id stringlengths 16 29 | text stringlengths 86 3.49k | source stringlengths 14 112 |
|---|---|---|
arxiv_dataset-96001803.09867 | Towards Human-Machine Cooperation: Self-supervised Sample Mining for
Object Detection
cs.CV
Though quite challenging, leveraging large-scale unlabeled or partially
labeled images in a cost-effective way has increasingly attracted interests for
its great importance to computer vision. To tackle this problem, many Active
Learning (AL) methods have been developed. However, these methods mainly define
their sample selection criteria within a single image context, leading to the
suboptimal robustness and impractical solution for large-scale object
detection. In this paper, aiming to remedy the drawbacks of existing AL
methods, we present a principled Self-supervised Sample Mining (SSM) process
accounting for the real challenges in object detection. Specifically, our SSM
process concentrates on automatically discovering and pseudo-labeling reliable
region proposals for enhancing the object detector via the introduced cross
image validation, i.e., pasting these proposals into different labeled images
to comprehensively measure their values under different image contexts. By
resorting to the SSM process, we propose a new AL framework for gradually
incorporating unlabeled or partially labeled data into the model learning while
minimizing the annotating effort of users. Extensive experiments on two public
benchmarks clearly demonstrate our proposed framework can achieve the
comparable performance to the state-of-the-art methods with significantly fewer
annotations.
| arxiv topic:cs.CV |
arxiv_dataset-96011803.09967 | Reinforcement Learning for Fair Dynamic Pricing
cs.LG cs.AI stat.ML
Unfair pricing policies have been shown to be one of the most negative
perceptions customers can have concerning pricing, and may result in long-term
losses for a company. Despite the fact that dynamic pricing models help
companies maximize revenue, fairness and equality should be taken into account
in order to avoid unfair price differences between groups of customers. This
paper shows how to solve dynamic pricing by using Reinforcement Learning (RL)
techniques so that prices are maximized while keeping a balance between revenue
and fairness. We demonstrate that RL provides two main features to support
fairness in dynamic pricing: on the one hand, RL is able to learn from recent
experience, adapting the pricing policy to complex market environments; on the
other hand, it provides a trade-off between short and long-term objectives,
hence integrating fairness into the model's core. Considering these two
features, we propose the application of RL for revenue optimization, with the
additional integration of fairness as part of the learning procedure by using
Jain's index as a metric. Results in a simulated environment show a significant
improvement in fairness while at the same time maintaining optimisation of
revenue.
| arxiv topic:cs.LG cs.AI stat.ML |
arxiv_dataset-96021803.10067 | Safe Non-blocking Synchronization in Ada 202x
cs.PL
The mutual-exclusion property of locks stands in the way to scalability of
parallel programs on many-core architectures. Locks do not allow progress
guarantees, because a task may fail inside a critical section and keep holding
a lock that blocks other tasks from accessing shared data. With non-blocking
synchronization, the drawbacks of locks are avoided by synchronizing access to
shared data by atomic read-modify-write operations. To incorporate non-blocking
synchronization in Ada~202x, programmers must be able to reason about the
behavior and performance of tasks in the absence of protected objects and
rendezvous. We therefore extend Ada's memory model by synchronized types, which
support the expression of memory ordering operations at a sufficient level of
detail. To mitigate the complexity associated with non-blocking
synchronization, we propose concurrent objects as a novel high-level language
construct. Entities of a concurrent object execute in parallel, due to a
fine-grained, optimistic synchronization mechanism. Synchronization is framed
by the semantics of concurrent entry execution. The programmer is only required
to label shared data accesses in the code of concurrent entries. Labels
constitute memory-ordering operations expressed through attributes. To the best
of our knowledge, this is the first approach to provide a non-blocking
synchronization construct as a first-class citizen of a high-level programming
language. We illustrate the use of concurrent objects by several examples.
| arxiv topic:cs.PL |
arxiv_dataset-96031803.10167 | The Poisson equation on manifolds with positive essential spectrum
math.DG math.AP
We show existence of solutions to the Poisson equation on Riemannian
manifolds with positive essential spectrum, assuming a sharp pointwise decay on
the source function. In particular we can allow the Ricci curvature to be
unbounded from below. In comparison with previous works, we can deal with a
more general setting both on the spectrum and on the curvature bounds.
| arxiv topic:math.DG math.AP |
arxiv_dataset-96041803.10267 | Real-Time Computability of Real Numbers by Chemical Reaction Networks
cs.CC cs.ET
We explore the class of real numbers that are computed in real time by
deterministic chemical reaction networks that are integral in the sense that
all their reaction rate constants are positive integers. We say that such a
reaction network computes a real number $\alpha$ in real time if it has a
designated species $X$ such that, when all species concentrations are set to
zero at time $t = 0$, the concentration $x(t)$ of $X$ is within $2^{-t}$ of
$|{\alpha}|$ at all times $t \ge 1$, and the concentrations of all other
species are bounded. We show that every algebraic number and some
transcendental numbers are real time computable by chemical reaction networks
in this sense. We discuss possible implications of this for the 1965
Hartmanis-Stearns conjecture, which says that no irrational algebraic number is
real time computable by a Turing machine.
| arxiv topic:cs.CC cs.ET |
arxiv_dataset-96051803.10367 | Non-Equilibrium Chemistry and Destruction of CO by X-ray Flares
astro-ph.GA astro-ph.HE
Sources of X-rays such as active galactic nuclei and X-ray binaries are often
variable by orders of magnitude in luminosity over timescales of years. During
and after these flares the surrounding gas is out of chemical and thermal
equilibrium. We introduce a new implementation of X-ray radiative transfer
coupled to a time-dependent chemical network for use in 3D
magnetohydrodynamical simulations. A static fractal molecular cloud is
irradiated with X-rays of different intensity, and the chemical and thermal
evolution of the cloud are studied. For a simulated $10^5$ M$_\odot$ fractal
cloud an X-ray flux $<0.01$ erg cm$^{-2}$ s$^{-1}$ allows the cloud to remain
molecular, whereas most of the CO and H$_2$ are destroyed for a flux of $>1$
erg cm$^{-2}$ s$^{-1}$. The effects of an X-ray flare, which suddenly increases
the X-ray flux by $10^5 \times$ are then studied. A cloud exposed to a bright
flare has 99% of its CO destroyed in 10-20 years, whereas it takes $>10^3$
years for 99% of the H$_2$ to be destroyed. CO is primarily destroyed by
locally generated far-UV emission from collisions between non-thermal electrons
and H$_2$; He$^+$ only becomes an important destruction agent when the CO
abundance is already very small. After the flare is over, CO re-forms and
approaches its equilibrium abundance after $10^3-10^5$ years. This implies that
molecular clouds close to Sgr A$^*$ in the Galactic Centre may still be out of
chemical equilibrium, and we predict the existence of clouds near flaring X-ray
sources in which CO has been mostly destroyed but H is fully molecular.
| arxiv topic:astro-ph.GA astro-ph.HE |
arxiv_dataset-96061803.10467 | A parametric symmetry breaking transducer
cond-mat.mes-hall
Force detectors rely on resonators to transduce forces into a readable
signal. Usually these resonators operate in the linear regime and their signal
appears amidst a competing background comprising thermal or quantum
fluctuations as well as readout noise. Here, we demonstrate that a parametric
symmetry breaking transduction leads to a novel and robust nonlinear force
detection in the presence of noise. The force signal is encoded in the
frequency at which the system jumps between two phase states which are
inherently protected against phase noise. Consequently, the transduction
effectively decouples from readout noise channels. For a controlled
demonstration of the method, we experiment with a macroscopic doubly-clamped
string. Our method provides a promising new paradigm for high-precision force
detection.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-96071803.10567 | Image Generation and Translation with Disentangled Representations
cs.CV cs.AI cs.NE
Generative models have made significant progress in the tasks of modeling
complex data distributions such as natural images. The introduction of
Generative Adversarial Networks (GANs) and auto-encoders lead to the
possibility of training on big data sets in an unsupervised manner. However,
for many generative models it is not possible to specify what kind of image
should be generated and it is not possible to translate existing images into
new images of similar domains. Furthermore, models that can perform
image-to-image translation often need distinct models for each domain, making
it hard to scale these systems to multiple domain image-to-image translation.
We introduce a model that can do both, controllable image generation and
image-to-image translation between multiple domains. We split our image
representation into two parts encoding unstructured and structured information
respectively. The latter is designed in a disentangled manner, so that
different parts encode different image characteristics. We train an encoder to
encode images into these representations and use a small amount of labeled data
to specify what kind of information should be encoded in the disentangled part.
A generator is trained to generate images from these representations using the
characteristics provided by the disentangled part of the representation.
Through this we can control what kind of images the generator generates,
translate images between different domains, and even learn unknown
data-generating factors while only using one single model.
| arxiv topic:cs.CV cs.AI cs.NE |
arxiv_dataset-96081803.10667 | Cubical rectangles and rectangular lattices
math.CO
Cubical rectangles are being defined and explored here over the
$n-$dimensional geometric cube $Q_n.$ They form a new class of geometric
objects that includes all the edges and all the squares of the $n-$cube. We
enumerate and characterize them here in order to construct new posets,
transforming into special lattices that will be called rectangular lattices. We
show that rectangular lattices are closely related to the class of cubical
lattices, that is, the face lattice of the $n-$cube.
| arxiv topic:math.CO |
arxiv_dataset-96091803.10767 | New aspect of critical nonlinearly charged black hole
gr-qc hep-th
The motion of a point charged particle moving in the background of the
critical power Maxwell charged AdS black holes, in a probe approximation is
studied. The extended phase space, where the cosmological constant appears as a
pressure, is regarded and the effective potential is investigated. At last, the
mass-to-charge ratio and the large q limit are studied.
| arxiv topic:gr-qc hep-th |
arxiv_dataset-96101803.10867 | Tuning the dipole-dipole interaction in a quantum gas with a rotating
magnetic field
cond-mat.quant-gas physics.atom-ph quant-ph
We demonstrate the tuning of the magnetic dipole-dipole interaction (DDI)
within a dysprosium Bose-Einstein condensate by rapidly rotating the
orientation of the atomic dipoles. The tunability of the dipolar mean-field
energy manifests as a modified gas aspect ratio after time-of-flight expansion.
We demonstrate that both the magnitude and the sign of the DDI can be tuned
using this technique. In particular, we show that a magic rotation angle exists
at which the mean-field DDI can be eliminated, and at this angle, we observe
that the expansion dynamics of the condensate is close to that predicted for a
non-dipolar gas. The ability to tune the strength of the DDI opens new avenues
toward the creation of exotic soliton and vortex states as well as unusual
quantum lattice phases and Weyl superfluids.
| arxiv topic:cond-mat.quant-gas physics.atom-ph quant-ph |
arxiv_dataset-96111803.10967 | Context-aware Synthesis for Video Frame Interpolation
cs.CV
Video frame interpolation algorithms typically estimate optical flow or its
variations and then use it to guide the synthesis of an intermediate frame
between two consecutive original frames. To handle challenges like occlusion,
bidirectional flow between the two input frames is often estimated and used to
warp and blend the input frames. However, how to effectively blend the two
warped frames still remains a challenging problem. This paper presents a
context-aware synthesis approach that warps not only the input frames but also
their pixel-wise contextual information and uses them to interpolate a
high-quality intermediate frame. Specifically, we first use a pre-trained
neural network to extract per-pixel contextual information for input frames. We
then employ a state-of-the-art optical flow algorithm to estimate bidirectional
flow between them and pre-warp both input frames and their context maps.
Finally, unlike common approaches that blend the pre-warped frames, our method
feeds them and their context maps to a video frame synthesis neural network to
produce the interpolated frame in a context-aware fashion. Our neural network
is fully convolutional and is trained end to end. Our experiments show that our
method can handle challenging scenarios such as occlusion and large motion and
outperforms representative state-of-the-art approaches.
| arxiv topic:cs.CV |
arxiv_dataset-96121803.11067 | Balanced representations, the asymptotic Plancherel formula, and
Lusztig's conjectures for $\tilde{C}_2$
math.RT
We prove Lusztig's conjectures ${\bf P1}$-${\bf P15}$ for the affine Weyl
group of type $\tilde{C}_2$ for all choices of positive weight function. Our
approach to computing Lusztig's $\mathbf{a}$-function is based on the notion of
a `balanced system of cell representations'. Once this system is established
roughly half of the conjectures ${\bf P1}$-${\bf P15}$ follow. Next we
establish an `asymptotic Plancherel Theorem' for type $\tilde{C}_2$, from which
the remaining conjectures follow. Combined with existing results in the
literature this completes the proof of Lusztig's conjectures for all rank $1$
and $2$ affine Weyl groups for all choices of parameters.
| arxiv topic:math.RT |
arxiv_dataset-96131803.11167 | Probing TeV scale origin of neutrino mass at future lepton colliders via
neutral and doubly-charged scalars
hep-ph hep-ex
We point out how future lepton colliders can provide unique insight into the
scalar sector of TeV scale models for neutrino masses with local $B-L$
symmetry. Our specific focus is on the TeV scale left-right model, which
naturally embeds this $B-L$ symmetry. In particular, we make a detailed study
of the lepton collider implications of the neutral ($H_3$) and doubly-charged
($H^{\pm\pm}$) scalars from the right-handed triplet Higgs that is responsible
for the spontaneous breaking of the $B-L$ symmetry and implementing the seesaw
mechanism. Due to mixing with other scalars, the neutral scalar $H_3$ could
acquire sizable flavor violating couplings to the charged leptons. Produced
on-shell or off-shell at the planned $e^+e^-$ colliders, it would induce
distinct lepton flavor violating signals like $e^+e^- \to \mu^\pm \tau^\mp ~
(+H_3)$, with the couplings probed up to $\sim 10^{-4}$ for a wide range of
neutral scalar mass, which is well beyond the reach of current searches for
charged lepton flavor violation. The Yukawa couplings of the doubly-charged
scalar $H^{\pm\pm}$ to the charged leptons might also be flavor-violating,
which is correlated to the heavy right-handed neutrino masses and mixings. With
a combination of the pair, single and off-shell production of $H^{\pm\pm}$ like
$e^+e^- \to H^{++} H^{--},\, H^{\pm\pm} e^\mp \mu^\mp,\, \mu^\pm \tau^\mp$, the
Yukawa couplings can be probed up to $10^{-3}$ at future lepton colliders,
which is allowed by current lepton flavor data in a large region of parameter
space. For both the neutral and doubly-charged cases, the scalar masses could
be probed up to the few-TeV range in the off-shell channel.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-96141803.11267 | Entangled Histories vs. the Two-State-Vector Formalism - Towards a
Better Understanding of Quantum Temporal Correlations
quant-ph
The Two-State-Vector formalism and the Entangled Histories formalism are
attempts to better understand quantum correlations in time. The main objective
of this paper is to show that, with appropriately defined scalar products, both
formalisms can be made isomorphic. We show that they treat operators and states
on equal footing leading to the same statistics for all measurements. In
particular, we discuss the topic of quantum correlations in time and show how
they can be generated and analyzed in a consistent way in these formalisms.
Furthermore, we elaborate on a novel behavior of quantum histories of evolving
multipartite systems which do not exhibit global non-local correlations in time
but nevertheless can lead to entangled reduced histories characterizing
evolution of an arbitrarily chosen sub-system.
| arxiv topic:quant-ph |
arxiv_dataset-96151803.11367 | Quantized transport in topological insulator n-p-n junctions
cond-mat.mes-hall
Electrical transport in three dimensional topological insulators(TIs) occurs
through spin-momentum locked topological surface states that enclose an
insulating bulk. In the presence of a magnetic field, surface states get
quantized into Landau levels giving rise to chiral edge states that are
naturally spin-polarized due to spin momentum locking. It has been proposed
that p-n junctions of TIs in the quantum Hall regime can manifest unique spin
dependent effects, apart from forming basic building blocks for highly
functional spintronic devices. Here, for the first time we study
electrostatically defined n-p-n junctions of bulk insulating topological
insulator BiSbTe$_{1.25}$Se$_{1.75}$ in the quantum Hall regime. We reveal the
remarkable quantization of longitudinal resistance into plateaus at 3/2 and 2/3
h/e$^2$, apart from several partially developed fractional plateaus.
Theoretical modeling combining the electrostatics of the dual gated TI n-p-n
junction with Landauer Buttiker formalism for transport through a network of
chiral edge states explains our experimental data, while revealing remarkable
differences from p-n junctions of graphene and two-dimensional electron gas
systems. Our work not only opens up a route towards exotic spintronic devices
but also provides a test bed for investigating the unique signatures of quantum
Hall effects in topological insulators.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-96161803.11467 | Local Control Regression: Improving the Least Squares Monte Carlo Method
for Portfolio Optimization
q-fin.PM q-fin.CP
The least squares Monte Carlo algorithm has become popular for solving
portfolio optimization problems. A simple approach is to approximate the value
functions on a discrete grid of portfolio weights, then use control regression
to generalize the discrete estimates. However, the classical global control
regression can be expensive and inaccurate. To overcome this difficulty, we
introduce a local control regression technique, combined with adaptive grids.
We show that choosing a coarse grid for local regression can produce
sufficiently accurate results.
| arxiv topic:q-fin.PM q-fin.CP |
arxiv_dataset-96171804.00007 | Topological Phases in Nodeless Tetragonal Superconductors
cond-mat.supr-con quant-ph
We compute the topological phase diagram of 2D tetragonal superconductors for
the only possible nodeless pairing channels compatible with that crystal
symmetry. Subject to a Zeeman field and spin-orbit coupling, we demonstrate
that these superconductors show surprising topological features: non-trivial
high Chern numbers, massive edge states, and zero-energy modes out of high
symmetry points, even though the edge states remain topologically protected.
Interestingly, one of these pairing symmetries, $d+id$, has been proposed to
describe materials such as water-intercalated sodium cobaltates, bilayer
silicene or highly doped monolayer graphene, which opens the way for further
applications of our results.
| arxiv topic:cond-mat.supr-con quant-ph |
arxiv_dataset-96181804.00107 | Evolution of complexity following a quantum quench in free field theory
hep-th cond-mat.stat-mech quant-ph
Using a recent proposal of circuit complexity in quantum field theories
introduced by Jefferson and Myers, we compute the time evolution of the
complexity following a smooth mass quench characterized by a time scale $\delta
t$ in a free scalar field theory. We show that the dynamics has two distinct
phases, namely an early regime of approximately linear evolution followed by a
saturation phase characterized by oscillations around a mean value. The
behavior is similar to previous conjectures for the complexity growth in
chaotic and holographic systems, although here we have found that the
complexity may grow or decrease depending on whether the quench increases or
decreases the mass, and also that the time scale for saturation of the
complexity is of order $\delta t$ (not parametrically larger).
| arxiv topic:hep-th cond-mat.stat-mech quant-ph |
arxiv_dataset-96191804.00207 | Quantum Wires and Waveguides Formed in Graphene by Strain
cond-mat.mes-hall cond-mat.mtrl-sci
Confinement of electrons in graphene to make devices has proven to be a
challenging task. Electrostatic methods fail because of Klein tunneling, while
etching into nanoribbons requires extreme control of edge terminations, and
bottom-up approaches are limited in size to a few nanometers. Fortunately, its
mechanical flexibility raises the possibility of using strain to alter
graphene's properties and create novel straintronic devices. Here, we report
transport studies of nanowires created by linearly-shaped strained regions
resulting from individual folds formed by layer transfer onto hexagonal boron
nitride. Conductance measurements across the folds reveal Coulomb blockade
signatures, indicating confined charges within these structures, which act as
quantum dots. Along folds, we observe sharp features in traverse resistivity
measurements, attributed to an amplification of the dot conductance modulations
by a resistance bridge incorporating the device. Our data indicates ballistic
transport up to ~1 um along the folds. Calculations using the Dirac model
including strain are consistent with measured bound state energies and predict
the existence of valley-polarized currents. Our results show that graphene
folds can act as straintronic quantum wires.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-96201804.00307 | Robust Fruit Counting: Combining Deep Learning, Tracking, and Structure
from Motion
cs.CV
We present a novel fruit counting pipeline that combines deep segmentation,
frame to frame tracking, and 3D localization to accurately count visible fruits
across a sequence of images. Our pipeline works on image streams from a
monocular camera, both in natural light, as well as with controlled
illumination at night. We first train a Fully Convolutional Network (FCN) and
segment video frame images into fruit and non-fruit pixels. We then track
fruits across frames using the Hungarian Algorithm where the objective cost is
determined from a Kalman Filter corrected Kanade-Lucas-Tomasi (KLT) Tracker. In
order to correct the estimated count from tracking process, we combine tracking
results with a Structure from Motion (SfM) algorithm to calculate relative 3D
locations and size estimates to reject outliers and double counted fruit
tracks. We evaluate our algorithm by comparing with ground-truth
human-annotated visual counts. Our results demonstrate that our pipeline is
able to accurately and reliably count fruits across image sequences, and the
correction step can significantly improve the counting accuracy and robustness.
Although discussed in the context of fruit counting, our work can extend to
detection, tracking, and counting of a variety of other stationary features of
interest such as leaf-spots, wilt, and blossom.
| arxiv topic:cs.CV |
arxiv_dataset-96211804.00407 | Convergence of energy functionals and stability of lower bounds of Ricci
curvature via metric measure foliation
math.MG
The notion of the metric measure foliation is introduced by Galaz-Garc\'ia,
Kell, Mondino, and Sosa. They studied the relation between a metric measure
space with a metric measure foliation and its quotient space. They showed that
the curvature-dimension condition and the Cheeger energy functional preserve
from a such space to its quotient space. Via the metric measure foliation, we
investigate the convergence theory for a sequence of metric measure spaces
whose dimensions are unbounded.
| arxiv topic:math.MG |
arxiv_dataset-96221804.00507 | Sinusoidal shaped hollow fibers for enhanced mass transfer
physics.flu-dyn
Inducing secondary flows and vortices is known to enhance mass transport.
They can be imposed by structured flow channels for instance. In particular,
these vortices reduce fouling and concentration polarization. In this work we
present a new method of producing hollow fiber membranes with a sinusoidal
change in diameter over the fiber length. We engineered a pulsation module that
imposes a sinusoidally fluctuating bore liquid flow rate. Harmonic bore flow
conditions can be varied over a wide range. The fluctuating bore liquid flow
rate translates into axial membrane properties varying with respect to inner
bore diameter and wall thickness. The resulting narrowing and widening of the
membrane lumen channel are hypothesized to induce secondary vortices to the
liquid inside the membrane lumen known as the Bellhouse effect. Improved oxygen
transport from shell-to-lumen side prove superiority over straight hollow fiber
membranes in G/L absorption process. We anticipate the dynamic flow module to
be easily integrated into currently existing hollow fiber membrane spinning
processes.
| arxiv topic:physics.flu-dyn |
arxiv_dataset-96231804.00607 | MegaDepth: Learning Single-View Depth Prediction from Internet Photos
cs.CV
Single-view depth prediction is a fundamental problem in computer vision.
Recently, deep learning methods have led to significant progress, but such
methods are limited by the available training data. Current datasets based on
3D sensors have key limitations, including indoor-only images (NYU), small
numbers of training examples (Make3D), and sparse sampling (KITTI). We propose
to use multi-view Internet photo collections, a virtually unlimited data
source, to generate training data via modern structure-from-motion and
multi-view stereo (MVS) methods, and present a large depth dataset called
MegaDepth based on this idea. Data derived from MVS comes with its own
challenges, including noise and unreconstructable objects. We address these
challenges with new data cleaning methods, as well as automatically augmenting
our data with ordinal depth relations generated using semantic segmentation. We
validate the use of large amounts of Internet data by showing that models
trained on MegaDepth exhibit strong generalization-not only to novel scenes,
but also to other diverse datasets including Make3D, KITTI, and DIW, even when
no images from those datasets are seen during training.
| arxiv topic:cs.CV |
arxiv_dataset-96241804.00707 | Phase Control in a Spin-Triplet SQUID
cond-mat.supr-con
It is now well established that a Josephson junction made from conventional
spin-singlet superconductors containing ferromagnetic layers can carry
spin-triplet supercurrent under certain conditions. The first experimental
signature of that fact is the propagation of such supercurrent over long
distances through strong ferromagnetic materials. Surprisingly, one of the most
salient predictions of the theory has yet to be verified experimentally --
namely that a Josephson junction containing three magnetic layers with coplanar
magnetizations should exhibit a ground-state phase shift of either zero or pi
depending on the relative orientations of those magnetizations. Here we
demonstrate this property using Josephson junctions containing three different
types of magnetic layers, chosen so that the magnetization of one layer can be
switched by 180 degrees without disturbing the other two. Phase-sensitive
detection is accomplished using a superconducting quantum interference device,
or SQUID. Such a phase-controllable junction could be used as the memory
element in a fully-superconducting computer.
| arxiv topic:cond-mat.supr-con |
arxiv_dataset-96251804.00807 | Full Characterization of Optimal Uncoded Placement for the Structured
Clique Cover Delivery of Nonuniform Demands
cs.IT math.IT
We investigate the problem of coded caching for nonuniform demands when the
structured clique cover algorithm proposed by Maddah-Ali and Niesen for
decentralized caching is used for delivery. We apply this algorithm to all user
demands regardless of their request probabilities. This allows for coding among
the files that have different request probabilities but makes the allocation of
memory to different files challenging during the content placement phase. As
our main contribution, we analytically characterize the optimal placement
strategy that minimizes the expected delivery rate under a storage capacity
constraint. It is shown that the optimal placement follows either a two or a
three group strategy, where a set of less popular files are not cached at all
and the files within each of the other sets are allocated identical amounts of
storage as if they had the same request probabilities. We show that for a
finite set of storage capacities, that we call the base-cases of the problem,
the two group strategy is always optimal. For other storage capacities, optimal
placement is achieved by memory sharing between certain base-cases and the
resulting placement either follows a two or a three group strategy depending on
the corresponding base-cases used. We derive a polynomial time algorithm that
determines the base-cases of the problem given the number of caches and
popularity distribution of files. Given the base-cases of the problem, the
optimal memory allocation parameters for any storage capacity are derived
analytically.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-96261804.00907 | Cognitive Radio from Hell: Flipping Attack on Direct-Sequence Spread
Spectrum
cs.IT math.IT
In this paper, we introduce a strong adversarial attack, referred to as the
flipping attack, on Direct-Sequence Spread Spectrum (DSSS) systems. In this
attack, the attacker, which is appropriately positioned between the transmitter
and the receiver, instantaneously flips the transmitted symbols in the air at
50% rate, thereby driving the channel capacity to zero. Unlike the traditional
jamming attack, this attack, when perfectly executed, cannot be detected at the
receiver using signal-to-noise-ratio measurements. However, this attack
necessitates the attacker to perfectly know the realizations of all the
channels in the model. We first introduce the consequences of the flipping
attack on narrowband frequency-flat channels, and subsequently discuss its
feasibility in wideband frequency-selective channels. From the legitimate
users' perspective, we present a method to detect this attack and also propose
heuristics to improve the error-performance under the attack. We emphasize that
future cyber-physical systems that employ DSSS should design transceivers to
detect the proposed flipping attack, and then apply appropriate
countermeasures.
| arxiv topic:cs.IT math.IT |
arxiv_dataset-96271804.01007 | On evaluation of the confluent Heun functions
math.NA
In this paper we consider the confluent Heun equation, which is a linear
differential equation of second order with three singular points --- two of
them are regular and the third one is irregular of rank 1. The purpose of the
work is to propose a procedure for numerical evaluation of the equation's
solutions (confluent Heun functions). A scheme based on power series,
asymptotic expansions and analytic continuation is described. Results of
numerical tests are given.
| arxiv topic:math.NA |
arxiv_dataset-96281804.01107 | Numerical exploration of trial wave functions for the
particle-hole-symmetric Pfaffian
cond-mat.str-el cond-mat.mes-hall
We numerically assess model wave functions for the recently proposed
particle-hole-symmetric Pfaffian (`PH-Pfaffian') topological order, a phase
consistent with the recently reported thermal Hall conductance [Banerjee et
al., Nature 559, 205 (2018)] at the ever enigmatic $\nu=5/2$ quantum-Hall
plateau. We find that the most natural Moore-Read-inspired trial state for the
PH-Pfaffian, when projected into the lowest Landau level, exhibits a remarkable
numerical similarity on accessible system sizes with the corresponding
(compressible) composite Fermi liquid. Consequently, this PH-Pfaffian trial
state performs reasonably well energetically in the half-filled lowest Landau
level, but is likely not a good starting point for understanding the $\nu=5/2$
ground state. Our results suggest that the PH-Pfaffian model wave function
either encodes anomalously weak $p$-wave pairing of composite fermions or fails
to represent a gapped, incompressible phase altogether.
| arxiv topic:cond-mat.str-el cond-mat.mes-hall |
arxiv_dataset-96291804.01207 | A Euclidean Algorithm for Binary Cycles with Minimal Variance
cs.DS
The problem is considered of arranging symbols around a cycle, in such a way
that distances between different instances of a same symbol be as uniformly
distributed as possible. A sequence of moments is defined for cycles, similarly
to the well-known praxis in statistics and including mean and variance. Mean is
seen to be invariant under permutations of the cycle. In the case of a binary
alphabet of symbols, a fast, constructive, sequencing algorithm is introduced,
strongly resembling the celebrated Euclidean method for greatest common divisor
computation, and the cycle returned is characterized in terms of symbol
distances. A minimal variance condition is proved, and the proposed Euclidean
algorithm is proved to satisfy it, thus being optimal. Applications to
productive systems and information processing are briefly discussed.
| arxiv topic:cs.DS |
arxiv_dataset-96301804.01307 | Btrfly Net: Vertebrae Labelling with Energy-based Adversarial Learning
of Local Spine Prior
cs.CV
Robust localisation and identification of vertebrae is essential for
automated spine analysis. The contribution of this work to the task is
two-fold: (1) Inspired by the human expert, we hypothesise that a sagittal and
coronal reformation of the spine contain sufficient information for labelling
the vertebrae. Thereby, we propose a butterfly-shaped network architecture
(termed Btrfly Net) that efficiently combines the information across
reformations. (2) Underpinning the Btrfly net, we present an energy-based
adversarial training regime that encodes local spine structure as an anatomical
prior into the network, thereby enabling it to achieve state-of-art performance
in all standard metrics on a benchmark dataset of 302 scans without any
post-processing during inference.
| arxiv topic:cs.CV |
arxiv_dataset-96311804.01407 | The X-ARAPUCA: An improvement of the ARAPUCA device
physics.ins-det
The ARAPUCA is a novel technology for the detection of liquid argon
scintillation light, which has been proposed for the far detector of the Deep
Underground Neutrino Experiment. The X-ARAPUCA is an improvement to the
original ARAPUCA design, retaining the original ARAPUCA concept of photon
trapping inside a highly reflective box while using a wavelength shifting slab
inside the box to increase the probability of collecting trapped photons onto a
silicon photomultiplier array. The X-ARAPUCA concept is presented and its
performances are compared to those of a standard ARAPUCA by means of analytical
calculations and Monte Carlo simulations.
| arxiv topic:physics.ins-det |
arxiv_dataset-96321804.01507 | Strategy for stopping failure cascades in interdependent networks
physics.soc-ph cond-mat.stat-mech
Interdependencies are ubiquitous throughout the world. Every real-world
system interacts with and is dependent on other systems, and this
interdependency affects their performance. In particular, interdependencies
among networks make them vulnerable to failure cascades, the effects of which
are often catastrophic. Failure propagation fragments network components,
disconnects them, and may cause complete systemic failure. We propose a
strategy of avoiding or at least mitigating the complete destruction of a
system of interdependent networks experiencing a failure cascade. Starting with
a fraction $1-p$ of failing nodes in one network, we reconnect with a
probability $\gamma$ every isolated component to a functional giant component
(GC), the largest connected cluster. We find that as $\gamma$ increases the
resilience of the system to cascading failure also increases. We also find that
our strategy is more effective when it is applied in a network of low average
degree. We solve the problem theoretically using percolation theory, and we
find that the solution agrees with simulation results.
| arxiv topic:physics.soc-ph cond-mat.stat-mech |
arxiv_dataset-96331804.01607 | Two component boson-fermion plasma at finite temperature
cond-mat.stat-mech cond-mat.mtrl-sci cond-mat.quant-gas physics.atm-clus
We discuss thermodynamic stability of neutral real (quantum) matter from the
point of view of a computer experiment at finite, non-zero, temperature. We
perform (restricted) path integral Monte Carlo simulations of the two component
plasma where the two species are all bosons, all fermions, and one boson and
one fermion. We calculate the structure of the plasma and discuss about the
formation of binded couples of oppositely charged particles. The purely bosonic
case is thermodynamically unstable. In this case we find an undetermined size
dependent contact value of the unlike partial radial distribution function. For
the purely fermionic case we find a demixing transition with binding also of
like species.
| arxiv topic:cond-mat.stat-mech cond-mat.mtrl-sci cond-mat.quant-gas physics.atm-clus |
arxiv_dataset-96341804.01707 | A formula for the associated Buchsbaum-Rim multiplicities of a direct
sum of cyclic modules
math.AC
In this article, we compute the Buchsbaum-Rim function of two variables
associated to a direct sum of cyclic modules and give a formula for the last
positive associated Buchsbaum-Rim multiplicity in terms of the ordinary
Hilbert-Samuel multiplicity of an ideal. This is a generalization of a formula
for the last positive Buchsbaum-Rim multiplicity given by Kirby and Rees.
| arxiv topic:math.AC |
arxiv_dataset-96351804.01807 | Bayesian Extreme Value Analysis of Stock Exchange Data
stat.AP
The Solvency II Directive and Solvency Assessment and Management (the South
African equivalent) give a Solvency Capital Requirement which is based on a
99.5% Value-at-Risk (VaR) calculation. This calculation involves aggregating
individual risks. When considering log returns of financial instruments,
especially with share prices, there are extreme losses that are observed from
time to time that often do not fit whatever model is proposed for the regular
trading behaviour. The problem of accurately modelling these extreme losses is
addressed, which, in turn, assists with the calculation of tail probabilities
such as the 99.5% VaR. The focus is on the fitting of the Generalized Pareto
Distribution (GPD) beyond a threshold. We show how objective Bayes methods can
improve parameter estimation and the calculation of risk measures. Lastly we
consider the choice of threshold. All aspects are illustrated using share
losses on the Johannesburg Stock Exchange (JSE).
| arxiv topic:stat.AP |
arxiv_dataset-96361804.01907 | Probabilistic representation for mild solution of the Navier-Stokes
equations
math.AP math.PR
This paper is based on a formulation of the Navier-Stokes equations developed
by Iyer and Constantin \cite{Cont} , where the velocity field of a viscous
incompressible fluid is written as the expected value of a stochastic process.
Our contribution is to establish this probabilistic representation formula for
mild solutions of the Navier-Stokes equations on $\mathbb{R}^{d} $.
| arxiv topic:math.AP math.PR |
arxiv_dataset-96371804.02007 | Design and test of 704 MHz and 2.1 GHz normal conducting cavities for
Low Energy RHIC electron Cooler
physics.acc-ph
The Low Energy RHIC electron Cooler (LEReC) is currently under commissioning
at BNL to improve RHIC luminosity for heavy ion beam energies below 10
GeV/nucleon. The linac of LEReC consists of a DC photoemission gun, one 704 MHz
superconducting radio frequency (SRF) booster cavity, and three normal
conducting cavities. It is designed to deliver a 1.6 MeV to 2.6 MeV electron
beam, with peak-to-peak momentum spread dp/p of less than 7e4. Two of the three
normal conducting cavities will be used in LEReC for energy spread correction.
A single-cell 704 MHz cavity for energy de-chirping and a three-cell 2.1 GHz
third harmonic cavity for RF curvature correction. In this paper, we present
the designs and RF test results of these two cavities.
| arxiv topic:physics.acc-ph |
arxiv_dataset-96381804.02107 | Detection of the Supercycle in V4140 Sagittarii: First Eclipsing ER
Ursae Majoris-like Object
astro-ph.SR
We observed the deeply eclipsing SU UMa-type dwarf nova V4140 Sgr and
established the very short supercycle of 69.7(3) d. There were several short
outbursts between superoutbursts. These values, together with the short orbital
period (0.06143 d), were similar to, but not as extreme as, those of ER
UMa-type dwarf novae. The object is thus the first, long sought, eclipsing ER
UMa-like object. This ER UMa-like nature can naturally explain the high
(apparent) quiescent viscosity and unusual temperature profile in quiescence,
which were claimed observational features against the thermal-tidal instability
model. The apparently unusual outburst behavior can be reasonably explained by
a combination of this ER UMa-like nature and the high orbital inclination and
there is no need for introducing mass transfer bursts from its donor star.
| arxiv topic:astro-ph.SR |
arxiv_dataset-96391804.02207 | An Energy-Efficient Framework for the Analysis of MIMO Slow Fading
Channels
cs.NI
In this work, a new energy-efficiency performance metric is proposed for MIMO
(multiple input multiple output) point-to-point systems. In contrast with
related works on energy-efficiency, this metric translates the effects of using
finite blocks for transmitting, using channel estimates at the transmitter and
receiver, and considering the total power consumed by the transmitter instead
of the radiated power only. The main objective pursued is to choose the best
pre-coding matrix used at the transmitter in the following two scenarios~: 1)
the one where imperfect channel state information (CSI) is available at the
transmitter and receiver~; 2) the one where no CSI is available at the
transmitter. In both scenarios, the problem of optimally tuning the total used
power is shown to be non-trivial. In scenario 2), the optimal fraction of
training time can be characterized by a simple equation. These results and
others provided in the paper, along with the provided numerical analysis, show
that the present work can therefore be used as a good basis for studying power
control and resource allocation in energy-efficient multiuser networks.
| arxiv topic:cs.NI |
arxiv_dataset-96401804.02307 | Accelerated Optimization in the PDE Framework: Formulations for the
Manifold of Diffeomorphisms
math.OC cs.CV cs.NA
We consider the problem of optimization of cost functionals on the
infinite-dimensional manifold of diffeomorphisms. We present a new class of
optimization methods, valid for any optimization problem setup on the space of
diffeomorphisms by generalizing Nesterov accelerated optimization to the
manifold of diffeomorphisms. While our framework is general for infinite
dimensional manifolds, we specifically treat the case of diffeomorphisms,
motivated by optical flow problems in computer vision. This is accomplished by
building on a recent variational approach to a general class of accelerated
optimization methods by Wibisono, Wilson and Jordan, which applies in finite
dimensions. We generalize that approach to infinite dimensional manifolds. We
derive the surprisingly simple continuum evolution equations, which are partial
differential equations, for accelerated gradient descent, and relate it to
simple mechanical principles from fluid mechanics. Our approach has natural
connections to the optimal mass transport problem. This is because one can
think of our approach as an evolution of an infinite number of particles
endowed with mass (represented with a mass density) that moves in an energy
landscape. The mass evolves with the optimization variable, and endows the
particles with dynamics. This is different than the finite dimensional case
where only a single particle moves and hence the dynamics does not depend on
the mass. We derive the theory, compute the PDEs for accelerated optimization,
and illustrate the behavior of these new accelerated optimization schemes.
| arxiv topic:math.OC cs.CV cs.NA |
arxiv_dataset-96411804.02407 | Self-sustaining star formation fronts in filaments during cosmic dawn
astro-ph.GA
We propose a new model for the ignition of star formation in low-mass halos
by a self-sustaining shock front in cosmic filaments at high redshifts. The
gaseous fuel for star formation resides in low mass halos which can not cool on
their own due to their primordial composition and low virial temperatures. We
show that star formation can be triggered in these filaments by a passing shock
wave. The shells swept-up by the shock cool and fragment into cold clumps that
form massive stars via thermal instability on a timescale shorter than the
front's dynamical timescale. The shock, in turn, is self-sustained by energy
injection from supernova explosions. The star formation front is analogous to a
detonation wave, which drives exothermic reactions powering the shock. We find
that sustained star formation would typically propel the front to a speed of
$\sim 300-700\,\rm km\,s^{-1}$ during the epoch of reionization. Future
observations by the $\textit{James Webb Space Telescope}$ could reveal the
illuminated regions of cosmic filaments, and constrain the initial mass
function of stars in them.
| arxiv topic:astro-ph.GA |
arxiv_dataset-96421804.02507 | A fully non-linear optimization approach to acousto-electric tomography
math.OC
This paper considers the non-linear inverse problem of reconstructing an
electric conductivity distribution from the interior power density in a bounded
domain. Applications include the novel tomographic method known as
acousto-electric tomography, in which the measurement setup in Electrical
Impedance Tomography is modulated by ultrasonic waves thus giving rise to a
method potentially having both high contrast and high resolution. We formulate
the inverse problem as a regularized non-linear optimization problem, show the
existence of a minimizer, and derive optimality conditions. We propose a
non-linear conjugate gradient scheme for finding a minimizer based on the
optimality conditions. All our numerical experiments are done in
two-dimensions. The experiments reveal new insight into the non-linear effects
in the reconstruction. One of the interesting features we observe is that,
depending on the choice of regularization, there is a trade-off between high
resolution and high contrast in the reconstructed images. Our proposed
non-linear optimization framework can be generalized to other hybrid imaging
modalities.
| arxiv topic:math.OC |
arxiv_dataset-96431804.02607 | Vector meson dominance in $\eta'\rightarrow\pi^0\gamma\gamma$ decay
hep-ph
The decay $\eta'\rightarrow\pi^0\gamma\gamma$ is studied theoretically in the
framework of the Vector Meson Dominance model (VMD). We find theoretically a
significant contribution of the interference of $\omega-\rho$ and provide
theoretical Dalitz-plots. Comparison with the experimental results of BES-III
\cite{BES-III} is done. We find some tension between our predicted value and
the observed result. Our calculations can be also checked using the data of
GAMS-$4\pi$.
| arxiv topic:hep-ph |
arxiv_dataset-96441804.02707 | Certifying reality of projections
math.AG math.NA
Computational tools in numerical algebraic geometry can be used to
numerically approximate solutions to a system of polynomial equations. If the
system is well-constrained (i.e., square), Newton's method is locally
quadratically convergent near each nonsingular solution. In such cases, Smale's
alpha theory can be used to certify that a given point is in the quadratic
convergence basin of some solution. This was extended to certifiably determine
the reality of the corresponding solution when the polynomial system is real.
Using the theory of Newton-invariant sets, we certifiably decide the reality of
projections of solutions. We apply this method to certifiably count the number
of real and totally real tritangent planes for instances of curves of genus 4.
| arxiv topic:math.AG math.NA |
arxiv_dataset-96451804.02807 | A derivation of the sharp Moser-Trudinger-Onofri inequalities from the
fractional Sobolev inequalities
math.AP math.DG math.FA
We derive the sharp Moser-Trudinger-Onofri inequalities on the standard
$n$-sphere and CR $(2n+1)$- sphere as the limit of the sharp fractional Sobolev
inequalities for all $n\ge 1$. On the $2$-sphere and $4$-sphere, this was
established recently by S.-Y. Chang and F. Wang. Our proof uses an alternative
and elementary argument.
| arxiv topic:math.AP math.DG math.FA |
arxiv_dataset-96461804.02907 | On the spherical quasi-convexity of quadratic functions
math.OC
In this paper the spherical quasi-convexity of quadratic functions on
spherically convex sets is studied. Several conditions characterizing the
spherical quasi-convexity of quadratic functions are presented. In particular,
conditions implying spherical quasi-convexity of quadratic functions on the
spherical positive orthant are given. Some examples are provided as an
application of the obtained results.
| arxiv topic:math.OC |
arxiv_dataset-96471804.03007 | Notes on finitely generated flat modules
math.AC
In this article, the projectivity of finitely generated flat modules of a
commutative ring are studied from a topological point of view. Then various
interesting results are obtained. For instance, it is shown that if a ring has
either a finitely many minimal primes or a finitely many maximal ideals then
every finitely generated flat module over it is projective. It is also shown
that if a particular subset of the prime spectrum of a ring satisfies some
certain ascending or descending chain conditions then every finitely generated
flat module over this ring is projective. These results generalize some major
results in the literature on the projectivity of finitely generated flat
modules.
| arxiv topic:math.AC |
arxiv_dataset-96481804.03107 | Signature of Fermi arc surface states in Andreev reflection at the
WTe$_2$ Weyl semimetal surface
cond-mat.mes-hall
We experimentally investigate charge transport through the interface between
a niobium superconductor and a three-dimensional WTe$_2$ Weyl semimetal. In
addition to classical Andreev reflection, we observe sharp non-periodic subgap
resistance resonances. From an analysis of their positions, magnetic field and
temperature dependencies, we can interpret them as an analog of Tomasch
oscillations for transport along the topological surface state across the
region of proximity-induced superconductivity at the Nb-WTe$_2$ interface.
Observation of distinct geometrical resonances implies a specific transmission
direction for carriers, which is a hallmark of the Fermi arc surface states.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-96491804.03207 | Comments on the $S_N$ orbifold CFT in the large $N$-limit
hep-th
We elaborate on various aspects of the conformal field theory of the
symmetric orbifold. We collect various results that have appeared in the
literature, and we present a coherent picture of the operator content of this
CFT, relying on the orbifold extension of the Virasoro algebra. We then focus
on the large $N$-limit of this theory, discuss the OPE of two twist operators,
and find various selection rules. We review how to calculate four-point
functions of twist operators, and we write down the most general four-point
function in the covering space for large $N$. We show that it depends on some
functions that obey a set of algebraic equations, that resemble the scattering
equations. Finally, we provide a recipe on how to calculate correlation
functions with insertions of the orbifold Virasoro generators.
| arxiv topic:hep-th |
arxiv_dataset-96501804.03307 | A Web-based Large-scale Timelapse Editor for Creating and Sharing Guided
Video Tours and Interactive Slideshows
cs.HC
Scientists, journalists, and photographers have used advanced camera
technology to capture extremely high-resolution timelapse and developed
information visualization tools for data exploration and analysis. However, it
takes a great deal of effort for professionals to form and tell stories after
exploring data, since these tools usually provide little aids in creating
visual elements. We present a web-based timelapse editor to support the
creation of guided video tours and interactive slideshows from a collection of
large-scale spatial and temporal images. Professionals can embed these two
visual elements into web pages in conjunction with various forms of digital
media to tell multimodal and interactive stories.
| arxiv topic:cs.HC |
arxiv_dataset-96511804.03407 | ModelFactory: A Matlab/Octave based toolbox to create human body models
cs.RO cs.GR q-bio.QM
Background: Model-based analysis of movements can help better understand
human motor control. Here, the models represent the human body as an
articulated multi-body system that reflects the characteristics of the human
being studied.
Results: We present an open-source toolbox that allows for the creation of
human models with easy-to-setup, customizable configurations. The toolbox
scripts are written in Matlab/Octave and provide a command-based interface as
well as a graphical interface to construct, visualize and export models.
Built-in software modules provide functionalities such as automatic scaling of
models based on subject height and weight, custom scaling of segment lengths,
mass and inertia, addition of body landmarks, and addition of motion capture
markers. Users can set up custom definitions of joints, segments and other body
properties using the many included examples as templates. In addition to the
human, any number of objects (e.g. exoskeletons, orthoses, prostheses, boxes)
can be added to the modeling environment.
Conclusions: The ModelFactory toolbox is published as open-source software
under the permissive zLib license. The toolbox fulfills an important function
by making it easier to create human models, and should be of interest to human
movement researchers.
This document is the author's version of this article.
| arxiv topic:cs.RO cs.GR q-bio.QM |
arxiv_dataset-96521804.03507 | The Effect of Pets on Happiness: A Large-scale Multi-Factor Analysis
using Social Multimedia
cs.CY cs.MM cs.SI
From reducing stress and loneliness, to boosting productivity and overall
well-being, pets are believed to play a significant role in people's daily
lives. Many traditional studies have identified that frequent interactions with
pets could make individuals become healthier and more optimistic, and
ultimately enjoy a happier life. However, most of those studies are not only
restricted in scale, but also may carry biases by using subjective
self-reports, interviews, and questionnaires as the major approaches. In this
paper, we leverage large-scale data collected from social media and the
state-of-the-art deep learning technologies to study this phenomenon in depth
and breadth. Our study includes four major steps: 1) collecting timeline posts
from around 20,000 Instagram users, 2) using face detection and recognition on
2-million photos to infer users' demographics, relationship status, and whether
having children, 3) analyzing a user's degree of happiness based on images and
captions via smiling classification and textual sentiment analysis, 3) applying
transfer learning techniques to retrain the final layer of the Inception v3
model for pet classification, and 4) analyzing the effects of pets on happiness
in terms of multiple factors of user demographics. Our main results have
demonstrated the efficacy of our proposed method with many new insights. We
believe this method is also applicable to other domains as a scalable,
efficient, and effective methodology for modeling and analyzing social
behaviors and psychological well-being. In addition, to facilitate the research
involving human faces, we also release our dataset of 700K analyzed faces.
| arxiv topic:cs.CY cs.MM cs.SI |
arxiv_dataset-96531804.03607 | Theory of the inverse spin galvanic effect in quantum wells
cond-mat.mes-hall
The understanding of the fundamentals of spin and charge densities and
currents interconversion by spin-orbit coupling can enable efficient
applications beyond the possibilities offered by conventional electronics. For
this purpose we consider various forms of the frequency-dependent inverse spin
galvanic effect (ISGE) in semiconductor quantum wells and epilayers taking into
account the cubic in the electron momentum spin-orbit coupling in the Rashba
and Dresselhaus forms, concentrating on the current-induced spin polarization
(CISP). We find that including the cubic terms qualitatively explains recent
findings of the CISP in InGaAs epilayers being the strongest if the internal
spin-orbit coupling field is the smallest and vice versa (Norman et . 2014,
Luengo et al. 2017), in contrast to the common understanding. Our results
provide a promising framework for the control of spin transport in future
spintronics devices.
| arxiv topic:cond-mat.mes-hall |
arxiv_dataset-96541804.03707 | A Tamper-Free Semi-Universal Communication System for Deletion Channels
stat.ML cs.CR cs.LG stat.AP
We investigate the problem of reliable communication between two legitimate
parties over deletion channels under an active eavesdropping (aka jamming)
adversarial model. To this goal, we develop a theoretical framework based on
probabilistic finite-state automata to define novel encoding and decoding
schemes that ensure small error probability in both message decoding as well as
tamper detecting. We then experimentally verify the reliability and
tamper-detection property of our scheme.
| arxiv topic:stat.ML cs.CR cs.LG stat.AP |
arxiv_dataset-96551804.03807 | A Blackbox Polynomial System Solver on Parallel Shared Memory Computers
cs.MS cs.DC cs.SC math.AG math.NA
A numerical irreducible decomposition for a polynomial system provides
representations for the irreducible factors of all positive dimensional
solution sets of the system, separated from its isolated solutions. Homotopy
continuation methods are applied to compute a numerical irreducible
decomposition. Load balancing and pipelining are techniques in a parallel
implementation on a computer with multicore processors. The application of the
parallel algorithms is illustrated on solving the cyclic $n$-roots problems, in
particular for $n = 8, 9$, and~12.
| arxiv topic:cs.MS cs.DC cs.SC math.AG math.NA |
arxiv_dataset-96561804.03907 | Polymer-based black phosphorus (bP) hybrid materials by in situ radical
polymerization: an effective tool to exfoliate bP and stabilize bP nanoflakes
cond-mat.mes-hall cond-mat.mtrl-sci physics.app-ph physics.chem-ph
Black phosphorus (bP) has been recently investigated for next generation
nanoelectronic multifunctional devices. However, the intrinsic instability of
exfoliated bP (the bP nanoflakes) towards both moisture and air has so far
overshadowed its practical implementation. In order to contribute to fill this
gap, we report here the preparation of new hybrid polymer-based materials where
bP nanoflakes exhibit a significantly improved stability. The new materials
have been prepared by different synthetic paths including: i) the mixing of
conventionally liquid-phase exfoliated bP (in DMSO) with PMMA solution; ii) the
direct exfoliation of bP in a polymeric solution; iii) the in situ radical
polymerization after exfoliating bP in the liquid monomer (methyl methacrylate,
MMA). This last methodology concerns the preparation of stable suspensions of
bPn-MMA by sonication-assisted liquid phase exfoliation (LPE) of bP in the
presence of MMA followed by radical polymerization. The hybrids characteristics
have been compared in order to evaluate the bP dispersion and the effectiveness
of the bPn interfacial interactions with polymer chains aimed at their
long-term environmental stabilization. The passivation of bPn results
particularly effective when the hybrid material is prepared by in situ
polymerization. By using this synthetic methodology, the nanoflakes, even if
with a gradient of dispersion (size of aggregates), preserve their chemical
structure from oxidation (as proved by both Raman and 31P-Solid State NMR
studies) and are particularly stable to air and UV light exposure.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci physics.app-ph physics.chem-ph |
arxiv_dataset-96571804.04007 | A closer look at the Barboza-Alcaniz equation of state parametrization
gr-qc
The Barboza-Alcaniz EoS parametrization has been considered and its
$q$-parametrization has been investigated in search for a thermodynamic
motivation. For this, we have studied the validity of the generalized second
law of thermodynamics as well as the thermodynamic equilibrium considering the
cosmological apparent horizon as the boundary. Also, an expression for the
particle creation rate has been obtained in terms of $q$ assuming an adiabatic
particle creation scenario and its behavior has been studied for consistency
during various phases of evolution of the Universe as suggested by various
thermodynamic arguments found in the literature.
| arxiv topic:gr-qc |
arxiv_dataset-96581804.04107 | Algebraic hyperbolicity of the very general quintic surface in
$\mathbb{P}^3$
math.AG
We prove that a curve of degree $dk$ on a very general surface of degree $d
\geq 5$ in $\mathbb{P}^3$ has geometric genus at least $\frac{dk(d-5)+k}{2} +
1$. This improves bounds given by G. Xu. As a corollary, we conclude that the
very general quintic surface in $\mathbb{P}^3$ is algebraically hyperbolic.
| arxiv topic:math.AG |
arxiv_dataset-96591804.04207 | Electronic properties of one-dimensional nanostructures of the
Bi$_2$Se$_3$ topological insulator
cond-mat.mes-hall cond-mat.mtrl-sci
We theoretically study the electronic structure and spin properties of
one-dimensional nanostructures of the prototypical bulk topological insulator
Bi$_2$Se$_3$. Realistic models of experimentally observed Bi$_2$Se$_3$
nanowires and nanoribbons are considered using the tight-binding method. At low
energies, the band structures are composed of a series of evenly spaced
degenerate sub-bands resulting from circumferential confinement of the
topological surface states. The direct band gaps due to the non-trivial $\pi$
Berry phase show a clear dependence on the circumference. The spin-momentum
locking of the topological surface states results in a pronounced 2$\pi$ spin
rotation around the circumference with the degree of spin polarization
dependent on the the momentum along the nanostructure. Overall, the band
structures and spin textures are more complicated for nanoribbons, which expose
two distinct facets. The effects of reduced dimensionality are rationalized
with the help of a simple model that considers circumferential quantization of
the topological surface states. Furthermore, the surface spin density induced
by electric current along the nanostructure shows a pronounced oscillatory
dependence on the charge-carrier energy, which can be exploited in spintronics
applications.
| arxiv topic:cond-mat.mes-hall cond-mat.mtrl-sci |
arxiv_dataset-96601804.04307 | Free operated monoids and Rewriting systems
math.RA
The construction of bases for quotients is an important problem. In this
paper, applying the method of rewriting systems, we give a unified approach to
construct sections---an alternative name for bases in semigroup theory---for
quotients of free operated monoids. As applications, we capture sections of
free $\ast$-monoids and free groups, respectively.
| arxiv topic:math.RA |
arxiv_dataset-96611804.04407 | Fragile detection of solar g modes by Fossat et al
astro-ph.SR
The internal gravity modes of the Sun are notoriously difficult to detect,
and the claimed detection of gravity modes presented in Fossat et al. 2017 is
thus very exciting. Given the importance of these modes for understanding solar
structure and dynamics, the results must be robust. While Fossat et al. 2017
described their method and parameter choices in detail, the sensitivity of
their results to several parameters were not presented. Therefore, we test the
sensitivity to a selection of them. The most concerning result is that the
detection vanishes when we adjust the start time of the 16.5 year velocity time
series by a few hours. We conclude that this reported detection of gravity
modes is extremely fragile and should be treated with utmost caution.
| arxiv topic:astro-ph.SR |
arxiv_dataset-96621804.04507 | Characterizing projections among positive operators in the unit sphere
math.OA
Let $E$ and $P$ be subsets of a Banach space $X$, and let us define the unit
sphere around $E$ in $P$ as the set $$Sph(E;P) :=\left\{ x\in P : \|x-b\|=1
\hbox{ for all } b\in E \right\}.$$ Given a C$^*$-algebra $A$, and a subset
$E\subset A,$ we shall write $Sph^+ (E)$ or $Sph_A^+ (E)$ for the set
$Sph(E;S(A^+)),$ where $S(A^+)$ stands for the set of all positive operators in
the unit sphere of $A$. We prove that, for an arbitrary complex Hilbert space
$H$, then a positive element $a$ in the unit sphere of $B(H)$ is a projection
if and only if $Sph^+_{B(H)} \left( Sph^+_{B(H)}(\{a\}) \right) =\{a\}$. We
also prove that the equivalence remains true when $B(H)$ is replaced with an
atomic von Neumann algebra or with $K(H_2)$, where $H_2$ is an
infinite-dimensional and separable complex Hilbert space. In the setting of
compact operators we prove a stronger conclusion by showing that the identity
$$Sph^+_{K(H_2)} \left( Sph^+_{K(H_2)}(a) \right) =\left\{ b\in S(K(H_2)^+) :
\!\! \begin{array}{c} s_{_{K(H_2)}} (a) \leq s_{_{K(H_2)}} (b), \hbox{ and }
\textbf{1}-r_{_{B(H_2)}}(a)\leq \textbf{1}-r_{_{B(H_2)}}(b) \end{array}\!\!
\right\},$$ holds for every $a$ in the unit sphere of $K(H_2)^+$, where
$r_{_{B(H_2)}}(a)$ and $s_{_{K(H_2)}} (a)$ stand for the range and support
projections of $a$ in $B(H_2)$ and $K(H_2)$, respectively.
| arxiv topic:math.OA |
arxiv_dataset-96631804.04607 | Reversible Computation in Petri Nets
cs.LO
Reversible computation is an unconventional form of computing where any
executed sequence of operations can be executed in reverse at any point during
computation. It has recently been attracting increasing attention in various
research communities as on the one hand it promises low-power computation and
on the other hand it is inherent or of interest in a variety of applications.
In this paper, we propose a reversible approach to Petri nets by introducing
machinery and associated operational semantics to tackle the challenges of the
three main forms of reversibility, namely, backtracking, causal reversing and
out-of-causal-order reversing. Our proposal concerns a variation of Petri nets
where tokens are persistent and are distinguished from each other by an
identity which allows for transitions to be reversed spontaneously in or out of
causal order. Our design decisions are influenced by applications in
biochemistry but the methodology can be applied to a wide range of problems
that feature reversibility. In particular, to demonstrate the applicability of
our approach we use an example of a biochemical system and an example of a
transaction-processing system both of which naturally embed reversible
behaviour.
| arxiv topic:cs.LO |
arxiv_dataset-96641804.04707 | Unveiling the chemistry of interstellar CH: Spectroscopy of the 2 THz
$N=2\leftarrow 1$ ground state line
astro-ph.GA
The methylidyne radical CH is commonly used as a proxy for H$_2$ in the cold,
neutral phase of the interstellar medium. The optical spectroscopy of CH is
limited by interstellar extinction, whereas far-infrared observations provide
an integral view through the Galaxy. While the HF ground state absorption,
another H$_2$ proxy in diffuse gas, frequently suffers from saturation, CH
remains transparent both in spiral-arm crossings and high-mass star forming
regions, turning this light hydride into a universal surrogate for H$_2$.
However, in slow shocks and in regions dissipating turbulence its abundance is
expected to be enhanced by an endothermic production path, and the idea of a
"canonical" CH abundance needs to be addressed. The $N=2\leftarrow 1$ ground
state transition of CH at $\lambda 149\,\mu$m has become accessible to
high-resolution spectroscopy thanks to GREAT aboard SOFIA. Its unsaturated
absorption and the absence of emission makes it an ideal candidate for the
determination of column densities with a minimum of assumptions. Here we
present an analysis of four sightlines towards distant, far-infrared bright
Galactic star forming regions. If combined with the sub-millimeter line of CH
at $\lambda 560\,\mu$m, environments forming massive stars can be analyzed. For
this we present a case study on the "proto-Trapezium" cluster W3 IRS5, and
demonstrate that the sub-millimeter/far-infrared lines of CH reliably trace not
only diffuse but also dense, molecular gas. While we confirm the global
correlation between the column densities of HF and those of CH, clear signposts
of an over-abundance of CH are observed towards lower densities. A quiescent
ion-neutral chemistry alone cannot account for this over-abundance. Vortices
forming in turbulent, diffuse gas may be the setting for an enhanced production
path.
| arxiv topic:astro-ph.GA |
arxiv_dataset-96651804.04807 | What is quantum in quantum randomness?
quant-ph
It is often said that quantum and classical randomness are of different
nature, the former being ontological and the latter epistemological. However,
so far the question of "What is quantum in quantum randomness", i.e. what is
the impact of quantization and discreteness on the nature of randomness,
remains to answer. In a first part, we explicit the differences between quantum
and classical randomness within a recently proposed ontology for quantum
mechanics based on contextual objectivity. In this view, quantum randomness is
the result of contextuality and quantization. We show that this approach
strongly impacts the purposes of quantum theory as well as its areas of
application. In particular, it challenges current programs inspired by
classical reductionism, aiming at the emergence of the classical world from a
large number of quantum systems. In a second part, we analyze quantum physics
and thermodynamics as theories of randomness, unveiling their mutual
influences. We finally consider new technological applications of quantum
randomness opened in the emerging field of quantum thermodynamics.
| arxiv topic:quant-ph |
arxiv_dataset-96661804.04907 | Social Physics: Uncovering Human Behaviour from Communication
physics.soc-ph cs.SI
In the post year 2000 era the technologies that facilitate human
communication have rapidly multiplied. While the adoption of these technologies
has hugely impacted the behaviour and sociality of people, specifically in
urban but also in rural environments, their "digital footprints" on different
data bases have become an active area of research. The existence and
accessibility of such large population-level datasets, has allowed scientists
to study and model innate human tendencies and social patterns in an
unprecedented way that complements traditional research approaches like
questionnaire studies. In this review we focus on data analytics and modelling
research - we call Social Physics - as it has been carried out using the mobile
phone data sets to get insight into the various aspects of human sociality,
burstiness in communication, mobility patterns, and daily rhythms.
| arxiv topic:physics.soc-ph cs.SI |
arxiv_dataset-96671804.05007 | An Approximation to Proof of the Circulant Hadamard Conjecture
math.CO math.GR
Turyn prove that if a circulant Hadamard matrix of order $n$ exists then $n$
must be of the form $n=4m^{2}$ for some odd integer $m$. In this paper we use
the structure constant of Schur ring of $\Z_{2}^{4m^{2}}$ to prove that there
is no circulant Hadamard matrix in $\Z_{2}^{4m^{2}}$ except possibly for
sequences with Hamming weight $a+b$, with $\frac{m^{2}-m}{2}\leq
a\leq\frac{3m^{2}-m}{2}$ and $b=2m^{2}-m-a$ and with $\frac{m^{2}+m}{2}\leq
2m^{2}-a\leq\frac{3m^{2}+m}{2}$ and $b=m+a$.
| arxiv topic:math.CO math.GR |
arxiv_dataset-96681804.05107 | On the global behavior of weak null quasilinear wave equations
math.AP
We consider a class of quasilinear wave equations in $3+1$ space-time
dimensions that satisfy the "weak null condition" as defined by Lindblad and
Rodnianski \cite{LR1}, and study the large time behavior of solutions to the
Cauchy problem. The prototype for the class of equations considered is
$-\partial_t^2 u + (1+u) \Delta u = 0$. Global solutions for such equations
have been constructed by Lindblad \cite{Lindblad1,Lindblad2} and Alinhac
\cite{Alinhac1}. Our main results are the derivation of a precise asymptotic
system with good error bounds, and a detailed description of the behavior of
solutions close to the light cone, including the blow-up at infinity.
| arxiv topic:math.AP |
arxiv_dataset-96691804.05207 | Weighted Finite Laplace Transform Operator: Spectral Analysis and
Quality of Approximation by its Eigenfunctions
math.CA
For two real numbers $c>0, \alpha> -1,$ we study some spectral properties of
the weighted finite bilateral Laplace transform operator, defined over the
space $E=L^2(I,\omega_{\alpha}),$ $I=[-1,1],$
$\omega_{\alpha}(x)=(1-x^2)^{\alpha},$ by ${\displaystyle \mathcal L_c^{\alpha}
f(x)= \int_I e^{cxy} f(y) \omega_{\alpha}(y)\, dy}.$ In particular, we use a
technique based on the Min-Max theorem to prove that the sequence of the
eigenvalues of this operator has a super-exponential decay rate to zero.
Moreover, we give a lower bound with a magnitude of order $e^c,$ for the
largest eigenvalue of the operator $\mathcal L_c^{\alpha}.$ Also, we give some
local estimates and bounds of the eigenfunctions $\varphi_{n,c}^{\alpha}$ of
$\mathcal L_c^{\alpha}.$ Moreover, we show that these eigenfunctions are good
candidates for the spectral approximation of a function that can be written as
a weighted finite Laplace transform of an other
$L^2(I,\omega_{\alpha})-$function.
Finally, we give some numerical examples that illustrate the different
results of this work. In particular, we provide an example that illustrate the
Laplace based spectral method, for the inversion of the finite Laplace
transform.
| arxiv topic:math.CA |
arxiv_dataset-96701804.05307 | Hyperspectral Super-Resolution: A Coupled Tensor Factorization Approach
eess.SP
Hyperspectral super-resolution refers to the problem of fusing a
hyperspectral image (HSI) and a multispectral image (MSI) to produce a
super-resolution image (SRI) that has fine spatial and spectral resolution.
State-of-the-art methods approach the problem via low-rank matrix
approximations to the matricized HSI and MSI. These methods are effective to
some extent, but a number of challenges remain. First, HSIs and MSIs are
naturally third-order tensors (data "cubes") and thus matricization is prone to
loss of structural information--which could degrade performance. Second, it is
unclear whether or not these low-rank matrix-based fusion strategies can
guarantee identifiability or exact recovery of the SRI. However,
identifiability plays a pivotal role in estimation problems and usually has a
significant impact on performance in practice. Third, the majority of the
existing methods assume that there are known (or easily estimated) degradation
operators applied to the SRI to form the corresponding HSI and MSI--which is
hardly the case in practice. In this work, we propose to tackle the
super-resolution problem from a tensor perspective. Specifically, we utilize
the multidimensional structure of the HSI and MSI to propose a coupled tensor
factorization framework that can effectively overcome the aforementioned
issues. The proposed approach guarantees the identifiability of the SRI under
mild and realistic conditions. Furthermore, it works with little knowledge of
the degradation operators, which is clearly an advantage over the existing
methods. Semi-real numerical experiments are included to show the effectiveness
of the proposed approach.
| arxiv topic:eess.SP |
arxiv_dataset-96711804.05407 | Asymptotic Expansion of the Heat Kernel Trace of Laplacians with
Polynomial Potentials
math-ph math.MP
It is well-known that the asymptotic expansion of the trace of the heat
kernel for Laplace operators on smooth compact Riemmanian manifolds can be
obtained through termwise integration of the asymptotic expansion of the
on-diagonal heat kernel. It is the purpose of this work to show that, in
certain circumstances, termwise integration can be used to obtain the
asymptotic expansion of the heat kernel trace for Laplace operators endowed
with a suitable polynomial potential on unbounded domains. This is achieved by
utilizing a resummed form of the asymptotic expansion of the on-diagonal heat
kernel.
| arxiv topic:math-ph math.MP |
arxiv_dataset-96721804.05507 | What's hard about Boolean Functional Synthesis
cs.LO
Given a relational specification between Boolean inputs and outputs, the goal
of Boolean functional synthesis is to synthesize each output as a function of
the inputs such that the specification is met. In this paper, we first show
that unless some hard conjectures in complexity theory are falsified, Boolean
functional synthesis must necessarily generate exponential-sized Skolem
functions, thereby requiring exponential time, in the worst-case. Given this
inherent hardness, what does one do to solve the problem? We present a
two-phase algorithm for Boolean functional synthesis, where the first phase is
efficient both in terms of time and sizes of synthesized functions, and solves
an overwhelming majority of benchmarks. To explain this surprisingly good
performance, we provide a sufficient condition under which the first phase must
produce exact correct answers. When this condition fails, the second phase
builds upon the result of the first phase, possibly requiring exponential time
and generating exponential-sized functions in the worst-case. Detailed
experimental evaluation shows our algorithm to perform better than
state-of-the-art techniques for a majority of benchmarks.
| arxiv topic:cs.LO |
arxiv_dataset-96731804.05607 | The Arches cluster revisited: II. A massive eclipsing spectroscopic
binary in the Arches cluster
astro-ph.SR
We have carried out a spectroscopic variability survey of some of the most
massive stars in the Arches cluster, using K-band observations obtained with
SINFONI on the VLT. One target, F2, exhibits substantial changes in radial
velocity; in combination with new KMOS and archival SINFONI spectra, its
primary component is found to undergo radial velocity variation with a period
of 10.483+/-0.002 d and an amplitude of ~350 km/s. A secondary radial velocity
curve is also marginally detectable. We reanalyse archival NAOS-CONICA
photometric survey data in combination with our radial velocity results to
confirm this object as an eclipsing SB2 system, and the first binary identified
in the Arches. We model it as consisting of an 82+/-12 M_sun WN8-9h primary and
a 60+/-8 M_sun O5-6 Ia+ secondary, and as having a slightly eccentric orbit,
implying an evolutionary stage prior to strong binary interaction. As one of
four X-ray bright Arches sources previously proposed as colliding-wind massive
binaries, it may be only the first of several binaries to be discovered in this
cluster, presenting potential challenges to recent models for the Arches' age
and composition. It also appears to be one of the most massive binaries
detected to date; the primary's calculated initial mass of >~120 M_sun would
arguably make this the most massive binary known in the Galaxy.
| arxiv topic:astro-ph.SR |
arxiv_dataset-96741804.05707 | N=1 QED in 2+1 dimensions: Dualities and enhanced symmetries
hep-th
We consider three-dimensional sQED with 2 flavors and minimal supersymmetry.
We discuss various models which are dual to Gross-Neveu-Yukawa theories. The
$U(2)$ ultraviolet global symmetry is often enhanced in the infrared, for
instance to $O(4)$ or $SU(3)$. This is analogous to the conjectured behaviour
of non-supersymmetric QED with 2 flavors. A perturbative analysis of the
Gross-Neveu-Yukawa models in the $D = 4 - \varepsilon$ expansion shows that the
$U(2)$ preserving superpotential deformations of the sQED (modulo tuning mass
terms to zero) are irrelevant, so the fixed points with enhanced symmetry are
stable. We also construct an example of $\mathcal{N} = 2$ sQED with 4 flavors
that exhibits enhanced $SO(6)$ symmetry.
| arxiv topic:hep-th |
arxiv_dataset-96751804.05807 | Exponential Functors, R-Matrices and Twists
math.AT math.KT
In this paper we show that each polynomial exponential functor on complex
finite-dimensional inner product spaces is defined up to equivalence of
monoidal functors by an involutive solution to the Yang-Baxter equation (an
involutive $R$-matrix), which determines an extremal character on $S_{\infty}$.
These characters are classified by Thoma parameters, and Thoma parameters
resulting from polynomial exponential functors are of a special kind. Moreover,
we show that each $R$-matrix with Thoma parameters of this kind yield a
corresponding polynomial exponential functor.
In the second part of the paper we use these functors to construct a higher
twist over $SU(n)$ for a localisation of $K$-theory that generalises the one
given by the basic gerbe. We compute the indecomposable part of the rational
characteristic classes of these twists in terms of the Thoma parameters of
their $R$-matrices.
| arxiv topic:math.AT math.KT |
arxiv_dataset-96761804.05907 | Automatic Detection of Indoor and Outdoor Scenarios using NMEA Message
Data from GPS Receivers
cs.OH
Detection of indoor and outdoor scenarios is an important resource for many
types of activities such as multisensor navigation and location-based services.
This research presents the use of NMEA data provided by GPS receivers to
characterize different types of scenarios automatically. A set of static tests
was performed to evaluate metrics such as number of satellites, positioning
solution geometry and carrier-to-receiver noise-density ratio values to detect
possible patterns to determine indoor and outdoor scenarios. Subsequently,
validation tests are applied to verify that parameters obtained are adequate.
| arxiv topic:cs.OH |
arxiv_dataset-96771804.06007 | Solitons in one-dimensional mechanical linkage
cond-mat.soft cond-mat.mes-hall
It has been observed that certain classical chains admit topologically
protected zero-energy modes that are localized on the boundaries. The static
features of such localized modes are captured by linearized equations of
motion, but the dynamical features are governed by its nonlinearity. We study
quasi-periodic solutions of nonlinear equations of motion of one-dimensional
classical chains. Such quasi-periodic solutions correspond to periodic
trajectories in the configuration space of the discrete systems, which allows
us to define solitons without relying on a continuum theory. Furthermore, we
study the dynamics of solitons in inhomogeneous systems by connecting two
chains with distinct parameter sets, where transmission or reflection of
solitons occurs at the boundary of the two chains.
| arxiv topic:cond-mat.soft cond-mat.mes-hall |
arxiv_dataset-96781804.06107 | Second order front tracking algorithm for Stefan problem on a regular
grid
physics.comp-ph cond-mat.mtrl-sci
A brief review of the Stefan problem of solidification from a mixture, and
its main numerical solution methods is given. Simulation of this problem in 2D
or 3D is most practically done on a regular grid, where a sharp solid-liquid
interface moves relative to the grid. For this problem, a new simulation method
is developed that manifestly conserves mass, and that simulates the motion of
the interface to second order in the grid size. When applied to an isothermal
simulation of solidification from solution in 1D at 50% supersaturation for
only 5 grid points, the motion of the interface is accurate to 5.5%; and for 10
points the result is accurate to 1.5%. The method should be applicable to 2D or
3D with relative ease. This opens the door to large scale simulations with
modest computer power.
| arxiv topic:physics.comp-ph cond-mat.mtrl-sci |
arxiv_dataset-96791804.06207 | MetaBags: Bagged Meta-Decision Trees for Regression
cs.LG stat.ML
Ensembles are popular methods for solving practical supervised learning
problems. They reduce the risk of having underperforming models in
production-grade software. Although critical, methods for learning
heterogeneous regression ensembles have not been proposed at large scale,
whereas in classical ML literature, stacking, cascading and voting are mostly
restricted to classification problems. Regression poses distinct learning
challenges that may result in poor performance, even when using well
established homogeneous ensemble schemas such as bagging or boosting.
In this paper, we introduce MetaBags, a novel, practically useful stacking
framework for regression. MetaBags is a meta-learning algorithm that learns a
set of meta-decision trees designed to select one base model (i.e. expert) for
each query, and focuses on inductive bias reduction. A set of meta-decision
trees are learned using different types of meta-features, specially created for
this purpose - to then be bagged at meta-level. This procedure is designed to
learn a model with a fair bias-variance trade-off, and its improvement over
base model performance is correlated with the prediction diversity of different
experts on specific input space subregions. The proposed method and
meta-features are designed in such a way that they enable good predictive
performance even in subregions of space which are not adequately represented in
the available training data.
An exhaustive empirical testing of the method was performed, evaluating both
generalization error and scalability of the approach on synthetic, open and
real-world application datasets. The obtained results show that our method
significantly outperforms existing state-of-the-art approaches.
| arxiv topic:cs.LG stat.ML |
arxiv_dataset-96801804.06307 | Influence of capillary viscous flow on melting dynamics
physics.comp-ph
The rate of melting of a solid and the rate of deformation of the resulting
melt due to capillary forces are comparable in additive manufacturing
applications. This dynamic structural change of a melting solid is extremely
challenging to study experimentally. Using meshless numerical simulations we
show the influence of the flow of the melt on the heat transfer and resulting
phase change. We introduce an accurate and robust Incompressible Smoothed
Particle Hydrodynamics method to simulate melting of solids and the ensuing
fluid-solid interaction. We present validation for the heat transfer across
free surface and the melting interface evolution, separately. We then present
two applications for this coupled multiphysics simulation method---the study of
rounding of an arbitrarily shaped particle during melting and the non-linear
structural evolution of three spheres undergoing agglomeration. In both the
studies we use realistic transport and thermal properties for the materials so
as to demonstrate readiness of the method for solving engineering problems in
additive manufacturing.
| arxiv topic:physics.comp-ph |
arxiv_dataset-96811804.06407 | Recipe for creating an arbitrary number of Floquet chiral edge states
cond-mat.mes-hall nlin.CD quant-ph
Floquet states of periodically driven systems could exhibit rich topological
properties. Many of them are absent in their static counterparts. One such
example is the chiral edge states in anomalous Floquet topological insulators,
whose description requires a new topological invariant and a novel type of
bulk-edge correspondence. In this work, we propose a prototypical quenched
lattice model, whose two Floquet bands could exchange their Chern numbers
periodically and alternatively via touching at quasienergies 0 and $\pi$ under
the change of a single system parameter. This process in principle allows the
generation of as many Floquet chiral edge states as possible in a highly
controllable manner. The quantized transmission of these edge states are
extracted from the Floquet scattering matrix of the system. The flexibility in
controlling the number of topological edge channels provided by our scheme
could serve as a starting point for the engineering of robust Floquet transport
devices.
| arxiv topic:cond-mat.mes-hall nlin.CD quant-ph |
arxiv_dataset-96821804.06507 | How should fishing mortality be distributed under balanced harvesting?
q-bio.PE
Zhou and Smith (2017) investigate different multi-species harvesting
scenarios using a simple Holling-Tanner model. Among these scenarios are two
methods for implementing balanced harvesting, where fishing is distributed
across trophic levels in accordance with their productivity. This note examines
the effects of a different quantitative implementation of balanced harvesting,
where the fishing mortality rate is proportional to the total production rate
of each trophic level. The results show that setting fishing mortality rate to
be proportional to total production rate, rather than to productivity per unit
biomass, better preserves trophic structure and provides a crucial safeguard
for rare and threatened ecological groups. This is a key ingredient of balanced
harvesting if it is to meet its objective of preserving biodiversity.
| arxiv topic:q-bio.PE |
arxiv_dataset-96831804.06607 | Suppression of quantum-mechanical collapse in bosonic gases with
intrinsic repulsion: A brief review
cond-mat.quant-gas nlin.PS physics.optics
It is well known that attractive potential which is inversely proportional to
the squared distance from the origin gives rise to the critical quantum
collapse in the framework of the three-dimensional (3D) linear Schroedinger
equation. This article summarizes theoretical analysis, chiefly published in
several original papers, which demonstrates suppression of the collapse caused
by this potential, and the creation of the otherwise missing ground state in a
3D gas of bosonic dipoles pulled by the same potential to the central charge,
with repulsive contact interactions between them, represented by the cubic term
in the respective Gross-Pitaevskii equation (GPE). In two dimensions (2D),
quintic self-repulsion is necessary for the suppression of the collapse;
alternatively, this may be provided by the effective quartic repulsion,
produced by the Lee-Huang-Yang correction to the GPE. 3D states carrying
angular momentum are constructed in the model with the symmetry reduced from
spherical to cylindrical by an external polarizing field. Interplay of the
collapse suppression and miscibility-immiscibility transition is considered in
a binary condensate. The consideration of the 3D setting in the form of the
many-body quantum system, with the help of the Monte Carlo method, demonstrates
that, although the quantum collapse cannot be fully suppressed, the
self-trapped states, predicted by the GPE, exist in the many-body setting as
metastable modes protected against the collapse by a tall potential barrier.
| arxiv topic:cond-mat.quant-gas nlin.PS physics.optics |
arxiv_dataset-96841804.06707 | Warranty Cost Analysis with an Alternating Geometric Process
q-fin.GN
In this study we model the warranty claims process and evaluate the warranty
servicing costs under non-renewing and renewing free repair warranties. We
assume that the repair time for rectifying the claims is non-zero and the
repair cost is a function of the length of the repair time. To accommodate the
ageing of the product and repair equipment, we use a decreasing geometric
process to model the consecutive operational times and an increasing geometric
process to model the consecutive repair times. We identify and study the
alternating geometric process (AGP), which is an alternating process with
cycles consisting of the item's operational time followed by the corresponding
repair time. We derive new results for the AGP in finite horizon and use them
to evaluate the warranty costs over the warranty period and over the life cycle
of the product under a non-renewing free repair warranty (NRFRW), a renewing
free repair warranty (RFRW) and a restricted renewing free repair warranty
(RRFRW(n)). Properties of the model are demonstrated using a simulation study.
| arxiv topic:q-fin.GN |
arxiv_dataset-96851804.06807 | An extremely low mid-infrared extinction law toward the Galactic Center
and 4% distance precision to 55 classical Cepheids
astro-ph.GA astro-ph.SR
Distances and extinction values are usually degenerate. To refine the
distance to the general Galactic Center region, a carefully determined
extinction law (taking into account the prevailing systematic errors) is
urgently needed. We collected data for 55 classical Cepheids projected toward
the Galactic Center region to derive the near- to mid-infrared extinction law
using three different approaches. The relative extinction values obtained are
AJ/AKs = 3.005, AH/AKs = 1.717, A[3.6]/AKs = 0.478, A[4.5]/AKs = 0.341,
A[5.8]/AKs = 0.234, A[8.0]/AKs = 0.321, AW1/AKs = 0.506, and AW2/AKs = 0.340.
We also calculated the corresponding systematic errors. Compared with previous
work, we report an extremely low and steep mid-infrared extinction law. Using a
seven-passband 'optimal distance' method, we improve the mean distance
precision to our sample of 55 Cepheids to 4%. Based on four confirmed Galactic
Center Cepheids, a solar Galactocentric distance of R_0 = 8.10\pm0.19\pm0.22
kpc is determined, featuring an uncertainty that is close to the limiting
distance accuracy (2.8%) for Galactic Center Cepheids.
| arxiv topic:astro-ph.GA astro-ph.SR |
arxiv_dataset-96861804.06907 | Computing FO-Rewritings in EL in Practice: from Atomic to Conjunctive
Queries
cs.AI
A prominent approach to implementing ontology-mediated queries (OMQs) is to
rewrite into a first-order query, which is then executed using a conventional
SQL database system. We consider the case where the ontology is formulated in
the description logic EL and the actual query is a conjunctive query and show
that rewritings of such OMQs can be efficiently computed in practice, in a
sound and complete way. Our approach combines a reduction with a decomposed
backwards chaining algorithm for OMQs that are based on the simpler atomic
queries, also illuminating the relationship between first-order rewritings of
OMQs based on conjunctive and on atomic queries. Experiments with real-world
ontologies show promising results.
| arxiv topic:cs.AI |
arxiv_dataset-96871804.07007 | QuaSE: Accurate Text Style Transfer under Quantifiable Guidance
cs.CL
We propose the task of Quantifiable Sequence Editing (QuaSE): editing an
input sequence to generate an output sequence that satisfies a given numerical
outcome value measuring a certain property of the sequence, with the
requirement of keeping the main content of the input sequence. For example, an
input sequence could be a word sequence, such as review sentence and
advertisement text. For a review sentence, the outcome could be the review
rating; for an advertisement, the outcome could be the click-through rate. The
major challenge in performing QuaSE is how to perceive the outcome-related
wordings, and only edit them to change the outcome. In this paper, the proposed
framework contains two latent factors, namely, outcome factor and content
factor, disentangled from the input sentence to allow convenient editing to
change the outcome and keep the content. Our framework explores the
pseudo-parallel sentences by modeling their content similarity and outcome
differences to enable a better disentanglement of the latent factors, which
allows generating an output to better satisfy the desired outcome and keep the
content. The dual reconstruction structure further enhances the capability of
generating expected output by exploiting the couplings of latent factors of
pseudo-parallel sentences. For evaluation, we prepared a dataset of Yelp review
sentences with the ratings as outcome. Extensive experimental results are
reported and discussed to elaborate the peculiarities of our framework.
| arxiv topic:cs.CL |
arxiv_dataset-96881804.07107 | The Curse of Ties in Congestion Games with Limited Lookahead
cs.GT
We introduce a novel framework to model limited lookahead in congestion
games. Intuitively, the players enter the game sequentially and choose an
optimal action under the assumption that the $k-1$ subsequent players play
subgame-perfectly. Our model naturally interpolates between outcomes of greedy
best-response ($k=1$) and subgame-perfect outcomes ($k=n$, the number of
players). We study the impact of limited lookahead (parameterized by $k$) on
the stability and inefficiency of the resulting outcomes. As our results
reveal, increased lookahead does not necessarily lead to better outcomes; in
fact, its effect crucially depends on the existence of ties and the type of
game under consideration.
More specifically, already for very simple network congestion games we show
that subgame-perfect outcomes (full lookahead) can be unstable, whereas greedy
best-response outcomes (no lookahead) are known to be stable. We show that this
instability is due to player indifferences (ties). If the game is generic (no
ties exist) then all outcomes are stable, independent of the lookahead $k$. In
particular, this implies that the price of anarchy of $k$-lookahead outcomes
(for arbitrary $k$) equals the standard price of anarchy. For special cases of
cost-sharing games and consensus games we show that no lookahead leads to
stable outcomes. Again this can be resolved by removing ties, though for
cost-sharing games only full lookahead provides stable outcomes. We also
identify a class of generic cost-sharing games for which the inefficiency
decreases as the lookahead $k$ increases.
| arxiv topic:cs.GT |
arxiv_dataset-96891804.07207 | The Effect of Mechanical Cold Work on the Magnetic Flux Expulsion of
Niobium
physics.acc-ph
Expulsion of ambient flux has been shown to be crucial to obtain high quality
factors in bulk niobium SRF cavities. However, there remain many questions as
to what properties of the niobium material determine its flux expulsion
behavior. In this paper, we present first results from a new study of two
cavities that were specially fabricated to study flux expulsion. Both cavities
were made from large grain ingot niobium slices, one of which had its slices
rolled prior to fabrication, and none these slices were annealed prior to
measurement. Expulsion measurements indicate that a dense network of grain
boundaries is not necessary for a cavity to have near-complete flux trapping
behavior up to large thermal gradients. The results also contribute to a body
of evidence that cold work is a strong determinant of flux expulsion behavior
in SRF-grade niobium.
| arxiv topic:physics.acc-ph |
arxiv_dataset-96901804.07307 | Deep Learning Identifies High-z Galaxies in a Central Blue Nugget Phase
in a Characteristic Mass Range
astro-ph.GA
We use machine learning to identify in color images of high-redshift galaxies
an astrophysical phenomenon predicted by cosmological simulations. This
phenomenon, called the blue nugget (BN) phase, is the compact star-forming
phase in the central regions of many growing galaxies that follows an earlier
phase of gas compaction and is followed by a central quenching phase. We train
a Convolutional Neural Network (CNN) with mock "observed" images of simulated
galaxies at three phases of evolution: pre-BN, BN and post-BN, and demonstrate
that the CNN successfully retrieves the three phases in other simulated
galaxies. We show that BNs are identified by the CNN within a time window of
$\sim0.15$ Hubble times. When the trained CNN is applied to observed galaxies
from the CANDELS survey at $z=1-3$, it successfully identifies galaxies at the
three phases. We find that the observed BNs are preferentially found in
galaxies at a characteristic stellar mass range, $10^{9.2-10.3} M_\odot$ at all
redshifts. This is consistent with the characteristic galaxy mass for BNs as
detected in the simulations, and is meaningful because it is revealed in the
observations when the direct information concerning the total galaxy luminosity
has been eliminated from the training set. This technique can be applied to the
classification of other astrophysical phenomena for improved comparison of
theory and observations in the era of large imaging surveys and cosmological
simulations.
| arxiv topic:astro-ph.GA |
arxiv_dataset-96911804.07407 | NLO QCD corrections to SM-EFT dilepton and electroweak Higgs boson
production, matched to parton shower in POWHEG
hep-ph hep-ex
We discuss the Standard Model Effective Field Theory (SM-EFT) contributions
to neutral- and charge-current Drell-Yan production, associated production of
the Higgs and a vector boson, and Higgs boson production via vector boson
fusion. We consider all the dimension-six SM-EFT operators that contribute to
these processes at leading order, include next-to-leading order QCD
corrections, and interface them with parton showering and hadronization in
Pythia8 according to the POWHEG method. We discuss existing constraints on the
coefficients of dimension-six operators and identify differential and angular
distributions that can differentiate between different effective operators,
pointing to specific features of Beyond-the-Standard-Model physics.
| arxiv topic:hep-ph hep-ex |
arxiv_dataset-96921804.07507 | Physics of polarized light scattering from weakly rough dielectric
surfaces: Yoneda and Brewster scattering phenomena
physics.optics
The optical Yoneda and Brewster scattering phenomena are studied
theoretically based on pertubative solutions of the reduced Rayleigh equations.
The Yoneda phenomenon is characterized as an enhancement of the intensity of
the diffuse light scattered by a randomly rough interface between two
dielectric media when the light is observed in the optically denser medium. The
intensity enhancement occurs above a critical angle of scattering which is
independent of the angle of incidence of the excitation. The Brewster
scattering phenomenon is characterized by a zero scattered intensity either in
the reflected or transmitted light for an angle of scattering which depends on
the angle of incidence. We also describe a generalization of the Brewster
scattering phenomenon for outgoing evanescent waves and circularly-polarized
waves. The physical mechanisms responsible for these phenomena are described in
terms of simple notions such as scalar waves, oscillating and rotating dipoles
and geometrical arguments, and are valid in a regime of weakly rough
interfaces.
| arxiv topic:physics.optics |
arxiv_dataset-96931804.07607 | A study of divergence from randomness in the distribution of prime
numbers within the arithmetic progressions 1+6n and 5+6n
math.GM
In this article I present results from a statistical study of prime numbers
that shows a behaviour that is not compatible with the thesis that they are
distributed randomly. The analysis is based on studying two arithmetical
progressions defined by the following polynomials: ($1+6n$, $5+6n$, $n\in{N}$)
whose respective numerical sequences have the characteristic of containing all
the prime numbers except $3$ and $2$. If prime numbers were distributed
randomly, we would expect the two polynomials to generate the same number of
primes. Instead, as the reported findings show, we note that the polynomial
$5+6n$ tends to generate many more primes, and that this divergence grows
progressively as more prime numbers are considered. A possible explanation for
this phenomenon can be found by calculating the number of products that
generate composite numbers which are expressible by the two polynomials. This
analysis reveals that the number of products that generate composite numbers
expressible by the polynomial $1+6n$ is $(n+1)^{ 2}$, while the number of
products that generate composites expressible by the polynomial $5+6n$ is
$(n+1)n$, con $n\in{N}$. As a composite number is a non-prime number, this
difference incited me to analyse the distribution of prime numbers generated by
the two polynomials. The results, based on studying the first (approx.) 500
million prime numbers, confirm the fact that the number of primes that can be
written using the polynomial $1+6n$ is lower than the number of primes that can
written using the polynomial $5+6n$, and that this divergence grows
progressively with the number of primes considered.
| arxiv topic:math.GM |
arxiv_dataset-96941804.07707 | Factorising AMR generation through syntax
cs.CL
Generating from Abstract Meaning Representation (AMR) is an underspecified
problem, as many syntactic decisions are not constrained by the semantic graph.
To explicitly account for this underspecification, we break down generating
from AMR into two steps: first generate a syntactic structure, and then
generate the surface form. We show that decomposing the generation process this
way leads to state-of-the-art single model performance generating from AMR
without additional unlabelled data. We also demonstrate that we can generate
meaning-preserving syntactic paraphrases of the same AMR graph, as judged by
humans.
| arxiv topic:cs.CL |
arxiv_dataset-96951804.07807 | Determining Genus From Sandpile Torsor Algorithms
math.CO
We provide a pair of ribbon graphs that have the same rotor routing and
Bernardi sandpile torsors, but different topological genus. This resolves a
question posed by M. Chan [Cha]. We also show that if we are given a graph, but
not its ribbon structure, along with the rotor routing sandpile torsors, we are
able to determine the ribbon graph's genus.
| arxiv topic:math.CO |
arxiv_dataset-96961804.07907 | The Cohomology Algebra of Polyhedral Product Objects
math.AT
In this paper, we compute the homology group and cohomology algebra of
various polyhedral product objects uniformly from the point of view of diagonal
tensor product. As applications, we introduce the polyhedral product method
into commutative algebra and show that the homotopy types of polyhedral product
spaces depend on not only the homotopy type of each summand pair but also on
the character coproduct of the pair.
| arxiv topic:math.AT |
arxiv_dataset-96971804.08007 | A Multilayer Comparative Study of XG-PON and 10G-EPON Standards
cs.NI
The purpose of this paper is to provide a multilayer review of the two major
standards in next generation Passive Optical Networks (PONs) and technologies,
the ITU-T 10-Gigabit-capable PON (XG-PON) and the IEEE 10 Gigabit Ethernet PON
(10G-EPON). A study and a discussion on the standards are performed. The main
intention of this paper is to compare XG-PON and 10G-EPON, mainly in terms of
physical and data link layers. The paper answers the question of what are the
common elements and the basic execution differences of the two standards.
Moreover, critical points are raised regarding the Dynamic Bandwidth Allocation
(DBA) schemes of both standards. Special focus is also pointed in the
coexistence of XG-PON and 10G-EPON. Finally, the paper includes a discussion of
open issues and continuing research regarding the two standards.
| arxiv topic:cs.NI |
arxiv_dataset-96981804.08107 | Are homeostatic states stable? Dynamical stability in morphoelasticity
physics.bio-ph cond-mat.soft q-bio.TO
Biological growth is often driven by mechanical cues, such as changes in
external pressure or tensile loading. Moreover, it is well known that many
living tissues actively maintain a preferred level of mechanical internal
stress, called the mechanical homeostasis. The tissue-level feedback mechanism
by which changes of the local mechanical stresses affect growth is called a
growth law within the theory of morphoelasticity, a theory for understanding
the coupling between mechanics and geometry in growing and evolving biological
materials. The goal of this article is to develop mathematical techniques to
analyze growth laws and to explore issues of heterogeneity and growth
stability. We discuss the growth dynamics of tubular structures, which are very
common in biology (e.g. arteries, plant stems, airways) and model the
homeostasis-driven growth dynamics of tubes which produces spatially
inhomogeneous residual stress. We show that the stability of the homeostatic
state depends nontrivially on the anisotropy of the growth response. The key
role of anisotropy may provide a foundation for experimental testing of
homeostasis-driven growth laws.
| arxiv topic:physics.bio-ph cond-mat.soft q-bio.TO |
arxiv_dataset-96991804.08207 | Collecting Diverse Natural Language Inference Problems for Sentence
Representation Evaluation
cs.CL
We present a large-scale collection of diverse natural language inference
(NLI) datasets that help provide insight into how well a sentence
representation captures distinct types of reasoning. The collection results
from recasting 13 existing datasets from 7 semantic phenomena into a common NLI
structure, resulting in over half a million labeled context-hypothesis pairs in
total. We refer to our collection as the DNC: Diverse Natural Language
Inference Collection. The DNC is available online at https://www.decomp.net,
and will grow over time as additional resources are recast and added from novel
sources.
| arxiv topic:cs.CL |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.