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arxiv_dataset-86001706.05265 | Electron plasma wake field acceleration in solar coronal and
chromospheric plasmas
astro-ph.SR physics.plasm-ph physics.space-ph
Three dimensional, particle-in-cell, fully electromagnetic simulations of
electron plasma wake field acceleration applicable to solar atmosphere are
presented. It is established that injecting driving and trailing electron
bunches into solar coronal and chromospheric plasmas, results in electric
fields ($-(20-5) \times 10^{6}$ V/m), leading to acceleration of the trailing
bunch up to 52 MeV, starting from initial 36 MeV. The results provide one of
potentially important mechanisms for the extreme energetic solar flare
electrons, invoking plasma wake field acceleration.
| arxiv topic:astro-ph.SR physics.plasm-ph physics.space-ph |
arxiv_dataset-86011706.05365 | Quasicontinuum $\gamma$-decay of $^{91,92}$Zr: benchmarking indirect
($n,\gamma$) cross section measurements for the $s$-process
nucl-ex
Nuclear level densities (NLDs) and $\gamma$-ray strength functions
($\gamma$SFs) have been extracted from particle-$\gamma$ coincidences of the
$^{92}$Zr($p,p' \gamma$)$^{92}$Zr and $^{92}$Zr($p,d \gamma$)$^{91}$Zr
reactions using the Oslo method. The new $^{91,92}$Zr $\gamma$SF data, combined
with photonuclear cross sections, cover the whole energy range from $E_{\gamma}
\approx 1.5$~MeV up to the giant dipole resonance at $E_{\gamma} \approx
17$~MeV. The wide-range $\gamma$SF data display structures at $E_{\gamma}
\approx 9.5$~MeV, compatible with a superposition of the spin-flip $M1$
resonance and a pygmy $E1$ resonance. Furthermore, the $\gamma$SF shows a
minimum at $E_{\gamma} \approx 2-3$~MeV and an increase at lower $\gamma$-ray
energies. The experimentally constrained NLDs and $\gamma$SFs are shown to
reproduce known ($n, \gamma$) and Maxwellian-averaged cross sections for
$^{91,92}$Zr using the {\sf TALYS} reaction code, thus serving as a benchmark
for this indirect method of estimating ($n, \gamma$) cross sections for Zr
isotopes.
| arxiv topic:nucl-ex |
arxiv_dataset-86021706.05465 | Plasmonic modes of polygonal particles calculated using a quantum
hydrodynamics method
cond-mat.mes-hall physics.optics physics.plasm-ph
Plasmonic resonances of nanoparticles have drawn lots of attentions due to
their interesting and useful properties such as strong field enhancements.
These systems are typically studied using either classical electrodynamics or
fully quantum theory. Each approach can handle some aspects of plasmonic
systems accurately and efficiently, while having its own limitation. The
self-consistent hydrodynamics model has the advantage that it can incorporate
the quantum effect of the electron gas into classical electrodynamics in a
consistent way. We use the method to study the plasmonic response of polygonal
particles under the influence of an external electromagnetic wave, and we pay
particular attention to the size and shape of the particle and the effect of
charging. We find that the particles support edge modes, face modes and hybrid
modes. The charges induced by the external field in the edge (face) modes
mainly localize at the edges (faces), while the induced charges in the hybrid
modes are distributed nearly evenly in both the edges and faces. The edge modes
are less sensitive to particle size than the face modes, but are sensitive to
the corner angles of the edges. When the number of sides of regular polygons
increases, the edge and face modes gradually change into the classical dipole
plasmonic mode of a cylinder. The hybrid modes are found to be the precursor of
the Bennett mode, which cannot be found in classical electrodynamics.
| arxiv topic:cond-mat.mes-hall physics.optics physics.plasm-ph |
arxiv_dataset-86031706.05565 | Towards Neural Phrase-based Machine Translation
cs.CL stat.ML
In this paper, we present Neural Phrase-based Machine Translation (NPMT). Our
method explicitly models the phrase structures in output sequences using
Sleep-WAke Networks (SWAN), a recently proposed segmentation-based sequence
modeling method. To mitigate the monotonic alignment requirement of SWAN, we
introduce a new layer to perform (soft) local reordering of input sequences.
Different from existing neural machine translation (NMT) approaches, NPMT does
not use attention-based decoding mechanisms. Instead, it directly outputs
phrases in a sequential order and can decode in linear time. Our experiments
show that NPMT achieves superior performances on IWSLT 2014
German-English/English-German and IWSLT 2015 English-Vietnamese machine
translation tasks compared with strong NMT baselines. We also observe that our
method produces meaningful phrases in output languages.
| arxiv topic:cs.CL stat.ML |
arxiv_dataset-86041706.05665 | Double-winding Wilson loops in the $SU(N)$ Yang-Mills theory
hep-th
We consider double-winding, triple-winding and multiple-winding Wilson loops
in the $SU(N)$ Yang-Mills gauge theory. We examine how the area law falloff of
the vacuum expectation value of a multiple-winding Wilson loop depends on the
number of color $N$. In sharp contrast to the difference-of-areas law recently
found for a double-winding $SU(2)$ Wilson loop average, we show irrespective of
the spacetime dimensionality that a double-winding $SU(3)$ Wilson loop follows
a novel area law which is neither difference-of-areas nor sum-of-areas law for
the area law falloff and that the difference-of-areas law is excluded and the
sum-of-areas law is allowed for $SU(N)$ ($N \ge 4$), provided that the string
tension obeys the Casimir scaling for the higher representations. Moreover, we
extend these results to arbitrary multi-winding Wilson loops. Finally, we argue
that the area law follows a novel law, which is neither sum-of-areas nor
difference-of-areas law when $N\ge 3$. In fact, such a behavior is exactly
derived in the $SU(N)$ Yang-Mills theory in the two-dimensional spacetime.
| arxiv topic:hep-th |
arxiv_dataset-86051706.05765 | An Empirical Study of Mini-Batch Creation Strategies for Neural Machine
Translation
cs.CL
Training of neural machine translation (NMT) models usually uses mini-batches
for efficiency purposes. During the mini-batched training process, it is
necessary to pad shorter sentences in a mini-batch to be equal in length to the
longest sentence therein for efficient computation. Previous work has noted
that sorting the corpus based on the sentence length before making mini-batches
reduces the amount of padding and increases the processing speed. However,
despite the fact that mini-batch creation is an essential step in NMT training,
widely used NMT toolkits implement disparate strategies for doing so, which
have not been empirically validated or compared. This work investigates
mini-batch creation strategies with experiments over two different datasets.
Our results suggest that the choice of a mini-batch creation strategy has a
large effect on NMT training and some length-based sorting strategies do not
always work well compared with simple shuffling.
| arxiv topic:cs.CL |
arxiv_dataset-86061706.05865 | Seeing double with K2: Testing re-inflation with two remarkably similar
planets around red giant branch stars
astro-ph.EP
Despite more than 20 years since the discovery of the first gas giant planet
with an anomalously large radius, the mechanism for planet inflation remains
unknown. Here, we report the discovery of EPIC228754001.01, an inflated gas
giant planet found with the NASA K2 Mission, and a revised mass for another
inflated planet, K2-97b. These planets reside on ~9 day orbits around host
stars which recently evolved into red giants. We constrain the irradiation
history of these planets using models constrained by asteroseismology and
Keck/HIRES spectroscopy and radial velocity measurements. We measure planet
radii of 1.31 +\- 0.11 Rjup and and 1.30 +\- 0.07 Rjup, respectively. These
radii are typical for planets receiving the current irradiation, but not the
former, zero age main sequence irradiation of these planets. This suggests that
the current sizes of these planets are directly correlated to their current
irradiation. Our precise constraints of the masses and radii of the stars and
planets in these systems allow us to constrain the planetary heating efficiency
of both systems as 0.03% +0.03%/-0.02%. These results are consistent with a
planet re-inflation scenario, but suggest the efficiency of planet re-inflation
may be lower than previously theorized. Finally, we discuss the agreement
within 10% of stellar masses and radii, and planet masses, radii, and orbital
periods of both systems and speculate that this may be due to selection bias in
searching for planets around evolved stars.
| arxiv topic:astro-ph.EP |
arxiv_dataset-86071706.05965 | Cauchy problem for effectively hyperbolic operators with triple
characteristics
math.AP
We study the Cauchy problem for effectively hyperbolic operators $P$ with
principal symbol $p(t, x,\tau,\xi)$ having triple characteristics on $t = 0$.
Under a condition (E) we show that such operators are strongly hyperbolic, that
is the Cauchy problem is well posed for $p(t, x,D_t, D_x) + Q(t, x, D_t, D_x)$
with arbitrary lower order term $Q$. The proof is based on energy estimates
with weight $t^{-N}$ for a first order pseudo-differential system, where $N$
depends on lower order terms. For our analysis we construct a non-negative
definite symmetrizer $S(t)$ and we prove a version of Fefferman-Phong type
inequality for ${\rm Re}\, (S(t)U, U)_{L^2({\mathbb R}^n)}$ with a lower bound
$-C t^{-1}\|\langle D \rangle^{-1}U\|_{L^2(\mathbb R^n)}$.
| arxiv topic:math.AP |
arxiv_dataset-86081706.06065 | Finite-resource teleportation stretching for continuous-variable systems
quant-ph
We show how adaptive protocols of quantum and private communication through
bosonic Gaussian channels can be simplified into much easier block versions
that involve resource states with finite energy. This is achieved by combining
the adaptive-to-block reduction technique devised earlier [S. Pirandola et al.,
Nat. Commun. 8, 15043 (2017)], based on teleportation stretching and relative
entropy of entanglement, with an alternative simulation of Gaussian channels
recently introduced by Liuzzo-Scorpo et al. [Phys. Rev. Lett. 119, 120503
(2017)]. In this way, we derive weak converse upper bounds for the secret-key
capacity of phase-insensitive Gaussian channels, which approximate the optimal
limit for infinite energy. Our results apply to both point-to-point and
repeater-assisted private communications.
| arxiv topic:quant-ph |
arxiv_dataset-86091706.06165 | Spontaneous generation of fractional vortex-antivortex pairs at single
edges of high-Tc superconductors
cond-mat.supr-con
Unconventional d-wave superconductors with pair-breaking edges are predicted
to have ground states with spontaneously broken time-reversal and translational
symmetries. We use the quasiclassical theory of superconductivity to
demonstrate that such phases can exist at any single pair-breaking facet. This
implies that a greater variety of systems, not necessarily mesoscopic in size,
should be unstable to such symmetry breaking. The density of states averaged
over the facet displays a broad peak centered at zero energy, which is
consistent with experimental findings of a broad zero-bias conductance peak
with a temperature-independent width at low temperatures.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-86101706.06265 | On excluded minors for classes of graphical matroids
math.CO
Frame matroids and lifted-graphic matroids are two distinct minor-closed
classes of matroids, each of which generalises the class of graphic matroids.
The class of quasi-graphic matroids, recently introduced by Geelen, Gerards,
and Whittle, simultaneously generalises both the classes of frame and
lifted-graphic matroids. Let $\mathcal{M}$ be one of these three classes, and
let $r$ be a positive integer. We show that $\mathcal{M}$ has only a finite
number of excluded minors of rank $r$.
| arxiv topic:math.CO |
arxiv_dataset-86111706.06365 | Control by time delayed feedback near a Hopf bifurcation point
math.DS math.CA
In this paper we study the stabilization of rotating waves using time delayed
feedback control. It is our aim to put some recent results in a broader context
by discussing two different methods to determine the stability of the target
periodic orbit in the controlled system: 1) by directly studying the Floquet
multipliers and 2) by use of the Hopf bifurcation theorem. We also propose an
extension of the Pyragas control scheme for which the controlled system becomes
a functional differential equation of neutral type. Using the observation that
we are able to determine the direction of bifurcation by a relatively simple
calculation of the root tendency, we find stability conditions for the periodic
orbit as a solution of the neutral type equation.
| arxiv topic:math.DS math.CA |
arxiv_dataset-86121706.06465 | The Auger Effect and Ionization of Inner Atomic Shells
physics.atom-ph
The Auger effect from inner shells, which arises from resonance excitation of
the valence electron of an atom by a weak electromagnetic wave, is discussed.
| arxiv topic:physics.atom-ph |
arxiv_dataset-86131706.06565 | On the Integrality Gap of the Prize-Collecting Steiner Forest LP
cs.DM cs.DS math.OC
In the prize-collecting Steiner forest (PCSF) problem, we are given an
undirected graph $G=(V,E)$, edge costs $\{c_e\geq 0\}_{e\in E}$, terminal pairs
$\{(s_i,t_i)\}_{i=1}^k$, and penalties $\{\pi_i\}_{i=1}^k$ for each terminal
pair; the goal is to find a forest $F$ to minimize $c(F)+\sum_{i:
(s_i,t_i)\text{ not connected in }F}\pi_i$. The Steiner forest problem can be
viewed as the special case where $\pi_i=\infty$ for all $i$. It was widely
believed that the integrality gap of the natural (and well-studied)
linear-programming (LP) relaxation for PCSF is at most 2. We dispel this belief
by showing that the integrality gap of this LP is at least $9/4$. This holds
even for planar graphs. We also show that using this LP, one cannot devise a
Lagrangian-multiplier-preserving (LMP) algorithm with approximation guarantee
better than $4$. Our results thus show a separation between the integrality
gaps of the LP-relaxations for prize-collecting and non-prize-collecting (i.e.,
standard) Steiner forest, as well as the approximation ratios achievable
relative to the optimal LP solution by LMP- and non-LMP- approximation
algorithms for PCSF. For the special case of prize-collecting Steiner tree
(PCST), we prove that the natural LP relaxation admits basic feasible solutions
with all coordinates of value at most $1/3$ and all edge variables positive.
Thus, we rule out the possibility of approximating PCST with guarantee better
than $3$ using a direct iterative rounding method.
| arxiv topic:cs.DM cs.DS math.OC |
arxiv_dataset-86141706.06665 | Fixed-point-free involutions and Schur P-positivity
math.CO math.RT
The orbits of the symplectic group acting on the type A flag variety are
indexed by the fixed-point-free involutions in a finite symmetric group. The
cohomology classes of the closures of these orbits have polynomial
representatives $\hat{\mathfrak{S}}^{\tt{FPF}}_z$ akin to Schubert polynomials.
We show that the fixed-point-free involution Stanley symmetric functions
$\hat{F}^{\tt{FPF}}_z$, which are stable limits of the polynomials
$\hat{\mathfrak{S}}^{\tt{FPF}}_z$, are Schur $P$-positive. To do so, we
construct an analogue of the Lascoux-Sch\"utzenberger tree, an algebraic
recurrence that computes Schubert polynomials. As a byproduct of our proof, we
obtain a Pfaffian formula of geometric interest for
$\hat{\mathfrak{S}}^{\tt{FPF}}_z$ when $z$ is a fixed-point-free version of a
Grassmannian permutation. We also classify the fixed-point-free involution
Stanley symmetric functions that are single Schur $P$-functions, and show that
the decomposition of $\hat{F}^{\tt{FPF}}_z$ into Schur $P$-functions is
unitriangular with respect to dominance order on strict partitions. These
results and proofs mirror previous work by the authors related to the
orthogonal group action on the type A flag variety.
| arxiv topic:math.CO math.RT |
arxiv_dataset-86151706.06765 | Wind, Sand and Water. The Orientation of the Late Roman Forts in the
Kharga Oasis (Egyptian Western Desert)
physics.hist-ph
The chain of late Roman fortified settlements built in the Kharga Oasis, in
Egypt Western Desert, represents an interesting case study to analyse how the
ancient Roman town planners interacted with the landscape. A peculiar feature
of the site is the existence of a prevailing, north westerly wind, and it is
possible to identify the average azimuth of the wind by measuring the central
axes of the halfmoon shaped sand dunes which characterize the landscape. Using
the methods of Archaeoastronomy, we compared these azimuths with the orthogonal
layout of both the settlements and the agricultural installations and showed
that these are oriented on the prevailing wind. A description and the possible
implications of this <<weathervane orientation>> are discussed in this article.
| arxiv topic:physics.hist-ph |
arxiv_dataset-86161706.06865 | EPIC 228735255b - An eccentric 6.57 day transiting hot Jupiter in Virgo
astro-ph.EP
We present the discovery of EPIC 228735255b, a P= 6.57 days Jupiter-mass
(M$_P$=1.019$\pm$0.070 M$_{Jup}$) planet transiting a V=12.5 (G5-spectral type)
star in an eccentric orbit (e=$0.120^{+0.056}_{-0.046}$) detected using a
combination of K2 photometry and ground-based observations. With a radius of
1.095$\pm$0.018R$_{Jup}$ the planet has a bulk density of
0.726$\pm$0.062$\rho_{Jup}$. The host star has a [Fe/H] of 0.12$\pm$0.045, and
from the K2 light curve we find a rotation period for the star of 16.3$\pm$0.1
days. This discovery is the 9th hot Jupiter from K2 and highlights K2's ability
to detect transiting giant planets at periods slightly longer than traditional,
ground-based surveys. This planet is slightly inflated, but much less than
others with similar incident fluxes. These are of interest for investigating
the inflation mechanism of hot Jupiters.
| arxiv topic:astro-ph.EP |
arxiv_dataset-86171706.06965 | 3D DNA origami crystals
cond-mat.soft
Engineering shape and interactions of nanoscopic building blocks allows for
the assembly of rationally designed macroscopic three-dimensional (3D)
materials with spatial accuracy inaccessible to top-down fabrication methods.
Owing to its sequence-specific interaction, DNA is often used as selective
binder to connect metallic nanoparticles into highly ordered lattices.
Moreover, 3D crystals assembled entirely from DNA have been proposed and
implemented with the declared goal to arrange guest molecules in predefined
lattices. This requires design schemes that provide high rigidity and
sufficiently large open guest space. We here present a DNA origami-based
tensegrity triangle structure that assembles into a 3D rhombohedral crystalline
lattice. We site-specifically place 10 nm and 20 nm gold particles within the
lattice, demonstrating that our crystals are spacious enough to host e.g.
ribosome-sized macromolecules. We validate the accurate assembly of the DNA
origami lattice itself as well as the precise incorporation of gold particles
by electron microscopy and small angle X-ray scattering (SAXS) experiments. Our
results show that it is possible to create DNA building blocks that assemble
into lattices with customized geometry. Site-specific hosting of nano objects
in the transparent DNA lattice sets the stage for metamaterial and structural
biology applications.
| arxiv topic:cond-mat.soft |
arxiv_dataset-86181706.07065 | A Stable Space-Time Finite Element Method for Parabolic Evolution
Problems
math.NA
This paper is concerned with the analysis of a new stable space-time finite
element method (FEM) for the numerical solution of parabolic evolution problems
in moving spatial computational domains. The discrete bilinear form is elliptic
on the FEM space with respect to a discrete energy norm. This property together
with a corresponding boundedness property, consistency and approximation
results for the FEM spaces yields an a priori discretization error estimate
with respect to the discrete norm. Finally, we confirm the theoretical results
with numerical experiments in spatial moving domains to confirm the theory
presented.
| arxiv topic:math.NA |
arxiv_dataset-86191706.07165 | Content-Centric Networking - Architectural Overview and Protocol
Description
cs.NI
This document describes the core concepts of the CCNx architecture and
presents a minimum network protocol based on two messages: Interests and
Content Objects. It specifies the set of mandatory and optional fields within
those messages and describes their behavior and interpretation. This
architecture and protocol specification is independent of a specific wire
encoding.
| arxiv topic:cs.NI |
arxiv_dataset-86201706.07265 | Phase and frequency linear response theory for hyperbolic chaotic
oscillators
nlin.CD math-ph math.MP
We formulate a linear phase and frequency response theory for hyperbolic
flows, which generalizes phase response theory for autonomous limit cycle
oscillators to hyperbolic chaotic dynamics. The theory is based on a shadowing
conjecture, stating the existence of a perturbed trajectory shadowing every
unperturbed trajectory on the system attractor for any small enough
perturbation of arbitrary duration and a corresponding unique time isomorphism,
which we identify as phase, such that phase shifts between the unperturbed
trajectory and its perturbed shadow are well defined. The phase sensitivity
function is the solution of an adjoint linear equation and can be used to
estimate the average change of phase velocity to small time dependent or
independent perturbations. These changes of frequency are experimentally
accessible giving a convenient way to define and measure phase response curves
for chaotic oscillators. The shadowing trajectory and the phase can be
constructed explicitly in the tangent space of an unperturbed trajectory using
co-variant Lyapunov vectors. It can also be used to identify the limits of the
regime of linear response.
| arxiv topic:nlin.CD math-ph math.MP |
arxiv_dataset-86211706.07365 | Pixels to Graphs by Associative Embedding
cs.CV cs.LG
Graphs are a useful abstraction of image content. Not only can graphs
represent details about individual objects in a scene but they can capture the
interactions between pairs of objects. We present a method for training a
convolutional neural network such that it takes in an input image and produces
a full graph definition. This is done end-to-end in a single stage with the use
of associative embeddings. The network learns to simultaneously identify all of
the elements that make up a graph and piece them together. We benchmark on the
Visual Genome dataset, and demonstrate state-of-the-art performance on the
challenging task of scene graph generation.
| arxiv topic:cs.CV cs.LG |
arxiv_dataset-86221706.07465 | Partial inertia induces additional phase transition in the explosive
majority vote model
cond-mat.stat-mech
Recently it has been aroused a great interest about explosive (i.e.,
discontinuous) transitions. They manifest in distinct systems, such as
synchronization in coupled oscillators, percolation regime, absorbing phase
transitions and more recently, in the majority-vote (MV) model with inertia. In
the latter, the model rules are slightly modified by the inclusion of a term
depending on the local spin (an inertial term). In such case, Chen et al. (Phys
Rev. E {5}, 042304 (2017)) have found that relevant inertia changes the nature
of the phase transition in complex networks, from continuous to discontinuous.
Here we give a further step by embedding inertia only in vertices with degree
larger than a threshold value $\langle k \rangle k^*$, $\langle k \rangle$
being the mean system degree and $k^*$ the fraction restriction. Our results,
from mean-field analysis and extensive numerical simulations, reveal that an
explosive transition is presented in both homogeneous and heterogeneous
structures for small and intermediate $k^*$'s. Otherwise, large restriction can
sustain a discontinuous transition only in the heterogeneous case. This shares
some similarity with recent results for the Kuramoto model (Phys Rev. E {91},
022818 (2015)). Surprisingly, intermediate restriction and large inertia are
responsible for the emergence of an extra phase, in which the system is
partially synchronized and the classification of phase transition depends on
the inertia and the lattice topology. In this case, the system exhibits two
phase transitions.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-86231706.07565 | Quantum Annealing Machine based on Floating Gate Array
quant-ph cond-mat.mes-hall
Quantum annealing machines based on superconducting qubits, which have the
potential to solve optimization problems faster than digital computers, are of
great interest not only to researchers but also to the general public. Here, we
propose a quantum annealing machine based on a semiconductor floating gate (FG)
array. We use the same device structure as that of the commercial FG NAND flash
memory except for small differences such as thinner tunneling barrier. We
theoretically derive an Ising Hamiltonian from the FG system in its
single-electron region. Recent high-density NAND flash memories are subject to
several problems that originate from their small FG cells. In order to store
information reliably, the number of electrons in each FG cell should be
sufficiently large. However, the number of electrons stored in each FG cell
becomes smaller and can be countable. So we utilize the countable electron
region to operate single-electron effects of FG cells. Second, in the
conventional NAND flash memory, the high density of FG cells induces the
problem of cell-to-cell interference through their mutual capacitive couplings.
This interference problem is usually solved by various methods using a software
of error-correcting codes. We derive the Ising interaction from this natural
capacitive coupling. Considering the size of the cell, 10 nm, the operation
temperature is expected to be approximately that of a liquid nitrogen. If a
commercial 64 Gbit NAND flash memory is used, ideally we expect it to be
possible to construct 2 megabytes (MB) entangled qubits by using the
conventional fabrication processes in the same factory as is used for
manufacture of NAND flash memory. A qubit system of highest density will be
obtained as a natural extension of the miniaturization of commonly used
memories in this society.
| arxiv topic:quant-ph cond-mat.mes-hall |
arxiv_dataset-86241706.07665 | Lorentz covariant and gauge invariant description of orbital and spin
angular momentum and the non-symmetric energy momentum tensor
physics.optics
Starting from covariant expressions, a gauge independent separation of
orbital and spin angular momentum for electrodynamics is presented. This
results from the non-symmetric canonical energy momentum tensor of the
electromagnetic field. The origin of the difficulty is discussed and a
covariant gauge invariant spin vector is derived. The paradox concerning the
spin angular momentum of a plane wave finds a natural solution.
| arxiv topic:physics.optics |
arxiv_dataset-86251706.07765 | Extending the Universal One-Loop Effective Action: Heavy-Light
Coefficients
hep-ph hep-th
The Universal One-Loop Effective Action (UOLEA) is a general expression for
the effective action obtained by evaluating in a model-independent way the
one-loop expansion of a functional path integral. It can be used to match UV
theories to their low-energy EFTs more efficiently by avoiding redundant steps
in the application of functional methods, simplifying the process of obtaining
Wilson coefficients of operators up to dimension six. In addition to loops
involving only heavy fields, matching may require the inclusion of loops
containing both heavy and light particles. Here we use the recently-developed
covariant diagram technique to extend the UOLEA to include heavy-light terms
which retain the same universal structure as the previously-derived heavy-only
terms. As an example of its application, we integrate out a heavy singlet
scalar with a linear coupling to a light doublet Higgs. The extension presented
here is a first step towards completing the UOLEA to incorporate all possible
structures encountered in a covariant derivative expansion of the one-loop path
integral.
| arxiv topic:hep-ph hep-th |
arxiv_dataset-86261706.07865 | Full Randomness in the Higher Difference Structure of Two-state Markov
Chains
math.PR
The paper studies the higher-order absolute differences taken from
progressive terms of time-homogenous binary Markov chains. Two theorems
presented are the limiting theorems for these differences, when their order $k$
converges to infinity. Theorems 1 and 2 assert that there exist some infinite
subsets $E$ of natural series such that $k$th order differences of every such
chain converge to the equi-distributed random binary process as $k$ growth to
infinity remaining on $E$. The chains are classified into two types and $E$
depend only on the type of a given chain. Two kinds of discrete capacities for
subsets of natural series are defined, and in their terms such sets $E$ are
described.
| arxiv topic:math.PR |
arxiv_dataset-86271706.07965 | A two-dimensional data-driven model for traffic flow on highways
physics.soc-ph math.NA
Based on experimental traffic data obtained from German and US highways, we
propose a novel two-dimensional first-order macroscopic traffic flow model. The
goal is to reproduce a detailed description of traffic dynamics for the real
road geometry. In our approach both the dynamic along the road and across the
lanes is continuous. The closure relations, being necessary to complete the
hydrodynamic equation, are obtained by regression on fundamental diagram data.
Comparison with prediction of one-dimensional models shows the improvement in
performance of the novel model.
| arxiv topic:physics.soc-ph math.NA |
arxiv_dataset-86281706.08065 | The problem with the SURF scheme
cs.CR
There is a serious problem with one of the assumptions made in the security
proof of the SURF scheme. This problem turns out to be easy in the regime of
parameters needed for the SURF scheme to work.
We give afterwards the old version of the paper for the reader's convenience.
| arxiv topic:cs.CR |
arxiv_dataset-86291706.08165 | There is but one PDS in $\mathbb{Z}^{3}$ inducing just square components
math.CO
It is known that in the unit distance graph of the lattice
$\mathbb{Z}^3\subset\mathbb{R}^3$ there exists a dominating set $S$ with
$4$-cycles as sole induced components and each vertex of $\mathbb{Z}^3\setminus
S$ having a unique neighbor in $S$. We show $S$ is unique.
| arxiv topic:math.CO |
arxiv_dataset-86301706.08265 | Celebrating 30 Years of Science from the James Clerk Maxwell Telescope
astro-ph.GA astro-ph.CO astro-ph.EP astro-ph.IM astro-ph.SR
The James Clerk Maxwell Telescope (JCMT) has been the world's most successful
single dish telescope at submillimetre wavelengths since it began operations in
1987. From the pioneering days of single-element photometers and mixers,
through the first modest imaging arrays, leading to the state-of-the-art
widefield camera SCUBA-2 and the spectrometer array HARP, the JCMT has been
associated with a number of major scientific discoveries. Famous for the
discovery of "SCUBA" galaxies, which are responsible for a large fraction of
the far-infrared background, to the first images of huge discs of cool debris
around nearby stars, possibly giving us clues to the evolution of planetary
systems, the JCMT has pushed the sensitivity limits more than any other
facility in this most difficult of wavebands in which to observe. Now
approaching the 30th anniversary of the first observations the telescope
continues to carry out unique and innovative science. In this review article we
look back on just some of the scientific highlights from the past 30 years.
| arxiv topic:astro-ph.GA astro-ph.CO astro-ph.EP astro-ph.IM astro-ph.SR |
arxiv_dataset-86311706.08365 | Optically and electrically controllable adatom spin-orbital dynamics in
transition metal dichalcogenides
cond-mat.mes-hall
We analyze the interplay of spin-valley coupling, orbital physics and
magnetic anisotropy taking place at single magnetic atoms adsorbed on
semiconducting transition-metal dichalcogenides, MX$_2$ (M = Mo, W; X = S, Se).
Orbital selection rules turn out to govern the kinetic exchange coupling
between the adatom and charge carriers in the MX$_2$ and lead to highly
orbitally dependent spin-flip scattering rates, as we illustrate for the
example of transition metal adatoms with $d^9$ configuration. Our ab initio
calculations suggest that $d^9$ configurations are realizable by single Co, Rh,
or Ir adatoms on MoS$_2$, which additionally exhibit a sizable magnetic
anisotropy. We find that the interaction of the adatom with carriers in the
MX$_2$ allows to tune its behavior from a quantum regime with full Kondo
screening to a regime of "Ising spintronics" where its spin-orbital moment acts
as classical bit, which can be erased and written electronically and optically.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-86321706.08465 | Paths in hypergraphs: a rescaling phenomenon
math.CO
Let $P^k_\ell$ denote the loose $k$-path of length $\ell$ and let define
$f^k_\ell(n,m)$ as the minimum value of $\Delta(H)$ over all $P^k_\ell$-free
$k$-graphs $H$ with $n$ vertices and $m$ edges. In the paper we study the
behavior of $f^4_2(n,m)$ and $f^3_3(n,m)$ and characterize the structure of
extremal hypergraphs. In particular, it is shown that when $m\sim n^2/8$ the
value of each of these functions drops down from $\Theta(n^2)$ to $\Theta(n)$.
| arxiv topic:math.CO |
arxiv_dataset-86331706.08565 | Satellite conjunction analysis and the false confidence theorem
math.ST stat.TH
Satellite conjunction analysis is the assessment of collision risk during a
close encounter between a satellite and another object in orbit. A
counterintuitive phenomenon has emerged in the conjunction analysis literature,
namely, probability dilution, in which lower quality data paradoxically appear
to reduce the risk of collision. We show that probability dilution is a symptom
of a fundamental deficiency in probabilistic representations of statistical
inference, in which there are propositions that will consistently be assigned a
high degree of belief, regardless of whether or not they are true. We call this
deficiency false confidence. In satellite conjunction analysis, it results in a
severe and persistent underestimate of collision risk exposure.
We introduce the Martin--Liu validity criterion as a benchmark by which to
identify statistical methods that are free from false confidence. Such
inferences will necessarily be non-probabilistic. In satellite conjunction
analysis, we show that uncertainty ellipsoids satisfy the validity criterion.
Performing collision avoidance maneuvers based on ellipsoid overlap will ensure
that collision risk is capped at the user-specified level. Further, this
investigation into satellite conjunction analysis provides a template for
recognizing and resolving false confidence issues as they occur in other
problems of statistical inference.
| arxiv topic:math.ST stat.TH |
arxiv_dataset-86341706.08665 | Hierarchical Model for Long-term Video Prediction
cs.CV
Video prediction has been an active topic of research in the past few years.
Many algorithms focus on pixel-level predictions, which generates results that
blur and disintegrate within a few frames. In this project, we use a
hierarchical approach for long-term video prediction. We aim at estimating
high-level structure in the input frame first, then predict how that structure
grows in the future. Finally, we use an image analogy network to recover a
realistic image from the predicted structure. Our method is largely adopted
from the work by Villegas et al. The method is built with a combination of
LSTMs and analogy-based convolutional auto-encoder networks. Additionally, in
order to generate more realistic frame predictions, we also adopt adversarial
loss. We evaluate our method on the Penn Action dataset, and demonstrate good
results on high-level long-term structure prediction.
| arxiv topic:cs.CV |
arxiv_dataset-86351706.08765 | Borel--de Siebenthal pairs, Global Weyl modules and Stanley--Reisner
rings
math.RT math.AC
We develop the theory of integrable representations for an arbitrary maximal
parabolic subalgebra of an affine Lie algebra. We see that such subalgebras can
be thought of as arising in a natural way from a Borel--de Siebenthal pair of
semisimple Lie algebras. We see that although there are similarities with the
represenation thery of the standard maximal parabolic subalgebra there are also
very interesting and non--trivial differences; including the fact that there
are examples of non--trivial global Weyl modules which are irreducible and
finite--dimensional. We also give a presentation of the endomorphism ring of
the global Weyl module; although these are no longer polynomial algebras we see
that for certain parabolics these algebras are Stanley--Reisner rings which are
both Koszul and Cohen--Macaualey.
| arxiv topic:math.RT math.AC |
arxiv_dataset-86361706.08865 | Quasi two-dimensional Fermi surface topography of the delafossite
PdRhO$_2$
cond-mat.mtrl-sci
We report on a combined study of the de Haas-van Alphen effect and angle
resolved photoemission spectroscopy on single crystals of the metallic
delafossite PdRhO$_2$ rounded off by \textit{ab initio} band structure
calculations. A high sensitivity torque magnetometry setup with SQUID readout
and synchrotron-based photoemission with a light spot size of
$~50\,\mu\mathrm{m}$ enabled high resolution data to be obtained from samples
as small as $150\times100\times20\,(\mu\mathrm{m})^3$. The Fermi surface shape
is nearly cylindrical with a rounded hexagonal cross section enclosing a
Luttinger volume of 1.00(1) electrons per formula unit.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-86371706.08965 | Black hole masses of tidal disruption event host galaxies
astro-ph.GA astro-ph.HE
The mass of the central black hole in a galaxy that hosted a tidal disruption
event (TDE) is an important parameter in understanding its energetics and
dynamics. We present the first homogeneously measured black hole masses of a
complete sample of 12 optically/UV selected TDE host galaxies (down to
$g_{host}$$\leq$22 mag and $z$=0.37) in the Northern sky. The mass estimates
are based on velocity dispersion measurements, performed on late time optical
spectroscopic observations. We find black hole masses in the range
3$\times$10$^5$ M$_{\odot}$$\leq$M$_{\rm BH}$$\leq$2$\times$10$^7$ M$_{\odot}$.
The TDE host galaxy sample is dominated by low mass black holes ($\sim$10$^6$
M$_{\odot}$), as expected from theoretical predictions. The blackbody peak
luminosity of TDEs with M$_{\rm BH}$$\leq$10$^{7.1}$ M$_{\odot}$ is consistent
with the Eddington limit of the SMBH, whereas the two TDEs with M$_{\rm
BH}$$\geq$10$^{7.1}$ M$_{\odot}$ have peak luminosities below their SMBH
Eddington luminosity, in line with the theoretical expectation that the
fallback rate for M$_{\rm BH}$$\geq$10$^{7.1}$ M$_{\odot}$ is sub-Eddington. In
addition, our observations suggest that TDEs around lower mass black holes
evolve faster. These findings corroborate the standard TDE picture in 10$^6$
M$_{\odot}$ black holes. Our results imply an increased tension between
observational and theoretical TDE rates. By comparing the blackbody emission
radius with theoretical predictions, we conclude that the optical/UV emission
is produced in a region consistent with the stream self-intersection radius of
shallow encounters, ruling out a compact accretion disk as the direct origin of
the blackbody radiation at peak brightness.
| arxiv topic:astro-ph.GA astro-ph.HE |
arxiv_dataset-86381706.09065 | The phenomenology of squeezing and its status in non-inflationary
theories
gr-qc
In this paper we skim the true phenomenological requirements behind the
concept of inflationary squeezing. We argue that all that is required is that
at horizon re-entry the fluctuations form standing waves with the correct
temporal phase (specifically, sine waves). We quantify this requirement and
relate it to the initial conditions fed into the radiation dominated epoch by
whatever phase of the Universe produced the fluctuations. The only relevant
quantity turns out to be the degree of suppression of the momentum, $p$, of the
fluctuations, $y$, which we measure by $\sigma\sim \omega^2 |y|^2/|p|^2$. Even
though $\sigma$ equals the squeezing parameter, $s$, in the case of inflation
and bimetric varying speed of light scenarios, this is not true in general,
specifically in some bouncing Universe models. It is also not necessary to
produce a large $\sigma$ at the end of the primordial phase: it is enough that
$\sigma$ be not too small. This is the case with scenarios based on modified
dispersion relations (MDR) emulating the dispersion relations of
Horava-Lifshitz theory, which produce $\sigma\sim 1$, enough to comply with the
observational requirements. Scenarios based on MDR leading to a slightly red
spectrum are also examined, and shown to satisfy the observational constraints.
| arxiv topic:gr-qc |
arxiv_dataset-86391706.09165 | Breaking Fitness Records without Moving: Reverse Engineering and
Spoofing Fitbit
cs.CR
Tens of millions of wearable fitness trackers are shipped yearly to consumers
who routinely collect information about their exercising patterns. Smartphones
push this health-related data to vendors' cloud platforms, enabling users to
analyze summary statistics on-line and adjust their habits. Third-parties
including health insurance providers now offer discounts and financial rewards
in exchange for such private information and evidence of healthy lifestyles.
Given the associated monetary value, the authenticity and correctness of the
activity data collected becomes imperative. In this paper, we provide an
in-depth security analysis of the operation of fitness trackers commercialized
by Fitbit, the wearables market leader. We reveal an intricate security through
obscurity approach implemented by the user activity synchronization protocol
running on the devices we analyze. Although non-trivial to interpret, we
reverse engineer the message semantics, demonstrate how falsified user activity
reports can be injected, and argue that based on our discoveries, such attacks
can be performed at scale to obtain financial gains. We further document a
hardware attack vector that enables circumvention of the end-to-end protocol
encryption present in the latest Fitbit firmware, leading to the spoofing of
valid encrypted fitness data. Finally, we give guidelines for avoiding similar
vulnerabilities in future system designs.
| arxiv topic:cs.CR |
arxiv_dataset-86401706.09265 | Weak index pairs and the Conley index for discrete multivalued dynamical
systems. Part II: properties of the index
math.DS
Motivation to revisit the Conley index theory for discrete multivalued
dynamical systems stems from the needs of broader real applications, in
particular in sampled dynamics or in combinatorial dynamics. The new
construction of the index in [B. Batko and M. Mrozek, {\em SIAM J. Applied
Dynamical Systems}, 15(2016), pp. 1143-1162] based on weak index pairs, under
the circumstances of the absence of index pairs caused by relaxing the
isolation property, seems to be a promising step towards this direction. The
present paper is a direct continuation of [B. Batko and M. Mrozek, {\em SIAM J.
Applied Dynamical Systems}, 15(2016), pp. 1143-1162] and concerns properties of
the index defined therin, namely Wa\.zewski property, the additivity property,
the homotopy (continuation) property and the commutativity property. We also
present the construction of weak index pairs in an isolating block.
| arxiv topic:math.DS |
arxiv_dataset-86411706.09365 | Bilateral multifactor CES general equilibrium with state-replicating
Armington elasticities
q-fin.EC
We measure elasticity of substitution between foreign and domestic
commodities by two-point calibration such that the Armington aggregator can
replicate the two temporally distant observations of market shares and prices.
Along with the sectoral multifactor CES elasticities which we estimate by
regression using a set of disaggregated linked input--output observations, we
integrate domestic production of two countries, namely, Japan and the Republic
of Korea, with bilateral trade models and construct a bilateral general
equilibrium model. Finally, we make an assessment of a tariff elimination
scheme between the two countries.
| arxiv topic:q-fin.EC |
arxiv_dataset-86421706.09465 | Critical scaling near the yielding transition in granular media
cond-mat.soft
We show that the yielding transition in granular media displays second-order
critical-point scaling behavior. We carry out discrete element simulations in
the low inertial number limit for frictionless, purely repulsive spherical
grains undergoing simple shear at fixed nondimensional shear stress $\Sigma$ in
two and three spatial dimensions. To find a mechanically stable (MS) packing
that can support the applied $\Sigma$, isotropically prepared states with size
$L$ must undergo a total strain $\gamma_{\rm ms}(\Sigma,L)$. The number density
of MS packings ($\propto \gamma_{\rm ms}^{-1}$) vanishes for $\Sigma > \Sigma_c
\approx 0.11$ according to a critical scaling form with a length scale $\xi
\propto |\Sigma - \Sigma_c|^{-\nu}$, where $\nu \approx 1.7-1.8$. Above the
yield stress ($\Sigma>\Sigma_c$), no MS packings that can support $\Sigma$
exist in the large system limit, $L/\xi \gg 1$. MS packings generated via shear
possess anisotropic force and contact networks, suggesting that $\Sigma_c$ is
associated with an upper limit in the degree to which these networks can be
deformed away from those for isotropic packings.
| arxiv topic:cond-mat.soft |
arxiv_dataset-86431706.09565 | Magnetically Induced Disk Winds and Transport in the HL Tau Disk
astro-ph.EP
The mechanism of angular momentum transport in protoplanetary disks is
fundamental to understand the distributions of gas and dust in the disks. The
unprecedented, high spatial resolution ALMA observations taken toward HL Tau
and subsequent radiative transfer modeling reveal that a high degree of dust
settling is currently achieved at the outer part of the HL Tau disk. Previous
observations however suggest a high disk accretion rate onto the central star.
This configuration is not necessarily intuitive in the framework of the
conventional viscous disk model, since efficient accretion generally requires a
high level of turbulence, which can suppress dust settling considerably. We
develop a simplified, semi-analytical disk model to examine under what
condition these two properties can be realized in a single model. Recent,
non-ideal MHD simulations are utilized to realistically model the angular
momentum transport both radially via MHD turbulence and vertically via
magnetically induced disk winds. We find that the HL Tau disk configuration can
be reproduced well when disk winds are properly taken into account. While the
resulting disk properties are likely consistent with other observational
results, such an ideal situation can be established only if the plasma $\beta$
at the disk midplane is $\beta_0 \simeq 2 \times 10^4$ under the assumption of
steady accretion. Equivalently, the vertical magnetic flux at 100 au is about
0.2 mG. More detailed modeling is needed to fully identify the origin of the
disk accretion and quantitatively examine plausible mechanisms behind the
observed gap structures in the HL Tau disk.
| arxiv topic:astro-ph.EP |
arxiv_dataset-86441706.09665 | Resonant Absorption of Axisymmetric Modes in Twisted Magnetic Flux Tubes
astro-ph.SR
It has been shown recently that magnetic twist and axisymmetric MHD modes are
ubiquitous in the solar atmosphere and therefore, the study of resonant
absorption for these modes have become a pressing issue as it can have
important consequences for heating magnetic flux tubes in the solar atmosphere
and the observed damping. In this investigation, for the first time, we
calculate the damping rate for axisymmetric MHD waves in weakly twisted
magnetic flux tubes. Our aim is to investigate the impact of resonant damping
of these modes for solar atmospheric conditions. This analytical study is based
on an idealized configuration of a straight magnetic flux tube with a weak
magnetic twist inside as well as outside the tube. By implementing the
conservation laws derived by \cite{Sakurai:1991aa} and the analytic solutions
for weakly twisted flux tubes obtained recently by \cite{Giagkiozis:2015apj},
we derive a dispersion relation for resonantly damped axisymmetric modes in the
spectrum of the Alfv\'{e}n continuum. We also obtain an insightful analytical
expression for the damping rate in the long wavelength limit. Furthermore, it
shown that both the longitudinal magnetic field and the density, which are
allowed to vary continuously in the inhomogeneous layer, have a significant
impact on the damping time. Given the conditions in the solar atmosphere,
resonantly damped axisymmetric modes are highly likely to be ubiquitous and
play an important role in energy dissipation.
We also suggest that given the character of these waves, it is likely that
they have already been observed in the guise of Alfv\'{e}n waves.
| arxiv topic:astro-ph.SR |
arxiv_dataset-86451706.09765 | Numerical Semigroups and Codes
math.NT cs.IT math.IT
A numerical semigroup is a subset of N containing 0, closed under addition
and with finite complement in N. An important example of numerical semigroup is
given by the Weierstrass semigroup at one point of a curve. In the theory of
algebraic geometry codes, Weierstrass semigroups are crucial for defining
bounds on the minimum distance as well as for defining improvements on the
dimension of codes. We present these applications and some theoretical problems
related to classification, characterization and counting of numerical
semigroups.
| arxiv topic:math.NT cs.IT math.IT |
arxiv_dataset-86461706.09865 | Generalising Random Forest Parameter Optimisation to Include Stability
and Cost
stat.ML cs.CY cs.LG
Random forests are among the most popular classification and regression
methods used in industrial applications. To be effective, the parameters of
random forests must be carefully tuned. This is usually done by choosing values
that minimize the prediction error on a held out dataset. We argue that error
reduction is only one of several metrics that must be considered when
optimizing random forest parameters for commercial applications. We propose a
novel metric that captures the stability of random forests predictions, which
we argue is key for scenarios that require successive predictions. We motivate
the need for multi-criteria optimization by showing that in practical
applications, simply choosing the parameters that lead to the lowest error can
introduce unnecessary costs and produce predictions that are not stable across
independent runs. To optimize this multi-criteria trade-off, we present a new
framework that efficiently finds a principled balance between these three
considerations using Bayesian optimisation. The pitfalls of optimising forest
parameters purely for error reduction are demonstrated using two publicly
available real world datasets. We show that our framework leads to parameter
settings that are markedly different from the values discovered by error
reduction metrics.
| arxiv topic:stat.ML cs.CY cs.LG |
arxiv_dataset-86471706.09965 | Shifted Poisson structures and moduli spaces of complexes
math.AG math.QA math.SG
In this paper we study the moduli stack of complexes of vector bundles (with
chain isomorphisms) over a smooth projective variety $X$ via derived algebraic
geometry. We prove that if $X$ is a Calabi-Yau variety of dimension $d$ then
this moduli stack has a $(1-d)$-shifted Poisson structure. In the case $d=1$,
we construct a natural foliation of the moduli stack by $0$-shifted symplectic
substacks. We show that our construction recovers various known Poisson
structures associated to complex elliptic curves, including the Poisson
structure on Hilbert scheme of points on elliptic quantum projective planes
studied by Nevins and Stafford, and the Poisson structures on the moduli spaces
of stable triples over an elliptic curves considered by one of us. We also
relate the latter Poisson structures to the semi-classical limits of the
elliptic Sklyanin algebras studied by Feigin and Odesskii.
| arxiv topic:math.AG math.QA math.SG |
arxiv_dataset-86481706.10065 | Theoretical investigation of an in situ k-restore process for damaged
ultra-low-k materials based on plasma enhanced fragmentation
cond-mat.mes-hall physics.comp-ph
We present theoretical investigations of a k-restore process for damaged
pourous ultra-low-k (ULK) materials. The process is based on plasma enhanced
fragmented silylation precursors to replace k-value damaging, polar Si-OH and
Si-H bonds by k-value lowering Si-CH$_{3}$ bonds. We employ density functional
theory (DFT) to determine the favored fragments of silylation precursors and
show the successful repair of damaged bonds on our model system. This model
system consists of a small set of ULK-fragments which represent various damaged
states of ULK materials. Our approach provides a fast scanning method for a
wide variety of possible repair reactions. Further, we show that oxygen
containing fragments are required to repair Si-H bonds and fragments with
dangling Si-bonds are most effective to repair polar Si-OH bonds.
| arxiv topic:cond-mat.mes-hall physics.comp-ph |
arxiv_dataset-86491706.10165 | Breaking ties in collective decision making
math.CO math.GR
Many classical social preference (multiwinner social choice) correspondences
are resolute only when two alternatives and an odd number of individuals are
considered. Thus, they generally admit several resolute refinements, each of
them naturally interpreted as a tie-breaking rule. In this paper we find out
conditions which make a social preference (multiwinner social choice)
correspondence admit a resolute refinement fulfilling suitable weak versions of
the anonymity and neutrality principles, as well as reversal symmetry (immunity
to the reversal bias).
| arxiv topic:math.CO math.GR |
arxiv_dataset-86501706.10265 | $q$-Poincar\'e supersymmetry in $AdS_5/CFT_4$
hep-th
We consider the exact S-matrix governing the planar spectral problem for
strings on $AdS_5\times S^5$ and $\mathcal N=4$ super Yang-Mills, and we show
that it is invariant under a novel "boost" symmetry, which acts as a
differentiation with respect to the particle momentum. This generator leads us
also to reinterpret the usual centrally extended $\mathfrak{psu}(2|2)$
symmetry, and to conclude that the S-matrix is invariant under a $q$-Poincar\'e
supersymmetry algebra, where the deformation parameter is related to the 't
Hooft coupling. We determine the two-particle action (coproduct) that turns out
to be non-local, and study the property of the new symmetry under crossing
transformations. We look at both the strong-coupling (large tension in the
string theory) and weak-coupling (spin-chain description of the gauge theory)
limits; in the former regime we calculate the cobracket utilising the universal
classical r-matrix of Beisert and Spill. In the eventuality that the boost has
higher partners, we also construct a quantum affine version of 2D Poincar\'e
symmetry, by contraction of the quantum affine algebra
$U_q(\widehat{\mathfrak{sl}_2})$ in Drinfeld's second realisation.
| arxiv topic:hep-th |
arxiv_dataset-86511707.00068 | Intrinsic translational symmetry breaking in a doped Mott insulator
cond-mat.str-el
A central issue of Mott physics, with symmetries being fully retained in the
spin background, concerns the charge excitation. In a two-leg spin ladder with
spin gap, an injected hole can exhibit either a Bloch wave or a density wave by
tuning the ladder anisotropy through a `quantum critical point' (QCP). The
nature of such a QCP has been a subject of recent studies by density matrix
renormalization group (DMRG). In this paper, we reexamine the ground state of
the one doped hole, and show that a two-component structure is present in the
density wave regime in contrast to the single component in the Bloch wave
regime. In the former, the density wave itself is still contributed by a
standing-wave-like component characterized by a quasiparticle spectral weight
$Z$ in a finite-size system. But there is an additional charge incoherent
component emerging, which intrinsically breaks the translational symmetry
associated with the density wave. The partial momentum is carried away by
neutral spin excitations. Such an incoherent part does not manifest in the
single-particle spectral function, directly probed by the angle-resolved
photoemission spectroscopy (ARPES) measurement, however it is demonstrated in
the momentum distribution function. The Landau's one-to-one correspondence
hypothesis for a Fermi liquid breaks down here. The microscopic origin of this
density wave state as an intrinsic manifestation of the doped Mott physics will
be also discussed.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-86521707.00168 | Study of the in-medium nucleon electromagnetic form factors using a
light-front nucleon wave function combined with the quark-meson coupling
model
hep-ph hep-ex nucl-ex nucl-th
We study the nucleon electromagnetic (EM) form factors in symmetric nuclear
matter as well as in vacuum within a light-front approach using the in-medium
inputs calculated by the quark-meson coupling model. The same in-medium quark
properties are used as those used for the study of in-medium pion properties.
The zero of the proton EM form factor ratio in vacuum, the electric to magnetic
form factor ratio $\mu_p G_{Ep}(Q^2)/G_{Mp}(Q^2)$ ($Q^2 = -q^2 > 0$ with $q$
being the four-momentum transfer), is determined including the latest
experimental data by implementing a hard constituent quark component in the
nucleon wave function. A reasonable fit is achieved for the ratio
$\mu_pG_{Ep}(Q^2)/G_{Mp}(Q^2)$ in vacuum, and we predict that the $Q_0^2$ value
to cross the zero of the ratio to be about 15 GeV$^2$. In addition the double
ratio data of the proton EM form factors in $^4$He and H nuclei, $[G^{^4{\rm
He}}_{Ep}(Q^2)/G^{^4{\rm He}}_{Mp}(Q^2)]/[G^{^1{\rm H}}_{Ep}(Q^2)/G^{^1{\rm
H}}_{Mp}(Q^2)]$, extracted by the polarized ($\vec{e}, e' \vec{p}$) scattering
experiment on $^4$He at JLab, are well described. We also predict that the
$Q_0^2$ value satisfying $\mu_pG_{Ep}(Q_0^2)/G_{Mp}(Q_0^2) = 0$ in symmetric
nuclear matter, shifts to a smaller value as increasing nuclear matter density,
which reflects the facts that the faster falloff of $G_{Ep}(Q^2)$ as increasing
$Q^2$ and the increase of the proton mean-square charge radius. Furthermore, we
calculate the neutron EM form factor double ratio in symmetric nuclear matter
for $0.1 < Q^2 < 1.0$ GeV$^2$. The result shows that the neutron double ratio
is enhanced relative to that in vacuum, while for the proton it is quenched,
and agrees with an existing theoretical prediction.
| arxiv topic:hep-ph hep-ex nucl-ex nucl-th |
arxiv_dataset-86531707.00268 | Predicting solar surface large-scale magnetic field of Cycle 24
astro-ph.SR
The Sun's surface field, especially the polar field, sets the boundary
condition for the coronal and heliospheric magnetic fields, but also provides
us insight into the dynamo process. The evolution of the polar fields results
from the emergence and subsequent evolution of magnetic flux through the solar
surface. In this paper we use a Monte Carlo approach to investigate the
evolution of the fields during the decay phase of cycle 24. Our simulations
include the emergence of flux through the solar surface with statistical
properties derived from previous cycles. The well-calibrated surface flux
transport model is used to follow the evolution of the large-scale field. We
find the polar field can be well reproduced one year in advance using the
observed synoptic magnetograms as the initial condition. The temporary
variation of the polar field measured by Wilcox Solar Observatory (WSO), e.g.,
the strong decrease of the south polar field during 2016-2017 which is not
shown by SDO/HMI and NSO/SOLIS data usually is not well reproduced. We suggest
observational effects, such as the effect of the large gradient of the magnetic
field around the southern polar cap and the low resolution of WSO might be
responsible. The northern hemisphere polar field is predicted to increase
during 2017. The southern polar field is predicted to be stable during
2017-2018. At the end of 2017, the magnetic field in two poles is predicted to
be similar (although of opposite polarities). The expected value for the dipole
moment around 2020 is 1.76$\pm$0.68 G and $2.11\pm0.69$ G based on the initial
conditions from SDO/HMI and NSO/SOLIS synoptic magnetograms, respectively. It
is comparable to that observed one at the end of Cycle 23 (about 1.6G based on
SOHO/MDI).
| arxiv topic:astro-ph.SR |
arxiv_dataset-86541707.00368 | Pushing the limits: detecting H2 emission from faint bipolar planetary
nebulae in the IPHAS sample
astro-ph.SR astro-ph.GA
We have obtained deep narrowband images in the near-infrared H2 (2.122
microns) emission line for a sample of 15 faint Isaac Newton Telescope
Photometric Halpha Survey (IPHAS) bipolar planetary nebulae (PNe) to search for
molecular material. H2 emission is found in most of them (14 out of 15), mostly
associated with rings at their equatorial regions and with their bipolar lobes.
These detections add to the high occurrence of H2 emission among bipolar PNe
reported in previous works, resulting from the large reservoir of molecular
material in these sources and the suitable excitation conditions for H2
emission. The correlation between detailed bipolar morphology and H2 luminosity
is also confirmed: bipolar PNe with broad equatorial rings (R-BPNe) have almost
no continuum emission, are H2 brighter and have larger H2/Brgamma line ratio
than bipolar PNe with pinched equatorial waists (W-BPNe). The origin of this
dichotomy is unclear. The larger size and age of R-BPNe are consistent with
shock excitation of H2, whereas ultraviolet pumping is most likely the
excitation mechanism in the smaller and younger W-BPNe, which would explain
their lower H2 luminosity. Although both types of bipolar PNe seem to proceed
from the same progenitor population, this does not imply that R-BPNe descend
from W-BPNe. Otherwise, we note that some of the H2-weak bipolar PNe harbor
post-common envelope binary systems and symbiotic stars. Finally, we suggest
that the long-living H2 emission from R-BPNe arises from a discrete
distribution of compact knots embedded within the ionized gas at the equatorial
region.
| arxiv topic:astro-ph.SR astro-ph.GA |
arxiv_dataset-86551707.00468 | Spatial filtering of audible sound with acoustic landscapes
physics.app-ph
Acoustic metasurfaces manipulate waves with specially designed structures and
achieve properties that natural materials cannot offer. Similar surfaces work
in audio frequency range as well and lead to marvelous acoustic phenomena that
can be perceived by human ears. Being intrigued by the famous Maoshan Bugle
phenomenon, we investigate large scale metasurfaces consisting of periodic
steps of sizes comparable to the wavelength of audio frequency in both time and
space domains. We propose a theoretical method to calculate the scattered sound
field and find that periodic corrugated surfaces work as spatial filters and
the frequency selective character can only be observed at the same side as the
incident wave. Maoshan Bugle phenomenon can be well explained with the method.
Finally, we demonstrate that the proposed method can be used to design
acoustical landscapes, which transform impulsive sound into famous trumpet
solos or other melodious sound.
| arxiv topic:physics.app-ph |
arxiv_dataset-86561707.00568 | On the interdependence of galaxy morphology, star formation, and
environment in massive galaxies in the nearby Universe
astro-ph.GA
Using multi-wavelength data, from UV-optical-near-mid IR, for $\sim$6000
galaxies in the local Universe, we study the dependence of star formation on
the morphological T-types for massive galaxies ($\log M_*/M_\odot \geq 10$). We
find that, early-type spirals (Sa-Sbc) and S0s predominate in the green valley,
which is a transition zone between the star forming and quenched regions.
Within the early-type spirals, as we move from Sa to Sbc spirals the fraction
of green valley and quenched galaxies decreases, indicating the important role
of the bulge in the quenching of galaxies. The fraction of early-type spirals
decreases as we enter the green valley from the blue cloud, which coincides
with the increase in the fraction of S0s. This points towards the morphological
transformation of early-type spiral galaxies into S0s which can happen due to
environmental effects such as ram-pressure stripping, galaxy harassment, or
tidal interactions. We also find a second population of S0s which are actively
star-forming and are present in all environments. Since morphological T-type,
specific star formation rate (sSFR), and environmental density are all
correlated with each other, we compute the partial correlation coefficient for
each pair of parameters while keeping the third parameter as a control
variable. We find that morphology most strongly correlates with sSFR,
independent of the environment, while the other two correlations
(morphology-density and sSFR-environment) are weaker. Thus, we conclude that,
for massive galaxies in the local Universe, the physical processes that shape
their morphology are also the ones that determine their star-forming state.
| arxiv topic:astro-ph.GA |
arxiv_dataset-86571707.00668 | Electron-positron annihilation into hadrons at the higher-loop levels
hep-ph hep-ex
The strong corrections to the R-ratio of electron-positron annihilation into
hadrons are studied at the higher-loop levels. Specifically, the essentials of
continuation of the spacelike perturbative results into the timelike domain are
elucidated. The derivation of a general form of the commonly employed
approximate expression for the R-ratio (which constitutes its truncated
re-expansion at high energies) is delineated, the appearance of the pertinent
$\pi^2$-terms is expounded, and their basic features are examined. It is
demonstrated that the validity range of such approximation is strictly limited
to $\sqrt{s}/\Lambda > \exp(\pi/2) \simeq 4.81$ and that it converges rather
slowly when the energy scale approaches this value. The spectral function
required for the proper calculation of the R-ratio is explicitly derived and
its properties at the higher-loop levels are studied. The developed method of
calculation of the spectral function enables one to obtain the explicit
expression for the latter at an arbitrary loop level. By making use of the
derived spectral function the proper expression for the R-ratio is calculated
up to the five-loop level and its properties are examined. It is shown that the
loop convergence of the proper expression for the R-ratio is better than that
of its commonly employed approximation. The impact of the omitted higher-order
$\pi^2$-terms on the latter is also discussed.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-86581707.00768 | Learning to Avoid Errors in GANs by Manipulating Input Spaces
stat.ML cs.LG
Despite recent advances, large scale visual artifacts are still a common
occurrence in images generated by GANs. Previous work has focused on improving
the generator's capability to accurately imitate the data distribution
$p_{data}$. In this paper, we instead explore methods that enable GANs to
actively avoid errors by manipulating the input space. The core idea is to
apply small changes to each noise vector in order to shift them away from areas
in the input space that tend to result in errors. We derive three different
architectures from that idea. The main one of these consists of a simple
residual module that leads to significantly less visual artifacts, while only
slightly decreasing diversity. The module is trivial to add to existing GANs
and costs almost zero computation and memory.
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-86591707.00868 | On fibrations between internal groupoids
math.CT
In order to deduce the internal version of the Brown exact sequence from the
internal version of the Gabriel-Zisman exact sequence, we characterize
fibrations and $\ast$-fibrations in the 2-category of internal groupoids in
terms of the comparison functor from certain pullbacks to the corresponding
strong homotopy pullbacks. A similar analysis in the category of arrows allows
us to give a characterization of protomodular categories using strong homotopy
kernels.
| arxiv topic:math.CT |
arxiv_dataset-86601707.00968 | Bernoulli Processes in Riesz spaces
math.FA
The action and averaging properties of conditional expectation operators are
studied in the, measure-free, Riesz space, setting of Kuo, Labuschagne and
Watson [{Conditional expectations on Riesz spaces}, J. Math. Anal. Appl., 303
(2005), 509-521] but on the abstract $L^2$ space, ${\cal L}^2(T)$ introduced by
Labuschagne and Watson [{ Discrete Stochastic Integration in Riesz Spaces},
Positivity, 14, (2010), 859 - 575]. In this setting it is shown that
conditional expectation operators leave ${\cal L}^2(T)$ invariant and the
Bienaym\'e equality and Tchebichev inequality are proved.
From this foundation Bernoulli processes are considered. Bernoulli's strong
law of large numbers and Poisson's theorem are formulated and proved.
| arxiv topic:math.FA |
arxiv_dataset-86611707.01068 | Maintaining cooperation in complex social dilemmas using deep
reinforcement learning
cs.AI cs.GT cs.MA
Social dilemmas are situations where individuals face a temptation to
increase their payoffs at a cost to total welfare. Building artificially
intelligent agents that achieve good outcomes in these situations is important
because many real world interactions include a tension between selfish
interests and the welfare of others. We show how to modify modern reinforcement
learning methods to construct agents that act in ways that are simple to
understand, nice (begin by cooperating), provokable (try to avoid being
exploited), and forgiving (try to return to mutual cooperation). We show both
theoretically and experimentally that such agents can maintain cooperation in
Markov social dilemmas. Our construction does not require training methods
beyond a modification of self-play, thus if an environment is such that good
strategies can be constructed in the zero-sum case (eg. Atari) then we can
construct agents that solve social dilemmas in this environment.
| arxiv topic:cs.AI cs.GT cs.MA |
arxiv_dataset-86621707.01168 | Nonlocal bunching of composite bosons
quant-ph
It was suggested that two entangled fermions can behave like a single boson
and that the bosonic quality is proportional to the degree of entanglement
between the two particles. The relation between bosonic quality and
entanglement is quite natural if one takes into account the fact that
entanglement appears in bound states of interacting systems. However,
entanglement can still be present in spatially separated subsystems that do not
interact anymore. These systems are often a subject of studies on quantum
nonlocality and foundations of quantum physics. Here, we ask whether an
entangled spatially separated fermionic pair can exhibit bosonic properties. We
show that in certain conditions the answer to this question can be positive. In
particular, we propose a nonlocal bunching scenario in which two such pairs
form an analogue of a two-partite bosonic Fock state.
| arxiv topic:quant-ph |
arxiv_dataset-86631707.01268 | Abundance analyses of the new R Coronae Borealis stars: ASAS-RCB-8 and
ASAS-RCB-10
astro-ph.SR
Abundance analyses of the two newly discovered R Coronae Borealis (RCB) stars
ASAS-RCB-8 and ASAS-RCB-10 were conducted using high-resolution optical spectra
and model atmospheres. Their chemical compositions place the pair among the
majority class of RCBs. ASAS-RCB-10 is one of the most N-poor majority RCBs
with an above average O abundance. Relative to ASAS-RCB-10, ASAS-RCB-8 is H
poor by 1.6 dex, O-poor by 0.7 dex but N-rich by 0.8 dex suggesting a higher
contamination by CNO-cycled material.
| arxiv topic:astro-ph.SR |
arxiv_dataset-86641707.01368 | How to place an obstacle having a dihedral symmetry centered at a given
point inside a disk so as to optimize the fundamental Dirichlet eigenvalue
math.AP
A generic model for the shape optimization problems we consider in this paper
is the optimization of the Dirichlet eigenvalues of the Laplace operator with a
volume constraint. We deal with an obstacle placement problem which can be
formulated as the following eigenvalue optimization problem: Fix two positive
real numbers $r_1$ and $A$. We consider a disk $B\subset \mathbb{R}^2$ having
radius $r_1$. We want to place an obstacle $P$ of area $A$ within $B$ so as to
maximize or minimize the fundamental Dirichlet eigenvalue $\lambda_1$ for the
Laplacian on $B\setminus P$. That is, we want to study the behavior of the
function $\rho \mapsto \lambda_1(B\setminus\rho(P))$, where $\rho$ runs over
the set of all rigid motions of the plane fixing the center of mass for $P$
such that $\rho(P)\subset B$. In this paper, we consider a non-concentric
obstacle placement problem. The extremal configurations correspond to the cases
where an axis of symmetry of $P$ coincide with an axis of symmetry of $B$. We
also characterize the maximizing and the minimizing configurations in our main
result, viz., Theorem 4.1. Equation (6), Propositions 5.1 and 5.2 imply Theorem
4.1. We give many different generalizations of our result. At the end, we
provide some numerical evidence to validate our main theorem for the case where
the obstacle $P$ has $\mathbb{D}_4$ symmetry. For the $n$ odd case, we identify
some of the extremal configuration for $\lambda_1$. We prove that equation (6)
and Proposition 5.1 hold true for $n$ odd too. We highlight some of the
difficulties faced in proving Proposition 5.2 for this case. We provide
numerical evidence for $n=5$ and conjecture that Theorem 4.1 holds true for $n$
odd too.
| arxiv topic:math.AP |
arxiv_dataset-86651707.01468 | One-Dimensional Nature of Pairing and Superconductivity at the
LaAlO$_3$/SrTiO$_3$ Interface
cond-mat.supr-con cond-mat.mes-hall
We examine superconductivity in LaAlO$_3$/SrTiO$_3$ channels in which the
channel width transitions from the 1D to 2D regime. The superconducting
critical current is independent of the channel width and increases
approximately linearly with the number of parallel channels. Signatures of
electron pairing outside of the superconducting phase are also independent of
channel width. Collectively, these results indicate that electron pairing and
superconductivity exist at the boundary of these channels and are absent within
the interior region of the channels. The intrinsic 1D nature of
superconductivity at the LaAlO$_3$/SrTiO$_3$ interface imposes strong physical
constraints on possible electron pairing mechanisms.
| arxiv topic:cond-mat.supr-con cond-mat.mes-hall |
arxiv_dataset-86661707.01568 | Sheaves of nonlinear generalized function spaces
math.FA
We provide a framework for the construction of diffeomorphism invariant
sheaves of nonlinear generalized functions spaces. As an application, global
algebras of generalized functions for distributions on manifolds and
diffeomorphism invariant algebras of generalized functions for
ultradistributions are constructed.
| arxiv topic:math.FA |
arxiv_dataset-86671707.01668 | Tame majorant analyticity for the Birkhoff map of the defocusing
Nonlinear Schr\"odinger equation on the circle
math.AP
For the defocusing Nonlinear Schr\"odinger equation on the circle, we
construct a Birkhoff map $\Phi$ which is tame majorant analytic in a
neighborhood of the origin. Roughly speaking, majorant analytic means that
replacing the coefficients of the Taylor expansion of $\Phi$ by their absolute
values gives rise to a series (the majorant map) which is uniformly and
absolutely convergent, at least in a small neighborhood. Tame majorant analytic
means that the majorant map of $\Phi$ fulfills tame estimates. The proof is
based on a new tame version of the Kuksin-Perelman theorem, which is an
infinite dimensional Vey type theorem.
| arxiv topic:math.AP |
arxiv_dataset-86681707.01768 | Entropic Entanglement: Information Prison Break
gr-qc hep-th
We argue certain nonviolent local quantum field theory (LQFT) modification
considered at the global horizon ($r=2M$) of a static spherically-symmetric
black hole can lead to adiabatic leakage of quantum information in the form of
Hawking particles. The source of the modification is (i) smooth at $r=2M$ and
(ii) rapidly vanishing at $r\gg2M$. Furthermore, we restore the unitary
evolution by introducing extra quanta which departs slightly from the generic
Hawking emission without changing the experience of an infalling observer (no
drama). Also, we suggest that a possible interpretation of the
Bekenstein-Hawking bound as entanglement entropy may yield a nonsingular
dynamical horizon behavior described by black hole thermodynamics. Hence by
treating gravity as a field theory, and considering its coupling to the matter
fields in the Minkowski vacuum, we derive the conjectured fluctuations of the
background geometry of a black hole.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-86691707.01868 | Segal-type models of higher categories
math.CT math.AT
Higher category theory is an exceedingly active area of research, whose rapid
growth has been driven by its penetration into a diverse range of scientific
fields. Its influence extends through key mathematical disciplines, notably
homotopy theory, algebraic geometry and algebra, mathematical physics, to
encompass important applications in logic, computer science and beyond. Higher
categories provide a unifying language whose greatest strength lies in its
ability to bridge between diverse areas and uncover novel applications.
In this foundational work we introduce a new approach to higher categories.
It builds upon the theory of iterated internal categories, one of the simplest
possible higher categorical structures available, by adopting a novel and
remarkably simple "weak globularity" postulate and demonstrating that the
resulting model provides a fully general theory of weak n-categories. The
latter are among the most complex of the higher structures, and are crucial for
applications. We show that this new model of "weakly globular n-fold
categories" is suitably equivalent to the well studied model of weak
n-categories due to Tamsamani and Simpson.
| arxiv topic:math.CT math.AT |
arxiv_dataset-86701707.01968 | An IMEX Finite Element Method for a linearized Cahn-Hilliard-Cook
equation driven by the space derivative of a space-time white noise
math.NA
We consider a model initial- and Dirichlet boundary- value problem for a
linearized Cahn-Hilliard-Cook equation, in one space dimension, forced by the
space derivative of a space-time white noise. First, we introduce a canvas
problem the solution to which is a regular approximation of the mild solution
to the problem and depends on a finite number of random variables. Then,
fully-discrete approximations of the solution to the canvas problem are
constructed using, for discretization in space, a Galerkin finite element
method based on $H^2$ piecewise polynomials, and, for time-stepping, an
implicit/explicit method. Finally, we derive a strong a priori estimate of the
error approximating the mild solution to the problem by the canvas problem
solution, and of the numerical approximation error of the solution to the
canvas problem.
| arxiv topic:math.NA |
arxiv_dataset-86711707.02068 | A new derivation of the relationship between diffusion coefficient and
entropy in classical Brownian motion by the ensemble method
cond-mat.stat-mech
The diffusion coefficient--a measure of dissipation, and the entropy--a
measure of fluctuation are found to be intimately correlated in many physical
systems. Unlike the fluctuation dissipation theorem in linear response theory,
the correlation is often strongly non-linear. To understand this complex
dependence, we consider the classical Brownian diffusion in this work. Under
certain rational assumption, i.e. in the bi-component fluid mixture, the mass
of the Brownian particle $M$ is far greater than that of the bath molecule $m$,
we can adopt the weakly couple limit. Only considering the first-order
approximation of the mass ratio $m/M$, we obtain a linear motion equation in
the reference frame of the observer as a Brownian particle. Based on this
equivalent equation, we get the Hamiltonian at equilibrium. Finally, using
canonical ensemble method, we define a new entropy that is similar to the
Kolmogorov-Sinai entropy. Further, we present an analytic expression of the
relationship between the diffusion coefficient $D$ and the entropy $S$ in the
thermal equilibrium, that is to say, $D =\frac{\hbar}{eM} \exp{[S/(k_Bd)]}$,
where $d$ is the dimension of the space, $k_B$ the Boltzmann constant, $\hbar $
the reduced Planck constant and $e$ the Euler number. This kind of scaling
relation has been well-known and well-tested since the similar one for single
component is firstly derived by Rosenfeld with the expansion of volume ratio.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-86721707.02168 | Dynamic dipole polarizabilities of heteronuclear alkali dimers: optical
response, trapping and control of ultracold molecules
quant-ph cond-mat.quant-gas physics.chem-ph
In this article we address the general approach for calculating dynamical
dipole polarizabilities of small quantum systems, based on a sum-over-states
formula involving in principle the entire energy spectrum of the system. We
complement this method by a few-parameter model involving a limited number of
effective transitions, allowing for a compact and accurate representation of
both the isotropic and anisotropic components of the polarizability. We apply
the method to the series of ten heteronuclear molecules composed of two of
($^7$Li,$^{23}$Na,$^{39}$K,$^{87}$Rb,$^{133}$Cs) alkali-metal atoms. We rely on
both up-to-date spectroscopically-determined potential energy curves for the
lowest electronic states, and on our systematic studies of these systems
performed during the last decade for higher excited states and for permanent
and transition dipole moments. Such a compilation is timely for the
continuously growing researches on ultracold polar molecules. Indeed the
knowledge of the dynamic dipole polarizabilities is crucial to model the
optical response of molecules when trapped in optical lattices, and to
determine optimal lattice frequencies ensuring optimal transfer to the absolute
ground state of initially weakly-bound molecules. When they exist, we determine
the so-called "magic frequencies" where the ac-Stark shift and thus the viewed
trap depth, is the same for both weakly-bound and ground-state molecules.
| arxiv topic:quant-ph cond-mat.quant-gas physics.chem-ph |
arxiv_dataset-86731707.02268 | Text Summarization Techniques: A Brief Survey
cs.CL
In recent years, there has been a explosion in the amount of text data from a
variety of sources. This volume of text is an invaluable source of information
and knowledge which needs to be effectively summarized to be useful. In this
review, the main approaches to automatic text summarization are described. We
review the different processes for summarization and describe the effectiveness
and shortcomings of the different methods.
| arxiv topic:cs.CL |
arxiv_dataset-86741707.02368 | Computation of orders and cycle lengths of automorphisms of finite
solvable groups
math.GR
Let $G$ be a finite solvable group, given through a refined consistent
polycyclic presentation, and $\alpha$ an automorphism of $G$, given through its
images of the generators of $G$. In this paper, we discuss algorithms for
computing the order of $\alpha$ as well as the cycle length of a given element
of $G$ under $\alpha$. We give correctness proofs and discuss the theoretical
complexity of these algorithms. Along the way, we carry out detailed complexity
analyses of several classical algorithms on finite polycyclic groups.
| arxiv topic:math.GR |
arxiv_dataset-86751707.02468 | Magnetic ground state and magnon-phonon interaction in multiferroic
h-YMnO$_3$
cond-mat.str-el
Inelastic neutron scattering has been used to study the magneto-elastic
excitations in the multiferroic manganite hexagonal YMnO$_3$. An avoided
crossing is found between magnon and phonon modes close to the Brillouin zone
boundary in the $(a,b)$-plane. Neutron polarization analysis reveals that this
mode has mixed magnon-phonon character. An external magnetic field along the
$c$-axis is observed to cause a linear field-induced splitting of one of the
spin wave branches. A theoretical description is performed, using a Heisenberg
model of localized spins, acoustic phonon modes and a magneto-elastic coupling
via the single-ion magnetostriction. The model quantitatively reproduces the
dispersion and intensities of all modes in the full Brillouin zone, describes
the observed magnon-phonon hybridized modes, and quantifies the magneto-elastic
coupling. The combined information, including the field-induced magnon
splitting, allows us to exclude several of the earlier proposed models and
point to the correct magnetic ground state symmetry, and provides an effective
dynamic model relevant for the multiferroic hexagonal manganites.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-86761707.02568 | Solving high-dimensional partial differential equations using deep
learning
math.NA cs.LG math.OC math.PR
Developing algorithms for solving high-dimensional partial differential
equations (PDEs) has been an exceedingly difficult task for a long time, due to
the notoriously difficult problem known as the "curse of dimensionality". This
paper introduces a deep learning-based approach that can handle general
high-dimensional parabolic PDEs. To this end, the PDEs are reformulated using
backward stochastic differential equations and the gradient of the unknown
solution is approximated by neural networks, very much in the spirit of deep
reinforcement learning with the gradient acting as the policy function.
Numerical results on examples including the nonlinear Black-Scholes equation,
the Hamilton-Jacobi-Bellman equation, and the Allen-Cahn equation suggest that
the proposed algorithm is quite effective in high dimensions, in terms of both
accuracy and cost. This opens up new possibilities in economics, finance,
operational research, and physics, by considering all participating agents,
assets, resources, or particles together at the same time, instead of making ad
hoc assumptions on their inter-relationships.
| arxiv topic:math.NA cs.LG math.OC math.PR |
arxiv_dataset-86771707.02668 | Exponential decay for the near-critical scaling limit of the planar
Ising model
math.PR math-ph math.MP
We consider the Ising model at its critical temperature with external
magnetic field $ha^{15/8}$ on the square lattice with lattice spacing $a$. We
show that the truncated two-point function in this model decays exponentially
with a rate independent of $a$. As a consequence, we show exponential decay in
the near-critical scaling limit Euclidean magnetization field. For the lattice
model with $a=1$, the mass (inverse correlation length) is of order $h^{8/15}$
as $h\downarrow 0$; for the Euclidean field, it equals exactly $Ch^{8/15}$ for
some $C$. Although there has been much progress in the study of critical
scaling limits, results on near-critical models are far fewer due to the lack
of conformal invariance away from the critical point. Our arguments combine
lattice and continuum FK representations, including coupled conformal loop and
measure ensembles, showing that such ensembles can be useful even in the study
of near-critical scaling limits. Thus we provide the first substantial
application of measure ensembles.
| arxiv topic:math.PR math-ph math.MP |
arxiv_dataset-86781707.02768 | On Concircular Transformations In Finsler Geometry
math.DG
A geodesic circle in Finsler geometry is a natural extension of that in a
Euclidean space. In this paper, we apply Lie derivatives and the Cartan
$Y$-connection to study geodesic circles and (infinitesimal) concircular
transformations on a Finsler manifold. We characterize a concircular vector
field with some PDEs on the tangent bundle, and then we obtain respective
necessary and sufficient conditions for a concircular vector field to be
conformal and a conformal vector field to be concircular. We also show
conditions for two conformally related Finsler metrics to be concircular, and
obtain some invariant curvature properties under conformal and concircular
transformations.
| arxiv topic:math.DG |
arxiv_dataset-86791707.02868 | A Low-Complexity Soft-Output wMD Decoding for Uplink MIMO Systems with
One-Bit ADCs
cs.IT math.IT
This paper considers an uplink multiuser multiple-input-multiple-output
(MU-MIMO) system with one-bit analog-to-digital converters (ADCs), in which $K$
users with a single transmit antenna communicate with one base station (BS)
with $N_{\rm r}$ receive antennas. In this system, a novel MU-MIMO detection
method, named weighted minimum distance (wMD) decoding, was recently proposed
by introducing an equivalent coding problem. Despite of its attractive
performance, the wMD decoding has the two limitations to be used in practice:
i) the hard-decision outputs can degrade the performance of a channel code; ii)
the computational complexity grows exponentially with the $K$. To address those
problems, we first present a soft-output wMD decoding that efficiently computes
soft metrics (i.e., log-likelihood ratios) from one-bit quantized observations.
We then construct a low-complexity (soft-output) wMD decoding by introducing
{\em hierarchical code partitioning}. This method can be regarded as a sphere
decoding in Hamming space, in that a search-spare is considerably reduced.
Finally, we demonstrate that the proposed method significantly performs the
state-of-the-art methods with a comparable complexity.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-86801707.02968 | Revisiting Unreasonable Effectiveness of Data in Deep Learning Era
cs.CV cs.AI
The success of deep learning in vision can be attributed to: (a) models with
high capacity; (b) increased computational power; and (c) availability of
large-scale labeled data. Since 2012, there have been significant advances in
representation capabilities of the models and computational capabilities of
GPUs. But the size of the biggest dataset has surprisingly remained constant.
What will happen if we increase the dataset size by 10x or 100x? This paper
takes a step towards clearing the clouds of mystery surrounding the
relationship between `enormous data' and visual deep learning. By exploiting
the JFT-300M dataset which has more than 375M noisy labels for 300M images, we
investigate how the performance of current vision tasks would change if this
data was used for representation learning. Our paper delivers some surprising
(and some expected) findings. First, we find that the performance on vision
tasks increases logarithmically based on volume of training data size. Second,
we show that representation learning (or pre-training) still holds a lot of
promise. One can improve performance on many vision tasks by just training a
better base model. Finally, as expected, we present new state-of-the-art
results for different vision tasks including image classification, object
detection, semantic segmentation and human pose estimation. Our sincere hope is
that this inspires vision community to not undervalue the data and develop
collective efforts in building larger datasets.
| arxiv topic:cs.CV cs.AI |
arxiv_dataset-86811707.03068 | Equidistribution for standard pairs in planar dispersing billiard flows
math.DS
We prove exponential correlation decay in dispersing billiard flows on the
2-torus assuming finite horizon and lack of corner points. With applications
aimed at describing heat conduction, the highly singular initial measures are
concentrated here on 1-dimensional submanifolds (given by standard pairs) and
the observables are supposed to satisfy a generalized H\"older continuity
property. The result is based on the exponential correlation decay bound of
Baladi, Demers and Liverani obtained recentlyfor H\"older continuous
observables in these billiards. The model dependence of the bounds is also
discussed.
| arxiv topic:math.DS |
arxiv_dataset-86821707.03168 | Denseness of volatile and nonvolatile sequences of functions
math.PR
In a recent paper by Jonasson and Steif, definitions to describe the
volatility of sequences of Boolean functions, \( f_n \colon \{ -1,1 \}^n \to \{
-1,1 \} \) were introduced. We continue their study of how these definitions
relate to noise stability and noise sensitivity. Our main results are that the
set of volatile sequences of Boolean functions is a natural way "dense" in the
set of all sequences of Boolean functions, and that the set of non-volatile
Boolean sequences is not "dense" in the set of noise stable sequences of
Boolean functions.
| arxiv topic:math.PR |
arxiv_dataset-86831707.03268 | Tensor-based approach to accelerate deformable part models
cs.CV
This article provides next step towards solving speed bottleneck of any
system that intensively uses convolutions operations (e.g. CNN). Method
described in the article is applied on deformable part models (DPM) algorithm.
Method described here is based on multidimensional tensors and provides
efficient tradeoff between DPM performance and accuracy. Experiments on various
databases, including Pascal VOC, show that the proposed method allows
decreasing a number of convolutions up to 4.5 times compared with DPM v.5,
while maintaining similar accuracy. If insignificant accuracy degradation is
allowable, higher computational gain can be achieved. The method consists of
filters tensor decomposition and convolutions shortening using the decomposed
filter. Mathematical overview of the proposed method as well as simulation
results are provided.
| arxiv topic:cs.CV |
arxiv_dataset-86841707.03368 | Spectral analysis of gravitational waves from binary neutron star merger
remnants
gr-qc
In this work we analyze the gravitational wave signal from hypermassive
neutron stars formed after the merger of binary neutron star systems, focusing
on its spectral features. The gravitational wave signals are extracted from
numerical relativity simulations of models already considered by De Pietri et
al. [Phys. Rev. D 93, 064047 (2016)], Maione et al. [Classical Quantum Gravity
33, 175009 (2016)], and Feo et al. [Classical Quantum Gravity 34, 034001
(2017)], and allow us to study the effect of the total baryonic mass of such
systems (from $2.4 M_{\odot}$ to $3 M_{\odot}$), the mass ratio (up to $q =
0.77$), and the neutron star equation of state, both in equal and highly
unequal mass binaries. We use the peaks we find in the gravitational spectrum
as an independent test of already published hypotheses of their physical origin
and empirical relations linking them with the characteristics of the merging
neutron stars. In particular, we highlight the effects of the mass ratio, which
in the past was often neglected. We also analyze the temporal evolution of the
emission frequencies. Finally, we introduce a modern variant of Prony's method
to analyze the gravitational wave postmerger emission as a sum of complex
exponentials, trying to overcome some drawbacks of both Fourier spectra and
least-squares fitting. Overall, the spectral properties of the postmerger
signal observed in our simulation are in agreement with those proposed by other
groups. More specifically, we find that the analysis of Bauswein and
Stergioulas [Phys. Rev. D 91, 124056 (2015)] is particularly effective for
binaries with very low masses or with a small mass ratio and that the
mechanical toy model of Takami et al. [Phys. Rev. D 91, 064001 (2015)] provides
a comprehensive and accurate description of the early stages of the postmerger.
| arxiv topic:gr-qc |
arxiv_dataset-86851707.03468 | Recovering Dense Tissue Multispectral Signal from in vivo RGB Images
cs.CV
Hyperspectral/multispectral imaging (HSI/MSI) contains rich information
clinical applications, such as 1) narrow band imaging for vascular
visualisation; 2) oxygen saturation for intraoperative perfusion monitoring and
clinical decision making [1]; 3) tissue classification and identification of
pathology [2]. The current systems which provide pixel-level HSI/MSI signal can
be generally divided into two types: spatial scanning and spectral scanning.
However, the trade-off between spatial/spectral resolution, the acquisition
time, and the hardware complexity hampers implementation in real-world
applications, especially intra-operatively. Acquiring high resolution images in
real-time is important for HSI/MSI in intra-operative imaging, to alleviate the
side effect caused by breathing, heartbeat, and other sources of motion.
Therefore, we developed an algorithm to recover a pixel-level MSI stack using
only the captured snapshot RGB images from a normal camera. We refer to this
technique as "super-spectral-resolution". The proposed method enables recovery
of pixel-level-dense MSI signals with 24 spectral bands at ~11 frames per
second (FPS) on a GPU. Multispectral data captured from porcine bowel and
sheep/rabbit uteri in vivo has been used for training, and the algorithm has
been validated using unseen in vivo animal experiments.
| arxiv topic:cs.CV |
arxiv_dataset-86861707.03568 | Hydrodynamics of moving contact lines: macroscopic versus microscopic
physics.flu-dyn
The fluid-mechanics community is currently divided in assessing the
boundaries of applicability of the macroscopic approach to fluid mechanical
problems. Can the dynamics of nano-droplets be described by the same
macroscopic equations as the ones used for macro-droplets? To the greatest
degree, this question should be addressed to the moving contact-line problem.
The problem is naturally multiscale, where even using a slip boundary condition
results in spurious numerical solutions and transcendental stagnation regions
in modelling in the vicinity of the contact line. In this publication, it has
been demonstrated via the mutual comparison between macroscopic modelling and
molecular dynamics simulations that a small, albeit natural, change in the
boundary conditions is all that is necessary to completely regularize the
problem and eliminate these nonphysical effects. The limits of macroscopic
approach applied to the moving contact-line problem have been tested and
validated from the first microscopic principles of molecular dynamic
simulations.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-86871707.03668 | Proceedings 15th Workshop on Quantitative Aspects of Programming
Languages and Systems
cs.PL cs.LO cs.SE
This volume of the EPTCS contains the proceedings of the 15th international
workshop on Qualitative Aspects of Programming Languages and Systems, QAPL
2017, held at April 23, 2017 in Uppsala, Sweden as a satellite event of ETAPS
2017, the 20th European Joint Conferencec on Theory and Practice of Software.
The volume contains two invited contributions by Erika Abraham and by Andrea
Vandin as well as six technical papers selected by the QAPL 2017 program
committee.
| arxiv topic:cs.PL cs.LO cs.SE |
arxiv_dataset-86881707.03768 | Constructibility and Reflexivity in non-Archimedean geometry
math.AG
We introduce a notion of constructibility for \'etale sheaves with torsion
coefficients over a suitable class of adic spaces. This notion is related to
the classical notion of constructibility for schemes via the nearby cycles
functor. We use the work of R. Huber to define an adic Verdier dual and
investigate the extent to which we have a 6-functor formalism in this context.
Lastly, we attempt to classify those sheaves which are reflexive with respect
to the adic Verdier dual.
| arxiv topic:math.AG |
arxiv_dataset-86891707.03868 | Effective Interactions in a Graphene Layer Induced by the Proximity to a
Ferromagnet
cond-mat.mes-hall
The proximity-induced couplings in graphene due to the vicinity of a
ferromagnetic insulator are analyzed. We combine general symmetry principles
and simple tight-binding descriptions to consider different orientations of the
magnetization. We find that, in addition to a simple exchange field, a number
of other terms arise. Some of these terms act as magnetic orbital couplings,
and others are proximity-induced spin-orbit interactions. The couplings are of
similar order of magnitude, and depend on the orientation of the magnetization.
A variety of phases, and anomalous Hall effect regimes, are possible.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-86901707.03968 | Predicting Causes of Reformulation in Intelligent Assistants
cs.CL
Intelligent assistants (IAs) such as Siri and Cortana conversationally
interact with users and execute a wide range of actions (e.g., searching the
Web, setting alarms, and chatting). IAs can support these actions through the
combination of various components such as automatic speech recognition, natural
language understanding, and language generation. However, the complexity of
these components hinders developers from determining which component causes an
error. To remove this hindrance, we focus on reformulation, which is a useful
signal of user dissatisfaction, and propose a method to predict the
reformulation causes. We evaluate the method using the user logs of a
commercial IA. The experimental results have demonstrated that features
designed to detect the error of a specific component improve the performance of
reformulation cause detection.
| arxiv topic:cs.CL |
arxiv_dataset-86911707.04068 | $B{\bar B}$ angular correlations at the LHC in parton Reggeization
approach merged with higher-order matrix elements
hep-ph
We calculate the angular distribution spectra between beauty ($B$) and
anti-beauty ($\bar B$) mesons in proton-proton collisions in the leading order
approximation of the parton Reggeization approach consistently merged with the
next-to-leading order corrections from the emission of additional hard gluon.
To describe b-quark hadronization we use the universal scale-depended
parton-to-meson fragmentation functions extracted from the world $e^+e^-$
annihilation data. We have obtained good agreement between our predictions and
data from the CMS Collaboration at the energy $\sqrt{S}=7$ TeV for $B \bar B$
angular correlations within uncertainties and without free parameters.
Predictions for analogous correlation observables at $\sqrt{S}=13$ TeV are
provided.
| arxiv topic:hep-ph |
arxiv_dataset-86921707.04168 | Galactic Orbits of Selected Companions of the Milky Way
astro-ph.GA
High-accuracy absolute proper motions, radial velocities, and distances have
now been measured for a number of dwarf-galaxy companions of the Milky Way,
making it possible to study their 3D dynamics. Galactic orbits for 11 such
galaxies (Fornax, Sagittarius, Ursa Minor, LMC, SMC, Sculptor, Sextans, Carina,
Draco, Leo I, Leo II) have been derived using two previously refined models for
the Galactic potential with the Navarro-Frenk-White and Allen-Santill'an
expressions for the potential of the dark-matter halo, and two different masses
for the Galaxy within 200 kpc - 0.75x10^12 Mo and 1.45x10^12 Mo. The character
of the orbits of most of these galaxies indicates that they are tightly
gravitationally bound to the Milky Way, even with the lower-mass model for the
gravitational potential. One exception is the most distant galaxy in the list,
Leo I, whose orbit demonstrates that it is only weakly gravitationally bound,
even using the higher-mass model of the gravitational potential.
| arxiv topic:astro-ph.GA |
arxiv_dataset-86931707.04268 | Linear complementarity problems on extended second order cones
math.OC
In this paper, we study the linear complementarity problems on extended
second order cones. We convert a linear complementarity problem on an extended
second order cone into a mixed complementarity problem on the non-negative
orthant. We state necessary and sufficient conditions for a point to be a
solution of the converted problem. We also present solution strategies for this
problem, such as the Newton method and Levenberg-Marquardt algorithm. Finally,
we present some numerical examples.
| arxiv topic:math.OC |
arxiv_dataset-86941707.04368 | Kernel Method for Detecting Higher Order Interactions in multi-view
Data: An Application to Imaging, Genetics, and Epigenetics
stat.ML
In this study, we tested the interaction effect of multimodal datasets using
a novel method called the kernel method for detecting higher order interactions
among biologically relevant mulit-view data. Using a semiparametric method on a
reproducing kernel Hilbert space (RKHS), we used a standard mixed-effects
linear model and derived a score-based variance component statistic that tests
for higher order interactions between multi-view data. The proposed method
offers an intangible framework for the identification of higher order
interaction effects (e.g., three way interaction) between genetics, brain
imaging, and epigenetic data. Extensive numerical simulation studies were first
conducted to evaluate the performance of this method. Finally, this method was
evaluated using data from the Mind Clinical Imaging Consortium (MCIC) including
single nucleotide polymorphism (SNP) data, functional magnetic resonance
imaging (fMRI) scans, and deoxyribonucleic acid (DNA) methylation data,
respectfully, in schizophrenia patients and healthy controls. We treated each
gene-derived SNPs, region of interest (ROI) and gene-derived DNA methylation as
a single testing unit, which are combined into triplets for evaluation. In
addition, cardiovascular disease risk factors such as age, gender, and body
mass index were assessed as covariates on hippocampal volume and compared
between triplets. Our method identified $13$-triplets ($p$-values $\leq 0.001$)
that included $6$ gene-derived SNPs, $10$ ROIs, and $6$ gene-derived DNA
methylations that correlated with changes in hippocampal volume, suggesting
that these triplets may be important in explaining schizophrenia-related
neurodegeneration. With strong evidence ($p$-values $\leq 0.000001$), the
triplet ({\bf MAGI2, CRBLCrus1.L, FBXO28}) has the potential to distinguish
schizophrenia patients from the healthy control variations.
| arxiv topic:stat.ML |
arxiv_dataset-86951707.04468 | Theoretical Investigation of $^{41}$K States Behavior under Strong
Magnetic Field and $\pi$ Polarized Laser Field
physics.atom-ph
Theoretically research of the behavior of $^{41}$K $D_1$ and $D_2$ lines for
$\pi$ polarized resonant light is conducted in the presence of strong magnetic
field when the total electronic angular momentum $J$ and nuclear spin $I$ are
decoupled. We show that in the case of linear polarization and for D1 line
there are two transitions, so called guiding transitions (GT) that maintain
their probabilities and frequency slopes. In Hyperfine Paschen-Back (HPB)
regime other transitions are coming together to those GTs, making 2 groups (4
in each). Each transition in the group has the same frequency slope and
probability as the GT in their group. It is demonstrated that from 12 ($D_1$)
and 20 ($D_2$) initially allowed Zeeman transitions (taking into account the
selection rules) at low B-field, only 8 transitions in each $D$ line remain in
absorption spectra at $B > 200$ G. A complete HPB regime for relatively low
magnetic fields $B \sim 200$ G has been observed. This value is the smallest
for all alkali metals.
| arxiv topic:physics.atom-ph |
arxiv_dataset-86961707.04568 | Systematic study of {\alpha} decay using different versions of proximity
formalism
nucl-th
Finding the best model to describe the {\alpha}-decay process is an old and
ongoing challenge in nuclear physics. The present work systematically studied
{\alpha}-decay half-lives for the favored ground-state-to-ground-state
transitions of 344 isotopes of nuclei with 52 <= Z <= 107 using 28 versions of
the proximity potential model in the framework of the WKB approximation. The
present study introduces the best proximity versions with the fewest deviations
with respect to experimental values. The models for Prox. 77-set 4, Prox.
77-set 5, and Dutt 2011 with the root-mean-square deviations (RMSDs) of <1 were
found to predict {\alpha}-decay half-lives better than the other models.
Comparison with fusion studies shows that Dutt 2011 is an appropriate model
both for {\alpha}-decay studies and for prediction of the barrier
characteristic in heavy-ion fusion reactions. The calculation of {\alpha}-decay
half-lives were repeated for even-even, even-odd, odd-even, and odd-odd nuclei.
This detailed comparative study reveals that for these versions the half-lives
of the even-even nuclei with RMSDs of <0.6 show less deviation than the
even-odd, odd-even, and odd-odd nuclei.
| arxiv topic:nucl-th |
arxiv_dataset-86971707.04668 | Stationary moments, diffusion limits, and extinction times for logistic
growth with random catastrophes
q-bio.PE
A central problem in population ecology is understanding the consequences of
stochastic fluctuations. Analytically tractable models with Gaussian driving
noise have led to important, general insights, but they fail to capture rare,
catastrophic events, which are increasingly observed at scales ranging from
global fisheries to intestinal microbiota. Due to mathematical challenges,
growth processes with random catastrophes are less well characterized and it
remains unclear how their consequences differ from those of Gaussian processes.
In the face of a changing climate and predicted increases in ecological
catastrophes, as well as increased interest in harnessing microbes for
therapeutics, these processes have never been more relevant. To better
understand them, I revisit here a differential equation model of logistic
growth coupled to density-independent catastrophes that arrive as a Poisson
process, and derive new analytic results that reveal its statistical structure.
First, I derive exact expressions for the model's stationary moments, revealing
a single effective catastrophe parameter that largely controls low order
statistics. Then, I use weak convergence theorems to construct its Gaussian
analog in a limit of frequent, small catastrophes, keeping the stationary
population mean constant for normalization. Numerically computing statistics
along this limit shows how they transform as the dynamics shifts from
catastrophes to diffusions, enabling quantitative comparisons. For example, the
mean time to extinction increases monotonically by orders of magnitude,
demonstrating significantly higher extinction risk under catastrophes than
under diffusions. Together, these results provide insight into a wide range of
stochastic dynamical systems important for ecology and conservation.
| arxiv topic:q-bio.PE |
arxiv_dataset-86981707.04768 | Robust optimal component design under consideration of local material
defects
math.OC
An important issue in additive manufacturing is the reliability and
reproducibility of parts. One major problem in achieving this are uncontrolled
local variations in the obtained material properties which arise in the complex
manufacturing process and are usually not taken into account in the design of
components.
We consider the optimal layout of a part to withstand a given loading, under
the assumption that the local material properties are not precisely known. The
material uncertainties are treated by a worst case approach. This means that
for each layout a given amount of defects in material properties is distributed
in the design domain, such that the stiffness of the component is maximally
weakened. As a consequence, an optimization result is obtained which is as
insensitive as possible with respect to unknown variations in the material
parameters.
The general model is introduced and an algorithm for its solution using
gradient based methods is suggested. Finally, numerical results are presented
and discussed.
| arxiv topic:math.OC |
arxiv_dataset-86991707.04868 | Forecasting the U.S. Real House Price Index
q-fin.CP
The 2006 sudden and immense downturn in U.S. House Prices sparked the 2007
global financial crisis and revived the interest about forecasting such
imminent threats for economic stability. In this paper we propose a novel
hybrid forecasting methodology that combines the Ensemble Empirical Mode
Decomposition (EEMD) from the field of signal processing with the Support
Vector Regression (SVR) methodology that originates from machine learning. We
test the forecasting ability of the proposed model against a Random Walk (RW)
model, a Bayesian Autoregressive and a Bayesian Vector Autoregressive model.
The proposed methodology outperforms all the competing models with half the
error of the RW model with and without drift in out-of-sample forecasting.
Finally, we argue that this new methodology can be used as an early warning
system for forecasting sudden house prices drops with direct policy
implications.
| arxiv topic:q-fin.CP |
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