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A family of quantum measures like the Shannon distinguishability is
presented. These measures are defined over the two classes of POVM measurements
and related to separate parts in the expression for mutual information. Changes
of Ky Fan's norms and the partitioned trace distances under the operation of
partial trace are discussed. Upper and lower bounds on the introduced
quantities are obtained in terms of partitioned trace distances and Uhlmann's
partial fidelities. These inequalities provide a kind of generalization of the
well-known bounds on the Shannon distinguishability. The notion of
cryptographic exponential indistinguishability for quantum states is revisited.
When exponentially fast convergence is required, all the metrics induced by
unitarily invariant norms are shown to be equivalent.
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We recently hypothesized that a distortion parameter exists such that its
signed sum for all images of singular gravitational lensing of a source
vanishes identically [K. S. Virbhadra, Phys. Rev. D {\bf 106}, 064038 (2022)].
We found a distortion parameter (the ratio of the tangential to radial
magnifications) that satisfied the hypothesis for the images of Schwarzschild
lensing with flying colors. We now show that another distortion parameter (the
difference of tangential and radial magnifications) also magnificently supports
our hypothesis when we perform computations with the primary-secondary and
relativistic images. The distortion parameters, which satisfy the aesthetically
appealing hypothesis, will likely aid in developing gravitational lensing
theory. Finally, we discuss the conservation of distortion of images in
gravitational lensing.
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A powerful tool for studying geometrical problems in Hilbert space is
developed. In particular, we study the quantum pure state tomography problem in
finite dimensions from the point of view of dynamical systems and bifurcations
theory. First, we introduce a generalization of the Hellinger metric for
probability distributions which allows us to find a geometrical interpretation
of the quantum state tomography problem. Thereafter, we prove that every
solution to the state tomography problem is an attractive fixed point of the
so-called physical imposition operator. Additionally, we demonstrate that
multiple states corresponding to the same experimental data are associated to
bifurcations of this operator. Such a kind of bifurcations only occurs when
informationally incomplete set of observables are considered. Finally, we prove
that the physical imposition operator has a non-contractive Lipschitz constant
2 for the Bures metric. This value of the Lipschitz constant manifests the
existence of the quantum tomography problem for pure states.
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Glucose homeostasis is controlled by the islets of Langerhans which are
equipped with alpha-cells increasing the blood glucose level, beta-cells
decreasing it, and delta-cells the precise role of which still needs
identifying. Although intercellular communications between these endocrine
cells have recently been observed, their roles in glucose homeostasis have not
been clearly understood. In this study, we construct a mathematical model for
an islet consisting of two-state alpha-, beta-, and delta-cells, and analyze
effects of known chemical interactions between them with emphasis on the
combined effects of those interactions. In particular, such features as
paracrine signals of neighboring cells and cell-to-cell variations in response
to external glucose concentrations as well as glucose dynamics, depending on
insulin and glucagon hormone, are considered explicitly. Our model predicts
three possible benefits of the cell-to-cell interactions: First, the asymmetric
interaction between alpha- and beta-cells contributes to the dynamic stability
while the perturbed glucose level recovers to the normal level. Second, the
inhibitory interactions of delta-cells for glucagon and insulin secretion
prevent the wasteful co-secretion of them at the normal glucose level. Finally,
the glucose dose-responses of insulin secretion is modified to become more
pronounced at high glucose levels due to the inhibition by delta-cells. It is
thus concluded that the intercellular communications in islets of Langerhans
should contribute to the effective control of glucose homeostasis.
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In this paper, we explore an efficient uncoupled unsourced random access
(UURA) scheme for 6G massive communication. UURA is a typical framework of
unsourced random access that addresses the problems of codeword detection and
message stitching, without the use of check bits. Firstly, we establish a
framework for UURA, allowing for immediate decoding of sub-messages upon
arrival. Thus, the processing delay is effectively reduced due to the
decreasing waiting time. Next, we propose an integrated decoding algorithm for
sub-messages by leveraging matrix information geometry (MIG) theory.
Specifically, MIG is applied to measure the feature similarities of codewords
belonging to the same user equipment, and thus sub-message can be stitched once
it is received. This enables the timely recovery of a portion of the original
message by simultaneously detecting and stitching codewords within the current
sub-slot. Furthermore, we analyze the performance of the proposed integrated
decoding-based UURA scheme in terms of computational complexity and convergence
rate. Finally, we present extensive simulation results to validate the
effectiveness of the proposed scheme in 6G wireless networks.
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In the clinic, resected tissue samples are stained with Hematoxylin-and-Eosin
(H&E) and/or Immunhistochemistry (IHC) stains and presented to the pathologists
on glass slides or as digital scans for diagnosis and assessment of disease
progression. Cell-level quantification, e.g. in IHC protein expression scoring,
can be extremely inefficient and subjective. We present DeepLIIF
(https://deepliif.org), a first free online platform for efficient and
reproducible IHC scoring. DeepLIIF outperforms current state-of-the-art
approaches (relying on manual error-prone annotations) by virtually restaining
clinical IHC slides with more informative multiplex immunofluorescence
staining. Our DeepLIIF cloud-native platform supports (1) more than 150
proprietary/non-proprietary input formats via the Bio-Formats standard, (2)
interactive adjustment, visualization, and downloading of the IHC
quantification results and the accompanying restained images, (3) consumption
of an exposed workflow API programmatically or through interactive plugins for
open source whole slide image viewers such as QuPath/ImageJ, and (4) auto
scaling to efficiently scale GPU resources based on user demand.
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In this article we show the following result: if $C$ is an $n$-dimensional
convex and compact subset, $f:C\rightarrow[0,\infty)$ is concave, and
$\phi:[0,\infty)\rightarrow[0,\infty)$ is a convex function with $\phi(0)=0$,
we then characterize the class of sets and concave functions that attain the
supremum \[ \sup_{C,f}\int_C\phi(f(x))dx, \] where the supremum ranges over all
sets $C$ with $n$-dimensional volume $|C|=c$ and the additional condition that
$f(x_{C,f})=k$ for some point $x_{C,f}\in C$ that we introduce in the article,
for two non-negative constants $c,k>0$.
As a consequence, we extend some results of Milman and Pajor in [MP] and some
in [Thm. 1.2, GoMe]. Besides, we also obtain some new estimates on the volume
of particular sections of a convex set $K$ passing through a new point of $K$.
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The main purpose of this study is to introduce a semi-classical model
describing betting scenarios in which, at variance with conventional
approaches, the payoff of the gambler is encoded into the internal degrees of
freedom of a quantum memory element. In our scheme, we assume that the invested
capital is explicitly associated with the quantum analog of the free-energy
(i.e. ergotropy functional by Allahverdyan, Balian, and Nieuwenhuizen) of a
single mode of the electromagnetic radiation which, depending on the outcome of
the betting, experiences attenuation or amplification processes which model
losses and winning events. The resulting stochastic evolution of the quantum
memory resembles the dynamics of random lasing which we characterize within the
theoretical setting of Bosonic Gaussian channels. As in the classical Kelly
Criterion for optimal betting, we define the asymptotic doubling rate of the
model and identify the optimal gambling strategy for fixed odds and
probabilities of winning. The performance of the model are hence studied as a
function of the input capital state under the assumption that the latter
belongs to the set of Gaussian density matrices (i.e. displaced, squeezed
thermal Gibbs states) revealing that the best option for the gambler is to
devote all her/his initial resources into coherent state amplitude.
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The partition function of a massless scalar field on a Euclidean spacetime
manifold $\mathbb{R}^{d-1}\times\mathbb{T}^2$ and with momentum operator in the
compact spatial dimension coupled through a purely imaginary chemical potential
is computed. It is modular covariant and admits a simple expression in terms of
a real analytic SL$(2,\mathbb{Z})$ Eisenstein series with $s=(d+1)/2$.
Different techniques for computing the partition function illustrate
complementary aspects of the Eisenstein series: the functional approach gives
its series representation, the operator approach yields its Fourier series,
while the proper time/heat kernel/world-line approach shows that it is the
Mellin transform of a Riemann theta function. High/low temperature duality is
generalized to the case of a non-vanishing chemical potential. By clarifying
the dependence of the partition function on the geometry of the torus, we
discuss how modular covariance is a consequence of full SL$(2,\mathbb{Z})$
invariance. When the spacetime manifold is
$\mathbb{R}^p\times\mathbb{T}^{q+1}$, the partition function is given in terms
of a SL$(q+1,\mathbb{Z})$ Eisenstein series again with $s=(d+1)/2$. In this
case, we obtain the high/low temperature duality through a suitably adapted
dual parametrization of the lattice defining the torus. On $\mathbb{T}^{d+1}$,
the computation is more subtle. An additional divergence leads to an harmonic
anomaly.
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A quantum walk algorithm can detect the presence of a marked vertex on a
graph quadratically faster than the corresponding random walk algorithm
(Szegedy, FOCS 2004). However, quantum algorithms that actually find a marked
element quadratically faster than a classical random walk were only known for
the special case when the marked set consists of just a single vertex, or in
the case of some specific graphs. We present a new quantum algorithm for
finding a marked vertex in any graph, with any set of marked vertices, that is
(up to a log factor) quadratically faster than the corresponding classical
random walk.
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We have calculated the rate coefficients for D(1s) + H^+ <--> D^+ + H(1s)
using recently published theoretical cross sections. We present results for
temperatures T from 1 K to 2x10^5 K and provide fits to our data for use in
plasma modeling. Our calculations are in good agreement with previously
published rate coefficients for 25 <= T <= 300 K, which covers most of the
limited range for which those results were given. Our new rate coefficients for
T >~ 100 K are significantly larger than the values most commonly used for
modeling the chemistry of the early universe and of molecular clouds. This may
have important implications for the predicted HD abundance in these
environments. Using our results, we have modeled the ionization balance in high
redshift QSO absorbers. We find that the new rate coefficients decrease the
inferred D/H ratio by <~ 0.4%. This is a factor of >~ 25 smaller than the
current >~ 10% uncertainties in QSO absorber D/H measurements.
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Large language model (LLM) performance on reasoning problems typically does
not generalize out of distribution. Previous work has claimed that this can be
mitigated with chain of thought prompting-a method of demonstrating solution
procedures-with the intuition that it is possible to in-context teach an LLM an
algorithm for solving the problem. This paper presents a case study of chain of
thought on problems from Blocksworld, a classical planning domain, and examines
the performance of two state-of-the-art LLMs across two axes: generality of
examples given in prompt, and complexity of problems queried with each prompt.
While our problems are very simple, we only find meaningful performance
improvements from chain of thought prompts when those prompts are exceedingly
specific to their problem class, and that those improvements quickly
deteriorate as the size n of the query-specified stack grows past the size of
stacks shown in the examples. We also create scalable variants of three domains
commonly studied in previous CoT papers and demonstrate the existence of
similar failure modes. Our results hint that, contrary to previous claims in
the literature, CoT's performance improvements do not stem from the model
learning general algorithmic procedures via demonstrations but depend on
carefully engineering highly problem specific prompts. This spotlights
drawbacks of chain of thought, especially the sharp tradeoff between possible
performance gains and the amount of human labor necessary to generate examples
with correct reasoning traces.
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These Monte Carlo studies describe the impact of higher order effects in both
QCD and EW $t\bar{t}W$ production. Both next-to-leading inclusive and multileg
setups are studied for $t\bar{t}W$ QCD production.
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Essential to understanding the cuprate pseudogap phase is a study of the
charge (and spin) response functions, which we address here via a consistent
approach to the Fermi arcs and the Fermi pockets scenario of Yang, Rice and
Zhang (YRZ). The two schemes are demonstrated to be formally similar, and to
share a common physics platform; we use this consolidation to address the
inclusion of vertex corrections which have been omitted in YRZ applications. We
show vertex corrections can be easily implemented in a fashion analytically
consistent with sum rules and that they yield important contributions to most
observables. A study of the charge ordering susceptibility of the YRZ scenario
makes their simple physics evident: they represent the inclusion of charged
bosonic, spin singlet degrees of freedom, and are found to lead to a double
peak structure.
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We provide an estimate on the absolute values of the emission rate of photon
pairs produced by spontaneous parametric down conversion in a bulk crystal when
all interacting fields are in single transverse Gaussian modes. Both collinear
and non-collinear configurations are covered, and we arrive at a fully
analytical expression for the collinear case. Our results agree reasonably well
with values found in typical experiments, which allows this model to be used
for understanding the dependency on the relevant experimental parameters.
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SARS-COV-2 is a positive single-strand RNA-based macromolecule that has
caused the death of more than 6.3 million people since June 2022. Moreover, by
disturbing global supply chains through lockdown, the virus has indirectly
caused devastating damage to the global economy. It is vital to design and
develop drugs for this virus and its various variants. In this paper, we
developed an in-silico study-based hybrid framework to repurpose existing
therapeutic agents in finding drug-like bioactive molecules that would cure
Covid-19. We employed the Lipinski rules on the retrieved molecules from the
ChEMBL database and found 133 drug-likeness bioactive molecules against SARS
coronavirus 3CL Protease. Based on standard IC50, the dataset was divided into
three classes active, inactive, and intermediate. Our comparative analysis
demonstrated that the proposed Extra Tree Regressor (ETR) based QSAR model has
improved prediction results related to the bioactivity of chemical compounds as
compared to Gradient Boosting, XGBoost, Support Vector, Decision Tree, and
Random Forest based regressor models. ADMET analysis is carried out to identify
thirteen bioactive molecules with ChEMBL IDs 187460, 190743, 222234, 222628,
222735, 222769, 222840, 222893, 225515, 358279, 363535, 365134 and 426898.
These molecules are highly suitable drug candidates for SARS-COV-2 3CL
Protease. In the next step, the efficacy of bioactive molecules is computed in
terms of binding affinity using molecular docking and then shortlisted six
bioactive molecules with ChEMBL IDs 187460, 222769, 225515, 358279, 363535, and
365134. These molecules can be suitable drug candidates for SARS-COV-2. It is
anticipated that the pharmacologist/drug manufacturer would further investigate
these six molecules to find suitable drug candidates for SARS-COV-2. They can
adopt these promising compounds for their downstream drug development stages.
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This paper studies the gap between quantum one-way communication complexity
$Q(f)$ and its classical counterpart $C(f)$, under the {\em unbounded-error}
setting, i.e., it is enough that the success probability is strictly greater
than 1/2. It is proved that for {\em any} (total or partial) Boolean function
$f$, $Q(f)=\lceil C(f)/2 \rceil$, i.e., the former is always exactly one half
as large as the latter. The result has an application to obtaining (again an
exact) bound for the existence of $(m,n,p)$-QRAC which is the $n$-qubit random
access coding that can recover any one of $m$ original bits with success
probability $\geq p$. We can prove that $(m,n,>1/2)$-QRAC exists if and only if
$m\leq 2^{2n}-1$. Previously, only the construction of QRAC using one qubit,
the existence of $(O(n),n,>1/2)$-RAC, and the non-existence of
$(2^{2n},n,>1/2)$-QRAC were known.
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Multistage robust optimization problems can be interpreted as two-person
zero-sum games between two players. We exploit this game-like nature and
utilize a game tree search in order to solve quantified integer programs
(QIPs). In this algorithmic environment relaxations are repeatedly called to
asses the quality of a branching variable and for the generation of bounds. A
useful relaxation, however, must be well balanced with regard to its quality
and its computing time. We present two relaxations that incorporate scenarios
from the uncertainty set, whereby the considered set of scenarios is
continuously adapted according to the latest information gathered during the
search process. Using selection, assignment, and runway scheduling problems as
a testbed, we show the impact of our findings.
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Cyclic Prefix Direct Sequence Spread Spectrum (CP-DSSS) is a promising
solution for futuristic 6G ultra-reliable low latency communications (URLLC)
and massive machine type communication (mMTC) applications. We propose that in
such applications, the CP-DSSS waveform would operate as a secondary network at
the same frequencies as the primary network but at much lower SNR. In this
paper, we evaluate per-user capacity of CP-DSSS when simple matched filtering
(MF) is performed on the uplink (UL) and time-reversal (TR) precoding is used
on the downlink (DL). In this setting when operating in the low SNR regime,
CP-DSSS achieves a per-user capacity that is near the optimum single-user
capacity. TR precoding converges to the optimal capacity as the number of
antennas at the hub/gateway increases. Using the estimated channel impulse
response for MF and TR introduces little to no capacity loss. Given the
near-optimal performance of MF detection and TR precoding for each of the
users, CP-DSSS can be implemented with simple device transceiver structures,
reducing per-unit cost for massively deployed 6G networks.
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While convergence of the Alternating Direction Method of Multipliers (ADMM)
on convex problems is well studied, convergence on nonconvex problems is only
partially understood. In this paper, we consider the Gaussian phase retrieval
problem, formulated as a linear constrained optimization problem with a
biconvex objective. The particular structure allows for a novel application of
the ADMM. It can be shown that the dual variable is zero at the global
minimizer. This motivates the analysis of a block coordinate descent algorithm,
which is equivalent to the ADMM with the dual variable fixed to be zero. We
show that the block coordinate descent algorithm converges to the global
minimizer at a linear rate, when starting from a deterministically achievable
initialization point.
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We present a preliminary report on a calculation of scattering length for I=2
$S$-wave two-pion system directly from the two-pion wave function. Results are
compared with those calculated from the time dependence of two-pion four-point
functions. Calculations are made with an RG-improved action for gluons and
improved Wilson action for quarks at $a^{-1}=1.207(12)$ GeV on $20^3 \times 48$
and $24^3 \times 48$ lattices.
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Quantum kinetic equations of motion for the description of the exciton spin
dynamics in II-VI diluted magnetic semiconductor quantum wells with laser
driving are derived. The model includes the magnetic as well as the nonmagnetic
carrier-impurity interaction, the Coulomb interaction, Zeeman terms, and the
light-matter coupling, allowing for an explicit treatment of arbitrary
excitation pulses. Based on a dynamics-controlled truncation scheme,
contributions to the equations of motion up to second order in the generating
laser field are taken into account. The correlations between the carrier and
the impurity subsystems are treated within the framework of a correlation
expansion. For vanishing magnetic field, the Markov limit of the quantum
kinetic equations formulated in the exciton basis agrees with existing theories
based on Fermi's golden rule. For narrow quantum wells excited at the $1s$
exciton resonance, numerical quantum kinetic simulations reveal pronounced
deviations from the Markovian behavior. In particular, the spin decays
initially with approximately half the Markovian rate and a non-monotonic decay
in the form of an overshoot of up to $10\,\%$ of the initial spin polarization
is predicted.
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We report scanning transmission X-ray microscopy of mixed helical and
skyrmion magnetic states in thin FeGe lamellae. This imaging of the
out-of-plane magnetism allows clear identification of the different magnetic
states, and reveals details about the coexistence of helical and skyrmion
states. In particular, our data show that finite length helices are
continuously deformable down to the size of individual skyrmions and are hence
topologically equivalent to skyrmions. Furthermore, we observe transition
states between helical and skyrmion states across the thickness of the lamella
that are evidence for frozen Bloch points in the sample after field cooling.
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Polymer nanocomposites based on 2D materials as fillers are the target in the
industrial sector, but the ability to manufacture them on a large scale is very
limited, and there is a lack of tools to scale up the manufacturing process of
these nanocomposites. Here, for the first time, a systematic and fundamental
study showing how 2D materials are inserted into the polymeric matrix in order
to obtain nanocomposites using conventional and industrially scalable polymer
processing machines leading to large-scale manufacturing are described. Two new
strategies were used to insert pre-exfoliated 2D material into the polymer
matrix, liquid-phase feeder, and solid-solid deposition. Characterizations were
beyond micro and nanoscale, allowing the evaluation of the morphology for
millimeter samples size. The methodologies described here are extendable to all
thermoplastic polymers and 2D materials providing nanocomposites with suitable
morphology to obtain singular properties and also triggering the start of the
manufacturing process on a large scale.
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We consider the effect of electron-phonon interactions on edge states in
quantum Hall systems with a single edge branch. The presence of electron-phonon
interactions modifies the single-particle propagator for general quantum Hall
edges, and, in particular, destroys the Fermi liquid even at integer filling.
The effect of the electron-phonon interactions may be detected experimentally
in the AC conductance or in the tunneling conductance between integer quantum
Hall edges.
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The new 1.4 MeV/u front end HSI (HochStromInjektor) of the Unilac accelerates
ions with A/q ratios of up to 65 and with beam intensities in emA of up to 0.25
A/q. The maximum beam pulse power is up to 1300 kW. During the stepwise linac
commissioning from April to Septem-ber 1999 the beam behind of each cavity was
analysed within two weeks. A very stable Ar1+ beam out of a vol-ume plasma
source MUCIS was used mainly. The meas-ured norm. 80 % emittance areas around
0.45 pi mm mrad are close to the results from beam simulations. Up to 80 % of
the design intensity at the linac exit were achieved. In February 2000 an U4+
beam from the MEVVA source was accelerated for the first time.
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Among the many experimental techniques available, those providing directional
information have the potential of yielding an unambiguous observation of WIMPs
even in the presence of insidious backgrounds. A measurement of the
distribution of arrival direction of WIMPs can also discriminate between
Galactic Dark Matter halo models. In this article, I will discuss the
motivation for directional detectors and review the experimental techniques
used by the various experiments. I will then describe one of them, the DMTPC
detector, in more detail.
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This current work is an extension to work previously done by the authors. The
dynamics of a baby skyrmion configuration, in a model Landau-Lifshitz equation,
was studied in the presence of various potential obstructions. The baby
skyrmion configuration was constructed from two Q=1 hedgehog solutions to the
new baby Skyrme model in $(2+1)$ dimensions.
The potential obstructions were created by introducing a new term into the
Lagrangian which resulted in a localised inhomogeneity in the potential term's
coefficient. In the barrier system the normal circular path was deformed as the
skyrmions traversed the barrier, after which the skyrmions orbited the boundary
of the system. For critical values of the barrier height and width the
skyrmions were no longer bound although the unbound behaviour is not clearly
distinct from the bound. In the case of a potential hole the dynamics of baby
skyrmions is dependent upon the binding energy of the system. Depending upon
its value, the skyrmions' behaviour varies. The angular momentum must be
modified to ensure overall conservation. We show that there exists a link
between the oscillation in the skyrmion's energy density and the periods of
non-conservation of the angular momentum in Landau-Lifshitz models.
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Spectral estimation can be preformed using the so called THREE-like approach.
Such method leads to a convex optimization problem whose solution is
characterized through its dual problem. In this paper, we show that the dual
problem can be seen as a new parametric spectral estimation problem. This
interpretation implies that the THREE-like solution is optimal in terms of
closeness to the correlogram over a certain parametric class of spectral
densities, enriching in this way its meaningfulness.
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Let $p^k m^2$ be an odd perfect number with special prime $p$. In this
article, we provide an alternative proof for the biconditional that
$\sigma(m^2) \equiv 1 \pmod 4$ holds if and only if $p \equiv k \pmod 8$. We
then give an application of this result to the case when $\sigma(m^2)/p^k$ is a
square.
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This work is concerned with the development of a numerical modelling approach
for studying the time-accurate response of aerospace fasteners subjected to
high electrical current loading from a simulated lightning strike. The
electromagnetic, thermal and elastoplastic response of individual fastener
components is captured by this method allowing a critical analysis of fastener
design and material layering. Under high electrical current loading, ionisation
of gas filled cavities in the fastener assembly can lead to viable current
paths across internal voids. This ionisation can lead to localised pockets of
high pressure plasma through the Joule heating effect. The multi-physics
approach developed in this paper extends an existing methodology that allows a
two-way dynamic non-linear coupling of the plasma arc, the titanium aerospace
fastener components, the surrounding aircraft panels, the internal supporting
structure and internal plasma-filled cavities. Results from this model are
compared with experimental measurements of a titanium fastener holding together
carbon composite panels separated by thin dielectric layers. The current
distribution measurements are shown to be accurately reproduced. A parameter
study is used to assess the internal cavity modelling strategy and to quantify
the relation between the internal cavity plasma pressure, the electrical
current distribution and changes in the internal cavity geometry.
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We report the first terahertz Kerr measurements on bulk crystals of the
topological insulator Bi2Se3. At T=10K and fields up to 8T, the real and
imaginary Kerr angle and reflectance measurements utilizing both linearly and
circularly polarized incident radiation were measured at a frequency of
5.24meV. A single fluid free carrier bulk response can not describe the
line-shape. Surface states with a small mass and surprisingly large associated
spectral weight quantitatively fit all data. However, carrier concentration
inhomogeneity has not been ruled out. A method employing a gate is shown to be
promising for separating surface from bulk effects.
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We show autoconsistent chemical and spectro-photometric evolution models
applied to spiral and irregular galaxies. Evolutionary synthesis models usually
used to explain the stellar component spectro-photometric data, are combined
with chemical evolution models, to determine precisely the evolutionary history
of spiral and irregular galaxies. In this piece of work we will show the
results obtained for a wide grid of modeled theoretical galaxies
|
Efficiency in passage times is an important issue in designing networks, such
as transportation or computer networks. The small-world networks have
structures that yield high efficiency, while keeping the network highly
clustered. We show that among all networks with the small-world structure, the
most efficient ones have a single ``center'', from which all shortcuts are
connected to uniformly distributed nodes over the network. The networks with
several centers and a connected subnetwork of shortcuts are shown to be
``almost'' as efficient. Genetic-algorithm simulations further support our
results.
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We present two ways of regularizing a one parameter family of piece-wise
smooth dynamical systems undergoing a codimension one grazing-sliding global
bifurcation of periodic orbits. First we use the Sotomayor-Teixeira
regularization and prove that the regularized family has a saddle-node
bifurcation of periodic orbits. Then we perform a hysteretic regularization and
show that the regularized family has chaotic dynamics. Our result shows that,
in spite that the two regularizations will give the same dynamics in the
sliding modes, when a tangency appears the hysteretic process generates chaotic
dynamics.
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We study the stability of the electroweak vacuum in the supersymmetric (SUSY)
standard model (SM), paying particular attention to its relation to the SUSY
contribution to the muon anomalous magnetic moment $a_\mu$. If the SUSY
contribution to $a_\mu$ is sizable, the electroweak vacuum may become unstable
because of enhanced trilinear scalar interactions in particular when the
sleptons are heavy. Consequently, assuming enhanced SUSY contribution to
$a_\mu$, an upper bound on the slepton masses is obtained. We give a detailed
prescription to perform a full one-loop calculation of the decay rate of the
electroweak vacuum for the case that the SUSY contribution to $a_\mu$ is
enhanced. We also give an upper bound on the slepton masses as a function of
the SUSY contribution to $a_\mu$.
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In this article, we employed nanosecond Z-scan technique to demonstrate the
nonlinear optical response in Ge30Se55Bi15 thin films after thermal and photo
annealing. The intensity dependent open aperture Z-scan traces reveal that for
all the samples, i.e. as-prepared, thermal and photo annealed thin films
exhibit reverse saturable absorption (RSA). The experimental results indicate
that both thermal and photo annealing can be efficiently used to enhance the
nonlinear absorption coefficient compared to as-prepared sample. We further
demonstrate that beta value of thermally annealed and as-prepared samples
increase significantly at higher intensities. On the contrary, beta for photo
annealed sample does not exhibit appreciable changes against the intensity
variation.
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Through a series of papers in the 1980's, Bouchet introduced isotropic
systems and the Tutte-Martin polynomial of an isotropic system. Then, Arratia,
Bollob\'as, and Sorkin developed the interlace polynomial of a graph in [ABS00]
in response to a DNA sequencing application. The interlace polynomial has
generated considerable recent attention, with new results including realizing
the original interlace polynomial by a closed form generating function
expression instead of by the original recursive definition (see Aigner and van
der Holst [AvdH04], and Arratia, Bollob\'as, and Sorkin [ABS04b]). Now, Bouchet
[Bou05] recognizes the vertex-nullity interlace polynomial of a graph as the
Tutte-Martin polynomial of an associated isotropic system. This suggests that
the machinery of isotropic systems may be well-suited to investigating
properties of the interlace polynomial. Thus, we present here an alternative
proof for the closed form presentation of the vertex-nullity interlace
polynomial using the machinery of isotropic systems. This approach both
illustrates the intimate connection between the vertex-nullity interlace
polynomial and the Tutte-Martin polynomial of an isotropic system and also
provides a concrete example of manipulating isotropic systems. We also provide
a brief survey of related work.
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An Automata Network is a map ${f:Q^n\rightarrow Q^n}$ where $Q$ is a finite
alphabet. It can be viewed as a network of $n$ entities, each holding a state
from $Q$, and evolving according to a deterministic synchronous update rule in
such a way that each entity only depends on its neighbors in the network's
graph, called interaction graph. A major trend in automata network theory is to
understand how the interaction graph affects dynamical properties of $f$. In
this work we introduce the following property called expansivity: the
observation of the sequence of states at any given node is sufficient to
determine the initial configuration of the whole network. Our main result is a
characterization of interaction graphs that allow expansivity. Moreover, we
show that this property is generic among linear automata networks over such
graphs with large enough alphabet. We show however that the situation is more
complex when the alphabet is fixed independently of the size of the interaction
graph: no alphabet is sufficient to obtain expansivity on all admissible
graphs, and only non-linear solutions exist in some cases. Finally, among other
results, we consider a stronger version of expansivity where we ask to
determine the initial configuration from any large enough observation of the
system. We show that it can be achieved for any number of nodes and naturally
gives rise to maximum distance separable codes.
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We present a numerically efficient approach for learning a risk-neutral
measure for paths of simulated spot and option prices up to a finite horizon
under convex transaction costs and convex trading constraints. This approach
can then be used to implement a stochastic implied volatility model in the
following two steps: 1. Train a market simulator for option prices, as
discussed for example in our recent; 2. Find a risk-neutral density,
specifically the minimal entropy martingale measure. The resulting model can be
used for risk-neutral pricing, or for Deep Hedging in the case of transaction
costs or trading constraints. To motivate the proposed approach, we also show
that market dynamics are free from "statistical arbitrage" in the absence of
transaction costs if and only if they follow a risk-neutral measure. We
additionally provide a more general characterization in the presence of convex
transaction costs and trading constraints. These results can be seen as an
analogue of the fundamental theorem of asset pricing for statistical arbitrage
under trading frictions and are of independent interest.
|
Propagation effects are one of the main sources of noise in high-precision
pulsar timing. For pulsars below an ecliptic latitude of $5^\circ$, the ionised
plasma in the solar wind can introduce dispersive delays of order 100
microseconds around solar conjunction at an observing frequency of 300 MHz. A
common approach to mitigate this assumes a spherical solar wind with a
time-constant amplitude. However, this has been shown to be insufficient to
describe the solar wind. We present a linear, Gaussian-process piecewise
Bayesian approach to fit a spherical solar wind of time-variable amplitude,
which has been implemented in the pulsar software run_enterprise. Through
simulations, we find that the current EPTA+InPTA data combination is not
sensitive to such variations; however, solar wind variations will become
important in the near future with the addition of new InPTA data and data
collected with the low-frequency LOFAR telescope. We also compare our results
for different high-precision timing datasets (EPTA+InPTA, PPTA, and LOFAR) of
three millisecond pulsars (J0030$+$0451, J1022$+$1001, J2145$-$0450), and find
that the solar-wind amplitudes are generally consistent for any individual
pulsar, but they can vary from pulsar to pulsar. Finally, we compare our
results with those of an independent method on the same LOFAR data of the three
millisecond pulsars. We find that differences between the results of the two
methods can be mainly attributed to the modelling of dispersion variations in
the interstellar medium, rather than the solar wind modelling.
|
We study the effect of an inhomogeneous gas density on positive streamer
discharges in air using a 3D fluid model with stochastic photoionization,
generalizing earlier work with a 2D axisymmetric model by Starikovskiy and
Aleksandrov (2019 Plasma Sources Sci. Technol. 28 095022). We consider various
types of planar and (hemi)spherical gas density gradients. Streamers propagate
from a region of density n0 towards a region of higher or lower gas density n1,
where n0 corresponds to 300 K and 1 bar. We observe that streamers can always
propagate into a region with a lower gas density. When streamers enter a region
with a higher gas density, branching can occur at the density gradient, with
branches growing in a flower-like pattern over the gradient surface. Depending
on the gas density ratio, the gradient width and other factors, narrow branches
are able to propagate into the higher-density gas. In a planar geometry, we
find that such propagation is possible up to a gas density slope of 3.5n0/mm,
although this value depends on a number of conditions, such as the gradient
angle. Surprisingly, a higher applied voltage makes it more difficult for
streamers to penetrate into the high-density region, due to an increase of the
primary streamer's radius.
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The Semimicroscopic Algebraic Cluster Model (SACM) is applied to 12C as a
system of three alpha- clusters. The microscopic model space, which observes
the Pauli-Exclusion-Principle (PEP), is constructed. It is shown that the 12C
nucleus can effectively be treated as a two-cluster system 8Be+alpha. The
experimental spectrum is well reproduced. The geometrical mapping is discussed
and it is shown that the ground state must correspond to a triangular
structure, which is in agreement with other microscopic calculations. The
non-zero B(E2; 0_2+ --> 2_1+) transition requires a mixing of SU(3) irreducible
representations (irreps) whose consequences are discussed. The Hoyle state
turns out to contain large shell excitations. The results are compared to
another phenomenological model, which assumes a triangular structure and, using
simple symmetry arguments, can reproduce the states observed at low energy.
This model does not observe the PEP and one objective of our contribution is to
verify the extend of importance of the PEP.
|
In this paper, we present a novel method for dynamically expanding
Convolutional Neural Networks (CNNs) during training, aimed at meeting the
increasing demand for efficient and sustainable deep learning models. Our
approach, drawing from the seminal work on Self-Expanding Neural Networks
(SENN), employs a natural expansion score as an expansion criteria to address
the common issue of over-parameterization in deep convolutional neural
networks, thereby ensuring that the model's complexity is finely tuned to the
task's specific needs. A significant benefit of this method is its eco-friendly
nature, as it obviates the necessity of training multiple models of different
sizes. We employ a strategy where a single model is dynamically expanded,
facilitating the extraction of checkpoints at various complexity levels,
effectively reducing computational resource use and energy consumption while
also expediting the development cycle by offering diverse model complexities
from a single training session. We evaluate our method on the CIFAR-10 dataset
and our experimental results validate this approach, demonstrating that
dynamically adding layers not only maintains but also improves CNN performance,
underscoring the effectiveness of our expansion criteria. This approach marks a
considerable advancement in developing adaptive, scalable, and environmentally
considerate neural network architectures, addressing key challenges in the
field of deep learning.
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It has been an ultimate but seemingly distant goal of nanofluidics to
controllably fabricate capillaries with dimensions approaching the size of
small ions and water molecules. We report ion transport through ultimately
narrow slits that are fabricated by effectively removing a single atomic plane
from a bulk crystal. The atomically flat angstrom-scale slits exhibit little
surface charge, allowing elucidation of the role of steric effects. We find
that ions with hydrated diameters larger than the slit size can still permeate
through, albeit with reduced mobility. The confinement also leads to a notable
asymmetry between anions and cations of the same diameter. Our results provide
a platform for studying effects of angstrom-scale confinement, which is
important for development of nanofluidics, molecular separation and other
nanoscale technologies.
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The electrical and magnetic properties of p-type cubic (Ga,Mn)N thin films
grown by plasma-assisted molecular beam epitaxy are reported. Hole
concentrations in excess of 1018 cm-3 at room temperature are observed.
Activated behaviour is observed down to around 150K, characterised by an
acceptor ionisation energy of around 45-60meV. The dependence of hole
concentration and ionisation energy on Mn concentration indicates that the
shallow acceptor level is not simply due to unintentional co-doping.
Thermopower measurements on freestanding films, CV profilometry, and the
dependence of conductivity on thickness and growth temperature, all show that
the conduction is not due to diffusion into the substrate. We therefore
associate the p-type conductivity with the presence of the Mn in the cubic GaN
films. Magnetometry measurements indicate a small room temperature
ferromagnetic phase, and a significantly larger magnetic coupling at low
temperatures.
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We characterize the existence of a nonnegative, sublinear and continuous
order-preserving function for a not necessarily complete preorder on a real
convex cone in an arbitrary topological real vector space. As a corollary of
the main result, we present necessary and sufficient conditions for the
existence of such an order-preserving function for a complete preorder.
|
Recent evidences show that heteroclinic bifurcations in magnetic islands may
be caused by the amplitude variation of resonant magnetic perturbations in
tokamaks. To investigate the onset of these bifurcations, we consider a large
aspect ratio tokamak with an ergodic limiter composed of two pairs of rings
that create external primary perturbations with two sets of wave numbers. An
individual pair produces hyperbolic and elliptic periodic points, and its
associated islands, that are consistent with the Poincar\'e-Birkhoff fixed
point theorem. However, for two pairs producing external perturbations resonant
on the same rational surface, we show that different configurations of
isochronous island chains may appear on phase space according to the amplitude
of the electric currents in each pair of the ergodic limiter. When one of the
electric currents increases, isochronous bifurcations take place and new
islands are created with the same winding number as the preceding islands. We
present examples of bifurcation sequences displaying (a) direct transitions
from the island chain configuration generated by one of the pairs to the
configuration produced by the other pair, and (b) transitions with intermediate
configurations produced by the limiter pairs coupling. Furthermore, we identify
shearless bifurcations inside some isochronous islands, originating
nonmonotonic local winding number profiles with associated shearless invariant
curves.
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Monolayer 2H-NbSe2 has recently been shown to be a 2-dimensional
superconductor, with a coexisting charge-density wave (CDW). As both phenomena
are intimately related to electron-lattice interaction, a natural question is
how superconductivity and CDW are interrelated through electron-phonon coupling
(EPC), which is important to the understanding of 2-dimensional
superconductivity. This work investigates the superconductivity of monolayer
NbSe2 in CDW phase using the anisotropic Migdal-Eliashberg formalism based on
first principles calculations. The mechanism of the competition between and
coexistence of the superconductivity and CDW is studied in detail by analyzing
EPC. It is found that the intra-pocket scattering is related to
superconductivity, leading to almost constant value of superconducting gaps on
parts of the Fermi surface. The inter-pocket scattering is found to be
responsible for CDW, leading to partial or full bandgap on the remaining Fermi
surface. Recent experiment indicates that there is transitioning from regular
superconductivity in thin-film NbSe2 to two-gap superconductivity in the bulk,
which is shown here to have its origin in the extent of Fermi surface gapping
of K and K' pockets induced by CDW. Overall blue shifts of the phonons and
sharp decrease of Eliashberg spectrum are found when the CDW forms.
|
We explore how the dilepton production rate is modified near the critical
temperature of color superconductivity and QCD critical point by the soft modes
inherently associated with the phase transitions of second-order. It is shown
that the soft modes affect the photon self-energy significantly through so
called the Aslamasov-Larkin, Maki-Thompson and density of states terms, which
are known responsible for the paraconductivity in the metalic
superconductivity, and cause an anomalous enhancement of the production rate in
the low energy/momentum region.
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In the present paper, we consider the initial value problem for the bipolar
Vlasov-Poisson-Boltzmann (bVPB) system and its corresponding modified
Vlasov-Poisson-Boltzmann (mVPB). We give the spectrum analysis on the
linearized bVPB and mVPB systems around their equilibrium state and show the
optimal convergence rate of global solutions. It was showed that the electric
field decays exponentially and the distribution function tends to the absolute
Maxwellian at the optimal convergence rate $(1+t)^{-3/4}$ for the bVPB system,
yet both the electric field and the distribution function converge to
equilibrium state at the optimal rate $(1+t)^{-3/4}$ for the mVPB system.
|
We introduce an analytic function $\Psi(s_1,\ldots,s_r;w)$ that interpolates
truncated multiple zeta functions $\zeta_N(s_1,\ldots,s_r)$. We represent this
interpolant as a Mellin transform of a function $G(q_1,\ldots,q_r;w)$ and,
using this expression, give the analytic continuation. Further, the harmonic
product relations for $\Psi$ and $G$ are established via relevant Hopf algebra
structures, and some properties of the function $G$ are provided.
|
Recent three-dimensional radiation hydrodynamic simulations by Wedemeyer et
al. (2004) suggest that the solar chromosphere is highly structured in space
and time on scales of only 1000 km and 20-25 sec, resp.. The resulting pattern
consists of a network of hot gas and enclosed cool regions which are due to the
propagation and interaction of shock fronts. In contrast to many other
diagnostics, the radio continuum at millimeter wavelengths is formed in LTE,
and provides a rather direct measure of the thermal structure. It thus
facilitates the comparison between numerical model and observation. While the
involved time and length scales are not accessible with todays equipment for
that wavelength range, the next generation of instruments, such as the Atacama
Large Millimeter Array (ALMA), will provide a big step towards the required
resolution. Here we present results of radiative transfer calculations at mm
and sub-mm wavelengths with emphasis on spatial and temporal resolution which
are crucial for the ongoing discussion about the chromospheric temperature
structure.
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Detection jitter quantifies variance introduced by the detector in the
determination of photon arrival time. It is a crucial performance parameter for
systems using superconducting nanowire single photon detectors (SNSPDs). In
this work, we have demonstrated that the detection timing jitter is limited in
part by the spatial variation of photon detection events along the length of
the wire. This distribution causes the generated electrical pulses to arrive at
the readout at varied times. We define this jitter source as geometric jitter
since it is related to the length and area of the SNSPD. To characterize the
geometric jitter, we have constructed a novel differential cryogenic readout
with less than 7 ps of electronic jitter that can amplify the pulses generated
from the two ends of an SNSPD. By differencing the measured arrival times of
the two electrical pulses, we were able to partially cancel out the difference
of the propagation times and thus reduce the uncertainty of the photon arrival
time. Our experimental data indicates that the variation of the differential
propagation time was a few ps for a 3 {\mu}m x 3 {\mu}m device while it
increased up to 50 ps for a 20 {\mu}m x 20 {\mu}m device. In a 20 {\mu}m x 20
{\mu}m large SNSPD, we achieved a 20% reduction in the overall detection timing
jitter for detecting telecom-wavelength photons by using the differential
cryogenic readout. The geometric jitter hypothesis was further confirmed by
studying jitter in devices that consisted of long wires with 1-{\mu}m-long
narrowed regions used for sensing photons.
|
The immense scalability of continuous-variable cluster states motivates their
study as a platform for quantum computing, with fault tolerance possible given
sufficient squeezing and appropriately encoded qubits [Menicucci, PRL 112,
120504 (2014)]. Here, we expand the scope of that result by showing that
additional anti-squeezing has no effect on the fault-tolerance threshold,
removing the purity requirement for experimental continuous-variable
cluster-state quantum computing. We emphasize that the appropriate experimental
target for fault-tolerant applications is to directly measure 15-17 dB of
squeezing in the cluster state rather than the more conservative upper bound of
20.5 dB.
|
Robust, high-precision global localization is fundamental to a wide range of
outdoor robotics applications. Conventional fusion methods use low-accuracy
pseudorange based GNSS measurements ($>>5m$ errors) and can only yield a coarse
registration to the global earth-centered-earth-fixed (ECEF) frame. In this
paper, we leverage high-precision GNSS carrier-phase positioning and aid it
with local visual-inertial odometry (VIO) tracking using an extended Kalman
filter (EKF) framework that better resolves the integer ambiguity concerned
with GNSS carrier-phase. %to achieve centimeter-level accuracy in the ECEF
frame. We also propose an algorithm for accurate GNSS-antenna-to-IMU extrinsics
calibration to accurately align VIO to the ECEF frame. Together, our system
achieves robust global positioning demonstrated by real-world hardware
experiments in severely occluded urban canyons, and outperforms the
state-of-the-art RTKLIB by a significant margin in terms of integer ambiguity
solution fix rate and positioning RMSE accuracy.
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In the context of the AdS/CFT correspondence we discuss the gravity dual of a
high energy collision in a strongly coupled ${\cal N}=4$ SYM gauge theory. We
suggest a setting in which two colliding objects are made of non-dynamical
heavy quarks and antiquarks, which allows to treat the process in classical
string approximation. Collision ``debris'' consist of closed as well as open
strings. If the latter have ends on two outgoing charges, and thus are being
``stretched'' along the collision axes. We discuss motion in AdS of some simple
objects first -- massless and massive particles -- and then focus on open
strings. We study the latter in a considerable detail, concluding that they
rapidly become ``rectangular'' in proper time -spatial rapidity $\tau-y$
coordinates with well separated fragmentation part and a near-free-falling
rapidity-independent central part. Assuming that in the collisions of ``walls''
of charges multiple stretching strings are created, we also consider the motion
of a 3d stretching membrane. We then argue that a complete solution can be
approximated by two different vacuum solutions of Einstein eqns, with matter
membrane separating them. We identify one of this solution with
Janik-Peschanski stretching black hole solution, and show that all objects
approach its (retreating) horizon in an universal manner.
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Employing ab initio electronic calculations, we propose a new type of
two-dimensional (2D) topological insulator (TI), monolayer (ML) low buckled
(LB) mercury telluride (HgTe) and mercury selenide (HgSe), with tunable band
gaps. Monolayer LB HgTe undergoes a transition to a topological nontrivial
phase under the appropriate in-plane tensile strain ({\epsilon} > 2.6%) due to
the combination effects of strain and spin orbital coupling (SOC). Under the
2.6%< {\epsilon} <4.2% tensile strain, the band inversion and topological
nontrivial gap are induced by the SOC. For {\epsilon} >4.2%, the band inversion
is already realized by strain but the topological gap is induced by SOC. The
band gap of monolayer LB HgTe TI phase can be tuned over a wide range from 0 eV
to 0.20 eV as the tensile strain increases from 2.6% to 7.4%. Similarly, the
topological phase transition of monolayer LB HgSe is induced by strain and SOC
as the strain {\epsilon} >3.1%. The topological band gap can be 0.05 eV as the
strain increases to about 4.6%. The large band gap of 2D LB HgTe and HgSe
monolayers make this type of material suitable for practical applications at
room-temperature.
|
The hyper-velocity star S5-HVS1, ejected 5 Myr ago from the Galactic Center
at 1800 km/s, was most likely produced by tidal break-up of a tight binary by
the supermassive black hole SgrA*. Taking a Monte Carlo approach, we show that
the former companion of S5-HVS1 was likely a main-sequence star between 1.2 and
6 solar masses and was captured into a highly eccentric orbit with pericenter
distance in the range 1-10 AU and semimajor axis about $10^3$ AU. We then
explore the fate of the captured star. We find that the heat deposited by
tidally excited stellar oscillation modes leads to runaway disruption if the
pericenter distance is smaller than about 3 AU. Over the past 5 Myr, its
angular momentum has been significantly modified by orbital relaxation, which
may stochastically drive the pericenter inwards below 3 AU and cause tidal
disruption. We find an overall survival probability in the range 5% to 50%,
depending on the local relaxation time in the close environment of the captured
star, and the initial pericenter at capture. The pericenter distance of the
surviving star has migrated to 10-100 AU, making it potentially the most
extreme member of the S-star cluster. From the ejection rate of S5-HVS1-like
stars, we estimate that there may currently be a few stars in such highly
eccentric orbits. They should be detectable (typically Ks < 18.5 mag) by the
GRAVITY instrument and by future Extremely Large Telescopes and hence provide
an extraordinary probe of the spin of SgrA*.
|
The topological sigma model with the semi-infinite cigar-like target space
(black hole geometry) is considered. The model is shown to possess unsuppressed
instantons. The noncompactness of the moduli space of these instantons is
responsible for an unusual physics. There is a stable vacuum state in which the
vacuum energy is zero, correlation functions are numbers thus the model is in
the topological phase. However, there are other vacuum states in which
correlation functions show the coordinate dependence. The estimation of the
vacuum energy indicates that it is nonzero. These states are interpreted as the
ones with broken BRST-symmetry.
|
When any extraordinary event takes place in the world wide area, it is the
social media that acts as the fastest carrier of the news along with the
consequences dealt with that event. One can gather much information through
social networks regarding the sentiments, behavior, and opinions of the people.
In this paper, we focus mainly on sentiment analysis of twitter data of India
which comprises of COVID-19 tweets. We show how Twitter data has been extracted
and then run sentimental analysis queries on it. This is helpful to analyze the
information in the tweets where opinions are highly unstructured,
heterogeneous, and are either positive or negative or neutral in some cases.
|
The torque on a moving electric or magnetic dipole in slow motion is deduced
using the Lorentz transformation of the fields to first order in v/c. It is
shown that the obtained equations are independent of the model adopted for the
dipole, whether it is of Amperian or Gilbertian type, thus showing the complete
validity of the Amp\`ere equivalence principle even in dynamical conditions.
The torque is made of three terms: beside that due to the direct torque on the
dipole there are two more terms: one due to the torque on the associated
perpendicular dual-dipole caused by motion, while the other is the inertial
torque due to the displacement of the dipole which carries with it the field
linear momentum, or the hidden momentum.
|
We review our recent results on short time approximations, with emphasis on
applications for which the system-environment interactions involve a general
non-Hermitian system operator and its conjugate. We evaluate the onset of
decoherence at low temperatures in open quantum systems. The developed approach
is complementary to Markovian approximations and appropriate for evaluation of
quantum computing schemes. Example of a spin system coupled to a bosonic heat
bath is discussed.
|
We give an elementary introduction to the theory of triangulated categories
covering their axioms, homological algebra in triangulated categories,
triangulated subcategories, and Verdier localization. We try to use a minimal
set of axioms for triangulated categories and derive all other statements from
these, including the existence of biproducts. We conclude with a list of
examples.
|
We report dc transport and magnetization measurements of Jc in MgB2 wires
fabricated by the powder-in-tube method, using commercial MgB2 powder with 5
%at Mg powder added as an additional source of magnesium, and stainless steel
as sheath material. By appropriate heat treatments, we have been able to
increase Jc by more than one order of magnitude from that of the as-drawn wire.
We show that one beneficial effect of the annealing is the elimination of most
of the micro-cracks, and we correlate the increase in Jc with the disappearance
of the weak-link-type behavior.
|
Given the closeness of the two open clusters Cr 135 and UBC 7 on the sky, we
investigate the possibility of the two clusters to be physically related. We
aim to recover the present-day stellar membership in the open clusters
Collinder 135 and UBC 7 (300 pc from the Sun), to constrain their kinematic
parameters, ages and masses, and to restore their primordial phase space
configuration. The most reliable cluster members are selected with our
traditional method modified for the use of Gaia DR2 data. Numerical simulations
use the integration of cluster trajectories backwards in time with our original
high order Hermite4 code \PGRAPE. We constrain the age, spatial coordinates and
velocities, radii and masses of the clusters. We estimate the actual separation
of the cluster centres equal to 24 pc. The orbital integration shows that the
clusters were much closer in the past if their current line-of-sight velocities
are very similar and the total mass is more than 7 times larger the mass of the
determined most reliable members. We conclude that the two clusters Cr 135 and
UBC 7 might very well have formed a physial pair, based on the observational
evidence as well as numerical simulations. The probability of a chance
coincidence is only about $2\%$.
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We study the Tevatron signatures of promptly-decaying slepton co-NLSPs in the
context of General Gauge Mediation (GGM). The signatures consist of trileptons
plus MET and same-sign dileptons plus MET. Focusing first on electroweak
production, where the Tevatron has an advantage over the early LHC, we
establish four simple benchmark scenarios within the parameter space of GGM
which qualitatively capture all the relevant phenomenology. We derive limits on
these benchmarks from existing searches, estimate the discovery potential with
10 fb^-1, and discuss ways in which these searches can be optimized for slepton
co-NLSPs. We also analyze the Tevatron constraints on a scenario with light
gluinos that could be discovered at the early LHC. Overall, we find that the
Tevatron still has excellent reach for the discovery of SUSY in multilepton
final states. Finally, we comment on the possible interpretation of a mild
"excess" in the CDF same-sign dilepton search in terms of slepton co-NLSPs.
|
We predict magnitudes for young planets embedded in transition discs, still
affected by extinction due to material in the disc. We focus on Jupiter-size
planets at a late stage of their formation, when the planet has carved a deep
gap in the gas and dust distributions and the disc starts being transparent to
the planet flux in the infrared (IR). Column densities are estimated by means
of three-dimensional hydrodynamical models, performed for several planet
masses. Expected magnitudes are obtained by using typical extinction properties
of the disc material and evolutionary models of giant planets. For the
simulated cases located at $5.2$ AU in a disc with local unperturbed surface
density of $127$ $\mathrm{g} \cdot \mathrm{cm}^{-2}$, a $1$ $M_J$ planet is
highly extincted in J-, H- and K-bands, with predicted absolute magnitudes $\ge
50$ mag. In L- and M-bands extinction decreases, with planet magnitudes between
$25$ and $35$ mag. In the N-band, due to the silicate feature on the dust
opacities, the expected magnitude increases to $40$ mag. For a $2$ $M_J$
planet, the magnitudes in J-, H- and K-bands are above $22$ mag, while for L-,
M- and N-bands the planet magnitudes are between $15$ and $20$ mag. For the $5$
$M_J$ planet, extinction does not play a role in any IR band, due to its
ability to open deep gaps. Contrast curves are derived for the transition discs
in CQ Tau, PDS70, HL Tau, TW Hya and HD163296. Planet mass upper-limits are
estimated for the known gaps in the last two systems.
|
We determine the mass profile of an ensemble cluster built from 3056 galaxies
in 59 nearby clusters observed in the ESO Nearby Abell Cluster Survey. The mass
profile is derived from the distribution and kinematics of the Early-type
(elliptical and S0) galaxies only, which are most likely to meet the conditions
for the application of the Jeans equation. We assume that the Early-type
galaxies have isotropic orbits, as supported by the shape of their velocity
distribution. The brightest ellipticals (with M_R < -22+5 log h), and the
Early-type galaxies in subclusters are excluded from the sample. Application of
the Jeans equation yields a non-parametric estimate of the cumulative mass
profile M(<r), which has a logarithmic slope of -2.4 +/- 0.4 in the density
profile at the virial radius. We compare our result with several analytical
models from the literature (NFW, Moore et al. 1999, softened isothermal sphere,
and Burkert 1995) and find that all are acceptable. However, our data do not
provide compelling evidence for the existence of a core; as a matter of fact,
the best-fitting core models have core-radii well below 100/h kpc. The upper
limit we put on the size of the core-radius provides a constraint for the
scattering cross-section of dark matter particles. The total-mass density
appears to be traced remarkably well by the luminosity density of the
Early-type galaxies. On the contrary, the luminosity density of the brightest
ellipticals increases faster towards the center than the mass density, while
the luminosity density profiles of the early and late spirals are somewhat
flatter than the mass density profile. (Abridged)
|
Centralized training methods have shown promising results in MR image
reconstruction, but privacy concerns arise when gathering data from multiple
institutions. Federated learning, a distributed collaborative training scheme,
can utilize multi-center data without the need to transfer data between
institutions. However, existing federated learning MR image reconstruction
methods rely on manually designed models which have extensive parameters and
suffer from performance degradation when facing heterogeneous data
distributions. To this end, this paper proposes a novel FederAted neUral
archiTecture search approach fOr MR Image reconstruction (FedAutoMRI). The
proposed method utilizes differentiable architecture search to automatically
find the optimal network architecture. In addition, an exponential moving
average method is introduced to improve the robustness of the client model to
address the data heterogeneity issue. To the best of our knowledge, this is the
first work to use federated neural architecture search for MR image
reconstruction. Experimental results demonstrate that our proposed FedAutoMRI
can achieve promising performances while utilizing a lightweight model with
only a small number of model parameters compared to the classical federated
learning methods.
|
A statistical structure $(g, T)$ on a smooth manifold $M$ induced by
$(\tilde M, \tilde g, \tilde T)$ is said to be {\em robust} if there exists
an open neighborhood of $(g,T)$ in the fine $C^{\infty}$-topology consisting of
statistical structures induced by $(\tilde M, \tilde g, \tilde T)$. Using
Nash--Gromov implicit function theorem, we show robustness of the generic
statistical structure induced on $M$ by the standard linear statistical
structure on ${\R}^N$, for $N$ sufficiently large.
|
Space-based instruments provide new and, in some cases, unique opportunities
to search for dark matter. In particular, if dark matter comprises sterile
neutrinos, the x ray detection of their decay line is the most promising
strategy for discovery. Sterile neutrinos with masses in the keV range could
solve several long-standing astrophysical puzzles, from supernova asymmetries
and the pulsar kicks to star formation, reionization, and baryogenesis. The
best current limits on sterile neutrinos come from Chandra and XMM-Newton.
Future advances can be achieved with a high-resolution x-ray spectrometry in
space.
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Here, we investigate the role of the interlayer magnetic ordering of CrSBr in
the framework of $\textit{ab initio}$ calculations and by using optical
spectroscopy techniques. These combined studies allow us to unambiguously
determine the nature of the optical transitions. In particular,
photoreflectance measurements, sensitive to the direct transitions, have been
carried out for the first time. We have demonstrated that optically induced
band-to-band transitions visible in optical measurement are remarkably well
assigned to the band structure by the momentum matrix elements and energy
differences for the magnetic ground state (A-AFM). In addition, our study
reveals significant differences in electronic properties for two different
interlayer magnetic phases. When the magnetic ordering of A-AFM to FM is
changed, the crucial modification of the band structure reflected in the
direct-to-indirect band gap transition and the significant splitting of the
conduction bands along the $\Gamma-Z$ direction are obtained. In addition,
Raman measurements demonstrate a splitting between the in-plane modes
$B^2_{2g}$/$B^2_{3g}$, which is temperature dependent and can be assigned to
different interlayer magnetic states, corroborated by the DFT+U study.
Moreover, the $B^2_{2g}$ mode has not been experimentally observed before.
Finally, our results point out the origin of interlayer magnetism, which can be
attributed to electronic rather than structural properties. Our results reveal
a new approach for tuning the optical and electronic properties of van der
Waals magnets by controlling the interlayer magnetic ordering in adjacent
layers.
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First-order methods with momentum such as Nesterov's fast gradient method are
very useful for convex optimization problems, but can exhibit undesirable
oscillations yielding slow convergence rates for some applications. An adaptive
restarting scheme can improve the convergence rate of the fast gradient method,
when the parameter of a strongly convex cost function is unknown or when the
iterates of the algorithm enter a locally strongly convex region. Recently, we
introduced the optimized gradient method, a first-order algorithm that has an
inexpensive per-iteration computational cost similar to that of the fast
gradient method, yet has a worst-case cost function rate that is twice faster
than that of the fast gradient method and that is optimal for large-dimensional
smooth convex problems. Building upon the success of accelerating the fast
gradient method using adaptive restart, this paper investigates similar
heuristic acceleration of the optimized gradient method. We first derive a new
first-order method that resembles the optimized gradient method for strongly
convex quadratic problems with known function parameters, yielding a linear
convergence rate that is faster than that of the analogous version of the fast
gradient method. We then provide a heuristic analysis and numerical experiments
that illustrate that adaptive restart can accelerate the convergence of the
optimized gradient method. Numerical results also illustrate that adaptive
restart is helpful for a proximal version of the optimized gradient method for
nonsmooth composite convex functions.
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Monte Carlo simulation has been performed on a classical two dimensional XY-
model with a modified form of interaction potential to investigate the role of
topological defects on the phase transition exhibited by the model. In
simulations in a restricted ensemble without defects, the system appears to
remain ordered at all temperatures. Suppression of topological defects on the
square plaquettes in the modified XY- model leads to complete elimination of
the phase transition observed in this model.
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Territoriality is a phenomenon exhibited throughout nature. On the individual
level, it is the processes by which organisms exclude others of the same
species from certain parts of space. On the population level, it is the
segregation of space into separate areas, each used by subsections of the
population. Proving mathematically that such individual-level processes can
cause observed population-level patterns to form is necessary for linking these
two levels of description in a non-speculative way. Previous mathematical
analysis has relied upon assuming animals are attracted to a central area. This
can either be a fixed geographical point, such as a den- or nest-site, or a
region where they have previously visited. However, recent simulation-based
studies suggest that this attractive potential is not necessary for territorial
pattern formation. Here, we construct a partial differential equation (PDE)
model of territorial interactions based on the individual-based model (IBM)
from those simulation studies. The resulting PDE does not rely on attraction to
spatial locations, but purely on conspecific avoidance, mediated via
scent-marking. We show analytically that steady-state patterns can form, as
long as (i) the scent does not decay faster than it takes the animal to
traverse the terrain, and (ii) the spatial scale over which animals detect
scent is incorporated into the PDE. As part of the analysis, we develop a
general method for taking the PDE limit of an IBM that avoids destroying any
intrinsic spatial scale in the underlying behavioral decisions.
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The presence of cosmological fluctuations influences the background cosmology
in which the perturbations evolve. This back-reaction arises as a second order
effect in the cosmological perturbation expansion. The effect is cumulative in
the sense that all fluctuation modes contribute to the change in the background
geometry, and as a consequence the back-reaction effect can be large even if
the amplitude of the fluctuation spectrum is small. We review two approaches
used to quantify back-reaction. In the first approach, the effect of the
fluctuations on the background is expressed in terms of an effective
energy-momentum tensor. We show that in the context of an inflationary
background cosmology, the long wavelength contributions to the effective
energy-momentum tensor take the form of a negative cosmological constant, whose
absolute value increases as a function of time since the phase space of
infrared modes is increasing. This then leads to the speculation that
gravitational back-reaction may lead to a dynamical cancellation mechanism for
a bare cosmological constant, and yield a scaling fixed point in the asymptotic
future in which the remnant cosmological constant satisfies $\Omega_{\Lambda}
\sim 1$. We then discuss how infrared modes effect local observables (as
opposed to mathematical background quantities) and find that the leading
infrared back-reaction contributions cancel in single field inflationary
models. However, we expect non-trivial back-reaction of infrared modes in
models with more than one matter field.
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Observations by LIGO--Virgo of binary black hole mergers suggest a possible
anti-correlation between black hole mass ratio ($q=m_{2}/m_{1}$) and the
effective inspiral spin parameter $\chi_{\rm eff}$, the mass-weighted spin
projection onto the binary orbital angular momentum (Callister et al. 2021). We
show that such an anti-correlation can naturally occur for binary black holes
assembled in active galactic nuclei (AGN) due to spherical and planar
symmetry-breaking effects. We describe a phenomenological model in which: 1)
heavier black holes live in the AGN disk and tend to spin up into alignment
with the disk; 2) lighter black holes with random spin orientations live in the
nuclear spheroid; 3) the AGN disk is dense enough to rapidly capture a fraction
of the spheroid component. but small in radial extent to limit the number of
bulk disk mergers; 4) migration within the disk is non-uniform, likely
disrupted by feedback from migrators or disk turbulence; 5) dynamical
encounters in the disk are common and preferentially disrupt binaries that are
retrograde around their center of mass, particularly at stalling orbits, or
traps. This model may explain trends in LIGO--Virgo data while offering
falsifiable predictions. Comparisons of predictions in ($q,\chi_{\rm eff}$)
parameter space for the different channels may allow us to distinguish their
fractional contributions to the observed merger rates.
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When using a recently developed method of Doppler-Zeeman mapping (Vasilchenko
et al., 1996) for analysis of a real star and real observational data, we are
confronted with limitations due to the model simplifications and unavoidable
errors in observed spectra.
We discuss the errors introduced by probable inaccurracies of the
mathematical model: analytical fit of the local Stokes parameters, influence of
magneto-optical effect, ignorance of the true atmosphere model to compute local
Stokes profiles, non-uniform surface brightness.
The magnetic field configuration is found in the form of arbitrarily shifted
dipole and sum of dipole and quadrupole, along with the distribution of Si, Ti,
Cr and Fe over the surface of the star.
Lines of different elements lead to the same magnetic field configuration,
which is reliably determined for the part of the stellar surface which faces
the observer. This allows to compare the magnetic field and chemical maps of
the surface of HD 215441. A large-scale ring structure with the magnetic pole
at its center is clearly seen on the abundance maps. Si, Cr and Ti are highly
deficient where the magnetic field lines are vertical (near the magnetic pole)
while Fe is highly overabundant there.
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We present an efficient implementation of the highly robust and scalable
GenEO preconditioner in the high-performance PDE framework DUNE. The GenEO
coarse space is constructed by combining low energy solutions of a local
generalised eigenproblem using a partition of unity. In this paper we
demonstrate both weak and strong scaling for the GenEO solver on over 15,000
cores by solving an industrially motivated problem with over 200 million
degrees of freedom. Further, we show that for highly complex parameter
distributions arising in certain real-world applications, established methods
become intractable while GenEO remains fully effective. The purpose of this
paper is two-fold: to demonstrate the robustness and high parallel efficiency
of the solver and to document the technical details that are crucial to the
efficiency of the code.
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High-precision spectrographs play a key role in exoplanet searches using the
radial velocity technique. But at the accuracy level of 1 m.s-1, required for
super-Earth characterization, stability of fiber-fed spectrograph performance
is crucial considering variable observing conditions such as seeing, guiding
and centering errors and, telescope vignetting. In fiber-fed spectrographs such
as HARPS or SOPHIE, the fiber link scrambling properties are one of the main
issues. Both the stability of the fiber near-field uniformity at the
spectrograph entrance and of the far-field illumination on the echelle grating
(pupil) are critical for high-precision radial velocity measurements due to the
spectrograph geometrical field and aperture aberrations. We conducted tests on
the SOPHIE spectrograph at the 1.93-m OHP telescope to measure the instrument
sensitivity to the fiber link light feeding conditions: star decentering,
telescope vignetting by the dome,and defocussing.
To significantly improve on current precision, we designed a fiber link
modification considering the spectrograph operational constraints. We have
developed a new link which includes a piece of octagonal-section fiber, having
good scrambling properties, lying inside the former circular-section fiber, and
we tested the concept on a bench to characterize near-field and far-field
scrambling properties.
This modification has been implemented in spring 2011 on the SOPHIE
spectrograph fibers and tested for the first time directly on the sky to
demonstrate the gain compared to the previous fiber link. Scientific validation
for exoplanet search and characterization has been conducted by observing
standard stars.
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On his way to General Relativity (GR) Einstein gave several arguments as to
why a special relativistic theory of gravity based on a massless scalar field
could be ruled out merely on grounds of theoretical considerations. We
re-investigate his two main arguments, which relate to energy conservation and
some form of the principle of the universality of free fall. We find that such
a theory-based a priori abandonment not to be justified. Rather, the theory
seems formally perfectly viable, though in clear contradiction with (later)
experiments. This may be of interest to those who teach GR and/or have an
active interest in its history.
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The system of N scalar particles with Grassmann-valued color charges plus the
color SU(3) Yang-Mills field is reformulated on spacelike hypersurfaces. The
Dirac observables are found and the physical invariant mass of the system in
the Wigner-covariant rest-frame instant form of dynamics (covariant Coulomb
gauge) is given. From the reduced Hamilton equations we extract the second
order equations of motion both for the reduced transverse color field and the
particles. Then, we study this relativistic scalar quark model, deduced from
the classical QCD Lagrangian and with the color field present, in the N=2
(meson) case. A special form of the requirement of having only color singlets,
suited for a field-independent quark model, produces a ``pseudoclassical
asymptotic freedom" and a regularization of the quark self-energy.
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Corrected trapezoidal rules are proved for $\int_a^b f(x)\,dx$ under the
assumption that $f"\in L^p([a,b])$ for some $1\leq p\leq\infty$. Such
quadrature rules involve the trapezoidal rule modified by the addition of a
term $k[f'(a)-f'(b)]$. The coefficient $k$ in the quadrature formula is found
that minimizes the error estimates. It is shown that when $f'$ is merely
assumed to be continuous then the optimal rule is the trapezoidal rule itself.
In this case error estimates are in terms of the Alexiewicz norm. This includes
the case when $f"$ is integrable in the Henstock--Kurzweil sense or as a
distribution. All error estimates are shown to be sharp for the given
assumptions on $f"$. It is shown how to make these formulas exact for all cubic
polynomials $f$. Composite formulas are computed for uniform partitions.
|
We present an active visual search model for finding objects in unknown
environments. The proposed algorithm guides the robot towards the sought object
using the relevant stimuli provided by the visual sensors. Existing search
strategies are either purely reactive or use simplified sensor models that do
not exploit all the visual information available. In this paper, we propose a
new model that actively extracts visual information via visual attention
techniques and, in conjunction with a non-myopic decision-making algorithm,
leads the robot to search more relevant areas of the environment. The attention
module couples both top-down and bottom-up attention models enabling the robot
to search regions with higher importance first.
The proposed algorithm is evaluated on a mobile robot platform in a 3D
simulated environment. The results indicate that the use of visual attention
significantly improves search, but the degree of improvement depends on the
nature of the task and the complexity of the environment. In our experiments,
we found that performance enhancements of up to 42\% in structured and 38\% in
highly unstructured cluttered environments can be achieved using visual
attention mechanisms.
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We have shown that a particular class of non-local free field theory has
conformal symmetry in arbitrary dimensions. Using the local field theory
counterpart of this class, we have found the Noether currents and Ward
identities of the translation, rotation and scale symmetries. The operator
product expansion of the energy-momentum tensor with quasi-primary fields is
also investigated.
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This contribution investigates the Degrees-of-Freedom region of a two-user
frequency correlated Multiple-Input-Single-Output (MISO) Broadcast Channel (BC)
with imperfect Channel State Information at the transmitter (CSIT). We assume
that the system consists of an arbitrary number of subbands, denoted as $L$.
Besides, the CSIT state varies across users and subbands. A tight outer-bound
is found as a function of the minimum average CSIT quality between the two
users. Based on the CSIT states across the subbands, the DoF region is
interpreted as a weighted sum of the optimal DoF regions in the scenarios where
the CSIT of both users are perfect, alternatively perfect and not known.
Inspired by the weighted-sum interpretation and identifying the benefit of the
optimal scheme for the unmatched CSIT proposed by Chen et al., we also design a
scheme achieving the upper-bound for the general $L$-subband scenario in
frequency domain BC, thus showing the optimality of the DoF region.
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Spatial heterogeneity can have dramatic effects on the biochemical networks
that drive cell regulation and decision-making. For this reason, a number of
methods have been developed to model spatial heterogeneity and incorporated
into widely used modeling platforms. Unfortunately, the standard approaches for
specifying and simulating chemical reaction networks become untenable when
dealing with multi-state, multi-component systems that are characterized by
combinatorial complexity. To address this issue, we developed MCell-R, a
framework that extends the particle-based spatial Monte Carlo simulator, MCell,
with the rule-based model specification and simulation capabilities provided by
BioNetGen and NFsim. The BioNetGen syntax enables the specification of
biomolecules as structured objects whose components can have different internal
states that represent such features as covalent modification and conformation
and which can bind components of other molecules to form molecular complexes.
The network-free simulation algorithm used by NFsim enables efficient
simulation of rule-based models even when the size of the network implied by
the biochemical rules is too large to enumerate explicitly, which frequently
occurs in detailed models of biochemical signaling. The result is a framework
that can efficiently simulate systems characterized by combinatorial complexity
at the level of spatially-resolved individual molecules over biologically
relevant time and length scales.
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Anonymous social networks present a number of new and challenging problems
for existing Social Network Analysis techniques. Traditionally, existing
methods for analysing graph structure, such as community detection, required
global knowledge of the graph structure. That implies that a centralised entity
must be given access to the edge list of each node in the graph. This is
impossible for anonymous social networks and other settings where privacy is
valued by its participants. In addition, using their graph structure inputs for
learning tasks defeats the purpose of anonymity. In this work, we hypothesise
that one can re-purpose the use of the HyperANF a.k.a HyperBall algorithm --
intended for approximate diameter estimation -- to the task of
privacy-preserving community detection for friend recommending systems that
learn from an anonymous representation of the social network graph structure
with limited privacy impact. This is possible because the core data structure
maintained by HyperBall is a HyperLogLog with a counter of the number of
reachable neighbours from a given node. Exchanging this data structure in
future decentralised learning deployments gives away no information about the
neighbours of the node and therefore does preserve the privacy of the graph
structure.
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Within leading-order perturbation theory, the Casimir-Polder potential of a
ground-state atom placed within an arbitrary arrangement of dispersing and
absorbing linear bodies can be expressed in terms of the polarizability of the
atom and the scattering Green tensor of the body-assisted electromagnetic
field. Based on a Born series of the Green tensor, a systematic expansion of
the Casimir-Polder potential in powers of the susceptibilities of the bodies is
presented. The Born expansion is used to show how and under which conditions
the Casimir-Polder force can be related to microscopic many-atom van der Waals
forces, for which general expressions are presented. As an application, the
Casimir-Polder potentials of an atom near a dielectric ring and an
inhomogeneous dielectric half space are studied and explicit expressions are
presented that are valid up to second order in the susceptibility.
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Distillation protocols enable generation of high quality entanglement even in
the presence of noise. Existing protocols ignore the presence of local
information in mixed states produced from some noise sources such as photon
loss, amplitude damping or thermalization. We propose new protocols that
exploit local information in mixed states. Our protocols converge to higher
fidelities in fewer rounds, and when local information is significant one of
our protocols consistently improves yields by 10 fold or more. We demonstrate
that our protocols can be compacted into an entanglement-pumping scheme,
allowing quantum computation in distributed systems with a few qubits per
location.
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Binding energy of the $1^-$ state (ortho-positronium) in QED is calculated
using the one-photon exchange Bethe-Salpeter equation in the Feynman and
Coulomb gauges for different coupling constants $\alpha$. Calculations show
there is a remarkable difference in values of the binding energy for different
coupling constants in these two gauges.
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This article provides a thorough meta-analysis of the anomaly detection
problem. To accomplish this we first identify approaches to benchmarking
anomaly detection algorithms across the literature and produce a large corpus
of anomaly detection benchmarks that vary in their construction across several
dimensions we deem important to real-world applications: (a) point difficulty,
(b) relative frequency of anomalies, (c) clusteredness of anomalies, and (d)
relevance of features. We apply a representative set of anomaly detection
algorithms to this corpus, yielding a very large collection of experimental
results. We analyze these results to understand many phenomena observed in
previous work. First we observe the effects of experimental design on
experimental results. Second, results are evaluated with two metrics, ROC Area
Under the Curve and Average Precision. We employ statistical hypothesis testing
to demonstrate the value (or lack thereof) of our benchmarks. We then offer
several approaches to summarizing our experimental results, drawing several
conclusions about the impact of our methodology as well as the strengths and
weaknesses of some algorithms. Last, we compare results against a trivial
solution as an alternate means of normalizing the reported performance of
algorithms. The intended contributions of this article are many; in addition to
providing a large publicly-available corpus of anomaly detection benchmarks, we
provide an ontology for describing anomaly detection contexts, a methodology
for controlling various aspects of benchmark creation, guidelines for future
experimental design and a discussion of the many potential pitfalls of trying
to measure success in this field.
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In recent work arXiv:2109.07820 we have shown the equivalence of the widely
used nonconvex (generalized) branched transport problem with a shape
optimization problem of a street or railroad network, known as (generalized)
urban planning problem. The argument was solely based on an explicit
construction and characterization of competitors. In the current article we
instead analyse the dual perspective associated with both problems. In more
detail, the shape optimization problem involves the Wasserstein distance
between two measures with respect to a metric depending on the street network.
We show a Kantorovich$\unicode{x2013}$Rubinstein formula for Wasserstein
distances on such street networks under mild assumptions. Further, we provide a
Beckmann formulation for such Wasserstein distances under assumptions which
generalize our previous result in arXiv:2109.07820. As an application we then
give an alternative, duality-based proof of the equivalence of both problems
under a growth condition on the transportation cost, which reveals that urban
planning and branched transport can both be viewed as two bilinearly coupled
convex optimization problems.
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A long-standing problem of astrophysical research is how to simultaneously
obtain spectra of thousands of sources randomly positioned in the field of view
of a telescope. Digital Micromirror Devices, used as optical switches, provide
a most powerful solution allowing to design a new generation of instruments
with unprecedented capabilities. We illustrate the key factors
(opto-mechanical, cryo-thermal, cosmic radiation environment,...) that
constrain the design of DMD-based multi-object spectrographs, with particular
emphasis on the IR spectroscopic channel onboard the EUCLID mission, currently
considered by the European Space Agency for a 2017 launch date.
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We study analogues of well-known relationships between Muckenhoupt weights
and $BMO$ in the setting of Bekoll\'e-Bonami weights. For Bekoll\'e-Bonami
weights of bounded hyperbolic oscillation, we provide distance formulas of
Garnett and Jones-type, in the context of $BMO$ on the unit disc and hyperbolic
Lipschitz functions. This leads to a characterization of all weights in this
class, for which any power of the weight is a Bekoll\'e-Bonami weight, which in
particular reveals an intimate connection between Bekoll\'e-Bonami weights and
Bloch functions. On the open problem of characterizing the closure of bounded
analytic functions in the Bloch space, we provide a counter-example to a
related recent conjecture. This shed light into the difficulty of preserving
harmonicity in approximation problems in norms equivalent to the Bloch norm.
Finally, we apply our results to study certain spectral properties of Cesar\'o
operators.
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Art history linked some early 20th Century avant-garde visual art movements
to contemporary systems of ideas in mathematics and theoretical physics. One of
the proposed connections is the one that might have existed between Cubism and
Relativity, or more precisely, between Picasso and Einstein. The suggested
links are similarity (in a weak version) or identity (in a strong version) in
matters of space, time and simultaneity. It is possible, however, that these
supposed links of Einstein and avant-garde art movements were more the product
of the imagination of historians and critics, than the result of connections
between painters and scientists. On the one hand, the visual arts (in contrast
to music, as far as we now) were of no interest to Einstein, who, moreover, did
not seem inclined or knowledgeable enough to appreciate advanced forms. On the
other hand, Einstein's theories fell outside the artists' ken, let alone their
understanding, although there are firm clues pointing to the fact that
repercussions of those theories in the press and in literary circles could have
fired the imagination of some artists.
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In this work, Machine Learning (ML) methods are used to efficiently identify
the unassociated sources and the Blazar Candidate of Uncertain types (BCUs) in
the Fermi-LAT Third Source Catalog (3FGL). The aims are twofold: 1) to
distinguish the Active Galactic Nuclei (AGNs) from others (non-AGNs) in the
unassociated sources; 2) to identify BCUs into BL Lacertae objects (BL Lacs) or
Flat Spectrum Radio Quasars (FSRQs). Two dimensional reduction methods are
presented to decrease computational complexity, where Random Forest (RF),
Multilayer Perceptron (MLP) and Generative Adversarial Nets (GAN) are trained
as individual models. In order to achieve better performance, the ensemble
technique is further explored. It is also demonstrated that grid search method
is of help to choose the hyper-parameters of models and decide the final
predictor, by which we have identified 748 AGNs out of 1010 unassociated
sources, with an accuracy of 97.04%. Within the 573 BCUs, 326 have been
identified as BL Lacs and 247 as FSRQs, with an accuracy of 92.13%.
|
Medical Dialogue Generation (MDG) is intended to build a medical dialogue
system for intelligent consultation, which can communicate with patients in
real-time, thereby improving the efficiency of clinical diagnosis with broad
application prospects. This paper presents our proposed framework for the
Chinese MDG organized by the 2021 China conference on knowledge graph and
semantic computing (CCKS) competition, which requires generating
context-consistent and medically meaningful responses conditioned on the
dialogue history. In our framework, we propose a pipeline system composed of
entity prediction and entity-aware dialogue generation, by adding predicted
entities to the dialogue model with a fusion mechanism, thereby utilizing
information from different sources. At the decoding stage, we propose a new
decoding mechanism named Entity-revised Diverse Beam Search (EDBS) to improve
entity correctness and promote the length and quality of the final response.
The proposed method wins both the CCKS and the International Conference on
Learning Representations (ICLR) 2021 Workshop Machine Learning for Preventing
and Combating Pandemics (MLPCP) Track 1 Entity-aware MED competitions, which
demonstrate the practicality and effectiveness of our method.
|
Scintillator detector response modelling has become an essential tool in
various research fields such as particle and nuclear physics, astronomy or
geophysics. Yet, due to the system complexity and the requirement for accurate
electron response measurements, model inference and calibration remains a
challenge. Here, we propose Compton edge probing to perform non-proportional
scintillation model (NPSM) inference for inorganic scintillators. We use
laboratory-based gamma-ray radiation measurements with a NaI(Tl) scintillator
to perform Bayesian inference on a NPSM. Further, we apply machine learning to
emulate the detector response obtained by Monte Carlo simulations. We show that
the proposed methodology successfully constrains the NPSM and hereby quantifies
the intrinsic resolution. Moreover, using the trained emulators, we can predict
the spectral Compton edge dynamics as a function of the parameterized
scintillation mechanisms. The presented framework offers a novel way to infer
NPSMs for any inorganic scintillator without the need for additional electron
response measurements.
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Subsets and Splits
Filtered Text Samples
Retrieves 100 samples of text containing the specific phrase "You are a helpful assistant", providing limited insight into the dataset.
Helpful Assistant Text Samples
Returns a limited set of rows containing the phrase 'helpful assistant' in the text, providing basic filtering of relevant entries.