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arxiv_dataset-84001704.05488 | Dramatic Impact of Dimensionality on the Electrostatics of PN Junctions
cond-mat.mes-hall
Low dimensional material systems provide a unique set of properties useful
for solid-state devices. The building block of these devices is the PN
junction. In this work, we present a dramatic difference in the electrostatics
of PN junctions in lower dimensional systems, as against the well understood
three dimensional systems. Reducing the dimensionality increases the depletion
width significantly. We propose a novel method to derive analytic equations in
2D and 1D that considers the impact of neutral regions. The analytical results
show an excellent match with both the experimental measurements and numerical
simulations. The square root dependence of the depletion width on the ratio of
dielectric constant and doping in 3D changes to a linear and exponential
dependence for 2D and 1D respectively. This higher sensitivity of 1D PN
junctions to its control parameters can be used towards new sensors.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-84011704.05588 | Learning to Fly by Crashing
cs.RO cs.CV cs.LG
How do you learn to navigate an Unmanned Aerial Vehicle (UAV) and avoid
obstacles? One approach is to use a small dataset collected by human experts:
however, high capacity learning algorithms tend to overfit when trained with
little data. An alternative is to use simulation. But the gap between
simulation and real world remains large especially for perception problems. The
reason most research avoids using large-scale real data is the fear of crashes!
In this paper, we propose to bite the bullet and collect a dataset of crashes
itself! We build a drone whose sole purpose is to crash into objects: it
samples naive trajectories and crashes into random objects. We crash our drone
11,500 times to create one of the biggest UAV crash dataset. This dataset
captures the different ways in which a UAV can crash. We use all this negative
flying data in conjunction with positive data sampled from the same
trajectories to learn a simple yet powerful policy for UAV navigation. We show
that this simple self-supervised model is quite effective in navigating the UAV
even in extremely cluttered environments with dynamic obstacles including
humans. For supplementary video see: https://youtu.be/u151hJaGKUo
| arxiv topic:cs.RO cs.CV cs.LG |
arxiv_dataset-84021704.05688 | Dynamical reduction of the dimensionality of exchange interactions and
the "spin-liquid" phase of $\kappa$-(BEDT-TTF)$_2X$
cond-mat.str-el cond-mat.supr-con
We show that the anisotropy of the effective spin model for the dimer Mott
insulator phase of $\kappa$-(BEDT-TTF)$_2X$ salts is dramatically different
from that of the underlying tight-binding model. Intra-dimer quantum
interference results in a model of coupled spin chains, where frustrated
interchain interactions suppress long-range magnetic order. Thus, we argue, the
"spin liquid" phase observed in some of these materials is a remnant of the
Tomonaga-Luttinger physics of a single chain. This is consistent with previous
experiments and resolves some outstanding puzzles. An erratum [Phys. Rev. Lett.
120, 199901 (2018).] is added as an appendix.
| arxiv topic:cond-mat.str-el cond-mat.supr-con |
arxiv_dataset-84031704.05788 | Tests for CPT sum rule and U-spin violation in Time-dependent CP
violation of $B^0_s \to K^+ K^-$ and $B^0_d \to \pi^+ \pi^-$
hep-ph hep-ex
Recent LHCb data for time-dependent CP violation in $B_d^0 \to \pi^+\pi^-$
and $B^0_s\to K^+K^-$ show deviations from theoretical predictions. Besides
their central values for $\mathcal C_{K^+K^-}$, $\mathcal S_{K^+K^-}$ and
$\mathcal A^{\Delta \Gamma}_{K^+K^-}$ violate quantum mechanic CPT invariant
sum rule (CPT sum rule) prediction of $|\mathcal C_{K^+K^-}|^2 + |\mathcal
S_{K^+K^-}| ^2 + |\mathcal A^{\Delta \Gamma}_{K^+K^-}|^2 = 1$ (LHCb data imply
the sum to be $0.67\pm 0.20$.), their values for $\mathcal C_{K^+ K^-}= 0.24\pm
0.06\pm {0.02}$ and $\mathcal C_{\pi^+ \pi^-} = - 0.24\pm 0.07\pm 0.01$ also
show large violation of SU(3) or its U-spin sub-group symmetry (SU(3)/U)
relation $\mathcal C_{K^+ K^-} /\mathcal C_{\pi^- \pi^+} = - \mathcal B(B_d^0
\to \pi^- \pi^+)\tau_{B^0_s}/\mathcal B(B^0_s \to K^+ K^-)\tau_{B_d^0}$ (LHCb
data imply the ratio of left-side to right-side to be $4.67\pm 1.88$.) . The
LHCb results need to be further confirmed to be taken seriously. We suggest to
use time-dependent CP violation in $B_s\to K^0\bar K^0, \pi^+\pi^-, \pi^0\pi^0$
to further test the CPT sum rule. Assuming that the sum rule holds, we propose
that violation of the SU(3)/U relation may indicate a large FSI phase
difference in the $\pi^+\pi^-$ and $K^+K^-$ re-scattering. We suggest several
other U-spin pairs of $B\to PP$ decays to further test SU(3)/U relations.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-84041704.05888 | Backreacting D-brane instantons on branes at singularities
hep-th
Non-perturbative D-brane instanton effects in 4d N = 1 string
compactifications can be geometrized in terms of a backreacted generalized
geometry. We extend earlier results to setups in which the D-brane instanton is
charged under the 4d gauge symmetries, and show that the backreacted topology
yields the correct charged field theory operators in the 4d effective action.
In type IIA models with D6-branes, the backreaction of D2-brane instantons
forces the recombination of D6-branes, such that the 4d charged field theory
operators arise from basic worldsheet instantons in the backreacted geometry.
We provide large classes of examples of D2-brane instanton effects on
intersecting D6-brane systems in local models mirror to D3-branes at
singularities. The backreacted geometry and the field theory operators are
easily encoded in terms of simple operation in the graphs arising from the
underlying dimer diagrams. This description agrees, in the appropriate cases,
with the complex deformations triggered by certain fractional branes at the
bottom of duality cascades.
| arxiv topic:hep-th |
arxiv_dataset-84051704.05988 | Photometric Redshifts for Hyper Suprime-Cam Subaru Strategic Program
Data Release 1
astro-ph.GA
Photometric redshifts are a key component of many science objectives in the
Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). In this paper, we
describe and compare the codes used to compute photometric redshifts for
HSC-SSP, how we calibrate them, and the typical accuracy we achieve with the
HSC five-band photometry (grizy). We introduce a new point estimator based on
an improved loss function and demonstrate that it works better than other
commonly used estimators. We find that our photo-z's are most accurate at
0.2<~zphot<~1.5, where we can straddle the 4000A break. We achieve
sigma(d_zphot/(1+zphot))~0.05 and an outlier rate of about 15% for galaxies
down to i=25 within this redshift range. If we limit to a brighter sample of
i<24, we achieve sigma~0.04 and ~8% outliers. Our photo-z's should thus enable
many science cases for HSC-SSP. We also characterize the accuracy of our
redshift probability distribution function (PDF) and discover that some codes
over/under-estimate the redshift uncertainties, which have implications for
N(z) reconstruction. Our photo-z products for the entire area in the Public
Data Release 1 are publicly available, and both our catalog products (such as
point estimates) and full PDFs can be retrieved from the data release site,
https://hsc-release.mtk.nao.ac.jp/.
| arxiv topic:astro-ph.GA |
arxiv_dataset-84061704.06088 | A dark asteroid family in the Phocaea region
astro-ph.EP
We report the discovery of a new asteroid family among the dark asteroids
residing in the Phocaea region the Tamara family. We make use of available
physical data to separate asteroids in the region according to their surface
reflectance properties, and establish the membership of the family. We
determine the slope of the cumulative magnitude distribution of the family, and
find it to be significantly steeper than the corresponding slope of all the
asteroids in the Phocaea region. This implies that sub-kilometer dark Phocaeas
are comparable in number to bright S-type objects, shedding light on an
entirely new aspect of the composition of small Phocaea asteroids. We then use
the Yarkovsky V-shape based method and estimate the age of the family to be
264$\pm$43 Myr. Finally, we carry out numerical simulations of the dynamical
evolution of the Tamara family. The results suggest that up to 50 Tamara
members with absolute magnitude H<19.4 may currently be found in the near-Earth
region. Despite their relatively small number in the near-Earth space, the rate
of Earth impacts by small, dark Phocaeas is non-negligible.
| arxiv topic:astro-ph.EP |
arxiv_dataset-84071704.06188 | A New Light Particle in B Decays?
hep-ph
We investigate the possibility whether the tensions with SM expectations
observed in several b -> sll transitions, including hints for lepton flavour
non-universality, could be due to the decay of B into a new light resonance. We
find that qualitative agreement with the data can be obtained with a light
vector resonance dominantly decaying invisibly. This scenario predicts a shift
in the muon anomalous magnetic moment that could explain the long-standing
discrepancy. The most stringent constraint comes from searches for B decays
with missing energy. A striking prediction is a strong q^2 dependence of the
lepton flavour universality ratios R_K and R_K* that should allow to clearly
confirm or rule out this possibility experimentally. We also comment on the
possible connection of the invisible decay product with Dark Matter.
| arxiv topic:hep-ph |
arxiv_dataset-84081704.06288 | Topological domain walls in helimagnets
cond-mat.str-el cond-mat.mes-hall cond-mat.mtrl-sci
A magnetic helix arises in chiral magnets with a wavelength set by the
spin-orbit coupling. We show that the helimagnetic order is a nanoscale analog
to liquid crystals, exhibiting topological structures and domain walls that are
distinctly different from classical magnets. Using magnetic force microscopy
and micromagnetic simulations, we demonstrate that - similar to cholesteric
liquid crystals - three fundamental types of domain walls are realized in the
helimagnet FeGe. We reveal the micromagnetic wall structure and show that they
can carry a finite skyrmion charge, permitting coupling to spin currents and
contributions to a topological Hall effect. Our study establishes a new class
of magnetic nano-objects with non-trivial topology, opening the door to
innovative device concepts based on helimagnetic domain walls.
| arxiv topic:cond-mat.str-el cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-84091704.06388 | Fast Quantization of Stochastic Volatility Models
q-fin.MF
Recursive Marginal Quantization (RMQ) allows fast approximation of solutions
to stochastic differential equations in one-dimension. When applied to two
factor models, RMQ is inefficient due to the fact that the optimization problem
is usually performed using stochastic methods, e.g., Lloyd's algorithm or
Competitive Learning Vector Quantization. In this paper, a new algorithm is
proposed that allows RMQ to be applied to two-factor stochastic volatility
models, which retains the efficiency of gradient-descent techniques. By
margining over potential realizations of the volatility process, a significant
decrease in computational effort is achieved when compared to current
quantization methods. Additionally, techniques for modelling the correct
zero-boundary behaviour are used to allow the new algorithm to be applied to
cases where the previous methods would fail. The proposed technique is
illustrated for European options on the Heston and Stein-Stein models, while a
more thorough application is considered in the case of the popular SABR model,
where various exotic options are also priced.
| arxiv topic:q-fin.MF |
arxiv_dataset-84101704.06488 | Raman study of the anharmonicity in YBa$_2$Cu$_3$O$_x$
cond-mat.supr-con
A systematic Raman study in the visible carried out on the YBa2Cu316,18Ox
(x=6-7) compounds, with isotopic substitution of 18O for 16O, has detected a
doping dependent deviation from harmonic behavior for the frequency shift of
the in-phase mode, a smaller amount of anharmonicity for the apex mode, and
almost no effect for the out-of-phase B1g-symmetry phonon. It appears that the
amount of anharmonicity depends strongly on the oxygen concentration; it
diminishes close to the tetragonal to orthorhombic structural phase transition
and close to optimal doping, while it reaches its maximum value for the
ortho-II and a tetragonal phase. The almost zero anharmonicity at optimal
doping persists even at 77K. The data in the overdoped oxygen concentration,
where a softening of the in-phase phonon frequency occurs, indicate that the
anharmonicity is not enhanced by the sudden increase in the CuO2 buckling. The
results fully agree with recent studies of the ortho-II phase but they do not
comply with a static double-well potential of the apical oxygen atom at optimal
doping.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-84111704.06588 | A tentative view on hadrons
physics.gen-ph
The present paper is based upon ideas and results obtained in an earlier
paper by the author devoted to a new formulation of quantum electrodynamics.
The equations derived in that paper depict the structure and properties of the
electron as well as of other leptons including neutrinos. Since in nature there
are only two stable charged elementary particles, the electron and proton (with
their antiparticles), it is logical to suppose that in nature there is a
protonic field too whose description is analogous with the one of the
electronic field. The equations obtained in the paper and describing the proton
and other baryons differ in some detail from the ones for the electronic field.
A section of the paper is devoted to nuclei where the electronic and protonic
fields are present simultaneously without neutrons. The neutron itself consists
of an electron and a proton. Mesons are short-lived combinations of the
electronic and protonic fields. The theory contains three dimensionless
constants whose value can be calculated.
| arxiv topic:physics.gen-ph |
arxiv_dataset-84121704.06688 | New bounding techniques for goal-oriented error estimation applied to
linear problems
math.NA
The paper deals with the accuracy of guaranteed error bounds on outputs of
interest computed from approximate methods such as the finite element method. A
considerable improvement is introduced for linear problems thanks to new
bounding techniques based on Saint-Venant's principle. The main breakthrough of
these optimized bounding techniques is the use of properties of homothetic
domains which enables to cleverly derive guaranteed and accurate boundings of
contributions to the global error estimate over a local region of the domain.
Performances of these techniques are illustrated through several numerical
experiments.
| arxiv topic:math.NA |
arxiv_dataset-84131704.06788 | Observation of Spin Nernst effect in Platinum
cond-mat.mes-hall
Central focus of spintronics is concentrated on generation of pure spin
current and associated spin torque. Pure spin current can be generated by spin
Hall effect in heavy metals by passing charge current. By spin Seebeck effect
pure spin current can also be generated in ferromagnet. In this work we
experimentally demonstrate that if heavy metals like Platinum with high spin
orbit coupling carry heat current it can convert it into spin current due to
relativistic spin orbit interaction. This conversion of heat current into spin
current in non magnet is equivalent of thermally driven spin Hall effect or it
is known as spin Nernst effect. We observed spin Nernst effect in Ni/Pt
bi-layer experimentally and we confirm that when Pt is replaced by low spin
orbit material like Al spin Nernst effect significantly reduces. So we have
detected spin Nernst effect unambiguously and compare its strength with
electrical spin Hall effect.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-84141704.06888 | Time-Contrastive Networks: Self-Supervised Learning from Video
cs.CV cs.RO
We propose a self-supervised approach for learning representations and
robotic behaviors entirely from unlabeled videos recorded from multiple
viewpoints, and study how this representation can be used in two robotic
imitation settings: imitating object interactions from videos of humans, and
imitating human poses. Imitation of human behavior requires a
viewpoint-invariant representation that captures the relationships between
end-effectors (hands or robot grippers) and the environment, object attributes,
and body pose. We train our representations using a metric learning loss, where
multiple simultaneous viewpoints of the same observation are attracted in the
embedding space, while being repelled from temporal neighbors which are often
visually similar but functionally different. In other words, the model
simultaneously learns to recognize what is common between different-looking
images, and what is different between similar-looking images. This signal
causes our model to discover attributes that do not change across viewpoint,
but do change across time, while ignoring nuisance variables such as
occlusions, motion blur, lighting and background. We demonstrate that this
representation can be used by a robot to directly mimic human poses without an
explicit correspondence, and that it can be used as a reward function within a
reinforcement learning algorithm. While representations are learned from an
unlabeled collection of task-related videos, robot behaviors such as pouring
are learned by watching a single 3rd-person demonstration by a human. Reward
functions obtained by following the human demonstrations under the learned
representation enable efficient reinforcement learning that is practical for
real-world robotic systems. Video results, open-source code and dataset are
available at https://sermanet.github.io/imitate
| arxiv topic:cs.CV cs.RO |
arxiv_dataset-84151704.06988 | Ensemble Kalman methods for high-dimensional hierarchical dynamic
space-time models
stat.ME stat.CO
We propose a new class of filtering and smoothing methods for inference in
high-dimensional, nonlinear, non-Gaussian, spatio-temporal state-space models.
The main idea is to combine the ensemble Kalman filter and smoother, developed
in the geophysics literature, with state-space algorithms from the statistics
literature. Our algorithms address a variety of estimation scenarios, including
on-line and off-line state and parameter estimation. We take a Bayesian
perspective, for which the goal is to generate samples from the joint posterior
distribution of states and parameters. The key benefit of our approach is the
use of ensemble Kalman methods for dimension reduction, which allows inference
for high-dimensional state vectors. We compare our methods to existing ones,
including ensemble Kalman filters, particle filters, and particle MCMC. Using a
real data example of cloud motion and data simulated under a number of
nonlinear and non-Gaussian scenarios, we show that our approaches outperform
these existing methods.
| arxiv topic:stat.ME stat.CO |
arxiv_dataset-84161704.07088 | Active Control of Laser Wavefronts in Atom Interferometers
physics.atom-ph
Wavefront aberrations are identified as a major limitation in quantum
sensors. They are today the main contribution in the uncertainty budget of best
cold atom interferometers based on two-photon laser beam splitters, and
constitute an important limit for their long-term stability, impeding these
instruments from reaching their full potential. Moreover, they will also remain
a major obstacle in future experiments based on large momentum beam splitters.
In this article, we tackle this issue by using a deformable mirror to control
actively the laser wavefronts in atom interferometry. In particular, we
demonstrate in an experimental proof of principle the efficient correction of
wavefront aberrations in an atomic gravimeter.
| arxiv topic:physics.atom-ph |
arxiv_dataset-84171704.07188 | Lieb-Thirring inequality with semiclassical constant and gradient error
term
math-ph math.MP math.SP
In 1975, Lieb and Thirring derived a semiclassical lower bound on the kinetic
energy for fermions, which agrees with the Thomas-Fermi approximation up to a
constant factor. Whenever the optimal constant in their bound coincides with
the semiclassical one is a long-standing open question. We prove an improved
bound with the semiclassical constant and a gradient error term which is of
lower order.
| arxiv topic:math-ph math.MP math.SP |
arxiv_dataset-84181704.07288 | Stochastic representation of tau functions of Korteweg-de Vries equation
math.PR math.AP
In this paper we express tau functions for the Korteweg de Vries (KdV)
equation, as Laplace transforms of iterated Skorohod integrals. Our main tool
is the notion of Fredholm determinant of an integral operator. Our result
extends the paper of Ikeda and Taniguchi who obtained a stochastic
representation of tau functions for the $N$-soliton solutions of KdV as the
Laplace transform of a quadratic functional of $N$ independent
Ornstein-Uhlenbeck processes. Our general result goes beyond the $N$-soliton
case and enables us to consider a non soliton solution of KdV associated to a
Gaussian process with Cauchy covariance function.
| arxiv topic:math.PR math.AP |
arxiv_dataset-84191704.07388 | Exceptional Composite Dark Matter
hep-ph astro-ph.CO
We study the dark matter phenomenology of non-minimal composite Higgs models
with $SO(7)$ broken to the exceptional group $G_2$. In addition to the Higgs,
three pseudo-Nambu-Goldstone bosons arise, one of which is electrically
neutral. A parity symmetry is enough to ensure this resonance is stable. In
fact, if the breaking of the Goldstone symmetry is driven by the fermion
sector, this $\mathbb{Z}_2$ symmetry is automatically unbroken in the
electroweak phase. In this case, the relic density, as well as the expected
indirect, direct and collider signals are then uniquely determined by the value
of the compositeness scale, $f$. Current experimental bounds allow to account
for a large fraction of the dark matter of the Universe if the dark matter
particle is part of an electroweak triplet. The totality of the relic abundance
can be accommodated if instead this particle is a composite singlet. In both
cases, the scale $f$ and the dark matter mass are of the order of a few TeV.
| arxiv topic:hep-ph astro-ph.CO |
arxiv_dataset-84201704.07488 | On the extreme value statistics of normal random matrices and 2D Coulomb
gases: Universality and finite N corrections
math-ph cond-mat.stat-mech math.MP
In this paper we extend the orthogonal polynomials approach for extreme value
calculations of Hermitian random matrices, developed by Nadal and Majumdar
[1102.0738], to normal random matrices and 2D Coulomb gases in general.
Firstly, we show that this approach provides an alternative derivation of
results in the literature. More precisely, we show convergence of the rescaled
eigenvalue with largest modulus of a normal Gaussian ensemble to a Gumbel
distribution, as well as universality for an arbitrary radially symmetric
potential. Secondly, it is shown that this approach can be generalised to
obtain convergence of the eigenvalue with smallest modulus and its universality
for ring distributions. Most interestingly, the here presented techniques are
used to compute all slowly varying finite N correction of the above
distributions, which is important for practical applications, given the slow
convergence. Another interesting aspect of this work is the fact that we can
use standard techniques from Hermitian random matrices to obtain the extreme
value statistics of non-Hermitian random matrices resembling the large N
expansion used in context of the double scaling limit of Hermitian matrix
models in string theory.
| arxiv topic:math-ph cond-mat.stat-mech math.MP |
arxiv_dataset-84211704.07588 | Relaxed enthalpy and volume during physical aging: Their interrelation
cond-mat.mtrl-sci
Several papers have recently presented results of measurements of physical
aging by studying the behavior of glassy materials quenched from temperatures
above their glass transition temperature $T_g$. The evolution of the aging
process is usually followed by plotting the relaxed enthalpy versus the
accompanying decrease in volume. Here, we focus on the slope of such plots,
which are found to be similar to the inverse value of the isothermal
compressibility close to $T_g$. An explanation of this empirical result is
attempted in the frame of a model that interconnects the defect Gibbs energy
with properties of the bulk material.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-84221704.07688 | Embeddability of arrangements of pseudocircles and graphs on surfaces
math.CO cs.CG math.GT
A pseudocircle is a simple closed curve on some surface; an arrangement of
pseudocircles is a collection of pseudocircles that pairwise intersect in
exactly two points, at which they cross. Ortner proved that an arrangement of
pseudocircles is embeddable into the sphere if and only if all of its
subarrangements of size at most four are embeddable into the sphere, and asked
if an analogous result holds for embeddability into orientable surfaces of
higher genus. We answer this question positively: An arrangement of
pseudocircles is embeddable into an orientable surface of genus~$g$ if and only
if all of its subarrangements of size at most $4g+4$ are. Moreover, this bound
is tight. We actually have similar results for a much general notion of
arrangement, which we call an \emph{arrangement of graphs}.
| arxiv topic:math.CO cs.CG math.GT |
arxiv_dataset-84231704.07788 | Properly embedded minimal annuli in $\mathbb{H}^2 \times \mathbb{R}$
math.DG
In this paper we study the moduli space of properly Alexandrov-embedded,
minimal annuli in $\mathbb{H}^2 \times \mathbb{R}$ with horizontal ends. We say
that the ends are horizontal when they are graphs of $\mathcal{C}^{2, \alpha}$
functions over $\partial_\infty \mathbb{H}^2$. Contrary to expectation, we show
that one can not fully prescribe the two boundary curves at infinity, but
rather, one can prescribe the bottom curve, but the top curve only up to a
translation and a tilt, along with the position of the neck and the vertical
flux of the annulus. We also prove general existence theorems for minimal
annuli with discrete groups of symmetries.
| arxiv topic:math.DG |
arxiv_dataset-84241704.07888 | Stochastic Optimization from Distributed, Streaming Data in Rate-limited
Networks
stat.ML cs.LG
Motivated by machine learning applications in networks of sensors,
internet-of-things (IoT) devices, and autonomous agents, we propose techniques
for distributed stochastic convex learning from high-rate data streams. The
setup involves a network of nodes---each one of which has a stream of data
arriving at a constant rate---that solve a stochastic convex optimization
problem by collaborating with each other over rate-limited communication links.
To this end, we present and analyze two algorithms---termed distributed
stochastic approximation mirror descent (D-SAMD) and accelerated distributed
stochastic approximation mirror descent (AD-SAMD)---that are based on two
stochastic variants of mirror descent and in which nodes collaborate via
approximate averaging of the local, noisy subgradients using distributed
consensus. Our main contributions are (i) bounds on the convergence rates of
D-SAMD and AD-SAMD in terms of the number of nodes, network topology, and ratio
of the data streaming and communication rates, and (ii) sufficient conditions
for order-optimum convergence of these algorithms. In particular, we show that
for sufficiently well-connected networks, distributed learning schemes can
obtain order-optimum convergence even if the communications rate is small.
Further we find that the use of accelerated methods significantly enlarges the
regime in which order-optimum convergence is achieved; this is in contrast to
the centralized setting, where accelerated methods usually offer only a modest
improvement. Finally, we demonstrate the effectiveness of the proposed
algorithms using numerical experiments.
| arxiv topic:stat.ML cs.LG |
arxiv_dataset-84251704.07988 | Joint Hybrid Precoder and Combiner Design for mmWave Spatial
Multiplexing Transmission
cs.IT math.IT
Millimeter-wave (mmWave) communications have been considered as a key
technology for future 5G wireless networks because of the orders-of-magnitude
wider bandwidth than current cellular bands. In this paper, we consider the
problem of codebook-based joint analog-digital hybrid precoder and combiner
design for spatial multiplexing transmission in a mmWave multiple-input
multiple-output (MIMO) system. We propose to jointly select analog precoder and
combiner pair for each data stream successively aiming at maximizing the
channel gain while suppressing the interference between different data streams.
After all analog precoder/combiner pairs have been determined, we can obtain
the effective baseband channel. Then, the digital precoder and combiner are
computed based on the obtained effective baseband channel to further mitigate
the interference and maximize the sum-rate. Simulation results demonstrate that
our proposed algorithm exhibits prominent advantages in combating interference
between different data streams and offer satisfactory performance improvement
compared to the existing codebook-based hybrid beamforming schemes.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-84261704.08088 | Enriching Complex Networks with Word Embeddings for Detecting Mild
Cognitive Impairment from Speech Transcripts
cs.CL
Mild Cognitive Impairment (MCI) is a mental disorder difficult to diagnose.
Linguistic features, mainly from parsers, have been used to detect MCI, but
this is not suitable for large-scale assessments. MCI disfluencies produce
non-grammatical speech that requires manual or high precision automatic
correction of transcripts. In this paper, we modeled transcripts into complex
networks and enriched them with word embedding (CNE) to better represent short
texts produced in neuropsychological assessments. The network measurements were
applied with well-known classifiers to automatically identify MCI in
transcripts, in a binary classification task. A comparison was made with the
performance of traditional approaches using Bag of Words (BoW) and linguistic
features for three datasets: DementiaBank in English, and Cinderella and
Arizona-Battery in Portuguese. Overall, CNE provided higher accuracy than using
only complex networks, while Support Vector Machine was superior to other
classifiers. CNE provided the highest accuracies for DementiaBank and
Cinderella, but BoW was more efficient for the Arizona-Battery dataset probably
owing to its short narratives. The approach using linguistic features yielded
higher accuracy if the transcriptions of the Cinderella dataset were manually
revised. Taken together, the results indicate that complex networks enriched
with embedding is promising for detecting MCI in large-scale assessments
| arxiv topic:cs.CL |
arxiv_dataset-84271704.08188 | $f(R)$ constant-roll inflation
astro-ph.CO gr-qc hep-th
The previously introduced class of two-parametric phenomenological
inflationary models in General Relativity in which the slow-roll assumption is
replaced by the more general, constant-roll condition is generalized to the
case of $f(R)$ gravity. A simple constant-roll condition is defined in the
original Jordan frame, and exact expressions for a scalaron potential in the
Einstein frame, for a function $f(R)$ (in the parametric form) and for
inflationary dynamics are obtained. The region of the model parameters
permitted by the latest observational constraints on the scalar spectral index
and the tensor-to-scalar ratio of primordial metric perturbations generated
during inflation is determined.
| arxiv topic:astro-ph.CO gr-qc hep-th |
arxiv_dataset-84281704.08288 | Lattice Gluon Propagator and One-Gluon-Exchange Potential
hep-lat
We consider the interquark potential in the one-gluon-exchange (OGE)
approximation, using a fully nonperturbative gluon propagator from large-volume
lattice simulations. The resulting VLGP potential is non-confining, showing
that the OGE approximation is not sufficient to describe the infrared sector of
QCD. Nevertheless, it represents an improvement over the perturbative
(Coulomb-like) potential, since it allows the description of a few low-lying
bound states of charmonium and bottomonium. In order to achieve a better
description of these spectra, we add to VLGP a linearly growing term. The
obtained results are comparable to the corresponding ones in the
Cornell-potential case. As a byproduct of our study, we estimate the interquark
distance for the considered charmonium and bottomonium states.
| arxiv topic:hep-lat |
arxiv_dataset-84291704.08388 | Duluth at Semeval-2017 Task 7 : Puns upon a midnight dreary, Lexical
Semantics for the weak and weary
cs.CL
This paper describes the Duluth systems that participated in SemEval-2017
Task 7 : Detection and Interpretation of English Puns. The Duluth systems
participated in all three subtasks, and relied on methods that included word
sense disambiguation and measures of semantic relatedness.
| arxiv topic:cs.CL |
arxiv_dataset-84301704.08488 | Optimal client recommendation for market makers in illiquid financial
products
q-fin.CP cs.LG stat.ML
The process of liquidity provision in financial markets can result in
prolonged exposure to illiquid instruments for market makers. In this case,
where a proprietary position is not desired, pro-actively targeting the right
client who is likely to be interested can be an effective means to offset this
position, rather than relying on commensurate interest arising through natural
demand. In this paper, we consider the inference of a client profile for the
purpose of corporate bond recommendation, based on typical recorded information
available to the market maker. Given a historical record of corporate bond
transactions and bond meta-data, we use a topic-modelling analogy to develop a
probabilistic technique for compiling a curated list of client recommendations
for a particular bond that needs to be traded, ranked by probability of
interest. We show that a model based on Latent Dirichlet Allocation offers
promising performance to deliver relevant recommendations for sales traders.
| arxiv topic:q-fin.CP cs.LG stat.ML |
arxiv_dataset-84311704.08588 | Modeling Events as Machines
cs.AI cs.SE
The notion of events has occupied a central role in modeling and has an
influence in computer science and philosophy. Recent developments in
diagrammatic modeling have made it possible to examine conceptual
representation of events. This paper explores some aspects of the notion of
events that are produced by applying a new diagrammatic methodology with a
focus on the interaction of events with such concepts as time and space,
objects. The proposed description applies to abstract machines where events
form the dynamic phases of a system. The results of this nontechnical research
can be utilized in many fields where the notion of an event is typically used
in interdisciplinary application.
| arxiv topic:cs.AI cs.SE |
arxiv_dataset-84321704.08688 | SIT: A Lightweight Encryption Algorithm for Secure Internet of Things
cs.CR cs.IT math.IT
The Internet of Things (IoT) being a promising technology of the future is
expected to connect billions of devices. The increased number of communication
is expected to generate mountains of data and the security of data can be a
threat. The devices in the architecture are essentially smaller in size and low
powered. Conventional encryption algorithms are generally computationally
expensive due to their complexity and requires many rounds to encrypt,
essentially wasting the constrained energy of the gadgets. Less complex
algorithm, however, may compromise the desired integrity. In this paper we
propose a lightweight encryption algorithm named as Secure IoT (SIT). It is a
64-bit block cipher and requires 64-bit key to encrypt the data. The
architecture of the algorithm is a mixture of feistel and a uniform
substitution-permutation network. Simulations result shows the algorithm
provides substantial security in just five encryption rounds. The hardware
implementation of the algorithm is done on a low cost 8-bit micro-controller
and the results of code size, memory utilization and encryption/decryption
execution cycles are compared with benchmark encryption algorithms. The MATLAB
code for relevant simulations is available online at https://goo.gl/Uw7E0W.
| arxiv topic:cs.CR cs.IT math.IT |
arxiv_dataset-84331704.08788 | The Multi-Wavelength Tully-Fisher relation with spatially resolved HI
kinematics
astro-ph.GA
In this paper we investigate the statistical properties of the Tully-Fisher
relation for a sample of 32 galaxies with measured distances from the Cepheid
period-luminosity relation and/or TRGB stars.
We take advantage of panchromatic photometry in 12 bands (from FUV to 4.5
$\mu$m) and of spatially resolved HI kinematics. We use these data together
with three kinematic measures ($W^{i}_{50}$, $V_{max}$ and $V_{flat}$)
extracted from the global HI profiles or HI rotation curves, so as to construct
36 correlations allowing us to select the one with the least scatter. We
introduce a tightness parameter $\sigma_{\perp}$ of the TFr, in order to obtain
a slope-independent measure of the goodness of fit. We find that the tightest
correlation occurs when we select the 3.6 $\mu$m photometric band together with
the $V_{flat}$ parameter extracted from the HI rotation curve.
| arxiv topic:astro-ph.GA |
arxiv_dataset-84341704.08888 | Simulations of Cold Electroweak Baryogenesis: Hypercharge U(1) and the
creation of helical magnetic fields
hep-ph hep-lat hep-th
We perform numerical simulations of Cold Electroweak Baryogenesis, including
for the first time in the Bosonic sector the full electroweak gauge group
SU(2)$\times$U(1) and CP-violation. We find that the maximum generated baryon
asymmetry is reduced by a factor of three relative to the SU(2)-only model, but
that the quench time dependence is very similar. In addition, we compute the
magnitude of the helical magnetic fields, and find that it is proportional to
the strength of CP-violation and dependent on quench time, but is not
proportional to the magnitude of the baryon asymmetry as proposed in the
literature. Astrophysical signatures of primordial magnetic helicity can
therefore not in general be used as evidence that electroweak baryogenesis has
taken place.
| arxiv topic:hep-ph hep-lat hep-th |
arxiv_dataset-84351704.08988 | Elastic and inelastic pion-nucleon scattering to fourth order in chiral
perturbation theory
nucl-th hep-ph
We extend our previous study of elastic pion-nucleon scattering in the
framework of chiral perturbation theory by performing a combined analysis of
the reactions $\pi N \to \pi N$ and $\pi N \to \pi \pi N$. The calculation is
carried out to fourth order in the chiral expansion using the heavy baryon
approach and the covariant formulation supplemented with a modified version of
the extended on-mass-shell renormalization scheme. We demonstrate that a
combined fit to experimental data in both channels leads to a reduced amount of
correlations between the low-energy constants. A satisfactory description of
the experimental data in both channels is obtained, which is further improved
upon including tree-level contributions of the $\Delta$(1232) resonance. We
also explore a possibility of using the empirical information about $\pi N$
subthreshold parameters obtained recently by means of the Roy-Steiner equations
to stabilize the fits.
| arxiv topic:nucl-th hep-ph |
arxiv_dataset-84361705.00059 | Random dynamical systems generated by coalescing stochastic flows on
$\mathbb{R}$
math.PR math.DS
Existence of random dynamical systems for a class of coalescing stochastic
flows on $\mathbb{R}$ is proved. A new state space for coalescing flows is
built. As particular cases coalescing flows of solutions to stochastic
differential equations independent before meeting time and coalescing Harris
flows are considered.
| arxiv topic:math.PR math.DS |
arxiv_dataset-84371705.00159 | Boundedness and absoluteness of some dynamical invariants in model
theory
math.LO math.DS math.GN
Let ${\mathfrak C}$ be a monster model of an arbitrary theory $T$, $\bar
\alpha$ any tuple of bounded length of elements of ${\mathfrak C}$, and $\bar
c$ an enumeration of all elements of ${\mathfrak C}$. By $S_{\bar
\alpha}({\mathfrak C})$ denote the compact space of all complete types over
${\mathfrak C}$ extending $tp(\bar \alpha/\emptyset)$, and $S_{\bar
c}({\mathfrak C})$ is defined analogously. Then $S_{\bar \alpha}({\mathfrak
C})$ and $S_{\bar c}({\mathfrak C})$ are naturally $Aut({\mathfrak C})$-flows.
We show that the Ellis groups of both these flows are of bounded size (i.e.
smaller than the degree of saturation of ${\mathfrak C}$), providing an
explicit bound on this size. Next, we prove that these Ellis groups do not
depend on the choice of the monster model ${\mathfrak C}$; thus, we say that
they are absolute. We also study minimal left ideals (equivalently subflows) of
the Ellis semigroups of the flows $S_{\bar \alpha}({\mathfrak C})$ and $S_{\bar
c}({\mathfrak C})$. We give an example of a NIP theory in which the minimal
left ideals are of unbounded size. We show that in each of these two cases,
boundedness of a minimal left ideal is an absolute property (i.e. it does not
depend on the choice of ${\mathfrak C}$) and that whenever such an ideal is
bounded, then its isomorphism type is also absolute.
Assuming NIP, we give characterizations of when a minimal left ideal of the
Ellis semigroup of $S_{\bar c}({\mathfrak C})$ is bounded. Then we adapt a
proof of Chernikov and Simon to show that whenever such an ideal is bounded,
the natural epimorphism (described by Krupinski, Pillay and Rzepecki) from the
Ellis group of the flow $S_{\bar c}({\mathfrak C})$ to the Kim-Pillay Galois
group $Gal_{KP}(T)$ is an isomorphism (in particular, $T$ is G-compact). We
provide some counter-examples for $S_{\bar \alpha}({\mathfrak C})$ in place of
$S_{\bar c}({\mathfrak C})$.
| arxiv topic:math.LO math.DS math.GN |
arxiv_dataset-84381705.00259 | Quasi adiabatic dynamics of energy eigenstates for solvable quantum
system at finite temperature
cond-mat.stat-mech
It is a fundamental problem to characterize the nonequilibrium processes. For
a slowly moving one-dimensional potential, we explore the quasi adiabatic
dynamics of the initial energy eigenstates for a confined quantum system
interacting with a large reservoir. For concreteness, we investigate a dragged
harmonic oscillator linearly interacting with an assembly of harmonic
oscillators, and explore the deviation from adiabatic processes by rigorously
calculating the so-called persistent amplitude. In this way, we also show that
the phase of the persistent amplitudes are common both for the ground and
excited states.
| arxiv topic:cond-mat.stat-mech |
arxiv_dataset-84391705.00359 | Search for Evergreens in Science: A Functional Data Analysis
stat.AP cs.DL
Evergreens in science are papers that display a continual rise in annual
citations without decline, at least within a sufficiently long time period.
Aiming to better understand evergreens in particular and patterns of citation
trajectory in general, this paper develops a functional data analysis method to
cluster citation trajectories of a sample of 1699 research papers published in
1980 in the American Physical Society (APS) journals. We propose a functional
Poisson regression model for individual papers' citation trajectories, and fit
the model to the observed 30-year citations of individual papers by functional
principal component analysis and maximum likelihood estimation. Based on the
estimated paper-specific coefficients, we apply the K-means clustering
algorithm to cluster papers into different groups, for uncovering general types
of citation trajectories. The result demonstrates the existence of an evergreen
cluster of papers that do not exhibit any decline in annual citations over 30
years.
| arxiv topic:stat.AP cs.DL |
arxiv_dataset-84401705.00459 | Comparison of lower order and higher order nonclassicality in photon
added and photon subtracted squeezed coherent states
quant-ph
Nonclassical properties of photon added and photon subtracted squeezed
coherent states have been compared with specific focus on the higher order
nonclassicalities, such as higher order squeezing, higher order sub-Poissonian
photon statistics, higher order antibunching. It is observed that both photon
added and photon subtracted squeezed coherent states are highly nonclassical as
they satisfy criteria for all of the above mentioned nonclassicalities and a
set of other criteria including negativity of Wigner function, Klyshko's
criterion and Agarwal's $(A_{3})$ parameter. Further, the amount of
nonclassicality present in these two types of states has been compared
quantitatively using a measure of nonclassicality known as nonclassical volume.
Variation in the amount of nonclassicality with the number of photon(s)
added/subtracted is also investigated, and it is found that the addition of
photons makes the squeezed coherent state more nonclassical than what is done
by the subtraction of photons.
| arxiv topic:quant-ph |
arxiv_dataset-84411705.00559 | Comparing a 41-year model hindcast with decades of wave measurements
from the Baltic Sea
physics.ao-ph
We present ice-free and ice-included statistics for the Baltic Sea using a
wave hindcast validated against data from 13 wave measurement sites. In the
hindcast 84% of wave events with a significant wave height over 7 m occurred
between November and January. The effect of the ice cover is largest in the Bay
of Bothnia, where the mean significant wave height is reduced by 30% when the
ice time is included in the statistics. The difference between these two
statistics are less than 0.05 m below a latitude of 59.5 degrees. The seasonal
ice cover also causes measurement gaps by forcing an early recovery of the
instruments. Including the time not captured by the wave buoy can affect the
estimates for the significant wave height by roughly 20%. The impact below the
99th percentiles are still under 5%. The significant wave height is modelled
accurately even close to the shore, but the highest peak periods are
underestimated in a narrow bay. Sensitivity test show that this underestimation
is most likely caused by an excessive refraction towards the shore.
Reconsidering the role of the spatial resolution and the physical processes
affecting the low-frequency waves is suggested as a possible solution.
| arxiv topic:physics.ao-ph |
arxiv_dataset-84421705.00659 | HD 202206 : A Circumbinary Brown Dwarf System
astro-ph.SR astro-ph.EP
With Hubble Space Telescope Fine Guidance Sensor astrometry and previously
published radial velocity measures we explore the exoplanetary system HD
202206. Our modeling results in a parallax, $\pi_{abs} = 21.96\pm0.12$
milliseconds of arc, a mass for HD 202206 B of M$_B = 0.089^{ +0.007}_{-0.006}$
Msun, and a mass for HD 202206 c of M$_c = 17.9 ^{ +2.9}_{-1.8}$ MJup. HD
202206 is a nearly face-on G+M binary orbited by a brown dwarf. The system
architecture we determine supports past assertions that stability requires a
5:1 mean motion resonance (we find a period ratio, $P_c/P_B = 4.92\pm0.04$) and
coplanarity (we find a mutual inclination, Phi = 6 \arcdeg \pm 2 \arcdeg).
| arxiv topic:astro-ph.SR astro-ph.EP |
arxiv_dataset-84431705.00759 | Controllability of Conjunctive Boolean Networks with Application to Gene
Regulation
math.DS math.CO math.OC
A Boolean network is a finite state discrete time dynamical system. At each
step, each variable takes a value from a binary set. The value update rule for
each variable is a local function which depends only on a selected subset of
variables. Boolean networks have been used in modeling gene regulatory
networks. We focus in this paper on a special class of Boolean networks, namely
the conjunctive Boolean networks (CBNs), whose value update rule is comprised
of only logic AND operations. It is known that any trajectory of a Boolean
network will enter a periodic orbit. Periodic orbits of a CBN have been
completely understood. In this paper, we investigate the orbit-controllability
and state-controllability of a CBN: We ask the question of how one can steer a
CBN to enter any periodic orbit or to reach any final state, from any initial
state. We establish necessary and sufficient conditions for a CBN to be
orbit-controllable and state-controllable. Furthermore, explicit control laws
are presented along the analysis.
| arxiv topic:math.DS math.CO math.OC |
arxiv_dataset-84441705.00859 | Partially-Connected Hybrid Precoding in mm-Wave Systems With Dynamic
Phase Shifter Networks
cs.IT math.IT
Hybrid precoding is a cost-effective approach to support directional
transmissions for millimeter wave (mm-wave) communications, and its design
challenge mainly lies in the analog component which consists of a network of
phase shifters. The partially-connected structure employs a small number of
phase shifters and therefore serves as an energy efficient solution for hybrid
precoding. In this paper, we propose a double phase shifter (DPS)
implementation for the phase shifter network in the partially-connected
structure, which allows more tractable and flexible hybrid precoder design. In
particular, the hybrid precoder design is identified as an eigenvalue problem.
To further enhance the performance, dynamic mapping from radio frequency (RF)
chains to antennas is proposed, for which a greedy algorithm and a modified
K-means algorithm are developed. Simulation results demonstrate the performance
gains of the proposed hybrid precoding algorithms with the DPS implementation
over existing ones. Given its low hardware complexity and high spectral
efficiency, the proposed structure is a promising candidate for 5G mm-wave
systems.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-84451705.00959 | Smart Assessment of and Tutoring for Computational Thinking MOOC
Assignments using MindReader
cs.PL
One of the major hurdles toward automatic semantic understanding of computer
programs is the lack of knowledge about what constitutes functional equivalence
of code segments. We postulate that a sound knowledgebase can be used to
deductively understand code segments in a hierarchical fashion by first
de-constructing a code and then reconstructing it from elementary knowledge and
equivalence rules of elementary code segments. The approach can also be
engineered to produce computable programs from conceptual and abstract
algorithms as an inverse function. In this paper, we introduce the core idea
behind the MindReader online assessment system that is able to understand a
wide variety of elementary algorithms students learn in their entry level
programming classes such as Java, C++ and Python. The MindReader system is able
to assess student assignments and guide them how to develop correct and better
code in real time without human assistance.
| arxiv topic:cs.PL |
arxiv_dataset-84461705.01059 | Higgs mediated CLFV processes $\mu N(eN)\rightarrow\tau X$ via gluon
operators
hep-ph hep-ex
We revisit charged lepton flavor violating (CLFV) scattering processes
$\ell_{i} N \to \tau X \, (\ell_{i} \ni e, \mu)$ mediated by Higgs. We point
out that a new subprocess $\ell_{i} g \to \tau g$ via the effective
interactions of Higgs and gluon gives the dominant contribution to $\ell_{i} N
\to \tau X$ for an incident beam energy of $E_{\ell} \lesssim 1\,\text{TeV}$ in
fixed target experiments. Furthermore, in the light of quark number
conservation, we consider quark pair-production processes $\ell_{i} g \to \tau
q \bar{q}$ ($q$ denotes quarks) instead of $\ell_{i} q \to \tau q$. This
corrects the threshold energy of each subprocess contributing to
$\sigma(\ell_{i} N \to \tau X)$. Reevaluation of $\sigma(\ell_{i} N \to \tau
X)$ including all of relevant subprocesses shows that the search for $\ell_{i}
N \to \tau X$ could serve a complementary opportunity with other relevant
processes to shed light on the Higgs CLFV.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-84471705.01159 | Spatial distribution of radionuclides in 3D models of SN 1987A and Cas A
astro-ph.HE astro-ph.SR hep-ph
Fostered by the possibilities of multi-dimensional computational modeling, in
particular the advent of three-dimensional (3D) simulations, our understanding
of the neutrino-driven explosion mechanism of core-collapse supernovae (SNe)
has experienced remarkable progress over the past decade. First
self-consistent, first-principle models have shown successful explosions in 3D,
and even failed cases may be cured by moderate changes of the microphysics
inside the neutron star (NS), better grid resolution, or more detailed
progenitor conditions at the onset of core collapse, in particular large-scale
perturbations in the convective Si and O burning shells. 3D simulations have
also achieved to follow neutrino-driven explosions continuously from the
initiation of the blast wave, through the shock breakout from the progenitor
surface, into the radioactively powered evolution of the SN, and towards the
free expansion phase of the emerging remnant. Here we present results from such
simulations, which form the basis for direct comparisons with observations of
SNe and SN remnants in order to derive constraints on the still disputed
explosion mechanism. It is shown that predictions based on hydrodynamic
instabilities and mixing processes associated with neutrino-driven explosions
yield good agreement with measured NS kicks, light-curve properties of SN
1987A, and asymmetries of iron and 44Ti distributions observed in SN 1987A and
Cassiopeia A.
| arxiv topic:astro-ph.HE astro-ph.SR hep-ph |
arxiv_dataset-84481705.01259 | Spinon confinement in a quasi one dimensional anisotropic Heisenberg
magnet
cond-mat.str-el
Confinement is a process by which particles with fractional quantum numbers
bind together to form quasiparticles with integer quantum numbers. The
constituent particles are confined by an attractive interaction whose strength
increases with increasing particle separation and as a consequence, individual
particles are not found in isolation. This phenomenon is well known in particle
physics where quarks are confined in baryons and mesons. An analogous
phenomenon occurs in certain magnetic insulators; weakly coupled chains of
spins S=1/2. The collective excitations in these systems is spinons (S=1/2). At
low temperatures weak coupling between chains can induce an attractive
interaction between pairs of spinons that increases with their separation and
thus leads to confinement. In this paper, we employ inelastic neutron
scattering to investigate the spinon confinement in the quasi-1D S=1/2 XXZ
antiferromagnet SrCo2V2O8. Spinon excitations are observed above TN in
quantitative agreement with established theory. Below TN the pairs of spinons
are confined and two sequences of meson-like bound states with longitudinal and
transverse polarizations are observed. Several theoretical approaches are used
to explain the data. A new theoretical technique based on Tangent-space Matrix
Product States gives a very complete description of the data and provides good
agreement not only with the energies of the bound modes but also with their
intensities. We also successfully explained the effect of temperature on the
excitations including the experimentally observed thermally induced resonance
between longitudinal modes below TN ,and the transitions between thermally
excited spinon states above TN. In summary, our work establishes SrCo2V2O8 as a
beautiful paradigm for spinon confinement in a quasi-1D quantum magnet and
provides a comprehensive picture of this process.
| arxiv topic:cond-mat.str-el |
arxiv_dataset-84491705.01359 | FOIL it! Find One mismatch between Image and Language caption
cs.CV cs.CL cs.MM
In this paper, we aim to understand whether current language and vision
(LaVi) models truly grasp the interaction between the two modalities. To this
end, we propose an extension of the MSCOCO dataset, FOIL-COCO, which associates
images with both correct and "foil" captions, that is, descriptions of the
image that are highly similar to the original ones, but contain one single
mistake ("foil word"). We show that current LaVi models fall into the traps of
this data and perform badly on three tasks: a) caption classification (correct
vs. foil); b) foil word detection; c) foil word correction. Humans, in
contrast, have near-perfect performance on those tasks. We demonstrate that
merely utilising language cues is not enough to model FOIL-COCO and that it
challenges the state-of-the-art by requiring a fine-grained understanding of
the relation between text and image.
| arxiv topic:cs.CV cs.CL cs.MM |
arxiv_dataset-84501705.01459 | Gravity with linear action and gravitational singularities
hep-th gr-qc
Motivated by quantum mechanical considerations we earlier suggested an
alternative action for discretised quantum gravity which has a dimension of
length. It is the so called "linear" action. The proposed action is a "square
root" of the classical area action in gravity and has in front of the action a
new constant of dimension one. Here we shall consider the continuous limit of
the discretised linear action. We shall demonstrate that in the modified theory
of gravity there appear space-time regions of the Schwarzschild radius scale
which are unreachable by test particles. These regions are located in the
places where standard theory of gravity has singularities. We are confronted
here with a drastically new concept that there may exist space-time regions
which are excluded from the physical scene, being physically unreachable by
test particles or observables. If this concept is accepted, then it seems
plausible that the gravitational singularities are excluded from the modified
theory.
| arxiv topic:hep-th gr-qc |
arxiv_dataset-84511705.01559 | The Dust Attenuation of Star-forming Galaxies at $z\sim3$ and Beyond:
New Insights from ALMA Observations
astro-ph.GA
We present results on the dust attenuation of galaxies at redshift $\sim3-6$
by studying the relationship between the UV spectral slope ($\beta_{\rm UV}$)
and the infrared excess (IRX; $L_{\rm IR}$/$L_{\rm UV}$) using ALMA
far-infrared continuum observations. Our study is based on a sample of 67
massive, star-forming galaxies with a median mass of $M_{\ast}\sim
10^{10.7}\,M_{\rm \odot}$ spanning a redshift range $z=2.6-3.7$ (median
$z=3.2$) that were observed with ALMA at $\lambda_{rest}=300\,{\rm \mu m}$.
Both the individual ALMA detections (41 sources) and stacks including all
galaxies show the IRX-$\beta_{\rm UV}$ relationship at $z\sim3$ is mostly
consistent with that of local starburst galaxies on average. However, we find
evidence for a large dispersion around the mean relationship by up to $\pm0.5$
dex. Nevertheless, the locally calibrated dust correction factors based on the
IRX-$\beta_{\rm UV}$ relation are on average applicable to main-sequence
$z\sim3$ galaxies. This does not appear to be the case at even higher
redshifts, however. Using public ALMA observations of $z\sim4-6$ galaxies we
find evidence for a significant evolution in the IRX-$\beta_{\rm UV}$ and the
IRX-$M_{\ast}$ relations beyond $z\sim3$ toward lower IRX values. We discuss
several caveats that could affect these results, including the assumed dust
temperature. ALMA observations of larger $z>3$ galaxy samples will be required
to confirm this intriguing redshift evolution.
| arxiv topic:astro-ph.GA |
arxiv_dataset-84521705.01659 | Graded hypoellipticity of BGG sequences
math.DG math.AP
This article studies hypoellipticity on general filtered manifolds. We extend
the Rockland criterion to a pseudodifferential calculus on filtered manifolds,
construct a parametrix and describe its precise analytic structure. We use this
result to study Rockland sequences, a notion generalizing elliptic sequences to
filtered manifolds. The main application that we present is to the analysis of
the Bernstein--Gelfand--Gelfand (BGG) sequences over regular parabolic
geometries. We do this by generalizing the BGG machinery to more general
filtered manifolds (in a non-canonical way) and show that the generalized BGG
sequences are Rockland in a graded sense.
| arxiv topic:math.DG math.AP |
arxiv_dataset-84531705.01759 | Deep 360 Pilot: Learning a Deep Agent for Piloting through 360{\deg}
Sports Video
cs.CV cs.GR cs.MM
Watching a 360{\deg} sports video requires a viewer to continuously select a
viewing angle, either through a sequence of mouse clicks or head movements. To
relieve the viewer from this "360 piloting" task, we propose "deep 360 pilot"
-- a deep learning-based agent for piloting through 360{\deg} sports videos
automatically. At each frame, the agent observes a panoramic image and has the
knowledge of previously selected viewing angles. The task of the agent is to
shift the current viewing angle (i.e. action) to the next preferred one (i.e.,
goal). We propose to directly learn an online policy of the agent from data. We
use the policy gradient technique to jointly train our pipeline: by minimizing
(1) a regression loss measuring the distance between the selected and ground
truth viewing angles, (2) a smoothness loss encouraging smooth transition in
viewing angle, and (3) maximizing an expected reward of focusing on a
foreground object. To evaluate our method, we build a new 360-Sports video
dataset consisting of five sports domains. We train domain-specific agents and
achieve the best performance on viewing angle selection accuracy and transition
smoothness compared to [51] and other baselines.
| arxiv topic:cs.CV cs.GR cs.MM |
arxiv_dataset-84541705.01859 | Entanglement Entropy, Chemical Potential, Current Source, and Wilson
Loop
hep-th cond-mat.stat-mech quant-ph
We construct and analytically compute entanglement and the R\'enyi entropies
of Dirac fermions on a 2 dimensional torus in the presence of background
chemical potential, current source and Wilson loop, by employing correlation
functions of the electromagnetic vertex operators of $\mathbb{Z}_n$ orbifold
theory. The entropies reveal numerous novelties. They probe the energy levels
of compact fermions through the chemical potential, demonstrate interference
phenomena with the current source being `beat frequency,' and experience
topological phase transitions by dialing the Wilson loop, in the low
temperature limit. In the large radius limit, they depend only on the Wilson
loop via topological transitions, which are tightly linked to conformal
dimension of the electromagnetic operators.
| arxiv topic:hep-th cond-mat.stat-mech quant-ph |
arxiv_dataset-84551705.01959 | On the spectrum of the multiplicative Hilbert matrix
math.FA math.SP
We study the multiplicative Hilbert matrix, i.e. the infinite matrix with
entries $(\sqrt{mn}\log(mn))^{-1}$ for $m,n\geq2$. This matrix was recently
introduced within the context of the theory of Dirichlet series, and it was
shown that the multiplicative Hilbert matrix has no eigenvalues and that its
continuous spectrum coincides with $[0,\pi]$. Here we prove that the
multiplicative Hilbert matrix has no singular continuous spectrum and that its
absolutely continuous spectrum has multiplicity one. Our argument relies on the
tools of spectral perturbation theory and scattering theory. Finding an
explicit diagonalisation of the multiplicative Hilbert matrix remains an
interesting open problem.
| arxiv topic:math.FA math.SP |
arxiv_dataset-84561705.02059 | Probing the phonon surface interaction by wave packet simulation: effect
of roughness and morphology
cond-mat.mes-hall physics.comp-ph
One way to reduce the lattice thermal conductivity of solids is to induce
additional phonon surface scattering through nanostructures. However, how
phonons interact with boundaries, especially at the atomic level, is not well
understood. In this work, we performed two-dimensional atomistic wave packet
simulations to investigate the phonon surface interaction. Emphasis has been
given to the angular-resolved phonon reflection at smooth, periodically rough,
and amorphous surfaces. We found that the acoustic phonon reflection at a
smooth surface is not simply specular. Mode conversion can occur after
reflection, and the detailed energy distribution after reflection will
dependent on surface condition and polarization of incident phonon. At
periodically rough surfaces, the reflected wave packet distribution does not
follow the well-known Ziman's model, but shows a nonmonotonic dependence on the
depth of surface roughness. When an amorphous layer is attached to the surface,
the incident wave packet will be absorbed by the amorphous region, and results
in quite diffusive reflection. Our results clearly show that the commonly used
specular-diffusive model is not enough to describe the phonon reflection at a
periodically rough surface, while an amorphous layer can induce strong
diffusive reflection. This work provides a careful analysis of phonon
reflection at a surface with different morphology, which is important to a
better understanding of thermal transport in various nanostructures.
| arxiv topic:cond-mat.mes-hall physics.comp-ph |
arxiv_dataset-84571705.02159 | Some remarks on Huisken's monotonicity formula for mean curvature flow
math.AP
We discuss a monotone quantity related to Huisken's monotonicity formula and
some technical consequences for mean curvature flow.
| arxiv topic:math.AP |
arxiv_dataset-84581705.02259 | Electronic band gaps of confined linear carbon chains ranging from
polyyne to carbyne
cond-mat.mtrl-sci physics.optics
Ultra long linear carbon chains of more than 6000 carbon atoms have recently
been synthesized within double-walled carbon nanotubes, and they show a
promising new route to one--atom--wide semiconductors with a direct band gap.
Theoretical studies predicted that this band gap can be tuned by the length of
the chains, the end groups, and their interactions with the environment.
However, different density functionals lead to very different values of the
band gap of infinitely long carbyne. In this work, we applied resonant Raman
excitation spectroscopy with more than 50 laser wavelengths to determine for
the first time the band gap of long carbon chains encapsulated inside DWCNTs.
The experimentally determined band gaps ranging from 2.253 to 1.848 eV follow a
linear relation with Raman frequency. This lower bound is the smallest band gap
of linear carbon chains observed so far. The comparison with experimental data
obtained for short chains in gas phase or in solution demonstrates the effect
of the DWCNT encapsulation, leading to an essential downshift of the band gap.
This is explained by the interaction between the carbon chain and the host
tube, which greatly modifies the chain's bond length alternation.
| arxiv topic:cond-mat.mtrl-sci physics.optics |
arxiv_dataset-84591705.02359 | Accretion-ejection morphology of the microquasar SS433 resolved at
sub-au scale
astro-ph.HE astro-ph.SR
We present the first optical observation at sub-milliarcsecond (mas) scale of
the microquasar SS 433 obtained with the GRAVITY instrument on the VLT
interferometer. The 3.5 hour exposure reveals a rich K-band spectrum dominated
by hydrogen Br$\gamma\ $ and \ion{He}{i} lines, as well as (red-shifted)
emission lines coming from the jets. The K-band continuum emitting region is
dominated by a marginally resolved point source ($<$ 1 mas) embedded inside a
diffuse background accounting for 10\% of the total flux. The jet line
positions agree well with the ones expected from the jet kinematic model, an
interpretation also supported by the consistent sign (i.e. negative/positive
for the receding/approaching jet component) of the phase shifts observed in the
lines. The significant visibility drop across the jet lines, together with the
small and nearly identical phases for all baselines, point toward a jet that is
offset by less than 0.5 mas from the continuum source and resolved in the
direction of propagation, with a typical size of 2 mas. The jet position angle
of $\sim$80$^{\circ}$ is consistent with the expected one at the observation
date. Jet emission so close to the central binary system would suggest that
line locking, if relevant to explain the amplitude and stability of the 0.26c
jet velocity, operates on elements heavier than hydrogen. The Br$\gamma\ $
profile is broad and double peaked. It is better resolved than the continuum
and the change of the phase signal sign across the line on all baselines
suggests an East-West oriented geometry alike the jet direction and supporting
a (polar) disk wind origin.
| arxiv topic:astro-ph.HE astro-ph.SR |
arxiv_dataset-84601705.02459 | Sequential Double Robustness in Right-Censored Longitudinal Models
stat.ME
Consider estimating the G-formula for the counterfactual mean outcome under a
given treatment regime in a longitudinal study. Bang and Robins provided an
estimator for this quantity that relies on a sequential regression formulation
of this parameter. This approach is doubly robust in that it is consistent if
either the outcome regressions or the treatment mechanisms are consistently
estimated. We define a stronger notion of double robustness, termed sequential
double robustness, for estimators of the longitudinal G-formula. The definition
emerges naturally from a more general definition of sequential double
robustness for the outcome regression estimators. An outcome regression
estimator is sequentially doubly robust (SDR) if, at each subsequent time
point, either the outcome regression or the treatment mechanism is consistently
estimated. This form of robustness is exactly what one would anticipate is
attainable by studying the remainder term of a first-order expansion of the
G-formula parameter. We show that a particular implementation of an existing
procedure is SDR. We also introduce a novel SDR estimator, whose development
involves a novel translation of ideas used in targeted minimum loss-based
estimation to the infinite-dimensional setting.
| arxiv topic:stat.ME |
arxiv_dataset-84611705.02559 | An equation for a time-dependent profit rate
q-fin.EC math.DS
Taking as a hypothesis a form of the labour theory of value, and $without$
$assuming$ $equilibrium$, we derive an equation that yields the profit-rate
$\pi$ as a function of time. For a mature economy, $\pi(t)$ reduces to the
product of two factors: ($i$) a certain $retarded$ $average$ of the sum of the
growth-rates of productivity and of the size of the labour-force measured by
hours worked, and ($ii$) the ratio of the current rate of surplus value to its
own retarded average. We also suggest an empirical test of the equation.
| arxiv topic:q-fin.EC math.DS |
arxiv_dataset-84621705.02659 | Mass modelling of superthin galaxies: IC5249, UGC7321 and IC2233
astro-ph.GA
Superthin galaxies are low surface brightness disc galaxies, characterised by
optical discs with strikingly high values of planar-to-vertical axes ratios
($>$ 10), the physical origin and evolution of which continue to be a puzzle.
We present mass models for three superthin galaxies: IC5249, UGC7321 and
IC2233. We use high resolution rotation curves and gas surface density
distributions obtained from HI 21 cm radio-synthesis observations, in
combination with their two-dimensional structural surface brightness
decompositions at Spitzer 3.6 $\mu$m band, all of which were available in the
literature. We find that while models with the pseudo-isothermal (PIS) and the
Navarro-Frenk-White (NFW) dark matter density profiles fit the observed
rotation curves of IC5249 and UGC7321 equally well, those with the NFW profile
does not comply with the slowly-rising rotation curve of IC2233. Interestingly,
for all of our sample galaxies, the best-fitting mass models with a PIS dark
matter density profile indicate a {\it compact} dark matter halo i.e.,
$R_c/R_D$ $<$ 2 where $R_c$ is the core radius of the PIS dark matter halo, and
$R_D$ is the radial scale-length of the exponential stellar disc. The compact
dark matter halo may be fundamentally responsible for the superthin nature of
the stellar disc, and therefore our results may have important implications for
the formation and evolution models of superthin galaxies in the universe.
| arxiv topic:astro-ph.GA |
arxiv_dataset-84631705.02759 | On toric face rings I
math.AG math.CO
We construct an explicit Deligne - Du Bois complex for algebraic varieties
which are locally analytically isomorphic to the spectrum of a toric face ring.
| arxiv topic:math.AG math.CO |
arxiv_dataset-84641705.02859 | Traveling-wave parametric amplifier based on three-wave mixing in a
Josephson metamaterial
cond-mat.supr-con quant-ph
We have developed a recently proposed Josephson traveling-wave parametric
amplifier with three-wave mixing [A. B. Zorin, Phys. Rev. Applied 6, 034006,
2016]. The amplifier consists of a microwave transmission line formed by a
serial array of nonhysteretic one-junction SQUIDs. These SQUIDs are flux-biased
in a way that the phase drops across the Josephson junctions are equal to 90
degrees and the persistent currents in the SQUID loops are equal to the
Josephson critical current values. Such a one-dimensional metamaterial
possesses a maximal quadratic nonlinearity and zero cubic (Kerr) nonlinearity.
This property allows phase matching and exponential power gain of traveling
microwaves to take place over a wide frequency range. We report the
proof-of-principle experiment performed at a temperature of T = 4.2 K on Nb
trilayer samples, which has demonstrated that our concept of a practical
broadband Josephson parametric amplifier is valid and very promising for
achieving quantum-limited operation.
| arxiv topic:cond-mat.supr-con quant-ph |
arxiv_dataset-84651705.02959 | Analysis of zero modes for Dirac operators with magnetic links
math-ph math.MP
In this paper we provide a means to approximate Dirac operators with magnetic
fields supported on links in $\mathbb{S}^3$ (and $\mathbb{R}^3$) by Dirac
operators with smooth magnetic fields. We then proceed to prove that under
certain assumptions, the spectral flow of paths along these operators is the
same in both the smooth and the singular case. We recently characterized the
spectral flow of such paths in the singular case. This allows us to show the
existence of new smooth, compactly supported magnetic fields in $\mathbb{R}^3$
for which the associated Dirac operator has a non-trivial kernel. Using
Clifford analysis, we also obtain criteria on the magnetic link for the
non-existence of zero modes.
| arxiv topic:math-ph math.MP |
arxiv_dataset-84661705.03059 | Automatic classification of automorphisms of lower-dimensional Lie
algebras
math.RA
We implement two algorithms in MATHEMATICA for classifying automorphisms of
lower-dimensional non-commutative Lie algebras. The first algorithm is a
brute-force approach whereas the second is an evolutionary strategy. These
algorithms are delivered as the MATHEMATICA package cwsAutoClass. In order to
facilitate the application of this package to symmetry Lie algebras of
differential equations, we also provide a package, cwsLieSymTools, for
manipulating finite-dimensional Lie algebras of vector fields. In particular,
this package allows the computations of Lie brackets, structure constants, and
the visualization of commutator tables. Several examples are provided to
illustrate the pertinence of our approach.
| arxiv topic:math.RA |
arxiv_dataset-84671705.03159 | Contour Detection from Deep Patch-level Boundary Prediction
cs.CV
In this paper, we present a novel approach for contour detection with
Convolutional Neural Networks. A multi-scale CNN learning framework is designed
to automatically learn the most relevant features for contour patch detection.
Our method uses patch-level measurements to create contour maps with
overlapping patches. We show the proposed CNN is able to to detect large-scale
contours in an image efficienly. We further propose a guided filtering method
to refine the contour maps produced from large-scale contours. Experimental
results on the major contour benchmark databases demonstrate the effectiveness
of the proposed technique. We show our method can achieve good detection of
both fine-scale and large-scale contours.
| arxiv topic:cs.CV |
arxiv_dataset-84681705.03259 | Personalized Brain-Computer Interface Models for Motor Rehabilitation
cs.HC
We propose to fuse two currently separate research lines on novel therapies
for stroke rehabilitation: brain-computer interface (BCI) training and
transcranial electrical stimulation (TES). Specifically, we show that BCI
technology can be used to learn personalized decoding models that relate the
global configuration of brain rhythms in individual subjects (as measured by
EEG) to their motor performance during 3D reaching movements. We demonstrate
that our models capture substantial across-subject heterogeneity, and argue
that this heterogeneity is a likely cause of limited effect sizes observed in
TES for enhancing motor performance. We conclude by discussing how our
personalized models can be used to derive optimal TES parameters, e.g.,
stimulation site and frequency, for individual patients.
| arxiv topic:cs.HC |
arxiv_dataset-84691705.03359 | Left-invariant Grauert tubes on SU(2)
math.DG
Let M be a real analytic Riemannian manifold. An adapted complex structure on
TM is a complex structure on a neighborhood of the zero section such that the
leaves of the Riemann foliation are complex submanifolds. This structure is
called entire if it may be extended to the whole of TM. We call such manifolds
Grauert tubes, or simply tubes. We consider here the case of M = G a compact
connected Lie group with a left-invariant metric, and try to determine for
which such metrics the associated tube is entire. It is well-known that the
Grauert tube of a bi-invariant metric on a Lie group is entire. The case of the
smallest group SU(2) is treated completely, thanks to the complete
integrability of the geodesic flow for such a metric, a standard result in
classical mechanics. Along the way we find a new obstruction to tubes being
entire which is made visible by the complete integrability. (New reference and
exposition shortened, 11/17/2017.)
| arxiv topic:math.DG |
arxiv_dataset-84701705.03459 | Bulk and surface electronic properties of SmB6: a hard x-ray
photoelectron spectroscopy study
cond-mat.mtrl-sci
We have carried out bulk-sensitive hard x-ray photoelectron spectroscopy
(HAXPES) measurements on in-situ cleaved and ex-situ polished SmB6 single
crystals. Using the multiplet-structure in the Sm 3d core level spectra, we
determined reliably that the valence of Sm in bulk SmB6 is close to 2.55 at ~5
K. Temperature dependent measurements revealed that the Sm valence gradually
increases to 2.64 at 300 K. From a detailed line shape analysis we can clearly
observe that not only the J=0 but also the J=1 state of the Sm 4f 6
configuration becomes occupied at elevated temperatures. Making use of the
polarization dependence, we were able to identify and extract the Sm 4f
spectral weight of the bulk material. Finally, we revealed that the oxidized or
chemically damaged surface region of the ex-situ polished SmB6 single crystal
is surprisingly thin, about 1 nm only.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-84711705.03559 | Tailoring Heterovalent Interface Formation with Light
cond-mat.mtrl-sci
Integrating different semiconductor materials into an epitaxial device
structure offers additional degrees of freedom to select for optimal material
properties in each layer. However, interface between materials with different
valences (i.e. III-V, II-VI and IV semiconductors) can be difficult to form
with high quality. Using ZnSe/GaAs as a model system, we explore the use of UV
illumination during heterovalent interface growth by molecular beam epitaxy as
a way to modify the interface properties. We find that UV illumination alters
the mixture of chemical bonds at the interface, permitting the formation of
Ga-Se bonds that help to passivate the underlying GaAs layer. Illumination also
helps to reduce defects in the ZnSe epilayer. These results suggest that
moderate UV illumination during growth may be used as a way to improve the
optical properties of both the GaAs and ZnSe layers on either side of the
interface.
| arxiv topic:cond-mat.mtrl-sci |
arxiv_dataset-84721705.03659 | Discussion on "Random-projection ensemble classification" by T. Cannings
and R. Samworth
stat.ME math.ST stat.TH
Discussion on "Random-projection ensemble classification" by T. Cannings and
R. Samworth. We believe that the proposed approach can find many applications
in economics such as credit scoring (e.g. Altman (1968)) and can be extended to
more general type of classifiers. In this discussion we would like to draw
authors attention to the copula-based discriminant analysis (Han et al. (2013)
and He et al. (2016)).
| arxiv topic:stat.ME math.ST stat.TH |
arxiv_dataset-84731705.03759 | Vietoris type theorem related to positivity of trigonometric polynomials
math.CA math.CV
In this work, a Vietoris type theorem for the positivity of sine and cosine
sum for a particular sequence of real numbers is provided. In this connection,
the positivity of a particular type of sine sum involving ratio of some
parameters is given, which is new in the literature. Various new results that
follow from the Vietoris type theorem include improved estimates for the
location of the zeros of a class of trigonometric polynomials and new positive
sums for orthogonal polynomials. An open problem is also provided for the
partial sums of the generalized polylogarithm.
| arxiv topic:math.CA math.CV |
arxiv_dataset-84741705.03859 | Modified Turaev-Viro Invariants from quantum sl(2|1)
math.GT math.QA
The category of finite dimensional module over the quantum superalgebra
U_q(sl(2|1)) is not semi-simple and the quantum dimension of a generic
U_q(sl(2|1))-module vanishes. This vanishing happens for any value of q (even
when q is not a root of unity). These properties make it difficult to create a
fusion or modular category. Loosely speaking, the standard way to obtain such a
category from a quantum group is: 1) specialize q to a root of unity; this
forces some modules to have zero quantum dimension, 2) quotient by morphisms of
modules with zero quantum dimension, 3) show the resulting category is finite
and semi-simple. In this paper we show an analogous construction works in the
context of U_q(sl(2|1)) by replacing the vanishing quantum dimension with a
modified quantum dimension. In particular, we specialize q to a root of unity,
quotient by morphisms of modules with zero modified quantum dimension and show
the resulting category is generically finite semi-simple. Moreover, we show the
categories of this paper are relative G-spherical categories. As a consequence
we obtain invariants of 3-manifold with additional structures.
| arxiv topic:math.GT math.QA |
arxiv_dataset-84751705.03959 | Uniqueness for weak solutions of parabolic equations with a fractional
time derivative
math.AP
We prove uniqueness for weak solutions to abstract parabolic equations with
the fractional Marchaud or Caputo time derivative. We consider weak solutions
in time for divergence form equations when the fractional derivative is
transferred to the test function.
| arxiv topic:math.AP |
arxiv_dataset-84761705.04059 | Rigid realizations of modular forms in Calabi--Yau threefolds
math.AG
We construct examples of modular rigid Calabi--Yau threefolds, which give a
realization of some new weight 4 cusp forms.
| arxiv topic:math.AG |
arxiv_dataset-84771705.04159 | Distributed Bayesian Probabilistic Matrix Factorization
cs.DC
Matrix factorization is a common machine learning technique for recommender
systems. Despite its high prediction accuracy, the Bayesian Probabilistic
Matrix Factorization algorithm (BPMF) has not been widely used on large scale
data because of its high computational cost. In this paper we propose a
distributed high-performance parallel implementation of BPMF on shared memory
and distributed architectures. We show by using efficient load balancing using
work stealing on a single node, and by using asynchronous communication in the
distributed version we beat state of the art implementations.
| arxiv topic:cs.DC |
arxiv_dataset-84781705.04259 | The Fast and the Fiducial: Augmented kludge waveforms for detecting
extreme-mass-ratio inspirals
gr-qc astro-ph.HE
The extreme-mass-ratio inspirals (EMRIs) of stellar-mass compact objects into
massive black holes are an important class of source for the future space-based
gravitational-wave detector LISA. Detecting signals from EMRIs will require
waveform models that are both accurate and computationally efficient. In this
paper, we present the latest implementation of an augmented analytic kludge
(AAK) model, publicly available at github.com/alvincjk/EMRI_Kludge_Suite as
part of an EMRI waveform software suite. This version of the AAK model has
improved accuracy compared to its predecessors, with two-month waveform
overlaps against a more accurate fiducial model exceeding 0.97 for a generic
range of sources; it also generates waveforms 5-15 times faster than the
fiducial model. The AAK model is well suited for scoping out data analysis
issues in the upcoming round of mock LISA data challenges. A simple analytic
argument shows that it might even be viable for detecting EMRIs with LISA
through a semi-coherent template bank method, while the use of the original
analytic kludge in the same approach will result in around 90% fewer
detections.
| arxiv topic:gr-qc astro-ph.HE |
arxiv_dataset-84791705.04359 | An Extreme Rotating Black Hole in New Massive Gravity Theory
gr-qc
New Massive Gravity is an alternative theory to General Relativity that is
used to describe the gravitational field in a (2+1)-dimensional spacetime.
Black hole solutions have been found in this theory, in particular an
asymptotically anti-de Sitter rotating black hole. We analyse some features of
this solution as its event horizon, black hole area and distance to the
horizon, specially in the rotating extreme case, showing that they have shared
features with extreme black holes in 4-dimensional General relativity. This
limit case is interesting in the search of geometric inequalities as the ones
found for the Kerr black hole in (3+1)-General Relativity.
| arxiv topic:gr-qc |
arxiv_dataset-84801705.04459 | Optimal estimates for the perfect conductivity problem with inclusions
close to the boundary
math.AP
When a convex perfectly conducting inclusion is closely spaced to the
boundary of the matrix domain, a bigger convex domain containing the inclusion,
the electric field can be arbitrary large. We establish both the pointwise
upper bound and the lower bound of the gradient estimate for this perfect
conductivity problem by using the energy method. These results give the optimal
blow-up rates of electric field for conductors with arbitrary shape and in all
dimensions. A particular case when a circular inclusion is close to the
boundary of a circular matrix domain in dimension two is studied earlier by
Ammari,Kang,Lee,Lee and Lim(2007). From the view of methodology, the technique
we develop in this paper is significantly different from the previous one
restricted to the circular case, which allows us further investigate the
general elliptic equations with divergence form.
| arxiv topic:math.AP |
arxiv_dataset-84811705.04559 | Quantum Coherent Control via Pauli Blocking
quant-ph
Coherent quantum control over many-particle quantum systems requires high
fidelity dynamics. One way of achieving this is to use adiabatic schemes where
the system follows an instantaneous eigenstate of the Hamiltonian over
timescales that do not allow transitions to other states. This, however, makes
control dynamics very slow. Here we introduce another concept that takes
advantage of preventing unwanted transitions in fermionic systems by using
Pauli blocking: excitations from a protected ground state to higher-lying
states are avoided by adding a layer of buffer fermions, such that the
protected fermions cannot make a transition to higher lying excited states
because these are already occupied. This allows to speed-up adiabatic
evolutions of the system. We do a thorough investigation of the technique, and
demonstrate its power by applying it to high fidelity transport, trap expansion
and splitting in ultracold atoms systems in anharmonic traps. Close analysis of
these processes also leads to insights into the structure of the orthogonality
catastrophe phenomenon.
| arxiv topic:quant-ph |
arxiv_dataset-84821705.04659 | Witt rings of quadratically presentable fields
math.RA
This paper introduces a novel approach to the axiomatic theory of quadratic
forms. We work internally in a category of certain partially ordered sets,
subject to additional conditions which amount to a strong form of local
presentability. We call such partial orders presentable. It turns out that the
classical notion of the Witt ring of symmetric bilinear forms over a field
makes sense in the context of quadratically presentable fields, that is fields
equipped with a presentable partial order inequationaly compatible with the
algebraic operations. As an application, we show that Witt rings of symmetric
bilinear forms over fields, of both characteristic 2 and not 2, are isomorphic
to Witt rings of suitably built quadratically presentable fields, which
therefore provide a uniform construction of Witt rings for all characteristics.
| arxiv topic:math.RA |
arxiv_dataset-84831705.04759 | Conditional phase gate and quantum state transfer via off-resonant
quantum Zeno dynamics
quant-ph
We propose a scheme to realize the conditional phase gate (CPG) and quantum
state transfer (QST) between two qubits (acted by nitrogen-vacancy (NV)
centers) based on off-resonant quantum Zeno dynamics. We also consider the
entanglement dynamics of two qubits in this system. Since no cavity photons or
excited levels of the NV center is populated during the whole process, the
scheme is immune to the decay of cavity and spontaneous emission of the NV
center. The strictly numerical simulation shows that the fidelities of QST and
CPG are high even in the presence of realistic imperfections.
| arxiv topic:quant-ph |
arxiv_dataset-84841705.04859 | Amplitudes, recursion relations and unitarity in the Abelian Higgs Model
hep-ph
The Abelian Higgs model forms an essential part of the electroweak standard
model: it is the sector containing only Z and Higgs bosons. We present a
diagram-based proof of the tree-level unitarity of this model inside the
unitary gauge, where only physical degrees of freedom occur. We derive
combinatorial recursion relations for off-shell amplitudes in the massless
approximation, which allows us to prove the cancellation of the first two
orders in energy of unitarity-violating high-energy behaviour for any
tree-level amplitude in this model. We describe a deformation of the amplitudes
by extending the physical phase space to at least 7 spacetime dimensions, which
leads to on-shell recursion relations a la BCFW. These lead to a simple proof
that all on-shell tree amplitudes obey partial-wave unitarity.
| arxiv topic:hep-ph |
arxiv_dataset-84851705.04959 | A simplex-type algorithm for continuous linear programs with constant
coefficients
math.OC
We consider continuous linear programs over a continuous finite time horizon
$T$, with a constant coefficient matrix, linear right hand side functions and
linear cost coefficient functions, where we search for optimal solutions in the
space of measures or of functions of bounded variation. These models generalize
the separated continuous linear programming models and their various duals, as
formulated in the past by Anderson, by Pullan, and by Weiss. In previous papers
we have shown that these problems possess optimal strongly dual solutions. We
also have presented a detailed description of optimal solutions and have
defined a combinatorial analogue to basic solutions of standard LP. In this
paper we present an algorithm which solves this class of problems in a finite
bounded number of steps, using an analogue of the simplex method, in the space
of measures.
| arxiv topic:math.OC |
arxiv_dataset-84861705.05059 | Electromagnetic Scattering Laws in Weyl Systems
physics.optics
Wavelength determines the length scale of the cross section when
electromagnetic waves are scattered by an electrically small object. The cross
section diverges for resonant scattering, and diminishes for non-resonant
scattering, when wavelength approaches infinity. This scattering law explains
the color of the sky as well as the strength of a mobile phone signal. We show
that such wavelength scaling comes from free space's conical dispersion at zero
frequency. Emerging Weyl systems, offering similar dispersion at non-zero
frequencies, lead to new laws of electromagnetic scattering that allow cross
sections to be decoupled from the wavelength limit. Diverging and diminishing
cross sections can be realized at any target wavelength in a Weyl system,
providing unprecedented ability to tailor the strength of wave-matter
interactions for radio-frequency and optical applications.
| arxiv topic:physics.optics |
arxiv_dataset-84871705.05159 | Diffusion in time-dependent random media and the Kardar-Parisi-Zhang
equation
cond-mat.dis-nn cond-mat.stat-mech
Although time-dependent random media with short range correlations lead to
(possibly biased) normal tracer diffusion, anomalous fluctuations occur away
from the most probable direction. This was pointed out recently in 1D lattice
random walks, where statistics related to the 1D Kardar- Parisi-Zhang (KPZ)
universality class, i.e. the GUE Tracy Widom distribution, were shown to arise.
Here we provide a simple picture for this correspondence, directly in the
continuum as well as for lattice models, which allows to study arbitrary space
dimension and to predict a variety of universal distributions. In $d = 1$ we
predict and verify numerically the emergence of the GOE Tracy-Widom
distribution for the fluctuations of the transition probability. In $d = 3$ we
predict a phase transition from Gaussian fluctuations to 3D-KPZ type
fluctuations as the bias is increased. We predict KPZ universal distributions
for the arrival time of a first particle from a cloud diffusing in such media.
| arxiv topic:cond-mat.dis-nn cond-mat.stat-mech |
arxiv_dataset-84881705.05259 | Reduction of quantum systems and the local Gauss law
math-ph math.MP math.OA
We give an operator-algebraic interpretation of the notion of an ideal
generated by the unbounded operators associated to the elements of the Lie
algebra of a Lie group that implements the symmetries of a quantum system. We
use this interpretation to establish a link between Rieffel induction and the
implementation of a local Gauss law in lattice gauge theories similar to the
method discussed by Kijowski and Rudolph in [5, 6].
| arxiv topic:math-ph math.MP math.OA |
arxiv_dataset-84891705.05359 | Remarks on regular black holes
gr-qc
Recently it has been claimed by Chinaglia and Zerbini that the curvature
singularity is present even in the so-called regular black hole solutions of
the Einstein equations. In this brief note we show that this criticism is
devoid of any physical content.
| arxiv topic:gr-qc |
arxiv_dataset-84901705.05459 | First- and Second-Order Models of Recursive Arithmetics
cs.LO
We study a quadruple of interrelated subexponential subsystems of arithmetic
WKL$_0^-$, RCA$^-_0$, I$\Delta_0$, and $\Delta$RA$_1$, which complement the
similarly related quadruple WKL$_0$, RCA$_0$, I$\Sigma_1$, and PRA studied by
Simpson, and the quadruple WKL$_0^\ast$, RCA$_0^\ast$, I$\Delta_0$(exp), and
EFA studied by Simpson and Smith. We then explore the space of subexponential
arithmetic theories between I$\Delta_0$ and I$\Delta_0$(exp). We introduce and
study first- and second-order theories of recursive arithmetic $A$RA$_1$ and
$A$RA$_2$ capable of characterizing various computational complexity classes
and based on function algebras $A$, studied by Clote and others.
| arxiv topic:cs.LO |
arxiv_dataset-84911705.05559 | On a non-solenoidal approximation to the incompressible Navier-Stokes
equations
math.AP
We establish an asymptotic profile that sharply describes the behavior as
$t\to\infty$ for solutions to a non-solenoidal approximation of the
incompressible Navier-Stokes equations introduced by Temam. The solutions of
Temam's model are known to converge to the corresponding solutions of the
classical Navier-Stokes, e.g., in $L^3\_{\rm loc} (R^+ \times R^3)$, provided
$\epsilon\to0$, where $\epsilon>0$ is the physical parameter related to the
artificial compressibility term. However, we show that such model is no longer
a good approximation of Navier-Stokes for large times: indeed, its solutions
can decay much slower as $t\to+\infty$ than the corresponding solutions of
Navier-Stokes.
| arxiv topic:math.AP |
arxiv_dataset-84921705.05659 | $B$ decays to radially excited $D$ mesons in Heavy Quark Effective
Theory
hep-ph hep-ex hep-lat
Semileptonic transitions $\overline{B} \to D^{(n)} \ell \overline{\nu}$,
where $D^{(n)} (n \not = 0)$ is a radially excited meson, have recently
attracted much attention as a way to understand some puzzles between theory and
data. Following closely the formalism of Falk and Neubert for the elastic case,
we study the $1/m_Q$ corrections to the heavy quark limit, in which the
inelastic Isgur-Wise function vanishes at zero recoil, $\xi^{(n)}(1) = 0\ (n
\not = 0)$. We find simple formulas that involve the derivative
$\xi^{(n)'}(1)$, and we propose a number of ways of isolating this quantity in
practice. We formulate also a generalization to the inelastic case of Luke's
theorem. On the other hand, although some $1/m_Q$ HQET results are satisfied in
the Bakamjian-Thomas relativistic quark model, we emphasize the problems
concerning these corrections in this scheme.
| arxiv topic:hep-ph hep-ex hep-lat |
arxiv_dataset-84931705.05759 | Electromagnetic Response during a Quench Dynamics to Superconducting
State: Time-Dependent Ginzburg-Landau Analysis
cond-mat.supr-con cond-mat.stat-mech
We use a numerical solution of the deterministic TDGL equations to determine
the response induced by a probe field in a material quenched into a
superconducting state. We characterize differences in response according to
whether the probe is applied before, during, or after the phase stiffness has
built up to its final steady state value.
| arxiv topic:cond-mat.supr-con cond-mat.stat-mech |
arxiv_dataset-84941705.05859 | Correlation Functions of the Pfaffian Schur Process Using Macdonald
Difference Operators
math.PR math-ph math.CO math.MP
We study the correlation functions of the Pfaffian Schur process. Borodin and
Rains [J. Stat. Phys. 121 (2005), 291-317] introduced the Pfaffian Schur
process and derived its correlation functions using a Pfaffian analogue of the
Eynard-Mehta theorem. We present here an alternative derivation of the
correlation functions using Macdonald difference operators.
| arxiv topic:math.PR math-ph math.CO math.MP |
arxiv_dataset-84951705.05959 | Constraint Energy Minimizing Generalized Multiscale Finite Element
Method in the Mixed Formulation
math.NA
This paper presents a novel mass-conservative mixed multiscale method for
solving flow equations in heterogeneous porous media. The media properties (the
permeability) contain multiple scales and high contrast. The proposed method
solves the flow equation in a mixed formulation on a coarse grid by
constructing multiscale basis functions. The resulting velocity field is mass
conservative on the fine grid. Our main goal is to obtain first-order
convergence in terms of the mesh size which is independent of local contrast.
This is achieved, first, by constructing some auxiliary spaces, which contain
global information that can not be localized, in general. This is built on our
previous work on the Generalized Multiscale Finite Element Method (GMsFEM). In
the auxiliary space, multiscale basis functions corresponding to small
(contrast-dependent) eigenvalues are selected. These basis functions represent
the high-conductivity channels (which connect the boundaries of a coarse
block). Next, we solve local problems to construct multiscale basis functions
for the velocity field. These local problems are formulated in the oversampled
domain taking into account some constraints with respect to auxiliary spaces.
The latter allows fast spatial decay of local solutions and, thus, allows
taking smaller oversampled regions. The number of basis functions depends on
small eigenvalues of the local spectral problems. Moreover, multiscale pressure
basis functions are needed in constructing the velocity space. Our multiscale
spaces have a minimal dimension, which is needed to avoid contrast-dependence
in the convergence. The method's convergence requires an oversampling of
several layers. We present an analysis of our approach. Our numerical results
confirm that the convergence rate is first order with respect to the mesh size
and independent of the contrast.
| arxiv topic:math.NA |
arxiv_dataset-84961705.06059 | Neutrino detectors for oscillation experiments
physics.ins-det hep-ex
A brief overview of the development of neutrino detectors for long-baseline
oscillation experiments at accelerators and reactors is presented. Basic
principles and main features of detectors of running accelerator experiments
T2K and NOvA sensitive to a first level of CP violation and neutrino mass
hierarchy, and reactor experiments Daya Bay, RENO and Double Chooz which
measured the mixing angle \theta_13 are discussed. A variety of different
experimental techniques is proposed and developed for the next generation
oscillation experiments: a 20 kt scintillator detector for the reactor
experiment JUNO, a 0.52 kt water-Cherenkov detector Hyper-Kamiokande, and a
massive liquid argon time-projection chamber neutrino detector envisaged for
the DUNE experiment. Present status of these detectors, recent progress in R&D
and future prospects are summarized in this paper.
| arxiv topic:physics.ins-det hep-ex |
arxiv_dataset-84971705.06159 | Fluctuations in quantum mechanics and field theories from a new version
of semiclassical theory. II
hep-th nucl-th quant-ph
This is the second paper on semiclassical approach based on the density
matrix given by the Euclidean time path integral with fixed coinciding
endpoints. The classical path, interpolating between this point and the
classical vacuum, called "flucton", plus systematic one- and two-loop
corrections, has been calculated in the first paper \cite{Escobar-Ruiz:2016aqv}
for double-well potential and now extended for a number of quantum-mechanical
problems (anharmonic oscillator, sine-Gordon potential). The method is based on
systematic expansion in Feynman diagrams and thus can be extended to QFTs. We
show that the loop expansion in QM reminds the leading log-approximations in
QFT. In this sequel we present complete set of results obtained using this
method in unified way. Alternatively, starting from the Schr\"{o}dinger
equation we derive a {\it generalized} Bloch equation which semiclassical-like,
iterative solution generates the loop expansion. We re-derive two loop
expansions for all three above potentials and now extend it to three loops,
which has not yet been done via Feynman diagrams. All results for both methods
are fully consistent with each other. Asymmetric (tilted) double-well potential
(non-degenerate minima) is also studied using the second method.
| arxiv topic:hep-th nucl-th quant-ph |
arxiv_dataset-84981705.06259 | Joint models for grid point and response processes in longitudinal and
functional data
stat.ME
The distribution of the grid points at which a response function is observed
in longitudinal or functional data applications is often informative and not
independent of the response process. In this paper we introduce a covariation
model to estimate and make inferences about this interrelation, by treating the
data as replicated realizations of a marked point process. We derive maximum
likelihood estimators, the asymptotic distribution of the estimators, and study
the estimators' behavior by simulation. We apply the model to an online auction
data set and show that there is a strong correlation between bidding patterns
and price trajectories.
| arxiv topic:stat.ME |
arxiv_dataset-84991705.06359 | Toric log del Pezzo surfaces with one singularity
math.AG math.CO
This paper focuses on the classification of all toric log Del Pezzo surfaces
with exactly one singularity up to isomorphism, and on the description of how
they are embedded as intersections of finitely many quadrics into suitable
projective spaces.
| arxiv topic:math.AG math.CO |
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