrices. Our
algorithm is simple to implement, automatically adapts to any working
precision, and is competitive with state-of-the-art algorithms. In the fully
uniform case, our algorithm is essentially the FFT. We also describe
quasi-optimal algorithms for the inverse NUDFT and two-dimensional NUDFTs.
| arxiv topic:math.NA |
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