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arxiv_dataset-89001709.05134 | On the structure and applications of the Bondi-Metzner-Sachs group
gr-qc hep-th
This work is a pedagogical review dedicated to a modern description of the
Bondi-Metzner-Sachs group. The curved space-times that will be taken into
account are the ones that suitably approach, at infinity, Minkowski space-time.
In particular we will focus on asymptotically flat space-times. In this work
the concept of asymptotic symmetry group of those space-times will be studied.
In the first two sections we derive the asymptotic group following the
classical approach which was basically developed by Bondi, van den Burg,
Metzner and Sachs. This is essentially the group of transformations between
coordinate systems of a certain type in asymptotically flat space-times. In the
third section the conformal method and the notion of asymptotic simplicity are
introduced, following mainly the works of Penrose. This section prepares us for
another derivation of the Bondi-Metzner-Sachs group which will involve the
conformal structure, and is thus more geometrical and fundamental. In the
subsequent sections we discuss the properties of the Bondi-Metzner-Sachs group,
e.g. its algebra and the possibility to obtain as its subgroup the Poincar\'e
group, as we may expect. The paper ends with a review of the
Bondi-Metzner-Sachs invariance properties of classical gravitational scattering
discovered by Strominger, that are finding application to black hole physics
and quantum gravity in the literature.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-89011709.05234 | Quasi-periodic oscillations in flares and coronal mass ejections
associated with magnetic reconnection
astro-ph.SR
We propose a mechanism for quasi-periodic oscillations of both coronal mass
ejections (CMEs) and flare loops as related to magnetic reconnection in
eruptive solar flares. We perform two-dimensional numerical MHD simulations of
magnetic flux rope eruption, with three different values of the global
Lundquist number. In the low Lundquist number run, no oscillatory behavior is
found. In the moderate Lunquist number run, on the other hand, quasi-periodic
oscillations are excited both at the bottom of the flux rope and at the flare
loop-top. In the high Lundquist number run, quasi-periodic oscillations are
also excited; in the meanwhile, the dynamics become turbulent due to the
formation of multiple plasmoids in the reconnection current sheet. In high and
moderate Lundquist number runs, thin reconnection jet collide with the flux
rope bottom or flare loop-top and dig them deeply. Steep oblique shocks are
formed as termination shocks where reconnection jet is bent (rather than
decelerated) in horizontal direction, resulting in supersonic back-flows. The
structure becomes unstable, and quasi-periodic oscillation of supersonic
back-flows appear at locally confined high-beta region at both the flux rope
bottom and flare loop-top. We compare the observational characteristics of
quasi-periodic oscillations in erupting flux ropes, post-CME current sheets,
flare ribbons and light curves, with corresponding dynamical structures found
in our simulation.
| arxiv topic:astro-ph.SR |
arxiv_dataset-89021709.05334 | Factorization of Dyck words and the distribution of the divisors of an
integer
math.NT
In [CaballeroHooleyDelta], we associated a Dyck word $\langle\! \langle n
\rangle\! \rangle_{\lambda}$ to any pair $(n, \lambda)$ consisting of an
integer $n \geq 1$ and a real number $\lambda > 1$. The goal of the present
paper is to show a relationship between the factorization of $\langle\! \langle
n \rangle\! \rangle_{\lambda}$ as the concatenation of irreducible Dyck words
and the distribution of the divisors of $n$. In particular, we will provide a
characterization of $\lambda$-densely divisible numbers (these numbers were
introduced in [castryck2014new]).
| arxiv topic:math.NT |
arxiv_dataset-89031709.05434 | Cherenkov Telescope Array: The Next Generation Gamma-ray Observatory
astro-ph.HE astro-ph.IM hep-ex
The Cherenkov Telescope Array (CTA) will be the next-generation gamma-ray
observatory, investigating gamma-ray and cosmic ray astrophysics at energies
from 20 GeV to more than 300 TeV. The observatory, consisting of large arrays
of imaging atmospheric Cherenkov telescopes in both the southern and northern
hemispheres, will provide full-sky coverage and will achieve a sensitivity
improved by up to an order of magnitude compared to existing instruments such
as H.E.S.S., MAGIC and VERITAS. CTA is expected to discover hundreds of new TeV
gamma- ray sources, allowing it to significantly advance our understanding of
the origin of cosmic rays, to probe much larger distances in the universe, and
to search for WIMP dark matter with unprecedented sensitivity in TeV mass
range.
The development of CTA is being carried out by a worldwide consortium of
scientists from 32 countries. Consortium scientists have developed the core
scientific programme of CTA and institutes of the Consortium are expected to
provide the bulk of the CTA components. The construction of CTA is overseen by
the CTA Observatory that will in the future manage observatory operations, the
guest observer programme, and data dissemination.
This talk will review the scientific motivation for CTA, focusing on the key
science projects that form the core programme of research. The talk will
outline the design of CTA, including the science drivers, overall concept,
performance optimization, and array layouts. The current status of CTA,
including sites, prototype telescope progress, and steps forward will also be
described.
| arxiv topic:astro-ph.HE astro-ph.IM hep-ex |
arxiv_dataset-89041709.05534 | An alternative to continuous univariate distributions supported on a
bounded interval: The BMT distribution
math.ST stat.AP stat.CO stat.TH
In this paper, we introduce the BMT distribution as an unimodal alternative
to continuous univariate distributions supported on a bounded interval. The
ideas behind the mathematical formulation of this new distribution come from
computer aid geometric design, specifically from Bezier curves. First, we
review general properties of a distribution given by parametric equations and
extend the definition of a Bezier distribution. Then, after proposing the BMT
cumulative distribution function, we derive its probability density function
and a closed-form expression for quantile function, median, interquartile
range, mode, and moments. The domain change from [0,1] to [c,d] is mentioned.
Estimation of parameters is approached by the methods of maximum likelihood and
maximum product of spacing. We test the numerical estimation procedures using
some simulated data. Usefulness and flexibility of the new distribution are
illustrated in three real data sets. The BMT distribution has a significant
potential to estimate domain parameters and to model data outside the scope of
the beta or similar distributions.
| arxiv topic:math.ST stat.AP stat.CO stat.TH |
arxiv_dataset-89051709.05634 | Label propagation for clustering
cs.SI physics.data-an physics.soc-ph
Label propagation is a heuristic method initially proposed for community
detection in networks, while the method can be adopted also for other types of
network clustering and partitioning. Among all the approaches and techniques
described in this book, label propagation is neither the most accurate nor the
most robust method. It is, however, without doubt one of the simplest and
fastest clustering methods. Label propagation can be implemented with a few
lines of programming code and applied to networks with hundreds of millions of
nodes and edges on a standard computer, which is true only for a handful of
other methods in the literature.
In this chapter, we present the basic framework of label propagation, review
different advances and extensions of the original method, and highlight its
equivalences with other approaches. We show how label propagation can be used
effectively for large-scale community detection, graph partitioning,
identification of structurally equivalent nodes and other network structures.
We conclude the chapter with a summary of the label propagation methods and
suggestions for future research.
| arxiv topic:cs.SI physics.data-an physics.soc-ph |
arxiv_dataset-89061709.05734 | Maps between curves and arithmetic obstructions
math.NT math.AG
Let X and Y be curves over a finite field. In this article we explore methods
to determine whether there is a rational map from Y to X by considering
L-functions of certain covers of X and Y and propose a specific family of
covers to address the special case of determining when X and Y are isomorphic.
We also discuss an application to factoring polynomials over finite fields.
| arxiv topic:math.NT math.AG |
arxiv_dataset-89071709.05834 | An automatic taxonomy of galaxy morphology using unsupervised machine
learning
astro-ph.IM astro-ph.CO astro-ph.GA
We present an unsupervised machine learning technique that automatically
segments and labels galaxies in astronomical imaging surveys using only pixel
data. Distinct from previous unsupervised machine learning approaches used in
astronomy we use no pre-selection or pre-filtering of target galaxy type to
identify galaxies that are similar. We demonstrate the technique on the HST
Frontier Fields. By training the algorithm using galaxies from one field (Abell
2744) and applying the result to another (MACS0416.1-2403), we show how the
algorithm can cleanly separate early and late type galaxies without any form of
pre-directed training for what an 'early' or 'late' type galaxy is. We then
apply the technique to the HST CANDELS fields, creating a catalogue of
approximately 60,000 classifications. We show how the automatic classification
groups galaxies of similar morphological (and photometric) type, and make the
classifications public via a catalogue, a visual catalogue and galaxy
similarity search. We compare the CANDELS machine-based classifications to
human-based classifications from the Galaxy Zoo: CANDELS project. Although
there is not a direct mapping between Galaxy Zoo and our hierarchical
labelling, we demonstrate a good level of concordance between human and machine
classifications. Finally, we show how the technique can be used to identify
rarer objects and present new lensed galaxy candidates from the CANDELS
imaging.
| arxiv topic:astro-ph.IM astro-ph.CO astro-ph.GA |
arxiv_dataset-89081709.05934 | Lattice Wigner equation
physics.comp-ph
We present a numerical scheme to solve the Wigner equation, based on a
lattice discretization of momentum space. The moments of the Wigner function
are recovered exactly, up to the desired order given by the number of discrete
momenta retained in the discretisation, which also determines the accuracy of
the method. The Wigner equation is equipped with an additional collision
operator, designed in such a way as to ensure numerical stability without
affecting the evolution of the relevant moments of the Wigner function. The
lattice Wigner scheme is validated for the case of quantum harmonic and
anharmonic potentials, showing good agreement with theoretical results. It is
further applied to the study of the transport properties of one and two
dimensional open quantum systems with potential barriers. Finally, the
computational viability of the scheme for the case of three- dimensional open
systems is also illustrated.
| arxiv topic:physics.comp-ph |
arxiv_dataset-89091709.06034 | Decomposibility and norm convergence properties in finite von Neumann
algebras
math.OA
We study Schur-type upper triangular forms for elements, T, of von Neumann
algebras equipped with faithful, normal, tracial states. These were introduced
in a paper of Dykema, Sukochev and Zanin; they are based on Haagerup-Schultz
projections. We investigate when the s.o.t.-quasinilpotent part of this
decomposition of T is actually quasinilpotent. We prove implications involving
decomposability and strong decomposability of T. We show this is related to
norm convergence properties of the sequence |T^n|^{1/n} which, by a result of
Haagerup and Schultz, is known to converge in strong operator topology. We
introduce a Borel decomposability, which is a property appropriate for elements
of finite von Neumann algebras, and show that the circular operator is Borel
decomposable. We also prove the existence of a thin-spectrum
s.o.t.-quasinilpotent operator in the hyperfinite II_1-factor.
| arxiv topic:math.OA |
arxiv_dataset-89101709.06134 | Discrete Dynamic Causal Modeling and Its Relationship with Directed
Information
q-bio.NC cs.IT math.IT stat.AP
This paper explores the discrete Dynamic Causal Modeling (DDCM) and its
relationship with Directed Information (DI). We prove the conditional
equivalence between DDCM and DI in characterizing the causal relationship
between two brain regions. The theoretical results are demonstrated using fMRI
data obtained under both resting state and stimulus based state. Our numerical
analysis is consistent with that reported in previous study.
| arxiv topic:q-bio.NC cs.IT math.IT stat.AP |
arxiv_dataset-89111709.06234 | Correlation between structure and Rayleigh parameters in the lead-free
piezoceramic (1-x)Ba(Ti0.88 Sn0.12)O3-x(Ba0.7Ca0.3)TiO3
cond-mat.mtrl-sci
Composition dependent Rayleigh and structural analysis was carried out on the
lead-free piezoceramics (1-x)(BaTi0.88Sn0.12)-x(Ba0.7Ca0.3)TiO3 at room
temperature. The system exhibits tetragonal (P4mm) structure for x > 0.21,
rhombohedral (R3m) for x < 0.13 and orthorhombic (Amm2) for 0.13<x<0.21.
Rayleigh analysis suggests that the irreversible contribution to the dielectric
response is enhanced in the single phase orthorhombic compositions in the
vicinity of the R3m-Amm2 and Amm2-P4mm phase boundaries, and not in
compositions exhibiting phase coexistences (x = 0.12 and 0.22). We also found a
correspondence between the irreversible Rayleigh parameter and the coercive
field in this system.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-89121709.06334 | On the number of representations of $n=a+b$ with $ab$ a multiple of a
polygonal number
math.NT
In this paper, we study the number of representations of a positive integer
$n$ by two positive integers whose product is a multiple of a polygonal number.
| arxiv topic:math.NT |
arxiv_dataset-89131709.06434 | Formality of $\mathbb{P}$-objects
math.AG math.CT
We show that a $\mathbb{P}$-object and simple configurations of
$\mathbb{P}$-objects have a formal derived endomorphism algebra. Hence the
triangulated category (classically) generated by such objects is independent of
the ambient triangulated category. We also observe that the category generated
by the structure sheaf of a smooth projective variety over the complex numbers
only depends on its graded cohomology algebra.
| arxiv topic:math.AG math.CT |
arxiv_dataset-89141709.06534 | BIOS ORAM: Improved Privacy-Preserving Data Access for Parameterized
Outsourced Storage
cs.CR cs.DS
Algorithms for oblivious random access machine (ORAM) simulation allow a
client, Alice, to obfuscate a pattern of data accesses with a server, Bob, who
is maintaining Alice's outsourced data while trying to learn information about
her data. We present a novel ORAM scheme that improves the asymptotic I/O
overhead of previous schemes for a wide range of size parameters for
client-side private memory and message blocks, from logarithmic to polynomial.
Our method achieves statistical security for hiding Alice's access pattern and,
with high probability, achieves an I/O overhead that ranges from $O(1)$ to
$O(\log^2 n/(\log\log n)^2)$, depending on these size parameters, where $n$ is
the size of Alice's outsourced memory. Our scheme, which we call BIOS ORAM,
combines multiple uses of B-trees with a reduction of ORAM simulation to
isogrammic access sequences.
| arxiv topic:cs.CR cs.DS |
arxiv_dataset-89151709.06634 | Neutron star mergers as a probe of modifications of general relativity
with finite-range scalar forces
gr-qc astro-ph.HE hep-ph hep-th
Observations of gravitational radiation from compact binary systems provide
an unprecedented opportunity to test General Relativity in the strong field
dynamical regime. In this paper, we investigate how future observations of
gravitational radiation from binary neutron star mergers might provide
constraints on finite-range forces from a universally coupled massive scalar
field. Such scalar degrees of freedom are a characteristic feature of many
extensions of General Relativity. For concreteness, we work in the context of
metric $f(R)$ gravity, which is equivalent to General Relativity and a
universally coupled scalar field with a non-linear potential whose form is
fixed by the choice of $f(R)$. In theories where neutron stars (or other
compact objects) obtain a significant scalar charge, the resulting attractive
finite-range scalar force has implications for both the inspiral and merger
phases of binary systems. We first present an analysis of the inspiral dynamics
in Newtonian limit, and forecast the constraints on the mass of the scalar and
charge of the compact objects for the Advanced LIGO gravitational wave
observatory. We then perform a comparative study of binary neutron star mergers
in General Relativity with those of a one-parameter model of $f(R)$ gravity
using fully relativistic hydrodynamical simulations. These simulations
elucidate the effects of the scalar on the merger and post-merger dynamics. We
comment on the utility of the full waveform (inspiral, merger, post-merger) to
probe different regions of parameter space for both the particular model of
$f(R)$ gravity studied here and for finite-range scalar forces more generally.
| arxiv topic:gr-qc astro-ph.HE hep-ph hep-th |
arxiv_dataset-89161709.06734 | Enhancing Quality for HEVC Compressed Videos
cs.MM
The latest High Efficiency Video Coding (HEVC) standard has been increasingly
applied to generate video streams over the Internet. However, HEVC compressed
videos may incur severe quality degradation, particularly at low bit-rates.
Thus, it is necessary to enhance the visual quality of HEVC videos at the
decoder side. To this end, this paper proposes a Quality Enhancement
Convolutional Neural Network (QE-CNN) method that does not require any
modification of the encoder to achieve quality enhancement for HEVC. In
particular, our QE-CNN method learns QE-CNN-I and QE-CNN-P models to reduce the
distortion of HEVC I and P frames, respectively. The proposed method differs
from the existing CNN-based quality enhancement approaches, which only handle
intra-coding distortion and are thus not suitable for P frames. Our
experimental results validate that our QE-CNN method is effective in enhancing
quality for both I and P frames of HEVC videos. To apply our QE-CNN method in
time-constrained scenarios, we further propose a Time-constrained Quality
Enhancement Optimization (TQEO) scheme. Our TQEO scheme controls the
computational time of QE-CNN to meet a target, meanwhile maximizing the quality
enhancement. Next, the experimental results demonstrate the effectiveness of
our TQEO scheme from the aspects of time control accuracy and quality
enhancement under different time constraints. Finally, we design a prototype to
implement our TQEO scheme in a real-time scenario.
| arxiv topic:cs.MM |
arxiv_dataset-89171709.06834 | Geodesics Currents and Counting Problems
math.GT math.DS
For every positive, continuous and homogeneous function $f$ on the space of
currents on a compact surface $\overline{\Sigma}$, and for every compactly
supported filling current $\alpha$, we compute as $L \to \infty$, the number of
mapping classes $\phi$ so that $f(\phi(\alpha))\leq L$. As an application, when
the surface in question is closed, we prove a lattice counting theorem for
Teichm\"uller space equipped with the Thurston metric.
| arxiv topic:math.GT math.DS |
arxiv_dataset-89181709.06934 | REACT to Cyber Attacks on Power Grids
cs.SY
Motivated by the recent cyber attack on the Ukrainian power grid, we study
cyber attacks on power grids that affect both the physical infrastructure and
the data at the control center. In particular, we assume that an adversary
attacks an area by: (i) remotely disconnecting some lines within the attacked
area, and (ii) modifying the information received from the attacked area to
mask the line failures and hide the attacked area from the control center. For
the latter, we consider two types of attacks: (i) data distortion: which
distorts the data by adding powerful noise to the actual data, and (ii) data
replay: which replays a locally consistent old data instead of the actual data.
We use the DC power flow model and prove that the problem of finding the set of
line failures given the phase angles of the nodes outside of the attacked area
is strongly NP-hard, even when the attacked area is known. However, we
introduce the polynomial time REcurrent Attack Containment and deTection
(REACT) Algorithm to approximately detect the attacked area and line failures
after a cyber attack. We numerically show that it performs very well in
detecting the attacked area, and detecting single, double, and triple line
failures in small and large attacked areas.
| arxiv topic:cs.SY |
arxiv_dataset-89191709.07034 | Cooling of Accretion-Heated Neutron Stars
astro-ph.HE
We present a brief, observational review about the study of the cooling
behaviour of accretion-heated neutron stars and the inferences about the
neutron-star crust and core that have been obtained from these studies.
Accretion of matter during outbursts can heat the crust out of thermal
equilibrium with the core and after the accretion episodes are over, the crust
will cool down until crust-core equilibrium is restored. We discuss the
observed properties of the crust cooling sources and what has been learned
about the physics of neutron-star crusts. We also briefly discuss those systems
that have been observed long after their outbursts were over, i.e, during times
when the crust and core are expected to be in thermal equilibrium. The surface
temperature is then a direct probe for the core temperature. By comparing the
expected temperatures based on estimates of the accretion history of the
targets with the observed ones, the physics of neutron-star cores can be
investigated. Finally, we discuss similar studies performed for strongly
magnetized neutron stars in which the magnetic field might play an important
role in the heating and cooling of the neutron stars.
| arxiv topic:astro-ph.HE |
arxiv_dataset-89201709.07134 | On the Schr\"odinger equations with time-dependent potentials growing
polynomially in the spatial direction
math.AP
The Cauchy problem for the Schr\"odinger equations is studied with
time-dependent potentials growing polynomially in the spatial direction. First
the existence and the uniqueness of solutions are shown in the weighted Sobolev
spaces. In addition, we suppose that our potentials are depending on a
parameter. Secondly it is shown that if potentials depend continuously and
differentiably on the parameter, the solutions to the Schr\"odinger equations
respectively become continuous and differentiable with respect to its
parameter.
| arxiv topic:math.AP |
arxiv_dataset-89211709.07234 | Role of QCD compositeness in the production of scalar and tensor mesons
through single-photon annihilation $e^+ e^- \to \gamma^* \to \gamma S(T)$
hep-ph
We study the exclusive production of scalar $S = 0^{++}$ and tensor $T =
2^{++}$ mesons through single-photon annihilation $e^+ e^- \to \gamma^* \to
\gamma S(T)$. Using QCD compositeness of the involved hadrons considered as
quark-antiquark systems, the prediction for the scaling of the differential
cross sections of these processes is $d\sigma/dt \sim 1/s^3$ at large $s$. We
further derive the scaling of the $\gamma^\ast \to \gamma S$ and $\gamma^\ast
\to \gamma T$ transition form factors: $F_{\gamma^\ast\gamma S}(s) \sim 1/s$
and $F_{\gamma^\ast\gamma T}(s) \sim 1/s^2$. Results for the respective cross
sections of the scalar and tensor meson production are presented. Note, when
scalar and tensor mesons are considered as tetraquark systems of two tightly
bound color diquarks, corresponding to them transition form factors and
differential cross sections have the same falloffs as in case of
quark-antiquark picture. For other tetraquark or two-hadron molecules
configurations the transition form factors $F_{\gamma^\ast\gamma S(T)}(s)$ and
the differential cross section $d\sigma/dt$ have additional $1/s$ and $1/s^2$
falloffs, respectively.
| arxiv topic:hep-ph |
arxiv_dataset-89221709.07334 | Observations et mod\'elisations spectro-interf\'erom\'etriques longue
base des \'etoiles et de leur environnement proche
astro-ph.SR
With the construction of the VLTI (Very Large Telescope Interferometer of the
European Observatory ESO for the southern hemisphere) it is now possible to
make observations with resolutions of the order of milli-arc-seconds,
especially in IR with AMBER instrument (Astronomical Multi Beam Recombine).
These new capabilities allow us to better constrain the stellar structures such
as polar jets, equatorial disks and flattened photospheres of rotating stars.
Thus the estimation of stellar fundamental parameters allows to explore in
detail the mechanisms of mass loss, pulsation and magnetism governing the
variability and the evolution of the stars.
This thesis presents the results of fast rotating stars observations carried
out on the AMBER spectro-interferometer VLTI in its high \& medium spectral
resolutions modes. The observations were highly degraded by the optical defects
of AMBER and their analysis required the development of specific digital
reduction tools to reach the necessary precision for the interferometric
measurements interpretation. In order to interpret those measures I developed a
chromatic semi-analytical model of rapidly rotating star that allowed me to
estimate, from the differential phases; the degree of flattening, the
equatorial radius, the rotation velocity, the angle of inclination, the
position angle of the star rotation axis in the sky, the local distribution of
the effective temperature and the surface gravity of the star within the von
Zeipel theorem. The results for four massive stars of spectral types B, A and F
have allowed me to characterize the mechanisms discussed above and thus open
some prospect for more systematic studies of similar objects, with extending
later these studies to the relationship photosphere - circumstellar envelope.
| arxiv topic:astro-ph.SR |
arxiv_dataset-89231709.07434 | Analyzing users' sentiment towards popular consumer industries and
brands on Twitter
cs.CL cs.IR cs.SI
Social media serves as a unified platform for users to express their thoughts
on subjects ranging from their daily lives to their opinion on consumer brands
and products. These users wield an enormous influence in shaping the opinions
of other consumers and influence brand perception, brand loyalty and brand
advocacy. In this paper, we analyze the opinion of 19M Twitter users towards 62
popular industries, encompassing 12,898 enterprise and consumer brands, as well
as associated subject matter topics, via sentiment analysis of 330M tweets over
a period spanning a month. We find that users tend to be most positive towards
manufacturing and most negative towards service industries. In addition, they
tend to be more positive or negative when interacting with brands than
generally on Twitter. We also find that sentiment towards brands within an
industry varies greatly and we demonstrate this using two industries as use
cases. In addition, we discover that there is no strong correlation between
topic sentiments of different industries, demonstrating that topic sentiments
are highly dependent on the context of the industry that they are mentioned in.
We demonstrate the value of such an analysis in order to assess the impact of
brands on social media. We hope that this initial study will prove valuable for
both researchers and companies in understanding users' perception of
industries, brands and associated topics and encourage more research in this
field.
| arxiv topic:cs.CL cs.IR cs.SI |
arxiv_dataset-89241709.07534 | MRNet-Product2Vec: A Multi-task Recurrent Neural Network for Product
Embeddings
cs.AI cs.LG stat.ML
E-commerce websites such as Amazon, Alibaba, Flipkart, and Walmart sell
billions of products. Machine learning (ML) algorithms involving products are
often used to improve the customer experience and increase revenue, e.g.,
product similarity, recommendation, and price estimation. The products are
required to be represented as features before training an ML algorithm. In this
paper, we propose an approach called MRNet-Product2Vec for creating generic
embeddings of products within an e-commerce ecosystem. We learn a dense and
low-dimensional embedding where a diverse set of signals related to a product
are explicitly injected into its representation. We train a Discriminative
Multi-task Bidirectional Recurrent Neural Network (RNN), where the input is a
product title fed through a Bidirectional RNN and at the output, product labels
corresponding to fifteen different tasks are predicted. The task set includes
several intrinsic characteristics about a product such as price, weight, size,
color, popularity, and material. We evaluate the proposed embedding
quantitatively and qualitatively. We demonstrate that they are almost as good
as sparse and extremely high-dimensional TF-IDF representation in spite of
having less than 3% of the TF-IDF dimension. We also use a multimodal
autoencoder for comparing products from different language-regions and show
preliminary yet promising qualitative results.
| arxiv topic:cs.AI cs.LG stat.ML |
arxiv_dataset-89251709.07634 | EraseReLU: A Simple Way to Ease the Training of Deep Convolution Neural
Networks
cs.CV
For most state-of-the-art architectures, Rectified Linear Unit (ReLU) becomes
a standard component accompanied with each layer. Although ReLU can ease the
network training to an extent, the character of blocking negative values may
suppress the propagation of useful information and leads to the difficulty of
optimizing very deep Convolutional Neural Networks (CNNs). Moreover, stacking
layers with nonlinear activations is hard to approximate the intrinsic linear
transformations between feature representations.
In this paper, we investigate the effect of erasing ReLUs of certain layers
and apply it to various representative architectures following deterministic
rules. It can ease the optimization and improve the generalization performance
for very deep CNN models. We find two key factors being essential to the
performance improvement: 1) the location where ReLU should be erased inside the
basic module; 2) the proportion of basic modules to erase ReLU; We show that
erasing the last ReLU layer of all basic modules in a network usually yields
improved performance. In experiments, our approach successfully improves the
performance of various representative architectures, and we report the improved
results on SVHN, CIFAR-10/100, and ImageNet. Moreover, we achieve competitive
single-model performance on CIFAR-100 with 16.53% error rate compared to
state-of-the-art.
| arxiv topic:cs.CV |
arxiv_dataset-89261709.07734 | Emulating many-body localization with a superconducting quantum
processor
quant-ph
The law of statistical physics dictates that generic closed quantum many-body
systems initialized in nonequilibrium will thermalize under their own dynamics.
However, the emergence of many-body localization (MBL) owing to the interplay
between interaction and disorder, which is in stark contrast to Anderson
localization that only addresses noninteracting particles in the presence of
disorder, greatly challenges this concept because it prevents the systems from
evolving to the ergodic thermalized state. One critical evidence of MBL is the
long-time logarithmic growth of entanglement entropy, and a direct observation
of it is still elusive due to the experimental challenges in multiqubit
single-shot measurement and quantum state tomography. Here we present an
experiment of fully emulating the MBL dynamics with a 10-qubit superconducting
quantum processor, which represents a spin-1/2 XY model featuring programmable
disorder and long-range spin-spin interactions. We provide essential signatures
of MBL, such as the imbalance due to the initial nonequilibrium, the violation
of eigenstate thermalization hypothesis, and, more importantly, the direct
evidence of the long-time logarithmic growth of entanglement entropy. Our
results lay solid foundations for precisely simulating the intriguing physics
of quantum many-body systems on the platform of large-scale multiqubit
superconducting quantum processors.
| arxiv topic:quant-ph |
arxiv_dataset-89271709.07834 | Freeze-out of baryon number in low-scale leptogenesis
hep-ph astro-ph.CO
Low-scale leptogenesis provides an economic and testable description of the
origin of the baryon asymmetry of the Universe. In this scenario, the baryon
asymmetry of the Universe is reprocessed from the lepton asymmetry by
electroweak sphaleron processes. Provided that sphalerons are fast enough to
maintain equilibrium, the values of the baryon and lepton asymmetries are
related to each other. Usually, this relation is used to find the value of the
baryon asymmetry at the time of the sphaleron freeze-out. To put in other
words, the formula which is valid only when the sphalerons are fast, is applied
at the moment when they are actually switched off. In this paper, we examine
the validity of such a treatment. To this end, we solve the full system of
kinetic equations for low-scale leptogenesis. This system includes equations
describing the production of the lepton asymmetry in oscillations of
right-handed neutrinos, as well as a separate kinetic equation for the baryon
asymmetry. We show that for some values of the model parameters, the
corrections to the standard approach are sizeable. We also present a feasible
improvement to the ordinary procedure, which accounts for these corrections.
| arxiv topic:hep-ph astro-ph.CO |
arxiv_dataset-89281709.07934 | Rigidity results for elliptic boundary value problems: stable solutions
for quasilinear equations with Neumann or Robin boundary conditions
math.AP
We provide a general approach to the classification results of stable
solutions of (possibly nonlinear) elliptic problems with Robin conditions.
The method is based on a geometric formula of Poincar\'e type, which is
inspired by a classical work of Sternberg and Zumbrun and which gives an
accurate description of the curvatures of the level sets of the stable
solutions. {F}rom this, we show that the stable solutions of a quasilinear
problem with Neumann data are necessarily constant.
As a byproduct of this, we obtain an alternative proof of a celebrated result
of Casten and Holland, and Matano.
In addition, we will obtain as a consequence a new proof of a result recently
established by Bandle, Mastrolia, Monticelli and Punzo.
| arxiv topic:math.AP |
arxiv_dataset-89291709.08034 | Prioritized Norms in Formal Argumentation
cs.AI
To resolve conflicts among norms, various nonmonotonic formalisms can be used
to perform prioritized normative reasoning. Meanwhile, formal argumentation
provides a way to represent nonmonotonic logics. In this paper, we propose a
representation of prioritized normative reasoning by argumentation. Using
hierarchical abstract normative systems, we define three kinds of prioritized
normative reasoning approaches, called Greedy, Reduction, and Optimization.
Then, after formulating an argumentation theory for a hierarchical abstract
normative system, we show that for a totally ordered hierarchical abstract
normative system, Greedy and Reduction can be represented in argumentation by
applying the weakest link and the last link principles respectively, and
Optimization can be represented by introducing additional defeats capturing the
idea that for each argument that contains a norm not belonging to the maximal
obeyable set then this argument should be rejected.
| arxiv topic:cs.AI |
arxiv_dataset-89301709.08134 | Option Pricing with Greed and Fear Factor: The Rational Finance Approach
q-fin.GN
We explain the main concepts of Prospect Theory and Cumulative Prospect
Theory within the framework of rational dynamic asset pricing theory. We derive
option pricing formulas when asset returns are altered with a generalized
Prospect Theory value function or a modified Prelec weighting probability
function and introduce new parametric classes for Prospect Theory value
functions and weighting probability functions consistent with rational dynamic
pricing Theory. We study the behavioral finance notion of greed and fear from
the point of view of rational dynamic asset pricing theory and derive the
corresponding option pricing formulas in the case of asset returns that follow
continuous diffusion or discrete binomial trees.
| arxiv topic:q-fin.GN |
arxiv_dataset-89311709.08234 | Elastic null curve flows, nonlinear $C$-integrable systems, and
geometric realization of Cole-Hopf transformations
math-ph math.MP nlin.SI
Elastic (stretching) flows of null curves are studied in three-dimensional
Minkowski space. As a main tool, a natural type of moving frame for null curves
is introduced, without use of the pseudo-arclength. This new frame is related
to a Frenet null frame by a gauge transformation that belongs to the little
group contained in the Lorentz group $SO(2,1)$ and provides an analog of the
Hasimoto transformation (relating a parallel frame to a Frenet frame for curves
in Euclidean space). The Cartan structure equations of the transformed frame
are shown to encode a hereditary recursion operator giving a two-component
generalization of the recursion operator of Burgers equation, as well as a
generalization of the Cole-Hopf transformation. Three different hierarchies of
integrable systems are obtained from the various symmetries of this recursion
operator. The first hierarchy contains two-component Burgers-type and nonlinear
Airy-type systems; the second hierarchy contains novel quasilinear
Schr\"odinger-type (NLS) systems; and the third hierarchy contains semilinear
wave equations (in two-component system form). Each of these integrable systems
is shown to correspond to a geometrical flow of a family of elastic null curves
in three-dimensional Minkowski space.
| arxiv topic:math-ph math.MP nlin.SI |
arxiv_dataset-89321709.08334 | Vortex stretching in self-gravitating protoplanetary discs
astro-ph.SR astro-ph.EP
Horseshoe-shaped brightness asymmetries of several transitional discs are
thought to be caused by large-scale vortices. Anticyclonic vortices are
efficiently collect dust particles, therefore they can play a major role in
planet formation. Former studies suggest that the disc self-gravity weakens
vortices formed at the edge of the gap opened by a massive planet in discs
whose masses are in the range of 0.01<=M_disc/M_*<=0.1. Here we present an
investigation on the long-term evolution of the large-scale vortices formed at
the viscosity transition of the discs' dead zone outer edge by means of
two-dimensional hydrodynamic simulations taking disc self-gravity into account.
We perform a numerical study of low mass, 0.001<=M_disc/M_*<=0.01, discs, for
which cases disc self-gravity was previously neglected. The large-scale
vortices are found to be stretched due to disc self-gravity even for low-mass
discs with M_disc/M_*>=0.005 where initially the Toomre Q-parameter was <=50 at
the vortex distance. As a result of stretching, the vortex aspect ratio
increases and a weaker azimuthal density contrast develops. The strength of the
vortex stretching is proportional to the disc mass. The vortex stretching can
be explained by a combined action of a non-vanishing gravitational torque
caused by the vortex, and the Keplerian shear of the disc. Self-gravitating
vortices are subject to significantly faster decay than non-self-gravitating
ones. We found that vortices developed at sharp viscosity transitions of
self-gravitating discs can be described by a GNG model as long as the disc
viscosity is low, i.e. alpha_dz<=10^-5.
| arxiv topic:astro-ph.SR astro-ph.EP |
arxiv_dataset-89331709.08434 | Dynamic Provable Data Possession Protocols with Public Verifiability and
Data Privacy
cs.CR
Cloud storage services have become accessible and used by everyone.
Nevertheless, stored data are dependable on the behavior of the cloud servers,
and losses and damages often occur. One solution is to regularly audit the
cloud servers in order to check the integrity of the stored data. The Dynamic
Provable Data Possession scheme with Public Verifiability and Data Privacy
presented in ACISP'15 is a straightforward design of such solution. However,
this scheme is threatened by several attacks. In this paper, we carefully
recall the definition of this scheme as well as explain how its security is
dramatically menaced. Moreover, we proposed two new constructions for Dynamic
Provable Data Possession scheme with Public Verifiability and Data Privacy
based on the scheme presented in ACISP'15, one using Index Hash Tables and one
based on Merkle Hash Trees. We show that the two schemes are secure and
privacy-preserving in the random oracle model.
| arxiv topic:cs.CR |
arxiv_dataset-89341709.08534 | Thouless-Valatin Rotational Moment of Inertia from the Linear Response
Theory
nucl-th
Spontaneous breaking of continuous symmetries of a nuclear many-body system
results in appearance of zero-energy restoration modes. Such modes introduce a
non-physical contributions to the physical excitations called spurious
Nambu-Goldstone modes. Since they represent a special case of collective
motion, they are sources of important information about the Thouless-Valatin
inertia. The main purpose of this work is to study the Thouless-Valatin
rotational moment of inertia as extracted from the Nambu-Goldstone restoration
mode that results from the zero-frequency response to the total angular
momentum operator. We examine the role and effects of the pairing correlations
on the rotational characteristics of heavy deformed nuclei in order to extend
our understanding of superfluidity in general. We use the finite amplitude
method of the quasiparticle random phase approximation on top of the Skyrme
energy density functional framework with the Hartree-Fock-Bogoliubov theory. We
have successfully extended this formalism and established a practical method
for extracting the Thouless-Valatin rotational moment of inertia from the
strength function calculated in the symmetry restoration regime. Our results
reveal the relation between the pairing correlations and the moment of inertia
of axially deformed nuclei of rare-earth and actinide regions of the nuclear
chart. We have also demonstrated the feasibility of the method for obtaining
the moment of inertia for collective Hamiltonian models. We conclude that from
the numerical and theoretical perspective, the finite amplitude method can be
widely used to effectively study rotational properties of deformed nuclei
within modern density functional approaches.
| arxiv topic:nucl-th |
arxiv_dataset-89351709.08634 | WISE data as a photometric redshift indicator for radio AGN
astro-ph.IM astro-ph.GA
We show that mid-infrared data from the all-sky WISE survey can be used as a
robust photometric redshift indicator for powerful radio AGN, in the absence of
other spectroscopic or multi-band photometric information. Our work is
motivated by a desire to extend the well-known K-z relation for radio galaxies
to the wavelength range covered by the all-sky WISE mid-infrared survey. Using
the LARGESS radio spectroscopic sample as a training set, and the mid-infrared
colour information to classify radio sources, we generate a set of redshift
probability distributions for the hosts of high-excitation and low-excitation
radio AGN. We test the method using spectroscopic data from several other radio
AGN studies, and find good agreement between our WISE-based redshift estimates
and published spectroscopic redshifts out to z ~ 1 for galaxies and z ~ 3-4 for
radio-loud QSOs. Our chosen method is also compared against other
classification methods and found to perform reliably. This technique is likely
to be particularly useful in the analysis of upcoming large-area radio surveys
with SKA pathfinder telescopes, and our code is publicly available. As a
consistency check, we show that our WISE-based redshift estimates for sources
in the 843 MHz SUMSS survey reproduce the redshift distribution seen in the
CENSORS study up to z ~ 2. We also discuss two specific applications of our
technique for current and upcoming radio surveys; an interpretation of large
scale HI absorption surveys, and a determination of whether low-frequency
peaked spectrum sources lie at high redshift.
| arxiv topic:astro-ph.IM astro-ph.GA |
arxiv_dataset-89361709.08734 | Spaces which invert weak homotopy equivalences
math.AT
It is well known that if $X$ is a CW-complex, then for every weak homotopy
equivalence $f:A\to B$, the map $f_*:[X,A]\to [X,B]$ induced in homotopy
classes is a bijection. For which spaces $X$ is $f^*:[B,X]\to [A,X]$ a
bijection for every weak equivalence $f$? This question was considered by J.
Strom and T. Goodwillie. In this note we prove that a non-empty space inverts
weak equivalences if and only if it is contractible.
| arxiv topic:math.AT |
arxiv_dataset-89371709.08834 | On the Lagrangian fillability of almost positive links
math.GT
In this paper, we prove that a link which has an almost positive diagram with
a certain condition is Lagrangian fillable.
| arxiv topic:math.GT |
arxiv_dataset-89381709.08934 | Interplay of interaction and disorder in the steady state of an open
quantum system
cond-mat.quant-gas cond-mat.dis-nn quant-ph
Many types of dissipative processes can be found in nature or be engineered,
and their interplay with a system can give rise to interesting phases of
matter. Here we study the interplay among interaction, tunneling, and disorder
in the steady state of a spin chain coupled to a tailored bath. We consider a
dissipation which, in contrast to disorder, tends to generate a homogeneously
polarized steady state. We find that the steady state can be highly sensitive
even to weak disorder. We also establish that, in the presence of such
dissipation, even in the absence of interaction, a finite amount of disorder is
needed for localization. Last, we show that for strong disorder the system
reveals signatures of localization both in the weakly and strongly interacting
regimes.
| arxiv topic:cond-mat.quant-gas cond-mat.dis-nn quant-ph |
arxiv_dataset-89391709.09034 | Stress-energy tensor of quantized massive fields in static wormhole
spacetimes
gr-qc
In order to be traversable, the static Lorentzian wormhole must be made out
of some exotic matter that violates the weak energy condition. The quantized
fields are the natural candidates as their stress-energy tensor, in many cases,
possesses desired properties. In this paper we construct and examine the
stress-energy tensor of the quantized massive scalar, spinor and vector fields
in six static wormhole spacetimes. We find that in all considered cases the
quantum fields violate the Morris-Thorne conditions and do not have the form
necessary to support the wormhole throat. This is in concord with the previous
results and indicates that the massive quantum fields make the wormholes less
operable.
| arxiv topic:gr-qc |
arxiv_dataset-89401709.09134 | Observing the sky at extremely high energies with the Cherenkov
Telescope Array: Status of the GCT project
astro-ph.HE astro-ph.IM
The Cherenkov Telescope Array is the main global project of ground-based
gamma-ray astronomy for the coming decades. Performance will be significantly
improved relative to present instruments, allowing a new insight into the
high-energy Universe [1]. The nominal CTA southern array will include a
sub-array of seventy 4 m telescopes spread over a few square kilometers to
study the sky at extremely high energies, with the opening of a new window in
the multi-TeV energy range. The Gamma-ray Cherenkov Telescope (GCT) is one of
the proposed telescope designs for that sub-array. The GCT prototype recorded
its first Cherenkov light on sky in 2015. After an assessment phase in 2016,
new observations have been performed successfully in 2017. The GCT
collaboration plans to install its first telescopes and cameras on the CTA site
in Chile in 2018-2019 and to contribute a number of telescopes to the
subsequent CTA production phase.
| arxiv topic:astro-ph.HE astro-ph.IM |
arxiv_dataset-89411709.09234 | Flexibility of geometrical and dynamical data in fixed conformal classes
math.DS math.DG math.SP
Consider a smooth closed surface $M$ of fixed genus $\geqslant 2$ with a
hyperbolic metric $\sigma$ of total area $A$. In this article, we study the
behavior of geometric and dynamical characteristics (e.g., diameter, Laplace
spectrum, Gaussian curvature and entropies) of nonpositively curved smooth
metrics with total area $A$ conformally equivalent to $\sigma$. For such
metrics, we show that the diameter is bounded above and the Laplace spectrum is
bounded below away from zero by constants which depend on $\sigma$. On the
other hand, we prove that the metric entropy of the geodesic flow with respect
to the Liouville measure is flexible. Consequently, we also provide the first
known example showing that the bottom of the $L^2$-spectrum of the Laplacian
cannot be bounded from above by a function of the metric entropy. We also
provide examples showing that our conditions are essential for the established
bounds.
| arxiv topic:math.DS math.DG math.SP |
arxiv_dataset-89421709.09334 | Zero-rating of Content and its Effect on the Quality of Service in the
Internet
econ.EM
The ongoing net neutrality debate has generated a lot of heated discussions
on whether or not monetary interactions should be regulated between content and
access providers. Among the several topics discussed, `differential pricing'
has recently received attention due to `zero-rating' platforms proposed by some
service providers. In the differential pricing scheme, Internet Service
Providers (ISPs) can exempt data access charges for on content from certain CPs
(zero-rated) while no exemption is on content from other CPs. This allows the
possibility for Content Providers (CPs) to make `sponsorship' agreements to
zero-rate their content and attract more user traffic. In this paper, we study
the effect of differential pricing on various players in the Internet. We first
consider a model with a monopolistic ISP and multiple CPs where users select
CPs based on the quality of service (QoS) and data access charges. We show that
in a differential pricing regime 1) a CP offering low QoS can make have higher
surplus than a CP offering better QoS through sponsorships. 2) Overall QoS
(mean delay) for end users can degrade under differential pricing schemes. In
the oligopolistic market with multiple ISPs, users tend to select the ISP with
lowest ISP resulting in same type of conclusions as in the monopolistic market.
We then study how differential pricing effects the revenue of ISPs.
| arxiv topic:econ.EM |
arxiv_dataset-89431709.09434 | Millisecond Pulsars, their Evolution and Applications
astro-ph.HE
Millisecond pulsars (MSPs) are short-period pulsars that are distinguished
from "normal" pulsars, not only by their short period, but also by their very
small spin-down rates and high probability of being in a binary system. These
properties are consistent with MSPs having a different evolutionary history to
normal pulsars, viz., neutron-star formation in an evolving binary system and
spin-up due to accretion from the binary companion. Their very stable periods
make MSPs nearly ideal probes of a wide variety of astrophysical phenomena. For
example, they have been used to detect planets around pulsars, to test the
accuracy of gravitational theories, to set limits on the low-frequency
gravitational-wave background in the Universe, and to establish pulsar-based
timescales that rival the best atomic-clock timescales in long-term stability.
MSPs also provide a window into stellar and binary evolution, often suggesting
exotic pathways to the observed systems. The X-ray accretion-powered MSPs, and
especially those that transition between an accreting X-ray MSP and a
non-accreting radio MSP, give important insight into the physics of accretion
on to highly magnetised neutron stars.
| arxiv topic:astro-ph.HE |
arxiv_dataset-89441709.09534 | Tweeting AI: Perceptions of Lay vs Expert Twitterati
cs.AI cs.CY cs.SI
With the recent advancements in Artificial Intelligence (AI), various
organizations and individuals are debating about the progress of AI as a
blessing or a curse for the future of the society. This paper conducts an
investigation on how the public perceives the progress of AI by utilizing the
data shared on Twitter. Specifically, this paper performs a comparative
analysis on the understanding of users belonging to two categories -- general
AI-Tweeters (AIT) and expert AI-Tweeters (EAIT) who share posts about AI on
Twitter. Our analysis revealed that users from both the categories express
distinct emotions and interests towards AI. Users from both the categories
regard AI as positive and are optimistic about the progress of AI but the
experts are more negative than the general AI-Tweeters. Expert AI-Tweeters
share relatively large percentage of tweets about their personal news compared
to technical aspects of AI. However, the effects of automation on the future
are of primary concern to AIT than to EAIT. When the expert category is
sub-categorized, the emotion analysis revealed that students and industry
professionals have more insights in their tweets about AI than academicians.
| arxiv topic:cs.AI cs.CY cs.SI |
arxiv_dataset-89451709.09634 | Real time text localization for Indoor Mobile Robot Navigation
cs.RO eess.IV
Scene text is an important feature to be extracted, especially in
vision-based mobile robot navigation as many potential landmarks such as
nameplates and information signs contain text. In this paper, a novel two-step
text localization method for Indoor Mobile Robot Navigation is introduced. This
method is based on morphological operators and machine learning techniques and
can be used in real time environments. The proposed method has two steps. At
First, a new set of morphological operators is applied with a particular
sequence to extract high contrast areas that have high probability of text
existence. Using of morphological operators has many advantages such as: high
computation speed, being invariant to several geometrical transformations like
translation, rotations, and scaling, and being able to extract all areas
containing text. After extracting text candidate regions, a set of nine
features are extracted for accurate detection and deletion of the regions that
don't have text. These features are descriptors for texture properties and are
computed in real time. Then, we use a SVM classifier to detect the existence of
text in the region. Performance of the proposed algorithm is compared against a
number of widely used text localization algorithms and the results show that
this method can quickly and effectively localize and extract text regions from
real scenes and can be used in mobile robot navigation under an indoor
environment to detect text based landmarks.
| arxiv topic:cs.RO eess.IV |
arxiv_dataset-89461709.09734 | From standard monomial theory to semi-toric degenerations via
Newton-Okounkov bodies
math.AG math.CO math.RA
The Hodge algebra structures on the homogeneous coordinate rings of Grassmann
varieties provide semi-toric degenerations of these varieties. In this paper we
construct these semi-toric degenerations using quasi-valuations and
triangulations of Newton-Okounkov bodies.
| arxiv topic:math.AG math.CO math.RA |
arxiv_dataset-89471709.09834 | The role of surface water in the geometry of Mars' valley networks and
its climatic implications
physics.geo-ph
Mars' surface bears the imprint of valley networks formed billions of years
ago and their relicts can still be observed today. However, whether these
networks were formed by groundwater sapping, ice melt, or fluvial runoff has
been continuously debated. These different scenarios have profoundly different
implications for Mars' climatic history, and thus for its habitability in the
distant past. Recent studies on Earth revealed that channel networks in arid
landscapes with more surface runoff branch at narrower angles, while in humid
environments with more groundwater flow, branching angles are much wider. We
find that valley networks on Mars generally tend to branch at narrow angles
similar to those found in arid landscapes on Earth. This result supports the
inference that Mars once had an active hydrologic cycle and that Mars' valley
networks were formed primarily by overland flow erosion with groundwater
seepage playing only a minor role.
| arxiv topic:physics.geo-ph |
arxiv_dataset-89481709.09934 | Average bounds for the $\ell$-torsion in class groups of cyclic
extensions
math.NT
For all positive integers $\ell$, we prove non-trivial bounds for the
$\ell$-torsion in the class group of $K$, which hold for almost all number
fields $K$ in certain families of cyclic extensions of arbitrarily large
degree. In particular, such bounds hold for almost all cyclic
degree-$p$-extensions of $F$, where $F$ is an arbitrary number field and $p$ is
any prime for which $F$ and the $p$-th cyclotomic field are linearly disjoint.
Along the way, we prove precise asymptotic counting results for the fields of
bounded discriminant in our families with prescribed splitting behavior at
finitely many primes.
| arxiv topic:math.NT |
arxiv_dataset-89491709.10034 | Topological critical slowing down: variations on a toy model
hep-lat cond-mat.stat-mech physics.comp-ph
Numerical simulations of lattice quantum field theories whose continuum
counterparts possess classical solutions with non-trivial topology face a
severe critical slowing down as the continuum limit is approached. Standard
Monte-Carlo algorithms develop a loss of ergodicity, with the system remaining
frozen in configurations with fixed topology. We analyze the problem in a
simple toy model, consisting of the path integral formulation of a quantum
mechanical particle constrained to move on a circumference. More specifically,
we implement for this toy model various techniques which have been proposed to
solve or alleviate the problem for more complex systems, like non-abelian gauge
theories, and compare them both in the regime of low temperature and in that of
very high temperature. Among the various techniques, we consider also a new
algorithm which completely solves the freezing problem, but unfortunately is
specifically tailored for this particular model and not easily exportable to
more complex systems.
| arxiv topic:hep-lat cond-mat.stat-mech physics.comp-ph |
arxiv_dataset-89501709.10134 | Closing in on the large-scale CMB power asymmetry
astro-ph.CO
Measurements of the cosmic microwave background (CMB) temperature
anisotropies have revealed a dipolar asymmetry in power at the largest scales,
in apparent contradiction with the statistical isotropy of standard
cosmological models. The significance of the effect is not very high, and is
dependent on a posteriori choices. Nevertheless, a number of models have been
proposed that produce a scale-dependent asymmetry. We confront several such
models for a physical, position-space modulation with CMB temperature
observations. We find that, while some models that maintain the standard
isotropic power spectrum are allowed, others, such as those with modulated
tensor or uncorrelated isocurvature modes, can be ruled out on the basis of the
overproduction of isotropic power. This remains the case even when an extra
isocurvature mode fully anti-correlated with the adiabatic perturbations is
added to suppress power on large scales.
| arxiv topic:astro-ph.CO |
arxiv_dataset-89511709.10234 | Borcherds-Bozec algebras, root multiplicities and the Schofield
construction
math.RT
Using the twisted denominator identity, we derive a closed form root
multiplicity formula for all symmetrizable Borcherds-Bozec algebras and discuss
its applications including the case of Monster Borcherds-Bozec algebra. In the
second half of the paper, we provide the Schofield constuction of symmetric
Borcherds-Bozec algebras.
| arxiv topic:math.RT |
arxiv_dataset-89521709.10334 | Wildness of the problems of classifying two-dimensional spaces of
commuting linear operators and certain Lie algebras
math.RT
For each two-dimensional vector space $V$ of commuting $n\times n$ matrices
over a field $\mathbb F$ with at least 3 elements, we denote by $\widetilde V$
the vector space of all $(n+1)\times(n+1)$ matrices of the form
$\left[\begin{smallmatrix}A&*\\0&0\end{smallmatrix}\right]$ with $A\in V$. We
prove the wildness of the problem of classifying Lie algebras $\widetilde V$
with the bracket operation $[u,v]:=uv-vu$. We also prove the wildness of the
problem of classifying two-dimensional vector spaces consisting of commuting
linear operators on a vector space over a field.
| arxiv topic:math.RT |
arxiv_dataset-89531709.10434 | Energy-stable linear schemes for polymer-solvent phase field models
math.NA
We present new linear energy-stable numerical schemes for numerical
simulation of complex polymer-solvent mixtures. The mathematical model proposed
by Zhou, Zhang and E (Physical Review E 73, 2006) consists of the Cahn-Hilliard
equation which describes dynamics of the interface that separates polymer and
solvent and the Oldroyd-B equations for the hydrodynamics of polymeric
mixtures. The model is thermodynamically consistent and dissipates free energy.
Our main goal in this paper is to derive numerical schemes for the
polymer-solvent mixture model that are energy dissipative and efficient in
time. To this end we will propose several problem-suited time discretizations
yielding linear schemes and discuss their properties.
| arxiv topic:math.NA |
arxiv_dataset-89541710.00017 | Hierarchical modeling of molecular energies using a deep neural network
stat.ML physics.chem-ph
We introduce the Hierarchically Interacting Particle Neural Network (HIP-NN)
to model molecular properties from datasets of quantum calculations. Inspired
by a many-body expansion, HIP-NN decomposes properties, such as energy, as a
sum over hierarchical terms. These terms are generated from a neural network--a
composition of many nonlinear transformations--acting on a representation of
the molecule. HIP-NN achieves state-of-the-art performance on a dataset of 131k
ground state organic molecules, and predicts energies with 0.26 kcal/mol mean
absolute error. With minimal tuning, our model is also competitive on a dataset
of molecular dynamics trajectories. In addition to enabling accurate energy
predictions, the hierarchical structure of HIP-NN helps to identify regions of
model uncertainty.
| arxiv topic:stat.ML physics.chem-ph |
arxiv_dataset-89551710.00117 | Lepton flavor violating meson decays
hep-ph hep-ex
We argue that lepton flavor violating (LFV) decays $M \to \ell_1
\overline{\ell}_2$ of meson states $M$ with different quantum numbers could be
used to put constraints on the Wilson coefficients of effective operators
describing LFV interactions at low energy scales. We note that the restricted
kinematics of the two-body decay of quarkonium or a heavy quark meson allows us
to select operators with particular quantum numbers, significantly reducing the
reliance on the $single \ operator \ dominance$ assumption that is prevalent in
constraining parameters of the effective LFV Lagrangian. We shall also argue
that studies of radiative lepton flavor violating $M \to \gamma \ell_1
\overline{\ell}_2$ decays could provide important complementary access to those
effective operators.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-89561710.00217 | Towards Inferring Mechanical Lock Combinations using Wrist-Wearables as
a Side-Channel
cs.CR
Wrist-wearables such as smartwatches and fitness bands are equipped with a
variety of high-precision sensors that support novel contextual and
activity-based applications. The presence of a diverse set of on-board sensors,
however, also expose an additional attack surface which, if not adequately
protected, could be potentially exploited to leak private user information. In
this paper, we investigate the feasibility of a new attack that takes advantage
of a wrist-wearable's motion sensors to infer input on mechanical devices
typically used to secure physical access, for example, combination locks. We
outline an inference framework that attempts to infer a lock's unlock
combination from the wrist motion captured by a smartwatch's gyroscope sensor,
and uses a probabilistic model to produce a ranked list of likely unlock
combinations. We conduct a thorough empirical evaluation of the proposed
framework by employing unlocking-related motion data collected from human
subject participants in a variety of controlled and realistic settings.
Evaluation results from these experiments demonstrate that motion data from
wrist-wearables can be effectively employed as a side-channel to significantly
reduce the unlock combination search-space of commonly found combination locks,
thus compromising the physical security provided by these locks.
| arxiv topic:cs.CR |
arxiv_dataset-89571710.00317 | Malaria intensity in Colombia by regions and populations
q-bio.PE
Determining the distribution of disease prevalence among heterogeneous
populations at the national scale is fundamental for epidemiology and public
health. Here, we use a combination of methods (spatial scan statistic,
topological data analysis, epidemic profile) to study measurable differences in
malaria intensity by regions and populations of Colombia. This study explores
three main questions: What are the regions of Colombia where malaria is
epidemic? What are the regions and populations in Colombia where malaria is
endemic? What associations exist between epidemic outbreaks between regions in
Colombia? \textit{Plasmodium falciparum} is most prevalent in the Pacific
Coast, some regions of the Amazon Basin, and some regions of the Magdalena
Basin. \textit{Plasmodium vivax} is the most prevalent parasite in Colombia,
particularly in the Northern Amazon Basin, the Caribbean, and municipalities of
Sucre, Antioquia and Cordoba. Malaria has been reported to be most common among
15-45 year old men. We find that the age-class suffering high risk of malaria
infection ranges from 20 to 30 with an acute peak at 25 years of age. Second,
this pattern was not found to be generalizable across Colombian populations,
Indigenous and Afrocolombian populations experience endemic malaria (with
household transmission). Third, clusters of epidemic malaria for
\textit{Plasmodium vivax} were detected across Southern Colombia including the
Amazon Basin and the Southern Pacific region. \textit{Plasmodium falciparum},
was is epidemic in 13 of the 1,123 municipalities (1.2\%). Some key locations
act as bridges between epidemic and endemic regions. Finally, we generate a
regional classification based on intensity and synchrony, dividing the country
into epidemic areas and bridge areas.
| arxiv topic:q-bio.PE |
arxiv_dataset-89581710.00417 | Second-order invariant domain preserving approximation of the Euler
equations using convex limiting
math.NA
A new second-order method for approximating the compressible Euler equations
is introduced. The method preserves all the known invariant domains of the
Euler system: positivity of the density, positivity of the internal energy and
the local minimum principle on the specific entropy. The technique combines a
first-order, invariant domain preserving, Guaranteed Maximum Speed method using
a Graph Viscosity (GMS-GV1) with an invariant domain violating, but entropy
consistent, high-order method. Invariant domain preserving auxiliary states,
naturally produced by the GMS-GV1 method, are used to define local bounds for
the high-order method which is then made invariant domain preserving via a
convex limiting process. Numerical tests confirm the second-order accuracy of
the new GMS-GV2 method in the maximum norm, where 2 stands for second-order.
The proposed convex limiting is generic and can be applied to other
approximation techniques and other hyperbolic systems.
| arxiv topic:math.NA |
arxiv_dataset-89591710.00517 | Temporal shape super-resolution by intra-frame motion encoding using
high-fps structured light
cs.CV
One of the solutions of depth imaging of moving scene is to project a static
pattern on the object and use just a single image for reconstruction. However,
if the motion of the object is too fast with respect to the exposure time of
the image sensor, patterns on the captured image are blurred and reconstruction
fails. In this paper, we impose multiple projection patterns into each single
captured image to realize temporal super resolution of the depth image
sequences. With our method, multiple patterns are projected onto the object
with higher fps than possible with a camera. In this case, the observed pattern
varies depending on the depth and motion of the object, so we can extract
temporal information of the scene from each single image. The decoding process
is realized using a learning-based approach where no geometric calibration is
needed. Experiments confirm the effectiveness of our method where sequential
shapes are reconstructed from a single image. Both quantitative evaluations and
comparisons with recent techniques were also conducted.
| arxiv topic:cs.CV |
arxiv_dataset-89601710.00617 | Distributed Low-Rank Adaptive Algorithms Based on Alternating
Optimization and Applications
cs.IT math.IT
This paper presents a novel distributed low-rank scheme and adaptive
algorithms for distributed estimation over wireless networks. The proposed
distributed scheme is based on a transformation that performs dimensionality
reduction at each agent of the network followed by transmission of a reduced
set of parameters to other agents and reduced-dimension parameter estimation.
Distributed low-rank joint iterative estimation algorithms based on alternating
optimization strategies are developed, which can achieve significantly reduced
communication overhead and improved performance when compared with existing
techniques. A computational complexity analysis of the proposed and existing
low-rank algorithms is presented along with an analysis of the convergence of
the proposed techniques. Simulations illustrate the performance of the proposed
strategies in applications of wireless sensor networks and smart grids.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-89611710.00717 | High Controllable and Robust 2D Spin-Orbit Coupling for Quantum Gases
cond-mat.quant-gas physics.atom-ph quant-ph
We report the realization of a robust and highly controllable two-dimensional
(2D) spin-orbit (SO) coupling with topological non-trivial band structure. By
applying a retro-reflected 2D optical lattice, phase tunable Raman couplings
are formed into the anti-symmetric Raman lattice structure, and generate the 2D
SO coupling with precise inversion and $C_4$ symmetries, leading to
considerably enlarged topological regions. The life time of the 2D SO coupled
Bose-Einstein condensate reaches several seconds, which enables the exploring
of fine tuning interaction effects. These essential advantages of the present
new realization open the door to explore exotic quantum many-body effects and
non-equilibrium dynamics with novel topology.
| arxiv topic:cond-mat.quant-gas physics.atom-ph quant-ph |
arxiv_dataset-89621710.00817 | Overload Control in SIP Networks: A Heuristic Approach Based on
Mathematical Optimization
cs.NI
The Session Initiation Protocol (SIP) is an application-layer control
protocol for creating, modifying and terminating multimedia sessions. An open
issue is the control of overload that occurs when a SIP server lacks sufficient
CPU and memory resources to process all messages. We prove that the problem of
overload control in SIP network with a set of n servers and limited resources
is in the form of NP-hard. This paper proposes a Load-Balanced Call Admission
Controller (LB-CAC), based on a heuristic mathematical model to determine an
optimal resource allocation in such a way that maximizes call admission rates
regarding the limited resources of the SIP servers. LB-CAC determines the
optimal "call admission rates" and "signaling paths" for admitted calls along
optimal allocation of CPU and memory resources of the SIP servers through a new
linear programming model. This happens by acquiring some critical information
of SIP servers. An assessment of the numerical and experimental results
demonstrates the efficiency of the proposed method.
| arxiv topic:cs.NI |
arxiv_dataset-89631710.00917 | On anisotropic Sobolev spaces
math.FA
We investigate two types of characterizations for anisotropic Sobolev and BV
spaces. In particular, we establish anisotropic versions of the
Bourgain-Brezis-Mironescu formula, including the magnetic case both for Sobolev
and BV functions.
| arxiv topic:math.FA |
arxiv_dataset-89641710.01017 | Hopping and emergent dynamics of optical localized states in a trapping
potential
physics.optics
The position and motion of localized states of light in propagative
geometries can be controlled via an adequate parameter modulation. Here, we
show theoretically and experimentally that this process can be accurately
described as the phase locking of oscillators to an external forcing and that
non-reciprocal interactions between light bits can drastically modify this
picture. Interactions lead to the convective motion of defects and to unlocking
as a collective emerging phenomenon.
| arxiv topic:physics.optics |
arxiv_dataset-89651710.01117 | A control mechanism for intramural periarterial drainage via astrocytes:
How neuronal activity could improve waste clearance from the brain
q-bio.TO cs.CE q-bio.NC
The mechanisms behind waste clearance from deep within the parenchyma of the
brain remain unclear to this date. Experimental evidence has shown that one
pathway for waste clearance, termed intramural periarterial drainage (IPAD), is
the rapid drainage of interstitial fluid (ISF) via basement membranes (BM) of
the smooth muscle cells (SMC) of cerebral arteries and its failure is closely
associated with the pathology of Alzheimer's disease (AD). We have previously
shown that arterial pulsations from the heart beat are not strong enough to
drive waste clearance. Here we demonstrate computational evidence for a
mechanism for cerebral waste clearance that is driven by functional hyperaemia,
that is, the dilation of cerebral arteries as a consequence of increased
neuronal demand. This mechanism is based on our model for fluid flow through
the vascular basement membrane. It accounts for waste clearance rates observed
in mouse experiments and aligns with pathological observations as well as
recommendations to lower the individual risk of AD, such as keeping mentally
and physically active.
| arxiv topic:q-bio.TO cs.CE q-bio.NC |
arxiv_dataset-89661710.01217 | Wide and deep volumetric residual networks for volumetric image
classification
cs.CV
3D shape models that directly classify objects from 3D information have
become more widely implementable. Current state of the art models rely on deep
convolutional and inception models that are resource intensive. Residual neural
networks have been demonstrated to be easier to optimize and do not suffer from
vanishing/exploding gradients observed in deep networks. Here we implement a
residual neural network for 3D object classification of the 3D Princeton
ModelNet dataset. Further, we show that widening network layers dramatically
improves accuracy in shallow residual nets, and residual neural networks
perform comparable to state-of-the-art 3D shape net models, and we show that
widening network layers improves classification accuracy. We provide extensive
training and architecture parameters providing a better understanding of
available network architectures for use in 3D object classification.
| arxiv topic:cs.CV |
arxiv_dataset-89671710.01317 | A unified model for age-velocity dispersion relations in Local Group
galaxies: Disentangling ISM turbulence and latent dynamical heating
astro-ph.GA
We analyze age-velocity dispersion relations (AVRs) from kinematics of
individual stars in eight Local Group galaxies ranging in mass from Carina
($M_{*} \sim 10^{6}$) to M31 ($M_{*} \sim 10^{11}$). Observationally the
$\sigma$ vs. stellar age trends can be interpreted as dynamical heating of the
stars by GMCs, bars/spiral arms, or merging subhalos; alternatively the stars
could have simply been born out of a more turbulent ISM at high redshift and
retain that larger velocity dispersion till present day - consistent with
recent IFU studies. To ascertain the dominant mechanism and better understand
the impact of instabilities and feedback, we develop models based on observed
SFHs of these Local Group galaxies in order to create an evolutionary formalism
which describes the ISM velocity dispersion due to a galaxy's evolving gas
fraction. These empirical models relax the common assumption that the stars are
born from gas which has constant velocity dispersion at all redshifts. Using
only the observed SFHs as input, the ISM velocity dispersion and a mid-plane
scattering model fits the observed AVRs of low mass galaxies without fine
tuning. Higher mass galaxies above $M_{vir} > 10^{11}$ need a larger
contribution from latent dynamical heating processes (for example minor
mergers), in excess of the ISM model. Using the SFHs we also find that
supernovae feedback does not appear to be a dominant driver of the gas velocity
dispersion compared to gravitational instabilities - at least for dispersions
$\sigma \gtrsim 25$ km/s. Together our results point to stars being born with a
velocity dispersion close to that of the gas at the time of their formation,
with latent dynamical heating operating with a galaxy mass-dependent
efficiency. These semi-empirical relations may help constrain the efficiency of
feedback and its impact on the physics of disk settling in galaxy formation
simulations.
| arxiv topic:astro-ph.GA |
arxiv_dataset-89681710.01417 | Robot-Initiated Specification Repair through Grounded Language
Interaction
cs.RO
Robots are required to execute increasingly complex instructions in dynamic
environments, which can lead to a disconnect between the user's intent and the
robot's representation of the instructions. In this paper we present a natural
language instruction grounding framework which uses formal synthesis to enable
the robot to identify necessary environment assumptions for the task to be
successful. These assumptions are then expressed via natural language questions
referencing objects in the environment. The user is prompted to confirm or
reject the assumption. We demonstrate our approach on two tabletop
pick-and-place tasks.
| arxiv topic:cs.RO |
arxiv_dataset-89691710.01517 | Computing $S$-unit groups of orders
math.NT
Based on the general strategy described by Borel and Serre and the Voronoi
algorithm for computing unit groups of orders we present an algorithm for
finding presentations of $S$-unit groups of orders. The algorithm is then used
for some investigations concerning the congruence subgroup property.
| arxiv topic:math.NT |
arxiv_dataset-89701710.01617 | From Kondo to local singlet state in graphene nanoribbons with magnetic
impurities
cond-mat.str-el
A detailed analysis of the Kondo effect of a magnetic impurity in a zigzag
graphene nanoribbon is addressed. An adatom is coupled to the graphene
nanoribbon via a hybridization amplitude $\Gamma_{imp}$ in a hollow or top site
configuration. In addition, the adatom is also weakly coupled to a metallic STM
tip by a hybridization function $\Gamma_{tip}$ that provides a Kondo screening
of its magnetic moment. The entire system is described by an Anderson-like
Hamiltonian whose low-temperature physics is accessed by employing the
numerical renormalization group approach, which allows us to obtain the
thermodynamic properties used to compute the Kondo temperature of the system.
We find two screening regimes when the adatom is close to the edge of the
zigazag graphene nanoribbon: (1) a weak coupling regime ($\Gamma_{imp}\ll
\Gamma_{tip}$), in which the edge states produce an enhancement of the Kondo
temperature $T_K$ and (2) a strong coupling regime ($\Gamma_{imp}\gg
\Gamma_{tip}$), in which a local singlet is formed, in detriment to the Kondo
screening by the STM tip. These two regimes can be clearly distinguished by the
dependence of their characteristic temperature $T^*$ on the coupling between
the adatom and the carbon sites of the graphene nanoribon ($V_{imp}$). We
observe that in the weak coupling regime $T^*$ increases exponentially with
$V_{imp}^2$. Differently, in the strong coupling regime, $T^*$ increases
linearly with $V_{imp}^2$.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-89711710.01717 | A New Correlator to Detect and Characterize the Chiral Magnetic Effect
physics.data-an nucl-ex nucl-th
A charge-sensitive in-event correlator is proposed and tested for its
efficacy to detect and characterize charge separation associated with the
Chiral Magnetic Effect (CME) in heavy ion collisions. Tests, performed with the
aid of two reaction models, indicate discernible responses for background- and
CME-driven charge separation, relative to the second- ($\Psi_{2}$) and
third-order ($\Psi_{3}$) event planes, which could serve to identify the CME.
The tests also indicate a degree of sensitivity which would enable robust
characterization of the CME via Anomalous Viscous Fluid Dynamics (AVFD) model
comparisons.
| arxiv topic:physics.data-an nucl-ex nucl-th |
arxiv_dataset-89721710.01817 | On the geometric fixed points of real topological Hochschild homology
math.AT
We compute the component group of the derived $G$-geometric fixed points of
the real topological Hochschild homology of a ring with anti-involution, where
$G$ denotes the Galois group Gal($\mathbb{C}$/$\mathbb{R}$) of order 2.
| arxiv topic:math.AT |
arxiv_dataset-89731710.01917 | On Highly-regular graphs
math.CO
Highly-regular graphs can be regarded as a combinatorial generalization of
distance-regular graphs. From this standpoint, we study combinatorial aspects
of highly-regular graphs. As a result, we give the following three main results
in this paper. Firstly, we give a characterization of a distance-regular graph
by using the index and diameter of a highly-regular graph. Secondly, we give
two constructions of highly-regular graphs. Finally, we generalize well-known
properties of the intersection numbers of a distance-regular graph.
| arxiv topic:math.CO |
arxiv_dataset-89741710.02017 | The programme "accurate masses for SB2 components"
astro-ph.SR
Accurate stellar masses are requested in order to improve our understanding
of stellar interiors, but they are still rather rare. Fortunately, the
forthcoming Gaia Mission will provide astrometric measurements permitting the
derivation of the orbital inclinations of nearby binaries which are also
observed as double-lined spectroscopic binaries (SB2s) with ground-based
telescopes. A programme of radial velocity (RV) measurements was initiated in
2010 with the Sophie spectrograph of the Haute-Provence observatory in order to
derive accurate SB2 orbits for a large set of stars. Therefore, combined
SB2+astrometric orbits will be derived thanks to Gaia, and masses with errors
around 1~\% are expected for both components. The programme includes 70 SB2s,
and the accurate SB2 orbits of 24 of them were already derived. In addition,
two complementary programmes devoted to southern stars or to late-type dwarf
stars were also initiated with the HERMES and the CARMENES spectrographs,
respectively. Interferometric measurements were obained with the VLTI/PIONIER
for 7 SB2s, and were taken from other sources for 4 others. Currently, combined
"visual binary" (VB) +SB2 solutions were derived for 7 binaries, leading to the
masses of the components and to the parallaxes. The parallaxes from the
Hipparcos 2 catalogue were corrected for orbital motion and compared to our
solution, confirming the high quality of Hipparcos 2.
| arxiv topic:astro-ph.SR |
arxiv_dataset-89751710.02117 | An Erd\H{o}s-Kac theorem for Smooth and Ultra-Smooth integers
math.NT
We prove an Erd\H{o}s-Kac type of theorem for the set $S(x,y)=\{n\leq x: p|n
\Rightarrow p\leq y \}$. If $\omega (n)$ is the number of prime factors of $n$,
we prove that the distribution of $\omega(n)$ for $n \in S(x,y)$ is Gaussian
for a certain range of $y$ using method of moments. The advantage of the
present approach is that it recovers classical results for the range $u=o(\log
\log x )$ where $u=\frac{\log x}{\log y}$, with a much simpler proof.
| arxiv topic:math.NT |
arxiv_dataset-89761710.02217 | Search for new resonances decaying into boosted W, Z and H bosons at CMS
hep-ex
An overview of the searches for new heavy resonances decaying to standard
model (SM) bosons at the TeV mass scale is presented. Results are based on data
corresponding to an integrated luminosity up to about $36\; \mathrm{fb}^{-1}$
recorded in proton-proton collisions at $\sqrt{s}=13$ TeV with the CMS detector
at the Large Hadron Collider at CERN. The bosons coming from the resonance
decay can be W, Z, or the SM Higgs. For very heavy resonances, bosons are
produced with momentum considerably higher than their mass, modifying in a very
appreciable way the event topology. The quarks originated from the hadronic
decay of the SM bosons will be collimated into a smaller area such that they
are clustered within a single large cone jet. Dedicated reconstruction
techniques are used to distinguish the merged decay products of W, Z and H
bosons produced with high transverse momentum, from jets that originate from
single partons.
| arxiv topic:hep-ex |
arxiv_dataset-89771710.02317 | Enumeration Problems for Regular Path Queries
cs.DB cs.FL
Evaluation of regular path queries (RPQs) is a central problem in graph
databases. We investigate the corresponding enumeration problem, that is, given
a graph and an RPQ, enumerate all paths in the graph that match the RPQ. We
consider several versions of this problem, corresponding to different semantics
of RPQs that have recently been considered: arbitrary paths, shortest paths,
simple paths, and trails. Whereas arbitrary and shortest paths can be
enumerated in polynomial delay, the situation is much more intricate for simple
paths and trails. For instance, already the question if a given graph contains
a simple path or trail of a certain length has cases with highly non-trivial
solutions and cases that are long-standing open problems. In this setting, we
study RPQ evaluation from a parameterized complexity perspective. We define a
class of simple transitive expressions that is prominent in practice and for
which we can prove two dichotomy-like results: one for simple paths and one for
trails paths. We observe that, even though simple path semantics and trail
semantics are intractable for RPQs in general, they are feasible for the vast
majority of the kinds of RPQs that users use in practice. At the heart of this
study is a result of independent interest on the parameterized complexity of
finding disjoint paths in graphs: the two disjoint paths problem is W[1]-hard
if parameterized by the length of one of the two paths.
| arxiv topic:cs.DB cs.FL |
arxiv_dataset-89781710.02417 | Holographic dark energy: constraints on the interaction from diverse
observational data sets
astro-ph.CO
The present work deals with holographic dark energy models with Hubble
horizon as the infra-red cut-off. The interaction rate between dark energy and
dark matter has been reconstructed with three different choices of the
interaction term. It is shown that the coupling parameter of the interaction
term should evolve with redshift to allow the successful transition from
decelerated to accelerated phase of expansion. Constraints on the model
parameters are obtained from Markov Chain Monte Carlo (MCMC) analysis using the
supernova distance modulus data and observational measurements of the Hubble
parameter. Results show that the model with the coupling parameter increasing
with redshift (z) or equivalently decreasing with the evolution, are ruled out.
On the other hand, coupling parameters, increasing or slowly varying with the
evolution, are consistent with the observed evolution scenario. A Bayesian
evidence calculation has been carried out for statistical selection of the
reconstructed models. Though the kinematical parameters are well behaved for
these models, the physical variables which determine the nature of the
components in the matter sector, are not at all realistic. We have concluded
that the existence of spatial curvature is essential for this particular type
of dark energy models.
| arxiv topic:astro-ph.CO |
arxiv_dataset-89791710.02517 | Dark Energy Survey Year 1 Results: Cross-Correlation Redshifts in the
DES -- Calibration of the Weak Lensing Source Redshift Distributions
astro-ph.CO
We present the calibration of the Dark Energy Survey Year 1 (DES Y1) weak
lensing source galaxy redshift distributions from clustering measurements. By
cross-correlating the positions of source galaxies with luminous red galaxies
selected by the redMaGiC algorithm we measure the redshift distributions of the
source galaxies as placed into different tomographic bins. These measurements
constrain any such shifts to an accuracy of $\sim0.02$ and can be computed even
when the clustering measurements do not span the full redshift range. The
highest-redshift source bin is not constrained by the clustering measurements
because of the minimal redshift overlap with the redMaGiC galaxies. We compare
our constraints with those obtained from $\texttt{COSMOS}$ 30-band photometry
and find that our two very different methods produce consistent constraints.
| arxiv topic:astro-ph.CO |
arxiv_dataset-89801710.02617 | Thermodynamic Limits of Energy Harvesting from Outgoing Thermal
Radiation
physics.optics physics.app-ph
We derive the thermodynamic limits of harvesting power from the outgoing
thermal radiation from the ambient to the cold outer space. The derivations are
based on a duality relation between thermal engines that harvest solar
radiation and those that harvest outgoing thermal radiation. In particular, we
derive the ultimate limit for harvesting outgoing thermal radiation, which is
analogous to the Landersberg limit for solar energy harvesting, and show that
the ultimate limit far exceeds what was previously thought to be possible. As
an extension of our work, we also derive the ultimate limit of efficiency of
thermophotovoltatic systems.
| arxiv topic:physics.optics physics.app-ph |
arxiv_dataset-89811710.02717 | Group Sparse CNNs for Question Classification with Answer Sets
cs.CL
Question classification is an important task with wide applications. However,
traditional techniques treat questions as general sentences, ignoring the
corresponding answer data. In order to consider answer information into
question modeling, we first introduce novel group sparse autoencoders which
refine question representation by utilizing group information in the answer
set. We then propose novel group sparse CNNs which naturally learn question
representation with respect to their answers by implanting group sparse
autoencoders into traditional CNNs. The proposed model significantly outperform
strong baselines on four datasets.
| arxiv topic:cs.CL |
arxiv_dataset-89821710.02817 | Discovery of Paradigm Dependencies
cs.DB
Missing and incorrect values often cause serious consequences. To deal with
these data quality problems, a class of common employed tools are dependency
rules, such as Functional Dependencies (FDs), Conditional Functional
Dependencies (CFDs) and Edition Rules (ERs), etc. The stronger expressing
ability a dependency has, data with the better quality can be obtained. To the
best of our knowledge, all previous dependencies treat each attribute value as
a non-splittable whole. Actually however, in many applications, part of a value
may contains meaningful information, indicating that more powerful dependency
rules to handle data quality problems are possible. In this paper, we consider
of discovering such type of dependencies in which the left hand side is part of
a regular-expression-like paradigm, named Paradigm Dependencies (PDs). PDs tell
that if a string matches the paradigm, element at the specified position can
decides a certain other attribute's value. We propose a framework in which
strings with similar coding rules and different lengths are clustered together
and aligned vertically, from which PDs can be discovered directly. The aligning
problem is the key component of this framework and is proved in NP-Complete. A
greedy algorithm is introduced in which the clustering and aligning tasks can
be accomplished simultaneously. Because of the greedy algorithm's high time
complexity, several pruning strategies are proposed to reduce the running time.
In the experimental study, three real datasets as well as several synthetical
datasets are employed to verify our methods' effectiveness and efficiency.
| arxiv topic:cs.DB |
arxiv_dataset-89831710.02917 | The SED Machine: a robotic spectrograph for fast transient
classification
astro-ph.IM
Current time domain facilities are finding several hundreds of transient
astronomical events a year. The discovery rate is expected to increase in the
future as soon as new surveys such as the Zwicky Transient Facility (ZTF) and
the Large Synoptic Sky Survey (LSST) come on line. At the present time, the
rate at which transients are classified is approximately one order or magnitude
lower than the discovery rate, leading to an increasing "follow-up drought".
Existing telescopes with moderate aperture can help address this deficit when
equipped with spectrographs optimized for spectral classification. Here, we
provide an overview of the design, operations and first results of the Spectral
Energy Distribution Machine (SEDM), operating on the Palomar 60-inch telescope
(P60). The instrument is optimized for classification and high observing
efficiency. It combines a low-resolution (R$\sim$100) integral field unit (IFU)
spectrograph with "Rainbow Camera" (RC), a multi-band field acquisition camera
which also serves as multi-band (ugri) photometer. The SEDM was commissioned
during the operation of the intermediate Palomar Transient Factory (iPTF) and
has already proved lived up to its promise. The success of the SEDM
demonstrates the value of spectrographs optimized to spectral classification.
Introduction of similar spectrographs on existing telescopes will help
alleviate the follow-up drought and thereby accelerate the rate of discoveries.
| arxiv topic:astro-ph.IM |
arxiv_dataset-89841710.03017 | Towards a Secure Smart Grid Storage Communications Gateway
cs.CR
This research in progress paper describes the role of cyber security measures
undertaken in an ICT system for integrating electric storage technologies into
the grid. To do so, it defines security requirements for a communications
gateway and gives detailed information and hands-on configuration advice on
node and communication line security, data storage, coping with backend M2M
communications protocols and examines privacy issues. The presented research
paves the road for developing secure smart energy communications devices that
allow enhancing energy efficiency. The described measures are implemented in an
actual gateway device within the HORIZON 2020 project STORY, which aims at
developing new ways to use storage and demonstrating these on six different
demonstration sites.
| arxiv topic:cs.CR |
arxiv_dataset-89851710.03117 | On classes of graphs with strongly sublinear separators
math.CO cs.DM
For real numbers c,epsilon>0, let G_{c,epsilon} denote the class of graphs G
such that each subgraph H of G has a balanced separator of order at most
c|V(H)|^{1-epsilon}. A class of graphs has strongly sublinear separators if it
is a subclass of G_{c,epsilon} for some c,epsilon>0. We investigate properties
of such graph classes, leading in particular to an approximate algorithm to
determine membership in G_{c,epsilon}: there exist c'>0 such that for each
input graph G, this algorithm in polynomial time determines either that G
belongs to G_{c',epsilon^2/160}, or that G does not belong to G_{c,epsilon}.
| arxiv topic:math.CO cs.DM |
arxiv_dataset-89861710.03217 | W-algebras associated to surfaces
math.AG math.QA
We define an integral form of the deformed W-algebra of type gl_r, and
construct its action on the K-theory groups of moduli spaces of rank r stable
sheaves on a smooth projective surface S, under certain assumptions. Our
construction generalizes the action studied by Nakajima, Grojnowski and
Baranovsky in cohomology, although the appearance of deformed W-algebras by
generators and relations is a new feature. Physically, this action encodes the
AGT correspondence for 5d supersymmetric gauge theory on S x circle.
| arxiv topic:math.AG math.QA |
arxiv_dataset-89871710.03317 | Protecting sensitive research data and meeting researchers needs: Duke
University's Protected Network
cs.CR
Research use of sensitive information -- personally identifiable information
(PII), protected health information (PHI), commercial or proprietary data, and
the like -- is increasing as researchers' skill with "big data" matures. Duke
University's Protected Network is an environment with technical controls in
place that provide research groups with essential pieces of security measures
needed for studies using sensitive information. The environment uses
virtualization and authorization groups extensively to isolate data, provide
elasticity of resources, and flexibly meet a range of computational
requirements within tightly controlled network boundaries. Since its beginning
in 2011, the environment has supported about 200 research projects and groups
and has served as a foundation for specialized and protected IT infrastructures
in the social sciences, population studies, and medical research. This article
lays out key features of the development of the Protected Network and outlines
the IT infrastructure design and organizational features that Duke has used in
establishing this resource for researchers. It consists of four sections: 1.
Context, 2. Infrastructure, 3. Authentication and identity management, and 4.
The infrastructure as a "platform."
| arxiv topic:cs.CR |
arxiv_dataset-89881710.03417 | Measurements of vector meson photoproduction with ALICE in
ultra-peripheral Pb-Pb collisions at $\bf{\sqrt{s_{\rm NN}} = 5.02}$ TeV
hep-ex nucl-ex
The intense photon fluxes of relativistic nuclei provide a possibility to
study photonuclear and two-photon interactions in ultra-peripheral collisions
(UPC) where the nuclei do not overlap and no strong nuclear interactions occur.
The study of such collisions provides information about the initial state of
nuclei. First ALICE results from the LHC Run 2 are presented for forward
exclusive \jpsi production in UPC, which is sensitive to the gluon distribution
in nuclei. The increased statistics and the higher collision energy allows for
a more detailed study at lower values of Bjorken-$x$. The analysis of the
$\gamma+A \rightarrow \rho^0+A$ process in UPC is a tool to test the so-called
black disk regime, where the target nucleus appears like a black disk and the
total $\rho^0+A$ cross section reaches its limit. ALICE reports new
measurements of \rrho photoproduction cross sections in Pb-Pb UPC at
$\sqrt{s_{\rm NN}}=5.02$ TeV at mid-rapidity, which are compared to
predictions.
| arxiv topic:hep-ex nucl-ex |
arxiv_dataset-89891710.03517 | A remark on the Farrell-Jones conjecture
math.KT math.AG math.AT
Assuming the classical Farrell-Jones conjecture we produce an explicit
(commutative) group ring $R$ and a thick subcategory $\mathsf{C}$ of perfect
$R$-complexes such that the Waldhausen $K$-theory space
$\mathrm{K}(\mathsf{C})$ is equivalent to a rational Eilenberg-Maclane space.
| arxiv topic:math.KT math.AG math.AT |
arxiv_dataset-89901710.03617 | Compactly-Supported Smooth Interpolators for Shape Modeling with Varying
Resolution
math.FA
In applications that involve interactive curve and surface modeling, the
intuitive manipulation of shapes is crucial. For instance, user interaction is
facilitated if a geometrical object can be manipulated through control points
that interpolate the shape itself. Additionally, models for shape
representation often need to provide local shape control and they need to be
able to reproduce common shape primitives such as ellipsoids, spheres,
cylinders, or tori. We present a general framework to construct families of
compactly-supported interpolators that are piecewise-exponential polynomial.
They can be designed to satisfy regularity constraints of any order and they
enable one to build parametric deformable shape models by suitable linear
combinations of interpolators. They allow to change the resolution of shapes
based on the refinability of B-splines. We illustrate their use on examples to
construct shape models that involve curves and surfaces with applications to
interactive modeling and character design.
| arxiv topic:math.FA |
arxiv_dataset-89911710.03717 | The three-dimensional electronic structure of the nematic and
antiferromagnetic phases of NaFeAs from detwinned ARPES measurements
cond-mat.supr-con cond-mat.str-el
We report a comprehensive ARPES study of NaFeAs, a prototypical parent
compound of the Fe-based superconductors. By mechanically detwinning the
samples, we show that in the nematic phase (below the structural transition at
$T_s$ = 54 K but above the antiferromagnetic transition at $T_N$ = 43 K)
spectral weight is detected on only the elliptical electron pocket along the
longer $a_{orth}$ axis. This dramatic anisotropy is likely to arise as a result
of coupling to a fluctuating antiferromagnetic order in the nematic phase. In
the long-range ordered antiferromagnetic state below $T_N$, this single
electron pocket is backfolded and hybridises with the hole bands, leading to
the reconstructed Fermi surface. By careful analysis of the $k_z$ variation, we
show that the backfolding of spectral weight in the magnetic phase has a
wavector of ($\pi$,0,$\pi$), with the $c$-axis component being in agreement
with the magnetic ordering in NaFeAs observed by neutron scattering. Our
results clarify the origin of the tiny Fermi surfaces of NaFeAs at low
temperatures and highlight the importance of the three-dimensional aspects of
the electronic and magnetic properties of Fe-based superconductors.
| arxiv topic:cond-mat.supr-con cond-mat.str-el |
arxiv_dataset-89921710.03817 | A shock wave instability induced on a periodically disturbed interface
physics.flu-dyn
The shock wave instability induced when interacting with a small waviness on
an interface was investigated analytically and numerically. The perturbation to
the shock was phenomenologically treated assuming this as the consequence of
the shock refraction. The instability develops in the form of wave-like
stretchings into the lower density medium followed with the loss of stability
in the flow behind it, and eventually evolving into an intense vortex
structure. The instability mode is aperiodical and unconditional, and either a
transition to another stable state or continuous development as a secondary
flow is possible. Among other interesting features are: a similarity law in the
spatial and temporal evolution of the perturbations with respect to the
interface curvature; the instability locus independence of the gas density
distribution thus identifying the interface conditions as the sole triggering
factor; the role of the density gradient in the instability evolution
discriminating between qualitatively different outcomes; and the possibility of
decay via non-viscous dumping mechanisms. The phenomenological connection
between the shock and the interface stability is discussed.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-89931710.03917 | Temperature-Dependent Electron-Electron Interaction in Graphene on
SrTiO3
cond-mat.mtrl-sci
The electron band structure of graphene on SrTiO3 substrate has been
investigated as a function of temperature. The high-resolution angle-resolved
photoemission study reveals that the spectral width at Fermi energy and the
Fermi velocity of graphene on SrTiO3 are comparable to those of graphene on a
BN substrate. Near the charge neutrality, the energy-momentum dispersion of
graphene exhibits a strong deviation from the well-known linearity, which is
magnified as temperature decreases. Such modification resembles the
characteristics of enhanced electron-electron interaction. Our results not only
suggest that SrTiO3 can be a plausible candidate as a substrate material for
applications in graphene-based electronics, but also provide a possible route
towards the realization of a new type of strongly correlated electron phases in
the prototypical two-dimensional system via the manipulation of temperature and
a proper choice of dielectric substrates.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-89941710.04017 | $\rho$-white noise solution to 2D stochastic Euler equations
math.PR
A stochastic version of 2D Euler equations with transport type noise in the
vorticity is considered, in the framework of Albeverio--Cruzeiro theory [1]
where the equation is considered with random initial conditions related to the
so called enstrophy measure. The equation is studied by an approximation scheme
based on random point vortices. Stochastic processes solving the Euler
equations are constructed and their density with respect to the enstrophy
measure is proved to satisfy a continuity equation in weak form. Relevant in
comparison with the case without noise is the fact that here we prove a
gradient type estimate for the density. Although we cannot prove uniqueness for
the continuity equation, we discuss how the gradient type estimate may be
related to this open problem.
| arxiv topic:math.PR |
arxiv_dataset-89951710.04117 | Analyzing Gender Stereotyping in Bollywood Movies
cs.SI cs.CY
The presence of gender stereotypes in many aspects of society is a well-known
phenomenon. In this paper, we focus on studying such stereotypes and bias in
Hindi movie industry (Bollywood). We analyze movie plots and posters for all
movies released since 1970. The gender bias is detected by semantic modeling of
plots at inter-sentence and intra-sentence level. Different features like
occupation, introduction of cast in text, associated actions and descriptions
are captured to show the pervasiveness of gender bias and stereo- type in
movies. We derive a semantic graph and compute centrality of each character and
observe similar bias there. We also show that such bias is not applicable for
movie posters where females get equal importance even though their character
has little or no impact on the movie plot. Furthermore, we explore the movie
trailers to estimate on-screen time for males and females and also study the
portrayal of emotions by gender in them. The silver lining is that our system
was able to identify 30 movies over last 3 years where such stereotypes were
broken.
| arxiv topic:cs.SI cs.CY |
arxiv_dataset-89961710.04217 | Subsampling large graphs and invariance in networks
math.ST math.PR stat.TH
Specify a randomized algorithm that, given a very large graph or network,
extracts a random subgraph. What can we learn about the input graph from a
single subsample? We derive laws of large numbers for the sampler output, by
relating randomized subsampling to distributional invariance: Assuming an
invariance holds is tantamount to assuming the sample has been generated by a
specific algorithm. That in turn yields a notion of ergodicity. Sampling
algorithms induce model classes---graphon models, sparse generalizations of
exchangeable graphs, and random multigraphs with exchangeable edges can all be
obtained in this manner, and we specialize our results to a number of examples.
One class of sampling algorithms emerges as special: Roughly speaking, those
defined as limits of random transformations drawn uniformly from certain
sequences of groups. Some known pathologies of network models based on graphons
are explained as a form of selection bias.
| arxiv topic:math.ST math.PR stat.TH |
arxiv_dataset-89971710.04317 | Harvested Power Maximization in QoS-Constrained MIMO SWIPT with Generic
RF Harvesting Model
cs.IT math.IT
We consider the problem of maximizing the harvested power in Multiple Input
Multiple Output (MIMO) Simultaneous Wireless Information and Power Transfer
(SWIPT) systems with power splitting reception. Different from recently
proposed designs, we target with our novel problem formulation at the jointly
optimal transmit precoding and receive uniform power splitting (UPS) ratio
maximizing the harvested power, while ensuring that the Quality-of-Service
(QoS) requirement of the MIMO link is satisfied. We assume generic practical
Radio Frequency (RF) Energy Harvesting (EH) receive operation that results in a
non-convex optimization problem for the design parameters, which we then solve
optimally after formulating it in an equivalent generalized convex form. Our
representative results including comparisons of achievable EH gains with
benchmark schemes provide key insights on various system parameters.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-89981710.04417 | Accreting CO material onto ONe white dwarfs towards accretion-induced
collapse
astro-ph.SR
The final outcomes of accreting ONe white dwarfs (ONe WDs) have been studied
for several decades, but there are still some issues not resolved. Recently,
some studies suggested that the deflagration of oxygen would occur for
accreting ONe WDs with Chandrasekhar masses. In this paper, we aim to
investigate whether ONe WDs can experience accretion-induced collapse (AIC) or
explosions when their masses approach the Chandrasekhar limit. Employing the
stellar evolution code modules for experiments in stellar astrophysics (MESA),
we simulate the long-term evolution of ONe WDs by accreting CO material. The
ONe WDs undergo weak multicycle carbon flashes during the mass-accretion
process, leading to the mass increase of the WDs. We found that different
initial WD masses and mass-accretion rates have influence on the evolution of
central density and temperature. However, the central temperature cannot reach
the explosive oxygen ignition temperature due to the neutrino cooling. This
work implies that the final outcome of accreting ONe WDs is electron-capture
induced collapse rather than thermonuclear explosion.
| arxiv topic:astro-ph.SR |
arxiv_dataset-89991710.04517 | Supersaturated sparse graphs and hypergraphs
math.CO
A central problem in extremal graph theory is to estimate, for a given graph
$H$, the number of $H$-free graphs on a given set of $n$ vertices. In the case
when $H$ is not bipartite, fairly precise estimates on this number are known.
In particular, thirty years ago, Erd\H{o}s, Frankl, and R\"odl proved that
there are $2^{(1+o(1))\text{ex}(n,H)}$ such graphs. In the bipartite case,
however, nontrivial bounds have been proven only for relatively few special
graphs $H$.
We make a first attempt at addressing this enumeration problem for a general
bipartite graph $H$. We show that an upper bound of $2^{O(\text{ex}(n,H))}$ on
the number of $H$-free graphs with $n$ vertices follows merely from a rather
natural assumption on the growth rate of $n \mapsto \text{ex}(n,H)$; an
analogous statement remains true when $H$ is a uniform hypergraph.
Subsequently, we derive several new results, along with most previously known
estimates, as simple corollaries of our theorem. At the heart of our proof lies
a general supersaturation statement that extends the seminal work of Erd\H{o}s
and Simonovits. The bounds on the number of $H$-free hypergraphs are derived
from it using the method of hypergraph containers.
| arxiv topic:math.CO |
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