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We study the phenomenology of the 4-site Higgsless model, based on the
$SU(2)_L\times SU(2)_1\times SU(2)_2\times U(1)_Y$ gauge symmetry, at present
colliders. The model predicts the existence of two neutral and four charged
extra gauge bosons, Z1,Z2,W1,W2. In this paper, we focus on the charged gauge
sector. We first derive limits on W1,W2-boson masses and couplings to SM
fermions from direct searches at the Tevatron. We then estimate at the 7 TeV
LHC the exclusion limits with the actual L=1 fb-1 and the discovery potential
with the expected L=10 fb-1. In contrast to the minimal (or 3-site) Higgsless
model which predicts almost fermiophobic extra gauge bosons, the
next-to-minimal (or 4-site) Higgsless model recovers sizeable W1,W2-boson
couplings to ordinary matter, expressing the non-fermiophobic multiresonance
inner nature of extra-dimensional theories. Owing to this feature, we find that
in one year from now the new heavy gauge bosons, W1 and W2, could be discovered
in the final state with an electron and large missing transverse energy at the
7 TeV LHC for W1,W2-boson masses in the TeV region, depending on model
parameters.
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In these notes we discuss the origin of shot noise ('Schroteffekt') of vacuum
tubes in detail. It will be shown that shot noise observed in vacuum tubes and
first described by W. Schottky in 1918 is a purely classical phenomenon. This
is in pronounced contrast to shot noise investigated in mesoscopic conductors
which is due to quantum mechanical diffraction of electron waves.
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The dramatic dynamic slowing down associated with the glass transition is
considered by many to be related to the existence of a static length scale that
grows when temperature decreases. Defining, identifying and measuring such a
length is a subtle and non-trivial problem. Recently, two proposals, based on
very different insights regarding the relevant physics, were put forward. One
approach is based on the point-to-set correlation technique and the other on
the scale where the lowest eigenvalue of the Hessian matrix becomes sensitive
to disorder. In this Letter we present numerical evidence that the two
approaches might result in the same identical length scale. This provides
further mutual support to their relevance and, at the same time, raise
interesting theoretical questions, discussed in the conclusion, concerning the
fundamental reason for their relationship.
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Understanding quantum theory in terms of a geometric picture sounds great.
There are different approaches to this idea. Here we shall present a geometric
picture of quantum theory using the de-Broglie--Bohm causal interpretation of
quantum mechanics. We shall show that it is possible to understand the key
character of de-Broglie--Bohm theory, the quantum potential, as the conformal
degree of freedom of the space--time metric. In this way, gravity should give
the causal structure of the space--time, while quantum phenomena determines the
scale. Some toy models in terms of tensor and scalar--tensor theories will be
presented. Then a few essential physical aspects of the idea including the
effect on the black holes, the initial Big--Bang singularity and non locality
are investigated. We shall formulate a quantum equivalence principle according
to which gravitational effects can be removed by going to a freely falling
frame while quantum effects can be eliminated by choosing an appropriate scale.
And we shall see that the best framework for both quantum and gravity is Weyl
geometry. Then we shall show how one can get the de-Broglie--Bohm quantum
theory out of a Weyl covariant theory. Extension to the case of many particle
systems and spinning particles is discussed at the end.
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We attempt to shed new light on the notion of 'tree-like' metric spaces by
focusing on an approach that does not use the four-point condition. Our key
question is: Given metric space $M$ on $n$ points, when does a fully labelled
positive-weighted tree $T$ exist on the same $n$ vertices that precisely
realises $M$ using its shortest path metric? We prove that if a spanning tree
representation, $T$, of $M$ exists, then it is isomorphic to the unique minimum
spanning tree in the weighted complete graph associated with $M$, and we
introduce a fourth-point condition that is necessary and sufficient to ensure
the existence of $T$ whenever each distance in $M$ is unique. In other words, a
finite median graph, in which each geodesic distance is distinct, is simply a
tree. Provided that the tie-breaking assumption holds, the fourth-point
condition serves as a criterion for measuring the goodness-of-fit of the
minimum spanning tree to $M$, i.e., the spanning tree-likeness of $M$. It is
also possible to evaluate the spanning path-likeness of $M$. These quantities
can be measured in $O(n^4)$ and $O(n^3)$ time, respectively.
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Federated learning (FL) enables collaborative learning of a deep learning
model without sharing the data of participating sites. FL in medical image
analysis tasks is relatively new and open for enhancements. In this study, we
propose FedDropoutAvg, a new federated learning approach for training a
generalizable model. The proposed method takes advantage of randomness, both in
client selection and also in federated averaging process. We compare
FedDropoutAvg to several algorithms in an FL scenario for real-world multi-site
histopathology image classification task. We show that with FedDropoutAvg, the
final model can achieve performance better than other FL approaches and closer
to a classical deep learning model that requires all data to be shared for
centralized training. We test the trained models on a large dataset consisting
of 1.2 million image tiles from 21 different centers. To evaluate the
generalization ability of the proposed approach, we use held-out test sets from
centers whose data was used in the FL and for unseen data from other
independent centers whose data was not used in the federated training. We show
that the proposed approach is more generalizable than other state-of-the-art
federated training approaches. To the best of our knowledge, ours is the first
study to use a randomized client and local model parameter selection procedure
in a federated setting for a medical image analysis task.
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We propose an implementation scheme for holonomic, i.e., geometrical, quantum
information processing based on semiconductor nanostructures. Our quantum
hardware consists of coupled semiconductor macroatoms addressed/controlled by
ultrafast multicolor laser-pulse sequences. More specifically, logical qubits
are encoded in excitonic states with different spin polarizations and
manipulated by adiabatic time-control of the laser amplitudes . The two-qubit
gate is realized in a geometric fashion by exploiting dipole-dipole coupling
between excitons in neighboring quantum dots.
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Martingale-like sequences in vector lattice and Banach lattice frameworks are
defined in the same way as martingales are defined in [Positivity 9 (2005),
437--456]. In these frameworks, a collection of bounded $X$-martingales is
shown to be a Banach space under the supremum norm, and under some conditions
it is also a Banach lattice with coordinate-wise order. Moreover, a necessary
and sufficient condition is presented for the collection of
$\mathcal{E}$-martingales to be a vector lattice with coordinate-wise order. It
is also shown that the collection of bounded $\mathcal{E}$-martingales is a
normed lattice but not necessarily a Banach space under the supremum norm.
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This paper has been withdrawn by the author
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In this paper we show that, with probability 1, a random Beltrami field
exhibits chaotic regions that coexist with invariant tori of complicated
topologies. The motivation to consider this question, which arises in the study
of stationary Euler flows in dimension 3, is V.I. Arnold's 1965 conjecture that
a typical Beltrami field exhibits the same complexity as the restriction to an
energy hypersurface of a generic Hamiltonian system with two degrees of
freedom. The proof hinges on the obtention of asymptotic bounds for the number
of horseshoes, zeros, and knotted invariant tori and periodic trajectories that
a Gaussian random Beltrami field exhibits, which we obtain through a nontrivial
extension of the Nazarov--Sodin theory for Gaussian random monochromatic waves
and the application of different tools from the theory of dynamical systems,
including KAM theory, Melnikov analysis and hyperbolicity. Our results hold
both in the case of Beltrami fields on $\mathbf{R}^3$ and of high-frequency
Beltrami fields on the 3-torus.
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The maximum particle kinetic energy that can be extracted from an initial
six-dimensional phase space distribution motivates the concept of free or
available energy. The free energy depends on the allowed operations that can be
performed. A key concept underlying the theoretical treatment of plasmas is the
Gardner free energy, where the exchange of the contents of equal phase volumes
is allowed. A second free energy concept is the diffusive free energy, in which
the contents of volumes are instead averaged. For any finite discretization of
phase space, the diffusive free energy is known to be less than the Gardner
free energy. However, despite the apparent fundamental differences between
these free energies, it is demonstrated here that the Gardner free energy may
be recovered from the continuous limit of the diffusive free energy, leading to
the surprise that macroscopic phase-space conservation can be achieved by
ostensibly entropy-producing microscopic operations.
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Prior research primarily examined differentially-private continual releases
against data streams, where entries were immutable after insertion. However,
most data is dynamic and housed in databases. Addressing this literature gap,
this article presents a methodology for achieving differential privacy for
continual releases in dynamic databases, where entries can be inserted,
modified, and deleted. A dynamic database is represented as a changelog,
allowing the application of differential privacy techniques for data streams to
dynamic databases. To ensure differential privacy in continual releases, this
article demonstrates the necessity of constraints on mutations in dynamic
databases and proposes two common constraints. Additionally, it explores the
differential privacy of two fundamental types of continual releases: Disjoint
Continual Releases (DCR) and Sliding-window Continual Releases (SWCR). The
article also highlights how DCR and SWCR can benefit from a hierarchical
algorithm for better privacy budget utilization. Furthermore, it reveals that
the changelog representation can be extended to dynamic entries, achieving
local differential privacy for continual releases. Lastly, the article
introduces a novel approach to implement continual release of randomized
responses.
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The purpose of this paper is to prove that the Hermitian Curvature Flow (HCF)
on an Hermitian manifold $(M,g,J)$ preserves many natural curvature positivity
conditions. Following Wilking, for an $Ad\,{GL(T^{1,0}M)}$-invariant subset
$S\subset End(T^{1,0}M)$ and a ncie function $F\colon End(T^{1,0}M)\to\mathbb
R$ we construct a convex set of curvature operators $C(S,F)$, which is
invariant under the HCF. Varying $S$ and $F$, we prove that the HCF preserves
Griffiths positivity, Dual-Nakano positivity, positivity of holomorphic
orthogonal bisectional curvature, lower bounds on the second scalar curvature.
As an application, we prove that periodic solutions to the HCF can exist only
on manifolds $M$ with the trivial canonical bundle on the universal cover
$\widetilde{M}$.
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Rate-Splitting Multiple Access (RSMA) is an emerging flexible, robust and
powerful multiple access scheme for downlink multi-antenna wireless networks.
RSMA relies on multi-antenna Rate-Splitting (RS) strategies at the transmitter
and Successive Interference Cancellation (SIC) at the receivers, and has the
unique ability to partially decode interference and partially treat
interference as noise so as to softly bridge the two extremes of fully decoding
interference (as in Non-Orthogonal Multiple Access, NOMA) and treating
interference as noise (as in Space Division Multiple Access, SDMA or Multi-User
Multiple-Input Multiple-Output, MU-MIMO). RSMA has been shown to provide
significant room for spectral efficiency, energy efficiency, Quality-of-Service
enhancements, robustness to Channel State Information (CSI) imperfections, as
well as feedback overhead and complexity reduction, in a wide range of network
loads (underloaded and overloaded regimes) and user deployments (with a
diversity of channel directions, channel strengths and qualities). RSMA is also
deeply rooted and motivated by recent advances in understanding the fundamental
limits of multi-antenna networks with imperfect CSI at the Transmitter (CSIT).
In this work, we leverage recent results on the optimization of RSMA and design
for the first time its physical layer, accounting for modulation, coding (using
polar codes), message split, adaptive modulation and coding, and SIC receiver.
Link-level evaluations confirm the significant throughput benefits of RSMA over
various baselines as SDMA and NOMA.
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A spectral representation for solutions to linear Hamilton equations with
nonnegative energy in Hilbert spaces is obtained. This paper continues our
previous work on Hamilton equations with positive definite energy. Our approach
is a special version of M. Krein's spectral theory of $J$-selfadjoint operators
in Hilbert spaces with indefinite metric.
As a principal application of these results, we justify the eigenfunction
expansion for linearized nonlinear relativistic Ginzburg-Landau equations.
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Populations of neurons display an extraordinary diversity in the behaviors
they affect and display. Machine learning techniques have recently emerged that
allow us to create networks of model neurons that display behaviours of similar
complexity. Here, we demonstrate the direct applicability of one such
technique, the FORCE method, to spiking neural networks. We train these
networks to mimic dynamical systems, classify inputs, and store discrete
sequences that correspond to the notes of a song. Finally, we use FORCE
training to create two biologically motivated model circuits. One is inspired
by the zebra-finch and successfully reproduces songbird singing. The second
network is motivated by the hippocampus and is trained to store and replay a
movie scene. FORCE trained networks reproduce behaviors comparable in
complexity to their inspired circuits and yield information not easily
obtainable with other techniques such as behavioral responses to
pharmacological manipulations and spike timing statistics.
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We give an elementary proof that Talagrand's sub-Gaussian concentration
inequality implies a limit shape theorem for first passage percolation on any
Cayley graph of Z^d, with a bound on the speed of convergence that slightly
improves Alexander's bounds. Our approach, which does not use the subadditive
theorem, is based on proving that the average distance is close to being
geodesic. Our key observation, of independent interest, is that the problem of
estimating the rate of convergence for the average distance is equivalent (in a
precise sense) to estimating its "level of geodesicity".
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The triple system HD158926 (lambda Sco) has been observed interferometrically
with the Sydney University Stellar Interferometer and the elements of the wide
orbit have been determined. These are significantly more accurate than the
previous elements found spectroscopically. The inclination of the wide orbit is
consistent with the inclination previously found for the orbit of the close
companion. The wide orbit also has low eccentricity, suggesting that the three
stars were formed at the same time.
The brightness ratio between the two B stars was also measured at lambda =
442nm and 700nm. The brightness ratio and colour index are consistent with the
previous classification of lambda Sco A as B1.5 and lambda Sco B as B2.
Evolutionary models show that the two stars lie on the main sequence. Since
they have have the same age and luminosity class (IV) the mass-luminosity
relation can be used to determine the mass ratio of the two stars: M_B/M_A =
0.76+/-0.04.
The spectroscopic data have been reanalyzed using the interferometric values
for P, T, e and omega, leading to revised values for a_1sin i and the mass
function. The individual masses can be found from the mass ratio, the mass
function, spectrum synthesis and the requirement that the age of both
components must be the same: M_A = 10.4+/-1.3 Msun and M_B = 8.1+/-1.0 Msun.
The masses, angular semimajor axis and the period of the system can be used
to determine the dynamical parallax. We find the distance to lambda Sco to be
112+/-5 pc, which is approximately a factor of two closer than the HIPPARCOS
value of 216+/-42 pc.
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Let $p$ be a prime number, and $h$ a positive integer such that
$\gcd(p,h)=1$. We prove, without invoking Dirichlet's theorem, that the
arithmetic progression $p\left(\mathbf{N}\cup \{0\}\right)+h$ contains
infinitely many prime numbers. This is a special case of Dirichlet's theorem
not considered by other authors.
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We consider Voevodsky's slice tower for a finite spectrum E in the motivic
stable homotopy category over a perfect field k. In case k has finite
cohomological dimension (in characteristic two, we also require that k is
infinite), we show that the slice tower converges, in that the induced
filtration on the bi-graded homotopy sheaves for each term in the tower for E
is finite, exhaustive and separated at each stalk. This partially verifies a
conjecture of Voevodsky.
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The generative aspect model is an extension of the multinomial model for text
that allows word probabilities to vary stochastically across documents.
Previous results with aspect models have been promising, but hindered by the
computational difficulty of carrying out inference and learning. This paper
demonstrates that the simple variational methods of Blei et al (2001) can lead
to inaccurate inferences and biased learning for the generative aspect model.
We develop an alternative approach that leads to higher accuracy at comparable
cost. An extension of Expectation-Propagation is used for inference and then
embedded in an EM algorithm for learning. Experimental results are presented
for both synthetic and real data sets.
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In recent years, assessing the performance of researchers has become a burden
due to the extensive volume of the existing research output. As a result,
evaluators often end up relying heavily on a selection of performance
indicators like the h-index. However, over-reliance on such indicators may
result in reinforcing dubious research practices, while overlooking important
aspects of a researcher's career, such as their exact role in the production of
particular research works or their contribution to other important types of
academic or research activities (e.g., production of datasets, peer reviewing).
In response, a number of initiatives that attempt to provide guidelines towards
fairer research assessment frameworks have been established. In this work, we
present BIP! Scholar, a Web-based service that offers researchers the
opportunity to set up profiles that summarise their research careers taking
into consideration well-established guidelines for fair research assessment,
facilitating the work of evaluators who want to be more compliant with the
respective practices.
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In this work we study a distributed optimal output consensus problem for
heterogeneous linear multi-agent systems where the agents aim to reach
consensus with the purpose of minimizing the sum of private convex costs. Based
on output feedback, a fully distributed control law is proposed by using the
proportional-integral (PI) control technique. For strongly convex cost
functions with Lipschitz gradients, the designed controller can achieve
convergence exponentially in an undirected and connected network. Furthermore,
to remove the requirement of continuous communications, the proposed control
law is then extended to periodic and event-triggered communication schemes,
which also achieve convergence exponentially. Two simulation examples are given
to verify the proposed control algorithms.
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In this paper anticliques for non-commutative operator graphs generated by
the generalized Pauli matrices are constructed. It is shown that application of
entangled states for the construction of code space K allows one to
substantially increase the dimension of a non-commutative operator graph for
which the projection on K is an anticlique.
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Let $G=(V,E)$ be a graph of density $p$ on $n$ vertices. Following Erd\H{o}s,
\L uczak and Spencer, an $m$-vertex subgraph $H$ of $G$ is called {\em full} if
$H$ has minimum degree at least $p(m - 1)$. Let $f(G)$ denote the order of a
largest full subgraph of $G$. If $p\binom{n}{2}$ is a non-negative integer,
define \[ f(n,p) = \min\{f(G) : \vert V(G)\vert = n, \ \vert E(G)\vert =
p\binom{n}{2} \}.\] Erd\H{o}s, \L uczak and Spencer proved that for $n \geq 2$,
\[ (2n)^{\frac{1}{2}} - 2 \leq f(n, {\frac{1}{2}}) \leq 4n^{\frac{2}{3}}(\log
n)^{\frac{1}{3}}.\] In this paper, we prove the following lower bound: for
$n^{-\frac{2}{3}} <p_n <1-n^{-\frac{1}{7}}$, \[ f(n,p) \geq
\frac{1}{4}(1-p)^{\frac{2}{3}}n^{\frac{2}{3}} -1.\] Furthermore we show that
this is tight up to a multiplicative constant factor for infinitely many $p$
near the elements of $\{\frac{1}{2},\frac{2}{3},\frac{3}{4},\dots\}$. In
contrast, we show that for any $n$-vertex graph $G$, either $G$ or $G^c$
contains a full subgraph on $\Omega(\frac{n}{\log n})$ vertices. Finally, we
discuss full subgraphs of random and pseudo-random graphs, and several open
problems.
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The method of simplest equation is applied for obtaining exact solitary
traveling-wave solutions of nonlinear partial differential equations that
contain monomials of odd and even grade with respect to participating
derivatives. The used simplest equation is $f_\xi^2 = n^2(f^2 -f^{(2n+2)/n})$.
The developed methodology is illustrated on two examples of classes of
nonlinear partial differential equations that contain: (i) only monomials of
odd grade with respect to participating derivatives; (ii) only monomials of
even grade with respect to participating derivatives. The obtained solitary
wave solution for the case (i) contains as particular cases the solitary wave
solutions of Korteweg-deVries equation and of a version of the modified
Korteweg-deVries equation.
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An infinite hierarchy of layering transitions exists for model polymers in
solution under poor solvent or low temperatures and near an attractive surface.
A flat histogram stochastic growth algorithm known as FlatPERM has been used on
a self- and surface interacting self-avoiding walk model for lengths up to 256.
The associated phases exist as stable equilibria for large though not infinite
length polymers and break the conjectured Surface Attached Globule phase into a
series of phases where a polymer exists in specified layer close to a surface.
We provide a scaling theory for these phases and the first-order transitions
between them.
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We use integrated-light spectroscopic observations to measure metallicities
and chemical abundances for two extragalactic young massive star clusters
(NGC1313-379 and NGC1705-1). The spectra were obtained with the X-Shooter
spectrograph on the ESO Very Large Telescope. We compute synthetic
integrated-light spectra, based on colour-magnitude diagrams for the brightest
stars in the clusters from Hubble Space Telescope photometry and theoretical
isochrones. Furthermore, we test the uncertainties arising from the use of
Colour Magnitude Diagram (CMD) +Isochrone method compared to an Isochrone-Only
method. The abundances of the model spectra are iteratively adjusted until the
best fit to the observations is obtained. In this work we mainly focus on the
optical part of the spectra. We find metallicities of [Fe/H] = $-$0.84 $\pm$
0.07 and [Fe/H] = $-$0.78 $\pm$ 0.10 for NGC1313-379 and NGC1705-1,
respectively. We measure [$\alpha$/Fe]=$+$0.06 $\pm$ 0.11 for NGC1313-379 and a
super-solar [$\alpha$/Fe]=$+$0.32 $\pm$ 0.12 for NGC1705-1. The roughly solar
[$\alpha$/Fe] ratio in NGC1313-379 resembles those for young stellar
populations in the Milky Way (MW) and the Magellanic Clouds, whereas the
enhanced [$\alpha$/Fe] ratio in NGC1705-1 is similar to that found for the
cluster NGC1569-B by previous studies. Such super-solar [$\alpha$/Fe] ratios
are also predicted by chemical evolution models that incorporate the bursty
star formation histories of these dwarf galaxies. Furthermore, our
$\alpha$-element abundances agree with abundance measurements from H II regions
in both galaxies. In general we derive Fe-peak abundances similar to those
observed in the MW and Large Magellanic Cloud (LMC) for both young massive
clusters. For these elements, however, we recommend higher-resolution
observations to improve the Fe-peak abundance measurements.
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We consider a Metropolis--Hastings method with proposal $\mathcal{N}(x,
hG(x)^{-1})$, where $x$ is the current state, and study its ergodicity
properties. We show that suitable choices of $G(x)$ can change these compared
to the Random Walk Metropolis case $\mathcal{N}(x, h\Sigma)$, either for better
or worse. We find that if the proposal variance is allowed to grow unboundedly
in the tails of the distribution then geometric ergodicity can be established
when the target distribution for the algorithm has tails that are heavier than
exponential, but that the growth rate must be carefully controlled to prevent
the rejection rate approaching unity. We also illustrate that a judicious
choice of $G(x)$ can result in a geometrically ergodic chain when probability
concentrates on an ever narrower ridge in the tails, something that is not true
for the Random Walk Metropolis.
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In this study, we investigate the phenomenon of mode conversion in elastic
bulk waves using coupled hexapole resonances. A metamaterial slab is proposed
enabling the complete conversion between longitudinal and transverse modes.
Each unit of the elastic metamaterial slab comprises a pair of scatterers, and
their relative direction is oriented at an oblique angle. The interaction
between the coupled hexapoles and the background results in oblique
displacements, which are responsible for the mode conversion. Moreover, this
conversion exhibits a broader frequency range compared to the quadrupole
resonance. This innovative design significantly broadens the range of
possibilities for developing mode-converting metamaterials.
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The kagom\'e lattice exhibits peculiar magnetic properties due to its
strongly frustated cristallographic structure, based on corner sharing
triangles. For nearest neighbour antiferromagnetic Heisenberg interactions
there is no Neel ordering at zero temperature both for quantum and classical s
pins. We show that, due to the peculiar structure, antisymmetric
Dzyaloshinsky-Moriya interactions (${\bf D} . ({\bf S}_i \times {\bf S}_j)$)
are present in this latt ice. In order to derive microscopically this
interaction we consider a set of localized d-electronic states. For classical
spins systems, we then study the phase diagram (T, D/J) through mean field
approximation and Monte-Carlo simulations and show that the antisymmetric
interaction drives this system to ordered states as soon as this interaction is
non zero. This mechanism could be involved to explain the magnetic structure of
Fe-jarosites.
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This thesis presents methods and approaches to image color correction, color
enhancement, and color editing. To begin, we study the color correction problem
from the standpoint of the camera's image signal processor (ISP). A camera's
ISP is hardware that applies a series of in-camera image processing and color
manipulation steps, many of which are nonlinear in nature, to render the
initial sensor image to its final photo-finished representation saved in the
8-bit standard RGB (sRGB) color space. As white balance (WB) is one of the
major procedures applied by the ISP for color correction, this thesis presents
two different methods for ISP white balancing. Afterward, we discuss another
scenario of correcting and editing image colors, where we present a set of
methods to correct and edit WB settings for images that have been improperly
white-balanced by the ISP. Then, we explore another factor that has a
significant impact on the quality of camera-rendered colors, in which we
outline two different methods to correct exposure errors in camera-rendered
images. Lastly, we discuss post-capture auto color editing and manipulation. In
particular, we propose auto image recoloring methods to generate different
realistic versions of the same camera-rendered image with new colors. Through
extensive evaluations, we demonstrate that our methods provide superior
solutions compared to existing alternatives targeting color correction, color
enhancement, and color editing.
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We study the connection between the magnetization profiles of models
described by a scalar field with marginal interaction term in a bounded domain
and the solutions of the so-called Yamabe problem in the same domain, which
amounts to finding a metric having constant curvature. Taking the slab as a
reference domain, we first study the magnetization profiles at the upper
critical dimensions $d=3$, $4$, $6$ for different (scale invariant) boundary
conditions. By studying the saddle-point equations for the magnetization, we
find general formulas in terms of Weierstrass elliptic functions, extending
exact results known in literature and finding new ones for the case of
percolation. The zeros and poles of the Weierstrass elliptic solutions can be
put in direct connection with the boundary conditions. We then show that, for
any dimension $d$, the magnetization profiles are solution of the corresponding
integer Yamabe equation at the same $d$ and with the same boundary conditions.
The magnetization profiles in the specific case of the $4$-dimensional Ising
model with fixed boundary conditions are compared with Monte Carlo simulations,
finding good agreement. These results explicitly confirm at the upper critical
dimension recent results presented in [1].
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In the finite difference method which is commonly used in computational
micromagnetics, the demagnetizing field is usually computed as a convolution of
the magnetization vector field with the demagnetizing tensor that describes the
magnetostatic field of a cuboidal cell with constant magnetization. An
analytical expression for the demagnetizing tensor is available, however at
distances far from the cuboidal cell, the numerical evaluation of the
analytical expression can be very inaccurate.
Due to this large-distance inaccuracy numerical packages such as OOMMF
compute the demagnetizing tensor using the explicit formula at distances close
to the originating cell, but at distances far from the originating cell a
formula based on an asymptotic expansion has to be used. In this work, we
describe a method to calculate the demagnetizing field by numerical evaluation
of the multidimensional integral in the demagnetization tensor terms using a
sparse grid integration scheme. This method improves the accuracy of
computation at intermediate distances from the origin.
We compute and report the accuracy of (i) the numerical evaluation of the
exact tensor expression which is best for short distances, (ii) the asymptotic
expansion best suited for large distances, and (iii) the new method based on
numerical integration, which is superior to methods (i) and (ii) for
intermediate distances. For all three methods, we show the measurements of
accuracy and execution time as a function of distance, for calculations using
single precision (4-byte) and double precision (8-byte) floating point
arithmetic. We make recommendations for the choice of scheme order and
integrating coefficients for the numerical integration method (iii).
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The influence of short-range correlations on the $p$-wave single-particle
spectral function in $^{16}{\rm O}$ is studied as a function of energy. This
influence, which is represented by the admixture of high-momentum components,
is found to be small in the $p$-shell quasihole wave functions. It is therefore
unlikely that studies of quasihole momentum distributions using the $(e,e'p)$
reaction will reveal a significant contribution of high momentum components.
Instead, high-momentum components become increasingly more dominant at higher
excitation energy. The above observations are consistent with the energy
distribution of high-momentum components in nuclear matter.
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Given a $C^2$- Anosov diffemorphism $f: M \rightarrow M,$ we prove that the
jacobian condition $Jf^n(p) = 1,$ for every point $p$ such that $f^n(p) = p,$
implies transitivity. As application in the celebrated theory of
Sinai-Ruelle-Bowen, this result allows us to state a classical theorem of
Livsic-Sinai without directly assuming transitivity as a general hypothesis. A
special consequence of our result is that every $C^2$-Anosov diffeomorphism,
for which every point is regular, is indeed transitive.
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Strong Coulomb repulsion and spin-orbit coupling are known to give rise to
exotic physical phenomena in transition metal oxides. Initial attempts to
investigate systems where both of these fundamental interactions are comparably
strong, such as 3d and 5d complex oxide superlattices, have revealed properties
that only slightly differ from the bulk ones of the constituent materials.
Here, we observe that the interfacial coupling between the 3d antiferromagnetic
insulator SrMnO3 and the 5d paramagnetic metal SrIrO3 is enormously strong,
yielding an anomalous Hall response as the result of charge transfer driven
interfacial ferromagnetism. These findings show that low dimensional spin-orbit
entangled 3d-5d interfaces provide an avenue to uncover technologically
relevant physical phenomena unattainable in bulk materials.
|
A strong analogy is found between the evolution of localized disturbances in
extended chaotic systems and the propagation of fronts separating different
phases. A condition for the evolution to be controlled by nonlinear mechanisms
is derived on the basis of this relationship. An approximate expression for the
nonlinear velocity is also determined by extending the concept of Lyapunov
exponent to growth rate of finite perturbations.
|
The detectability of moons of extra-solar planets is investigated, focussing
on the time-of-arrival perturbation technique, a method for detecting moons of
pulsar planets, and the photometric transit timing technique, a method for
detecting moons of transiting planets. Realistic thresholds are derived and
analysed in the in the context of the types of moons that are likely to form
and be orbitally stable for the lifetime of the system.
For the case of the time-of-arrival perturbation technique, the analysis is
conducted in two stages. First, a preliminary investigation is conducted
assuming that planet and moon's orbit are circular and coplanar. This analysis
is then applied to the case of the pulsar planet PSR B1620-26 b, and used to
conclude that a stable moon orbiting this pulsar planet could be detected, if
its mass was >5% of its planet's mass (2.5 Jupiter masses), and if the
planet-moon distance was ~ 2% of the planet-pulsar separation (23 AU).
Time-of-arrival expressions are then derived for mutually inclined as well as
non-circular orbits.
For the case of the photometric transit timing technique, a different
approach is adopted. First, analytic expressions for the timing perturbation
due to the moon are derived for the case where the orbit of the moon is
circular and coplanar with that of the planet and where the planet's orbit is
circular and aligned to the line-of-sight, circular and inclined with respect
to the line-of-sight or eccentric and aligned to the line-of-sight. Second, the
timing noise is investigated analytically, for the case of white photometric
noise, and numerically, using SOHO lightcurves, for the case of realistic and
filtered realistic photometric noise. [...] Abstract truncated due to the
limitations of astroph. See full abstract in the thesis.
|
We study the effect of asperity size on the adhesion properties of metal
contact using atomistic simulations. The simulated size effect of individual
nanoscale asperityies is applied to macroscopic rough surfaces by introducing a
curvature radius distribution to a continuum-mechanics-based contact model. Our
results indicate that the contact adhesion can be optimized by changing the
curvature radius distribution of the asperity summits.
|
While artificial intelligence (AI) offers significant benefits, it also has
negatively impacted humans and society. A human-centered AI (HCAI) approach has
been proposed to address these issues. However, current HCAI practices have
shown limited contributions due to a lack of sociotechnical thinking. To
overcome these challenges, we conducted a literature review and comparative
analysis of sociotechnical characteristics between the non-AI and AI eras.
Then, we propose updated sociotechnical systems (STS) design principles. Based
on these findings, this paper introduces a concept of intelligent
sociotechnical systems (iSTS) to enhance traditional STS theory and meet the
demands of the AI era. The iSTS concept emphasizes human-centered joint
optimization across individual, organizational, ecosystem, and social levels.
The paper further integrates iSTS with current HCAI practices, proposing a
hierarchical HCAI framework. This framework offers a structured approach to
address challenges in HCAI practices from a broader sociotechnical perspective.
Finally, we provide recommendations to advance HCAI practice.
|
We determine the structure of linear maps on the tensor product of matrices
which preserve the numerical range or numerical radius.
|
Let F_2 denote the free group of rank 2. Our main technical result of
independent interest is: for any element u of F_2, there is g in F_2 such that
no cyclically reduced image of u under an automorphism of F_2 contains g as a
subword. We then address computational complexity of the following version of
the Whitehead automorphism problem: given a fixed u in F_2, decide, on an input
v in F_2 of length n, whether or not v is an automorphic image of u. We show
that there is an algorithm that solves this problem and has constant (i.e.,
independent of n) average-case complexity.
|
Object-oriented maps are important for scene understanding since they jointly
capture geometry and semantics, allow individual instantiation and meaningful
reasoning about objects. We introduce FroDO, a method for accurate 3D
reconstruction of object instances from RGB video that infers object location,
pose and shape in a coarse-to-fine manner. Key to FroDO is to embed object
shapes in a novel learnt space that allows seamless switching between sparse
point cloud and dense DeepSDF decoding. Given an input sequence of localized
RGB frames, FroDO first aggregates 2D detections to instantiate a
category-aware 3D bounding box per object. A shape code is regressed using an
encoder network before optimizing shape and pose further under the learnt shape
priors using sparse and dense shape representations. The optimization uses
multi-view geometric, photometric and silhouette losses. We evaluate on
real-world datasets, including Pix3D, Redwood-OS, and ScanNet, for single-view,
multi-view, and multi-object reconstruction.
|
In 1979 Lusztig proposed a conjectural construction of supercuspidal
representations of reductive p-adic groups, which is similar to the well known
construction of Deligne and Lusztig in the setting of finite reductive groups.
We present a general method for explicitly calculating the representations
arising from Lusztig's construction and illustrate it with several examples.
The techniques we develop also provide background for the author's joint work
with Weinstein on a purely local and explicit proof of the local Langlands
correspondence.
|
Black holes arising in the context of scalar-tensor gravity theories, where
the scalar field is non-minimally coupled to the curvature term, have zero
surface gravity. Hence, it is generally stated that their Hawking temperature
is zero, irrespectivelly of their gravitational and scalar charges. The proper
analysis of the Hawking temperature requires to study the propagation of
quantum fields in the space-time determined by these objects. We study scalar
fields in the vicinity of the horizon of these black holes. It is shown that
the scalar modes do not form an orthonormal set. Hence, the Hilbert space is
ill-definite in this case, and no notion of temperature can be extracted for
such objects.
|
In connection with the 150-th Anniversary of P. N. Lebedev, we present
historical aspects of his scientific and organizing activity and recall his
famous experimental observations and proof of the existence of light pressure
along with other results that essentially influenced the development of physics
in Russia and in the whole world as well. We discuss the relationship of these
studies of electromagnetic waves and other kinds of vibrational phenomena
investigated by P. N. Lebedev to modern studies of the interaction of photons
with mirrors, gravitational waves, acoustic waves, nonstationary (dynamical)
Casimir effect of photon creation in resonators with vibrating boundaries, and
vibrations of voltage and current in superconducting circuits realizing the
states of qubits and qudits. We discuss the possibility of existence of the
nonstationary Casimir effect for gravitational waves and sound in liquid
helium.
|
This paper establishes a mathematical foundation for the Adam optimizer,
elucidating its connection to natural gradient descent through Riemannian and
information geometry. We provide an accessible and detailed analysis of the
diagonal empirical Fisher information matrix (FIM) in Adam, clarifying all
detailed approximations and advocating for the use of log probability functions
as loss, which should be based on discrete distributions, due to the
limitations of empirical FIM. Our analysis uncovers flaws in the original Adam
algorithm, leading to proposed corrections such as enhanced momentum
calculations, adjusted bias corrections, adaptive epsilon, and gradient
clipping. We refine the weight decay term based on our theoretical framework.
Our modified algorithm, Fisher Adam (FAdam), demonstrates superior performance
across diverse domains including LLM, ASR, and VQ-VAE, achieving
state-of-the-art results in ASR.
|
We probe the existence of a many-body localized phase (MBL-phase) in a
spinless fermionic Hubbard chain with algebraically localized single-particle
states, by investigating both static and dynamical properties of the system.
This MBL-phase can be characterized by an extensive number of integrals of
motion which develop algebraically decaying tails, unlike the case of
exponentially localized single-particle states. We focus on the implications
for the quantum information propagation through the system. We provide evidence
that the bipartite entanglement entropy after a quantum quench has an unbounded
algebraic growth in time, while the quantum Fisher information grows
logarithmically.
|
The dependence of function renormalization group equation on regulators is
investigated. A parameter is introduced to control the suppression of
regulators. Functional renormalization group equations will become
regulator-independent if this newly introduced parameter is sent to infinity in
the end of calculation. One-loop renormalization flow equations of QCD are
derived. The novelty is that both the coupling running equation and the mass
running equation are mass-dependent. Different flow patterns are explored. A
mechanism for non-occurrence of dynamical chiral symmetry breaking is arrived
at. The existence of a conformal window is also discussed in the language of
renormalization flow.
|
In the covariant quark-diquark model the effective Bethe-Salpeter (BS)
equations for the nucleon and the $\Delta$ are solved including scalar {\em and
axialvector} diquark correlations. Their quark substructure is effectively
taken into account in both, the interaction kernel of the BS equations and the
currents employed to calculate nucleon observables. Electromagnetic current
conservation is maintained. The electric form factors of proton and neutron
match the data. Their magnetic moments improve considerably by including
axialvector diquarks and photon induced scalar-axialvector transitions. The
isoscalar magnetic moment can be reproduced, the isovector contribution is
about 15% too small. The ratio $\mu G_E/G_M$ and the axial and strong couplings
$g_A$, $g_{\pi NN}$, provide an upper bound on the relative importance of
axialvector diquarks confirming that scalar diquarks nevertheless describe the
dominant 2-quark correlations inside nucleons.
|
In this work, we introduce a Variational Multi-Scale (VMS) method for the
numerical approximation of parabolic problems, where sub-grid scales are
approximated from the eigenpairs of associated elliptic operator. The abstract
method is particularized to the one-dimensional advection-diffusion equations,
for which the sub-grid components are exactly calculated in terms of a spectral
expansion when the advection velocity is approximated by piecewise constant
velocities on the grid elements.
We prove error estimates that in particular imply that when Lagrange finite
element discretisations in space are used, the spectral VMS method coincides
with the exact solution of the implicit Euler semi-discretisation of the
advection-diffusion problem at the Lagrange interpolation nodes. We also build
a feasible method to solve the evolutive advection-diffusion problems by means
of an offline/online strategy with reduced computational complexity.
We perform some numerical tests in good agreement with the theoretical
expectations, that show an improved accuracy with respect to several stabilised
methods.
|
Joint speech-language training is challenging due to the large demand for
training data and GPU consumption, as well as the modality gap between speech
and language. We present ComSL, a speech-language model built atop a composite
architecture of public pretrained speech-only and language-only models and
optimized data-efficiently for spoken language tasks. Particularly, we propose
to incorporate cross-modality learning into transfer learning and conduct them
simultaneously for downstream tasks in a multi-task learning manner. Our
approach has demonstrated effectiveness in end-to-end speech-to-text
translation tasks, achieving a new state-of-the-art average BLEU score of 31.5
on the multilingual speech to English text translation task for 21 languages,
as measured on the public CoVoST2 evaluation set.
|
We present a unifying treatment of dark energy and modified gravity that
allows distinct conformal-disformal couplings of matter species to the
gravitational sector. In this very general approach, we derive the conditions
to avoid ghost and gradient instabilities. We compute the equations of motion
for background quantities and linear perturbations. We illustrate our formalism
with two simple scenarios, where either cold dark matter or a relativistic
fluid is nonminimally coupled. This extends previous studies of coupled dark
energy to a much broader spectrum of gravitational theories.
|
Raw videos have been proven to own considerable feature redundancy where in
many cases only a portion of frames can already meet the requirements for
accurate recognition. In this paper, we are interested in whether such
redundancy can be effectively leveraged to facilitate efficient inference in
continuous sign language recognition (CSLR). We propose a novel adaptive model
(AdaBrowse) to dynamically select a most informative subsequence from input
video sequences by modelling this problem as a sequential decision task. In
specific, we first utilize a lightweight network to quickly scan input videos
to extract coarse features. Then these features are fed into a policy network
to intelligently select a subsequence to process. The corresponding subsequence
is finally inferred by a normal CSLR model for sentence prediction. As only a
portion of frames are processed in this procedure, the total computations can
be considerably saved. Besides temporal redundancy, we are also interested in
whether the inherent spatial redundancy can be seamlessly integrated together
to achieve further efficiency, i.e., dynamically selecting a lowest input
resolution for each sample, whose model is referred to as AdaBrowse+. Extensive
experimental results on four large-scale CSLR datasets, i.e., PHOENIX14,
PHOENIX14-T, CSL-Daily and CSL, demonstrate the effectiveness of AdaBrowse and
AdaBrowse+ by achieving comparable accuracy with state-of-the-art methods with
1.44$\times$ throughput and 2.12$\times$ fewer FLOPs. Comparisons with other
commonly-used 2D CNNs and adaptive efficient methods verify the effectiveness
of AdaBrowse. Code is available at
\url{https://github.com/hulianyuyy/AdaBrowse}.
|
Accretion onto protostars may occur in sharp bursts. Accretion bursts during
the embedded phase of young protostars are probably most intense, but can only
be inferred indirectly through long-wavelength observations. We perform
radiative transfer calculations for young stellar objects (YSOs) formed in
hydrodynamic simulations to predict the long wavelength, sub-mm and mm, flux
responses to episodic accretion events, taking into account heating from the
young protostar and from the interstellar radiation field. We find that the
flux increase due to episodic accretion events is more prominent at sub-mm
wavelengths than at mm wavelengths; e.g. a factor of ~570 increase in the
luminosity of the young protostar leads to a flux increase of a factor of 47 at
250 micron but only a factor of 10 at 1.3 mm. Heating from the interstellar
radiation field may reduce further the flux increase observed at longer
wavelengths. We find that during FU Ori-type outbursts the bolometric
temperature and luminosity may incorrectly classify a source as a more evolved
YSO, due to a larger fraction of the radiation of the object being emitted at
shorter wavelengths
|
MadGraph 5 is the new version of the MadGraph matrix element generator,
written in the Python programming language. It implements a number of new,
efficient algorithms that provide improved performance and functionality in all
aspects of the program. It features a new user interface, several new output
formats including C++ process libraries for Pythia 8, and full compatibility
with FeynRules for new physics models implementation, allowing for event
generation for any model that can be written in the form of a Lagrangian.
MadGraph 5 builds on the same philosophy as the previous versions, and its
design allows it to be used as a collaborative platform where theoretical,
phenomenological and simulation projects can be developed and then distributed
to the high-energy community. We describe the ideas and the most important
developments of the code and illustrate its capabilities through a few simple
phenomenological examples.
|
In this report, we study in detail the competitor to the FM metallic state at
electronic density $x=1/4$ in the CMR regime using the two-orbital
double-exchange model with Jahn-Teller lattice distortions on two-dimensional
clusters, employing a very careful large-scale cooling down process in the
Monte Carlo simulations to avoid being trapped in metastable states. Our
investigations show that this competing insulator has a very unexpected complex
structure, involving diagonal stripes with alternating regions with FM and
CE-like order. The level of complexity of this new state even surpasses that of
the recently unveiled spin-orthogonal-stripe states and their associated high
degeneracy. This new state complements the long-standing scenario of phase
separation, since the alternating FM-CE pattern appears even in the present
study which is carried out in the clean limit. The present and recent
investigations are also in agreement with the many "glassy" characteristics of
the CMR state found experimentally, due to the high degeneracy of the
insulating states involved in the process. Results for the spin-structure
factor of the new states are also here provided to facilitate the analysis of
neutron scattering experiments for these materials.
|
Optical modulation of high-harmonics generation in solids enables the
detection of material properties such as the band structure and promising new
applications such as super-resolution imaging in semiconductors. Various recent
studies have shown optical modulation of high-harmonics generation in solids,
in particular, suppression of high-harmonics generation has been observed by
synchronized or delayed multi-pulse sequences. Here we provide an overview of
the underlying mechanisms attributed to this suppression and provide a
perspective on the challenges and opportunities regarding these mechanisms.
All-optical control of high-harmonic generation allows for femtosecond, and in
the future possibly subfemtosecond, switching, which has numerous possible
applications: These range from super-resolution microscopy, to nanoscale
controlled chemistry, and highly tunable nonlinear light sources.
|
A perturbative description of Large Scale Structure is a cornerstone of our
understanding of the observed distribution of matter in the universe.
Renormalization is an essential and defining step to make this description
physical and predictive. Here we introduce a systematic renormalization
procedure, which neatly associates counterterms to the UV-sensitive diagrams
order by order, as it is commonly done in quantum field theory. As a concrete
example, we renormalize the one-loop power spectrum and bispectrum of both
density and velocity. In addition, we present a series of results that are
valid to all orders in perturbation theory. First, we show that while
systematic renormalization requires temporally non-local counterterms, in
practice one can use an equivalent basis made of local operators. We give an
explicit prescription to generate all counterterms allowed by the symmetries.
Second, we present a formal proof of the well-known general argument that the
contribution of short distance perturbations to large scale density contrast
$\delta$ and momentum density $\mathbf\pi(\mathbf k)$ scale as $k^2$ and $k$,
respectively. Third, we demonstrate that the common practice of introducing
counterterms only in the Euler equation when one is interested in correlators
of $ \delta$ is indeed valid to all orders.
|
We compare large $N$ expansion of the localization result for the free energy
$F$ in the 3d $\mathcal{N}=6$ superconformal $U(N)_k \times U(N)_{-k}$
Chern-Simons-matter theory to its AdS/CFT counterpart, i.e. to the perturbative
expansion of M-theory partition function on AdS$_{4}\times
S^{7}/\mathbb{Z}_{k}$ and to the weak string coupling expansion of type IIA
effective action on AdS$_{4}\times {\rm CP}^3$. We show that the general form
of the perturbative expansions of $F$ on the two sides of the AdS/CFT duality
is indeed the same. Moreover, the transcendentality properties of the
coefficients in the large $N$, large $k$ expansion of $F$ match those in the
corresponding M-theory or string theory expansions. To shed light on the
structure of the 1-loop M-theory partition function on AdS$_{4}\times
S^{7}/\mathbb{Z}_{k}$ we use the expression for the 1-loop 4-graviton
scattering amplitude in the 11d supergravity. We also use the known information
about the transcendental coefficients of the leading curvature invariants in
the low-energy effective action of type II string theory. Matching of the
remaining rational factors in the coefficients requires a precise information
about currently unknown RR field strength terms in the corresponding
superinvariants.
|
Discrete Floquet time crystals (DFTC) are characterized by the spontaneous
breaking of the discrete time-translational invariance characteristic of
Floquet driven systems. In analogy with equilibrium critical points, also
time-crystalline phases display critical behaviour of different order, i.e.,
oscillations whose period is a multiple $p > 2$ of the Floquet driving period.
Here, we introduce a new, experimentally-accessible, order parameter which is
able to unambiguously detect crystalline phases regardless of the value of $p$
and, at the same time, is a useful tool for chaos diagnostic. This new paradigm
allows us to investigate the phase diagram of the long-range (LR) kicked Ising
model to an unprecedented depth, unveiling a rich landscape characterized by
self-similar fractal boundaries. Our theoretical picture describes the
emergence of DFTCs phase both as a function of the strength and period of the
Floquet drive, capturing the emergent $\mathbb{Z}_p$ symmetry in the
Floquet-Bloch waves.
|
The honeycomb Kitaev model describes a $Z_2$ spin liquid with topological
order and fractionalized excitations consisting of gapped $\pi$-fluxes and free
Majorana fermions. Competing interactions, even when not very strong, are known
to destabilize the Kitaev spin liquid. Magnetic fields are a convenient
parameter for tuning between different phases of the Kitaev systems, and have
even been investigated for potentially counteracting the effects of other
destabilizing interactions leading to a revival of the topological phase. Here
we review the progress in understanding the effects of magnetic fields on some
of the perturbed Kitaev systems, particularly on fractionalization and
topological order.
|
We demonstrate an injection-seeded thin-disk Yb:YAG laser at 1030 nm,
stabilized by the Pound-Drever-Hall (PDH) method. We modified the PDH scheme to
obtain an error signal free from Trojan locking points, which allowed robust
re-locking of the laser and reliable long-term operation. The single-frequency
pulses have 50 mJ energy (limited to avoid laser-induced damage) with a beam
quality of $\text{M}^2$ < 1.1 and an adjustable length of 55-110 ns. Heterodyne
measurements confirmed a spectral linewidth of 3.7 MHz. The short pulse
build-up time (850 ns) makes this laser suitable for laser spectroscopy of
muonic hydrogen, pursued by the CREMA collaboration.
|
High-speed railway stations are crucial junctions in high-speed railway
networks. Compared to operations on the tracks between stations, trains have
more routing possibilities within stations. As a result, track allocation at a
station is relatively complicated. In this study, we aim to solve the train
platforming problem for a busy high-speed railway station by considering
comprehensive track resources and interlocking configurations. A two-level
space-time network is constructed to capture infrastructure information at
various levels of detail from both macroscopic and microscopic perspectives.
Additionally, we propose a nonlinear programming model that minimizes a
weighted sum of total travel time and total deviation time for trains at the
station. We apply a Two-level Lagrangian Relaxation (2-L LR) to a linearized
version of the model and demonstrate how this induces a decomposable
train-specific path choice problem at the macroscopic level that is guided by
Lagrange multipliers associated with microscopic resource capacity violation.
As case studies, the proposed model and solution approach are applied to a
small virtual railway station and a high-speed railway hub station located on
the busiest high-speed railway line in China. Through a comparison of other
approaches that include Logic-based Benders Decomposition (LBBD), we highlight
the superiority of the proposed method; on realistic instances, the 2-L LR
method finds solution that are, on average, approximately 2% from optimality.
Finally, we test algorithm performance at the operational level and obtain
near-optimal solutions, with optimality gaps of approximately 1%, in a very
short time.
|
Despite extensive efforts, only two quasars have been found at $z>7$ to date
due to a combination of low spatial density and high contamination from more
ubiquitous Galactic cool dwarfs in quasar selection. This limits our current
knowledge of the super-massive black hole (SMBH) growth mechanism and
reionization history. In this letter, we report the discovery of a luminous
quasar at $z=7.021$, DELS J003836.10$-$152723.6 (hereafter J0038$-$1527),
selected using photometric data from DESI Legacy imaging Survey (DELS),
Pan-STARRS1 (PS1) imaging Survey, as well as Wide-field Infrared Survey Explore
($WISE$) mid-infrared all-sky survey. With an absolute magnitude of
$M_{1450}$=$-$27.1 and bolometric luminosity of $L_{\rm
Bol}$=5.6$\times$10$^{13}$ $L_\odot$, J0038$-$1527 is the most luminous quasar
known at $z>7$. Deep optical to near infrared spectroscopic observations
suggest that J0038-1527 hosts a 1.3 billion solar mass BH accreting at the
Eddington limit, with an Eddington ratio of 1.25$\pm$0.19. The CIV broad
emission line of J0038$-$1527 is blue-shifted by more than 3000 km s$^{-1}$ to
the systemic redshift. More detailed investigations of the high quality spectra
reveal three extremely high velocity CIV broad absorption lines (BALs) with
velocity from 0.08 to 0.14 times the speed of light and total balnicity index
of more than 5000 km s$^{-1}$, suggesting the presence of relativistic
outflows. J0038$-$1527 is the first quasar found at the epoch of reionization
(EoR) with such strong outflows and provides a unique laboratory to investigate
AGN feedback on the formation and growth of the most massive galaxies in the
early universe.
|
First non-trivial chiral corrections to the magnetic moments of triplet (T)
and sextet (S^(*)) heavy baryons are calculated using Heavy Hadron Chiral
Perturbation Theory. Since magnetic moments of the T-hadrons vanish in the
limit of infinite heavy quark mass (m_Q->infinity), these corrections occur at
order O(1/(m_Q \Lambda_\chi^2)) for T-baryons while for S^(*)-baryons they are
of order O(1/\Lambda_\chi^2). The renormalization of the chiral loops is
discussed and relations among the magnetic moments of different hadrons are
provided. Previous results for T-baryons are revised.
|
A growing number of papers are published in the area of superconducting
materials science. However, novel text and data mining (TDM) processes are
still needed to efficiently access and exploit this accumulated knowledge,
paving the way towards data-driven materials design. Herein, we present
SuperMat (Superconductor Materials), an annotated corpus of linked data derived
from scientific publications on superconductors, which comprises 142 articles,
16052 entities, and 1398 links that are characterised into six categories: the
names, classes, and properties of materials; links to their respective
superconducting critical temperature (Tc); and parametric conditions such as
applied pressure or measurement methods. The construction of SuperMat resulted
from a fruitful collaboration between computer scientists and material
scientists, and its high quality is ensured through validation by domain
experts. The quality of the annotation guidelines was ensured by satisfactory
Inter Annotator Agreement (IAA) between the annotators and the domain experts.
SuperMat includes the dataset, annotation guidelines, and annotation support
tools that use automatic suggestions to help minimise human errors.
|
We propose new proximal bundle algorithms for minimizing a nonsmooth convex
function. These algorithms are derived from the application of Nesterov fast
gradient methods for smooth convex minimization to the so-called Moreau-Yosida
regularization $F_\mu$ of $f$ w.r.t. some $\mu>0$. Since the exact values and
gradients of $F_\mu$ are difficult to evaluate, we use approximate proximal
points thanks to a bundle strategy to get implementable algorithms. One of
these algorithms appears as an implementable version of a special case of
inertial proximal algorithm. We give their complexity estimates in terms of the
original function values, and report some preliminary numerical results.
|
Bayesian methods offer a coherent and efficient framework for implementing
uncertainties into induction problems. In this article, we review how this
approach applies to the analysis of dark matter direct detection experiments.
In particular we discuss the exclusion limit of XENON100 and the debated hints
of detection under the hypothesis of a WIMP signal. Within parameter inference,
marginalizing consistently over uncertainties to extract robust posterior
probability distributions, we find that the claimed tension between XENON100
and the other experiments can be partially alleviated in isospin violating
scenario, while elastic scattering model appears to be compatible with the
frequentist statistical approach. We then move to model comparison, for which
Bayesian methods are particularly well suited. Firstly, we investigate the
annual modulation seen in CoGeNT data, finding that there is weak evidence for
a modulation. Modulation models due to other physics compare unfavorably with
the WIMP models, paying the price for their excessive complexity. Secondly, we
confront several coherent scattering models to determine the current best
physical scenario compatible with the experimental hints. We find that
exothermic and inelastic dark matter are moderatly disfavored against the
elastic scenario, while the isospin violating model has a similar evidence.
Lastly the Bayes' factor gives inconclusive evidence for an incompatibility
between the data sets of XENON100 and the hints of detection. The same question
assessed with goodness of fit would indicate a 2 sigma discrepancy. This
suggests that more data are therefore needed to settle this question.
|
This note defines a flag vector for $i$-graphs. The construction applies to
any finite combinatorial object that can be shelled. Two possible connections
to quantum topology are mentioned. Further details appear in the author's "On
quantum topology, hypergraphs and flag vectors", (preprint q-alg/9708001).
|
Kardar-Parisi-Zhang interface depinning with quenched noise is studied in an
ensemble that leads to self-organized criticality in the quenched
Edwards-Wilkinson (QEW) universality class and related sandpile models. An
interface is pinned at the boundaries, and a slowly increasing external drive
is added to compensate for the pinning. The ensuing interface behavior
describes the integrated toppling activity history of a QKPZ cellular
automaton. The avalanche picture consists of several phases depending on the
relative importance of the terms in the interface equation. The SOC state is
more complicated than in the QEW case and it is not related to the properties
of the bulk depinning transition.
|
In this paper, we mainly study a hydrodynamic system modeling the flow of
nematic liquid crystals. In three dimensions, we first establish local
well-posedness of the initial-boundary value problem of the system. Then, we
prove the existence of global strong solution to the system with small
initial-boundary condition.
|
The advantages of operating selected transmission lines at frequencies other
than the standard 50 or 60 Hz are numerous, encompassing increased power
transfer capacity and better utilization of existing infrastructure. While high
voltage DC (HVDC) is by far the most well-established example, there has been
an emerging interest low frequency AC (LFAC) transmission in applications
ranging from offshore wind to railway systems and mining. In this paper, we
investigate the use of LFAC as a transmission upgrade and propose models and
analysis methods to determine the optimal choice of frequency. The paper first
presents an optimal power flow model with frequency as a variable, assuming
modular multilevel converters for frequency conversion. Using this model, we
analyze LFAC as an embedded upgrade in a transmission system using existing
lines. We quantify the system-wide advantages from improved power flow control
and frequency reduction and find that an LFAC upgrade achieves similar and
sometimes better results compared with HVDC upgrades. Finally, we analyze the
factors which determine the optimal frequency for these upgraded transmission
lines, and we demonstrate the benefits of changing the frequency in response to
different system topologies and operating conditions.
|
Range-View(RV)-based 3D point cloud segmentation is widely adopted due to its
compact data form. However, RV-based methods fall short in providing robust
segmentation for the occluded points and suffer from distortion of projected
RGB images due to the sparse nature of 3D point clouds. To alleviate these
problems, we propose a new LiDAR and Camera Range-view-based 3D point cloud
semantic segmentation method (LaCRange). Specifically, a
distortion-compensating knowledge distillation (DCKD) strategy is designed to
remedy the adverse effect of RV projection of RGB images. Moreover, a
context-based feature fusion module is introduced for robust and preservative
sensor fusion. Finally, in order to address the limited resolution of RV and
its insufficiency of 3D topology, a new point refinement scheme is devised for
proper aggregation of features in 2D and augmentation of point features in 3D.
We evaluated the proposed method on large-scale autonomous driving datasets \ie
SemanticKITTI and nuScenes. In addition to being real-time, the proposed method
achieves state-of-the-art results on nuScenes benchmark
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We consider penalized extremum estimation of a high-dimensional, possibly
nonlinear model that is sparse in the sense that most of its parameters are
zero but some are not. We use the SCAD penalty function, which provides model
selection consistent and oracle efficient estimates under suitable conditions.
However, asymptotic approximations based on the oracle model can be inaccurate
with the sample sizes found in many applications. This paper gives conditions
under which the bootstrap, based on estimates obtained through SCAD
penalization with thresholding, provides asymptotic refinements of size \(O
\left( n^{- 2} \right)\) for the error in the rejection (coverage) probability
of a symmetric hypothesis test (confidence interval) and \(O \left( n^{- 1}
\right)\) for the error in the rejection (coverage) probability of a one-sided
or equal tailed test (confidence interval). The results of Monte Carlo
experiments show that the bootstrap can provide large reductions in errors in
rejection and coverage probabilities. The bootstrap is consistent, though it
does not necessarily provide asymptotic refinements, even if some parameters
are close but not equal to zero. Random-coefficients logit and probit models
and nonlinear moment models are examples of models to which the procedure
applies.
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It is the aim of this paper to summarize results about the construction of
amplitudes, which rigorously satisfy Mandelstam analyticity, crossing symmetry,
and (at least partly) the constraints imposed by elastic and inelastic
unitarity. The results are discussed under particular emphasis of a strong
increase of the absorptive part of the forward amplitude and the saturation of
the Froissart bound.
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The Dynamical Mean-Field theory (DMFT) approach to the Hubbard model requires
a method to solve the problem of a quantum impurity in a bath of
non-interacting electrons. Iterated Perturbation Theory (IPT) has proven its
effectiveness as a solver in many cases of interest. Based on general
principles and on comparisons with an essentially exact Continuous-Time Quantum
Monte Carlo (CTQMC) solver, here we show that the standard implementation of
IPT fails away from half-filling when the interaction strength is much larger
than the bandwidth. We propose a slight modification to the IPT algorithm that
replaces one of the equations by the requirement that double occupancy
calculated with IPT gives the correct value. We call this method IPT-$D$. We
recover the Fermi liquid ground state away from half-filling. The Fermi liquid
parameters, density of states, chemical potential, energy and specific heat on
the FCC lattice are calculated with both IPT-$D$ and CTQMC as benchmark
examples. We also calculated the resistivity and the optical conductivity
within IPT-$D$. Particle-hole asymmetry persists even at coupling twice the
bandwidth. Several algorithms that speed up the calculations are described in
appendices.
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S. Kov\'acs proposed a conjecture on rigidity results induced by ample
subsheaves of some exterior power of tangent bundles for projective manifolds.
We verify the conjecture in the case of second exterior products under a rank
condition. Besides, we prove a structure theorem satisfied by projective
manifolds whose third exterior power of tangent bundle is nef. Additionally, we
prove a weaker version of log Campana-Peternell conjecture for fourfolds.
Finally, we give the structure of manifolds with a regular foliation whose
exterior powers are strictly nef.
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We present a systematic exploration of dark energy and modified gravity
models containing a single scalar field non-minimally coupled to the metric.
Even though the parameter space is large, by exploiting an effective field
theory (EFT) formulation and by imposing simple physical constraints such as
stability conditions and (sub-)luminal propagation of perturbations, we arrive
at a number of generic predictions. (1) The linear growth rate of matter
density fluctuations is generally suppressed compared to $\Lambda$CDM at
intermediate redshifts ($0.5 \lesssim z \lesssim 1$), despite the introduction
of an attractive long-range scalar force. This is due to the fact that, in
self-accelerating models, the background gravitational coupling weakens at
intermediate redshifts, over-compensating the effect of the attractive scalar
force. (2) At higher redshifts, the opposite happens; we identify a period of
super-growth when the linear growth rate is larger than that predicted by
$\Lambda$CDM. (3) The gravitational slip parameter $\eta$ - the ratio of the
space part of the metric perturbation to the time part - is bounded from above.
For Brans-Dicke-type theories $\eta$ is at most unity. For more general
theories, $\eta$ can exceed unity at intermediate redshifts, but not more than
about $1.5$ if, at the same time, the linear growth rate is to be compatible
with current observational constraints. We caution against phenomenological
parametrization of data that do not correspond to predictions from viable
physical theories. We advocate the EFT approach as a way to constrain new
physics from future large-scale-structure data.
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A significant amount of hazardous waste generated from health sectors and
industrial processes has posed a major threat to human health by causing
environmental issues and contamination of air, soil, and water resources. This
paper presents a multi-objective mixed-integer nonlinear programming (MINLP)
formulation for a sustainable hazardous waste location-routing problem. The
location of the facilities and routing decisions for transporting hazardous
waste and the waste residue is considered to design a suitable waste collection
system. The presented model simultaneously minimizes the total costs of the
waste management system, total risks from transportation and facilities, along
with CO2 emissions. A real-world case study is presented to illustrate the
applicability of the proposed model. To illustrate the significance of
sustainability, the results of the original model are compared with the results
of the model without considering sustainability. It indicates that, under the
condition when sustainability is not taken into account, total cost,
transportation, and site risk along with CO2 emission increased, which in turn
demonstrated the importance of sustainability. Furthermore, the managerial
insights gained from the optimal results would enable the managers to make
better decisions in the hazardous waste management system.
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We explore the convergence rate of the Ka\v{c}anov iteration scheme for
different models of shear-thinning fluids, including Carreau and power-law type
explicit quasi-Newtonian constitutive laws. It is shown that the energy
difference contracts along the sequence generated by the iteration. In
addition, an a posteriori computable contraction factor is proposed, which
improves, on finite-dimensional Galerkin spaces, previously derived bounds on
the contraction factor in the context of the power-law model. Significantly,
this factor is shown to be independent of the choice of the cut-off parameters
whose use was proposed in the literature for the Ka\v{c}anov iteration applied
to the power-law model. Our analytical findings are confirmed by a series of
numerical experiments.
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We study the conversion of fast magneto-acoustic waves to Alfven waves by
means of 2.5D numerical simulations in a sunspot-like magnetic configuration. A
fast, essentially acoustic, wave of a given frequency and wave number is
generated below the surface and propagates upward though the Alfven/acoustic
equipartition layer where it splits into upgoing slow (acoustic) and fast
(magnetic) waves. The fast wave quickly reflects off the steep Alfven speed
gradient, but around and above this reflection height it partially converts to
Alfven waves, depending on the local relative inclinations of the background
magnetic field and the wavevector. To measure the efficiency of this conversion
to Alfven waves we calculate acoustic and magnetic energy fluxes. The
particular amplitude and phase relations between the magnetic field and
velocity oscillations help us to demonstrate that the waves produced are indeed
Alfven waves. We find that the conversion to Alfven waves is particularly
important for strongly inclined fields like those existing in sunspot
penumbrae. Equally important is the magnetic field orientation with respect to
the vertical plane of wave propagation, which we refer to as "field azimuth".
For field azimuth less than 90 degrees the generated Alfven waves continue
upwards, but above 90 degrees downgoing Alfven waves are preferentially
produced. This yields negative Alfven energy flux for azimuths between 90 and
180 degrees. Alfven energy fluxes may be comparable to or exceed acoustic
fluxes, depending upon geometry, though computational exigencies limit their
magnitude in our simulations.
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Magnetic energy is one the main agents powering our society: generating
energy in power plants, keeping information in magnetic memories, moving our
devices with motors. All of these applications require a certain spatial
distribution of magnetic energy, for example concentrating it in a transformer
core or in a magnetic sensor. We introduce in this work a way to collect
magnetic energy and distribute it in space with unprecedented efficiency and
flexibility, allowing very large concentration of magnetic energy in a free
space region, an enhanced magnetic coupling between two magnetic sources, and
the transfer of magnetic energy from a source to a given distant point
separated by empty space. All these features are achieved with a single device,
a magnetic shell designed by transformation optics.
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In this paper we employ three recent analytical approaches to investigate the
possible classes of traveling wave solutions of some members of a family of
so-called short-pulse equations (SPE). A recent, novel application of
phase-plane analysis is first employed to show the existence of breaking kink
wave solutions in certain parameter regimes. Secondly, smooth traveling waves
are derived using a recent technique to derive convergent multi-infinite series
solutions for the homoclinic (heteroclinic) orbits of the traveling-wave
equations for the SPE equation, as well as for its generalized version with
arbitrary coefficients. These correspond to pulse (kink or shock) solutions
respectively of the original PDEs.
Unlike the majority of unaccelerated convergent series, high accuracy is
attained with relatively few terms. And finally, variational methods are
employed to generate families of both regular and embedded solitary wave
solutions for the SPE PDE. The technique for obtaining the embedded solitons
incorporates several recent generalizations of the usual variational technique
and it is thus topical in itself. One unusual feature of the solitary waves
derived here is that we are able to obtain them in analytical form (within the
assumed ansatz for the trial functions). Thus, a direct error analysis is
performed, showing the accuracy of the resulting solitary waves. Given the
importance of solitary wave solutions in wave dynamics and information
propagation in nonlinear PDEs, as well as the fact that not much is known about
solutions of the family of generalized SPE equations considered here, the
results obtained are both new and timely.
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Humans demonstrate a variety of interesting behavioral characteristics when
performing tasks, such as selecting between seemingly equivalent optimal
actions, performing recovery actions when deviating from the optimal
trajectory, or moderating actions in response to sensed risks. However,
imitation learning, which attempts to teach robots to perform these same tasks
from observations of human demonstrations, often fails to capture such
behavior. Specifically, commonly used learning algorithms embody inherent
contradictions between the learning assumptions (e.g., single optimal action)
and actual human behavior (e.g., multiple optimal actions), thereby limiting
robot generalizability, applicability, and demonstration feasibility. To
address this, this paper proposes designing imitation learning algorithms with
a focus on utilizing human behavioral characteristics, thereby embodying
principles for capturing and exploiting actual demonstrator behavioral
characteristics. This paper presents the first imitation learning framework,
Bayesian Disturbance Injection (BDI), that typifies human behavioral
characteristics by incorporating model flexibility, robustification, and risk
sensitivity. Bayesian inference is used to learn flexible non-parametric
multi-action policies, while simultaneously robustifying policies by injecting
risk-sensitive disturbances to induce human recovery action and ensuring
demonstration feasibility. Our method is evaluated through risk-sensitive
simulations and real-robot experiments (e.g., table-sweep task, shaft-reach
task and shaft-insertion task) using the UR5e 6-DOF robotic arm, to demonstrate
the improved characterisation of behavior. Results show significant improvement
in task performance, through improved flexibility, robustness as well as
demonstration feasibility.
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[abridged] Protoplanetary disks with AU-scale inner clearings, often referred
to as transitional disks, provide a unique sample for understanding disk
dissipation mechanisms and possible connections to planet formation.
Observations of young stellar clusters with the Spitzer Space Telescope have
amassed mid-infrared spectral energy distributions for thousands of star-disk
systems from which transition disks can be identified. From a sample of 8
relatively nearby young regions (d <= 400 pc), we have identified about 20 such
objects, which we term "classical" transition disks, spanning a wide range of
stellar age and mass. We also identified two additional categories representing
more ambiguous cases: "warm excess" objects with transition-like spectral
energy distributions but moderate excess at 5.8 microns, and "weak excess"
objects with smaller 24 micron excess that may be optically thin or exhibit
advanced dust grain growth and settling. From existing Halpha emission
measurements, we find evidence for different accretion activity among the three
categories, with a majority of the classical and warm excess transition objects
still accreting gas through their inner holes and onto the central stars, while
a smaller fraction of the weak transition objects are accreting at detectable
rates. We find a possible age dependence to the frequency of classical
transition objects, with fractions relative to the total population of disks in
a given region of a few percent at 1-2 Myr rising to 10-20% at 3-10 Myr. The
trend is even stronger if the weak and warm excess objects are included.
Classical transition disks appear to be less common, and weak transition disks
more common, around lower-mass stars (M <= 0.3 Msun).
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This paper addresses some questions which have arisen from the use of the
S\'ersic r^{1/n} law in modelling the luminosity profiles of early type
galaxies. The first issue deals with the trend between the half-light radius
and the structural parameter n. We show that the correlation between these two
parameters is not only real, but is a natural consequence from the previous
relations found to exist between the model-independent parameters: total
luminosity, effective radius and effective surface brightness. We also define a
new galaxy concentration index which is largely independent of the image
exposure depth, and monotonically related with n. The second question concerns
the curious coincidence between the form of the Fundamental Plane and the
coupling between <I>_e and r_e when modelling a light profile. We explain,
through a mathematical analysis of the S\'ersic law, why the quantity
r_e<I>_e^{0.7} appears almost constant for an individual galaxy, regardless of
the value of n (over a large range) adopted in the fit to the light profile.
Consequently, Fundamental Planes of the form r_e<I>_e^{0.7} propto sigma_0^x
(for any x, and where sigma_0 is the central galaxy velocity dispersion) are
insensitive to galaxy structure. Finally, we address the problematic issue of
the use of model-dependent galaxy light profile parameters versus
model-independent quantities for the half-light radii, mean surface brightness
and total galaxy magnitude. The former implicitly assume that the light profile
model can be extrapolated to infinity, while the latter quantities, in general,
are derived from a signal-to-noise truncated profile. We quantify
(mathematically) how these parameters change as one reduces the outer radius of
an r^{1/n} profile, and reveal how these can vary substantially when n>4.
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From the spread of pollutants in the atmosphere to the transmission of
nutrients across cell membranes, anomalous diffusion processes are ubiquitous
in natural systems. The ability to understand and control the mechanisms
guiding such processes across various scales has important application to
research in materials science, finance, medicine, and energetics. Here we
present a numerical study of anomalous diffusion of light through a
semi-crystalline polymer structure where transport is guided by random disorder
and nonlocal interactions. The numerical technique examines diffusion
properties in one-dimensional (1D) space via the spectrum of an Anderson-type
Hamiltonian with a discrete fractional Laplacian operator (-{\Delta})^s, 0<s<2
and a random distribution of disorder. The results show enhanced transport for
s<1 (super-diffusion) and enhanced localization for s>1 (sub-diffusion) for
most examined cases. An important finding of the present study is that
transport can be enhanced at key spatial scales in the sub-diffusive case,
where all states are normally expected to be localized for a (1D) disordered
system.
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The dynamics of two interacting quantum particles on a weakly disordered
chain is investigated. Spatial quantum interference between them is
characterized through the statistics of two-particle transition amplitudes,
related to Hanbury Brown-Twiss correlations in optics. The fluctuation profile
of the signal can discern whether the interacting parties are behaving like
identical bosons, fermions, or distinguishable particles. An analog fully
developed speckle regime displaying Rayleigh statistics is achieved for
interacting bosons. Deviations toward long-tailed distributions echo quantum
correlations akin to non-interacting identical particles. In the limit of
strong interaction, two-particle bound states obey generalized Rician
distributions.
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An effective theory to treat the dense nuclear medium by the perturbative
expansion method is proposed as a natural extension of the Heavy Baryon Chiral
Perturbation Theory (HBChPT). Treating the Fermi momentum scale as a separate
scale of the system, we get an improved convergence and the conceptually clear
interpretation. We compute the pion decay constant and the pion velocity in the
nuclear medium, and find their characters different from what the usual HBChPT
predicts. We also obtain the Debye screening scale at the normal nuclear matter
density, and the damping scale of the pion wave. Those results indicate that
the present theory, albeit its improvement over the HBChPT, has the limitation
yet to go over to the medium of about 1.3 times of normal matter density due to
the absence of the intrinsic density dependence of the coupling constants. We
discuss how we overcome this limitation in terms of the renormalization method.
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We investigate experimentally a Bose Einstein condensate placed in a 1D
optical lattice whose phase is modulated at a frequency large compared to all
characteristic frequencies. As a result, the depth of the periodic potential is
renormalized by a Bessel function which only depends on the amplitude of
modulation, a prediction that we have checked quantitatively using a careful
calibration scheme. This renormalization provides an interesting tool to
engineer in time optical lattices. For instance, we have used it to perform
simultaneously a sudden $\pi$-phase shift (without phase residual errors)
combined with a change of lattice depth, and to study the subsequent
out-of-equilibrium dynamics.
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We consider the Schr\"odinger operator on the real line with an even quartic
potential. Our main result is a product formula of the type $\psi_k(x)\psi_k(y)
= \int_{\mathbb{R}} \psi_k(z)\mathcal{K}(x,y,z)dz$ for its eigenfunctions
$\psi_k$. The kernel function $\mathcal{K}$ is given explicitly in terms of the
Airy function $\mathrm{Ai}(x)$, and is positive for appropriate parameter
values. As an application, we obtain a particular asymptotic expansion of the
eigenfunctions $\psi_k$.
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We design two Recoverable Mutual Exclusion (RME) locks for the system-wide
crash model. Our first algorithm requires only $O(1)$ space per process, and
achieves $O(1)$ worst-case RMR complexity in the CC model. Our second algorithm
enhances the first algorithm to achieve (the same) $O(1)$ space per process and
$O(1)$ worst-case RMR complexity in both the CC and DSM models. Furthermore,
both algorithms allow dynamically created threads of arbitrary names to join
the protocol and access the locks. To our knowledge, these are the only RME
locks to achieve worst-case $O(1)$ RMR complexity assuming nothing more than
standard hardware support. In light of Chan and Woelfel's $\Omega(\log n /
\log\log n)$ worst-case RMR lower bound for RME in the individual crash model,
our results show a separation between the system-wide crash and individual
crash models in worst-case RMR complexity in both the CC and DSM models.
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A new technique for estimation of magnetic interaction effects of initial
magnetization curves has been proposed. It deals with remanence, and initial
irreversible magnetization, curves. The method is applied for single-phase
polycrystalline Ni0.85-xCu0.15ZnxFe2O4, (x = 0, 0.2, 0.4 and 0.6), which were
synthesized by a standard ceramic technology. A study of the initial reversible
and irreversible magnetization processes in ferrite materials was carried out.
The field dependence of the irreversible, and reversible, magnetizations was
determined by magnetic losses of minor hysteresis loops obtained from different
points of an initial magnetization curve. The influence of Zn-substitutions in
Ni-Cu ferrites over irreversible magnetization processes and interactions in
magnetic systems has been analyzed.
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Thermoelectric materials traditionally incorporate heavy metals to achieve
low lattice thermal conductivity. However, elements such as Te, Bi, and Pb are
costly and pose environmental hazards. In this study, we introduce a novel
design strategy for thermoelectric materials, focusing on room-temperature,
light-element, and high-ZT materials such as coronene-cyclobutadienoid graphene
nanoribbons (cor4GNRs). This material demonstrates a ZT value exceeding 2.1,
attributed to its exceptionally low phonon thermal conductivity resulting from
its unique edge structure. Importantly, its electrical conductance and Seebeck
coefficient remain relatively high and nearly unaffected by the edge structure.
This distinct behavior in phonon and electronic transport properties leads to a
remarkably high ZT value. Additionally, we discover that applying strain can
significantly reduce phonon thermal conductivity, potentially increasing the ZT
value to over 3.0. Our findings provide innovative insights for the design and
application of advanced thermoelectric materials.
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We consider the category of comodules over a smash coproduct coalgebra
$C\smashco H$. We show that there is a Grothendieck spectral sequence
connecting the derived functors of the Hom functors coming from $C\smashco
H$-colinear, $H$-colinear and rational $C$-colinear morphisms. We give several
applications and connect our results to existing spectral sequences in the
literature.
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Recent {\it Hubble Space Telescope} photometry in the nearby elliptical
galaxy NGC 5128 shows that its halo field star population is dominated by
moderately metal-rich stars, with a peak at [m/H] $\simeq$ -0.4 and with a very
small fraction of metal-poor ([m/H] $<$ -1.0) stars. In order to investigate
the physical processes which may have produced this metallicity distribution
function (MDF), we consider a model in which NGC 5128 is formed by merging of
two major spiral galaxies. We find that the halo of an elliptical formed this
way is predominantly populated by moderately metal-rich stars with [m/H] $\sim$
-0.4 which were initially within the outer parts of the two merging discs and
were tidally stripped during the merger. To match the NGC 5128 data, we find
that the progenitor spiral discs must have rather steep metallicity gradients
similar to the one defined by the Milky Way open clusters, as well as sparse
metal-poor haloes (5% or less of the disc mass). Very few stars from the
central bulges of the spiral galaxies end up in the halo, so the results are
not sensitive to the relative sizes (bulge-to-disc ratios) or metallicities of
the initial bulges. Finally, we discuss the effects on the globular cluster
system (GCS). The emergent elliptical will end up with metal-poor halo clusters
from the original spiral haloes, but with moderately metal-rich halo stars from
the progenitor discs, thus creating a mean offset between the MDFs of the halo
stars and the GCS.
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Majorana-based quantum gates are not complete for performing universal
topological quantum computation while Fibonacci-based gates are difficult to be
realized electronically and hardly coincide with the conventional quantum
circuit models. In Ref. \cite{hukane}, it has been shown that a strongly
correlated Majorana edge mode in a chiral topological superconductor can be
decomposed into a Fibobacci anyon $\tau$ and a thermal operator anyon
$\varepsilon$ in the tricritical Ising model. The deconfinement of $\tau$ and
$\varepsilon$ via the interaction between the fermion modes yields the anyon
{collisions} and gives the braiding of either $\tau$ or $\varepsilon$. With
these braidings, the complete members {of} a set of universal gates, the Pauli
gates, the Hadamard gate and extra phase gates for 1-qubit as well as
controlled-not gate for 2-qubits, are topologically assembled. Encoding quantum
information and reading out the computation results can be carried out through
electric signals. With the sparse-dense mixed encodings, we set up the quantum
circuit {where the controlled-not gate turns out { to be} a probabilistic gate}
and design the corresponding devices with thin films of the chiral topological
superconductor. As an example of the universal topological quantum computing,
we show the application to Shor's integer factorization algorithm.
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Linear optics quantum logic operations enabled the observation of a
four-photon cluster state. We prove genuine four-partite entanglement and study
its persistency, demonstrating remarkable differences to the usual GHZ state.
Efficient analysis tools are introduced in the experiment, which will be of
great importance in further studies on multi-particle entangled states.
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