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We take advantage of the high sensitivity of the IBIS/ISGRI telescope and the
improvements in the data analysis software to investigate the nature of the
still poorly known X-ray source AX J1910.7+0917, and search for close-by
previously undetected objects. We analyze all publicly available INTEGRAL data
of AX J1910.7+0917, together with a number of archival observations that were
carried out in the direction of the source with Chandra, XMM-Newton, and ASCA.
In the IBIS/ISGRI field-of-view around AX J1910.7+0917, we discovered three new
sources: IGR J19173+0747, IGR J19294+1327 and IGR J19149+1036; the latter is
positionally coincident with the Einstein source 2E 1912.5+1031. For the first
two sources, we also report the results of follow-up observations carried out
with Swift/XRT. AX J1910.7+0917 features a clear variability in the X-rays. Its
spectrum can be well described with an absorbed (N_H~6x10^(22) cm^(-2))
power-law ({\Gamma}~1.5) model plus an iron line at ~6.4 keV. We also obtained
a refined position and report on possible infrared counterparts. The present
data do not allow for a unique classification of the sources. Based on the
property of its X-ray emission and the analysis of a likely infrared
counterpart, we investigate different possibilities for the nature of AX
J1910.7+0917.
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We consider the problem of estimating a network's eigenvector centrality only
from data on the nodes, with no information about network topology. Leveraging
the versatility of graph filters to model network processes, data supported on
the nodes is modeled as a graph signal obtained via the output of a graph
filter applied to white noise. We seek to simplify the downstream task of
centrality ranking by bypassing network topology inference methods and,
instead, inferring the centrality structure of the graph directly from the
graph signals. To this end, we propose two simple algorithms for ranking a set
of nodes connected by an unobserved set of edges. We derive asymptotic and
non-asymptotic guarantees for these algorithms, revealing key features that
determine the complexity of the task at hand. Finally, we illustrate the
behavior of the proposed algorithms on synthetic and real-world datasets.
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We consider L-infinity quasi-isomorphisms for Hochschild cochains whose
structure maps admit "graphical expansion". We introduce the notion of stable
formality quasi-isomorphism which formalizes such an L-infinity
quasi-isomorphism. We define a homotopy equivalence on the set of stable
formality quasi-isomorphisms and prove that the set of homotopy classes of
stable formality quasi-isomorphisms form a torsor for the group corresponding
to the zeroth cohomology of the full (directed) graph complex. This result may
be interpreted as a complete description of homotopy classes of formality
quasi-isomorphisms for Hochschild cochains in the "stable setting".
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We present a detailed analysis of high resolution near-infrared imaging and
spectroscopy of the potential star cluster IRS13E very close to the massive
black hole in the Galactic Center. We detect 19 objects in IRS13E from Ks-band
images, 15 of which are also detected reliably in H-band. We derive consistent
proper motions for these objects from the two bands. Most objects share a
similar westward proper motion. We characterize the objects using spectroscopy
(1.45 to 2.45 micrometer) and (narrow-band) imaging from H- (1.66 mircrometer)
to L'-band (3.80 micrometer). Nine of the objects detected in both Ks- and
H-band are very red, and we find that they are all consistent with being warm
dust clumps. The dust emission may be caused by the colliding winds of the two
Wolf-Rayet stars in the cluster. Three of the six detected stars do not share
the motion or spectral properties of the three bright stars. This leaves only
the three bright, early-type stars as potential cluster members. It is unlikely
that these stars are a chance configuration. Assuming the presence of an IMBH,
a mass of about 14000 solar masses follows from the velocities and positions of
these three stars. However, our acceleration limits make such an IMBH nearly as
unlikely as a chance occurrence of such a star association. Furthermore, there
is no variable X-ray source in IRS13E despite the high density of dust and gas.
Therefore, we conclude that is unlikely that IRS13E hosts a black hole massive
enough to bind the three stars.
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The low cost and high resolution gas-based Multi-gap Resistive Plate Chamber
(MRPC) opens a new possibility to find an efficient alternative detector for
Time of Flight (TOF) based Positron Emission Tomography, where the sensitivity
of the system depends largely on the time resolution of the detector. Suitable
converters can be used to increase the efficiency of detection of photons from
annihilation. In this work, we perform a detailed GEANT4 simulation to optimize
the converter thickness thereby improving the efficiency of photon conversion.
Also we have developed a Monte Carlo based simulation of MRPC response thereby
obtaining the intrinsic time resolution of the detector, making it possible to
simulate the final response of MRPC-based systems for PET imaging. The result
of the cosmic ray test of a four-gap Bakelite-based MRPC operating in streamer
mode is discussed.
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The motivation of this work is the detection of cerebrovascular accidents by
microwave tomographic imaging. This requires the solution of an inverse problem
relying on a minimization algorithm (for example, gradient-based), where
successive iterations consist in repeated solutions of a direct problem. The
reconstruction algorithm is extremely computationally intensive and makes use
of efficient parallel algorithms and high-performance computing. The
feasibility of this type of imaging is conditioned on one hand by an accurate
reconstruction of the material properties of the propagation medium and on the
other hand by a considerable reduction in simulation time. Fulfilling these two
requirements will enable a very rapid and accurate diagnosis. From the
mathematical and numerical point of view, this means solving Maxwell's
equations in time-harmonic regime by appropriate domain decomposition methods,
which are naturally adapted to parallel architectures.
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Modeling of textures in natural images is an important task to make a
microscopic model of natural images. Portilla and Simoncelli proposed a
generative texture model, which is based on the mechanism of visual systems in
brains, with a set of texture features and a feature matching. On the other
hand, the texture features, used in Portillas' model, have redundancy between
its components came from typical natural textures. In this paper, we propose a
contracted texture model which provides a dimension reduction for the
Portillas' feature. This model is based on a hierarchical principal components
analysis using known group structure of the feature. In the experiment, we
reveal effective dimensions to describe texture is fewer than the original
description. Moreover, we also demonstrate how well the textures can be
synthesized from the contracted texture representations.
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The theory of minimal K-types for p-adic reductive groups was developed in
part to classify irreducible admissible representations with wild ramification.
An important observation was that minimal K-types associated to such
representations correspond to fundamental strata. These latter objects are
triples (x, r, beta), where x is a point in the Bruhat-Tits building of the
reductive group G, r is a nonnegative real number, and beta is a semistable
functional on the degree r associated graded piece of the Moy-Prasad filtration
corresponding to x.
Recent work on the wild ramification case of the geometric Langlands
conjectures suggests that fundamental strata also play a role in the geometric
setting. In this paper, we develop a theory of minimal K-types for formal flat
G-bundles. We show that any formal flat G-bundle contains a fundamental
stratum; moreover, all such strata have the same rational depth. We thus obtain
a new invariant of a flat G-bundle called the slope, generalizing the classical
definition for flat connections. The slope can also be realized as the minimum
depth of a stratum contained in the flat G-bundle, and in the case of positive
slope, all such minimal depth strata are fundamental. Finally, we show that a
flat G-bundle is irregular singular if and only if it has positive slope.
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We establish global existence in 3+1 dimensions of small-amplitude solutions
of quasilinear Dirichlet-wave equations satisfying the null condition outside
of star-shapped obstacles.
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Dielectric Assist Accelerating (DAA) structures based on ultralow-loss
ceramic are being studied as an alternative to conventional disk-loaded copper
cavities. This accelerating structure consists of dielectric disks with irises
arranged periodically in metallic structures working under the TM$_{02}$-$\pi$
mode. In this paper, the numerical design of an S-band DAA structure for low
beta particles, such as protons or carbon ions used for Hadrontherapy
treatments, is shown. Four dielectric materials with different permittivity and
loss tangent are studied as well as different particle velocities. Through
optimization, a design that concentrates most of the RF power in the vacuum
space near the beam axis is obtained, leading to a significant reduction of
power loss on the metallic walls. This allows to fabricate cavities with an
extremely high quality factor, over 100 000, and shunt impedance over 300
M$\Omega$/m at room temperature. During the numerical study, the design
optimization has been improved by adjusting some of the cell parameters in
order to both increase the shunt impedance and reduce the peak electric field
in certain locations of the cavity, which can lead to instabilities in its
normal functioning.
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Recent advances in image generation gave rise to powerful tools for semantic
image editing. However, existing approaches can either operate on a single
image or require an abundance of additional information. They are not capable
of handling the complete set of editing operations, that is addition,
manipulation or removal of semantic concepts. To address these limitations, we
propose SESAME, a novel generator-discriminator pair for Semantic Editing of
Scenes by Adding, Manipulating or Erasing objects. In our setup, the user
provides the semantic labels of the areas to be edited and the generator
synthesizes the corresponding pixels. In contrast to previous methods that
employ a discriminator that trivially concatenates semantics and image as an
input, the SESAME discriminator is composed of two input streams that
independently process the image and its semantics, using the latter to
manipulate the results of the former. We evaluate our model on a diverse set of
datasets and report state-of-the-art performance on two tasks: (a) image
manipulation and (b) image generation conditioned on semantic labels.
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We present flavour-symmetric results for the couplings of quark-antiquark
systems to meson-meson channels in the harmonic-oscillator expansion. We
tabulate their values for all possible open and closed decay channels of
pseudo-scalar, vector and scalar mesons. We compare the predictions of a model
that employs these flavour-symmetric couplings, both with the results of a
model which uses explicitly flavour-dependent couplings, and with experiment.
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One of the distinguishing aspects of human language is its compositionality,
which allows us to describe complex environments with limited vocabulary.
Previously, it has been shown that neural network agents can learn to
communicate in a highly structured, possibly compositional language based on
disentangled input (e.g. hand- engineered features). Humans, however, do not
learn to communicate based on well-summarized features. In this work, we train
neural agents to simultaneously develop visual perception from raw image
pixels, and learn to communicate with a sequence of discrete symbols. The
agents play an image description game where the image contains factors such as
colors and shapes. We train the agents using the obverter technique where an
agent introspects to generate messages that maximize its own understanding.
Through qualitative analysis, visualization and a zero-shot test, we show that
the agents can develop, out of raw image pixels, a language with compositional
properties, given a proper pressure from the environment.
|
The nonlinear magnetic induction equation with Hall effect can be used to
model magnetic fields, e.g. in astrophysical plasma environments. In order to
give reliable results, numerical simulations should be carried out using
effective and efficient schemes. Thus, high-order stable schemes are
investigated here.
Following the approach provided recently by Nordstr\"om (J Sci Comput 71.1,
pp. 365--385, 2017), an energy analysis for both the linear and the nonlinear
induction equation including boundary conditions is performed at first. Novel
outflow boundary conditions for the Hall induction equation are proposed,
resulting in an energy estimate. Based on an energy analysis of the initial
boundary value problem at the continuous level, semidiscretisations using
summation by parts (SBP) operators and simultaneous approximation terms are
created. Mimicking estimates at the continuous level, several energy stable
schemes are obtained in this way and compared in numerical experiments.
Moreover, stabilisation techniques correcting errors in the numerical
divergence of the magnetic field via projection methods are studied from an
energetic point of view in the SBP framework. In particular, the treatment of
boundaries is investigated and a new approach with some improved properties is
proposed.
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In dimensions congruent to 1 modulo 4, we prove that the cotangent bundle of
an exotic sphere which does not bound a parallelisable manifold is not
symplectomorphic to the cotangent bundle of the standard sphere. More
precisely, we prove that such an exotic sphere cannot embed as a Lagrangian in
the cotangent bundle of the standard sphere. The main ingredients of the
construction are (1) the fact that the graph of the Hopf fibration embeds the
standard sphere, and hence any Lagrangian which embeds in its cotangent bundle,
as a displaceable Lagrangian in the product a symplectic vector space of the
appropriate dimension with its complex projective space, and (2) a moduli space
of solutions to a perturbed Cauchy-Riemann equation introduced by Gromov.
|
We study the charmonium suppression in different evolutions of quark gluon
plasma (QGP) based on the transport model. In the colliding energies of Large
Hadron Collider, charmonium final yields are dominated by the recombination of
charm and anti-charm quarks in the deconfined phase. Heavy quark diffusions
depend less on the shear viscosity of the bulk medium, which makes the J/psi
nuclear modification factor in the entire pT bin shows weak dependence on the
shear viscosity of QGP. However, charmonium with high transverse momentum pT,
can only be produced in the early stage of nuclear collisions, and is sensitive
to the initial energy density (or temperature) of QGP, and can be a probe of
the initial dynamical evolutions of quark gluon plasma.
|
We introduce the notion of (Ramsey) action of a tree on a (filtered)
semigroup. We then prove in this setting a general result providing a common
generalization of the infinitary Gowers Ramsey theorem for multiple tetris
operations, the infinitary Hales--Jewett theorems (for both located and
nonlocated words), and the Farah--Hindman--McLeod Ramsey theorem for layered
actions on partial semigroups. We also establish a polynomial version of our
main result, recovering the polynomial Milliken--Taylor theorem of
Bergelson--Hindman--Williams as a particular case. We present applications of
our Ramsey-theoretic results to the structure of delta sets in amenable groups.
|
The paper discusses ISW estimates through EMU-ASKAP survey.
The main ideas this paper covers include:
1- Discussion on source distribution, confusion, position accuracy and
shotnoise (with discussion focusing on SN ratios).
2- Selection of maximum redshift and maximum 'l' ranges in relation with SN
ratios.
Note: Complete abstract is available in the document.
|
In this work we consider general fermion systems in two spatial dimensions,
both with and without charge conservation symmetry, which realize a nontrivial
fermionic topological order with only Abelian anyons. We address the question
of precisely how these quantum phases differ from their bosonic counterparts,
both in terms of their edge physics and in the way one would identify them in
numerics. As in previous works, we answer these questions by studying the
theory obtained after gauging the global fermion parity symmetry, which turns
out to have a special and simple structure. Using this structure, a minimal
scheme is outlined for how to numerically identify a general Abelian fermionic
topological order, without making use of fermion number conservation. Along the
way, some subtleties of the momentum polarization technique are discussed.
Regarding the edge physics, it is shown that the gauged theory can have a
(bosonic) gapped boundary to the vacuum if and only if the ungauged fermion
theory has a gapped boundary as well.
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A new and independent determination of the Gamow-Teller branching ratio in
the beta-decay of 21Na is reported. The value obtained of 5.13 +- 0.43 % is in
agreement with the currently adopted value and the most recent measurement. In
contrast to previous experiments, the present method was based on the counting
of the parent 21Na ions and the resulting 351 keV gamma-rays without coincident
beta-particle detection.
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Let $G$ be a real linear reductive group and let $H$ be a unimodular, locally
algebraic subgroup. Let $\operatorname{supp} L^2(G/H)$ be the set of
irreducible unitary representations of $G$ contributing to the decomposition of
$L^2(G/H)$, namely the support of the Plancherel measure. In this paper, we
will relate $\operatorname{supp} L^2(G/H)$ with the image of moment map from
the cotangent bundle $T^*(G/H)\to \mathfrak{g}^*$. For the homogeneous space
$X=G/H$, we attach a complex Levi subgroup $L_X$ of the complexification of $G$
and we show that in some sense "most" of representations in
$\operatorname{supp} L^2(G/H)$ are obtained as quantizations of coadjoint
orbits $\mathcal{O}$ such that $\mathcal{O}\simeq G/L$ and that the
complexification of $L$ is conjugate to $L_X$. Moreover, the union of such
coadjoint orbits $\mathcal{O}$ coincides asymptotically with the moment map
image. As a corollary, we show that $L^2(G/H)$ has a discrete series if the
moment map image contains a nonempty subset of elliptic elements.
|
We present a new approach to component separation in multifrequency CMB
experiments by formulating the problem as that of partitioning the sky into
pixel clusters such that within each pixel cluster the foregrounds have similar
spectrum, using only the information available in the data. Only spectral
information is used for partitioning, allowing spatially far away pixels to
belong to the same cluster if their foreground properties are close. We then
apply a modified internal linear combination method to each pixel cluster.
Since the foregrounds have similar spectrum within each cluster, the number of
components required to describe the foregrounds is smaller compared to all data
taken together and simple pixel based ILC algorithm works extremely well. We
test our algorithm in the full focal plane simulations provided by the Planck
collaboration. We apply our algorithm to the Planck full mission data and
compare our CMB maps with the CMB maps released by the Planck collaboration. We
show that our CMB maps are clean and unbiased on a larger fraction of the sky,
especially at the low Galactic latitudes, compared to publicly available maps
released by the Planck collaboration. This is important for constraining beyond
the simplest $\Lambda$CDM cosmological models and study of anomalies. Our
cleaned CMB maps are made publicly available for use by the cosmology
community.
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Let S be a planar point set. Krznaric and Levcopoulos proved that given the
Delaunay triangulation DT(S) for S, one can find the greedy triangulation GT(S)
in linear time. We provide a (partial) converse of this result: given GT(S), it
is possible to compute DT(S) in linear expected time. Thus, these structures
are basically equivalent.
To obtain our result, we generalize another algorithm by Krznaric and
Levcopoulos to find a hierarchical clustering for S in linear time, once DT(S)
is known. We show that their algorithm remains (almost) correct for any
triangulation of bounded dilation, i.e., any triangulation in which the
shortest path distance between any two points approximates their Euclidean
distance. In general, however, the resulting running time may be superlinear.
Nonetheless, we can show that the properties of the greedy triangulation
suffice to guarantee a linear time bound.
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We consider the growth rate of the Mahler measure in discrete dynamical
systems with the Laurent property, and in cluster algebras, and compare this
with other measures of growth. In particular, we formulate the conjecture that
the growth rate of the logarithmic Mahler measure coincides with the algebraic
entropy, which is defined in terms of degree growth. Evidence for this
conjecture is provided by exact and numerical calculations of the Mahler
measure for a family of Laurent polynomials generated by rank 2 cluster
algebras, for a recurrence of third order related to the Markoff numbers, and
for the Somos-4 recurrence. Also, for the sequence of Laurent polynomials
associated with the Kronecker quiver (the cluster algebra of affine type
$\tilde{A}_1)$ we prove a precise formula for the leading order asymptotics of
the logarithmic Mahler measure, which grows linearly.
|
We present the results of a deep (J ~ 21 mag at 5 sigma) infrared photometric
survey of a 0.95 square degree area in the central region of the Upper Sco
association. The photometric observations consist of a deep (Y+J)-band images
obtained with the WFCAM camera on the UKIRT InfraRed Telescope (UKIRT) with
partly coverage in Z complemented by methane ON and OFF conducted with WIRCam
on the Canada France Hawaii Telescope. We have selected five potential T-type
objects belonging to the Upper Sco association on the basis of their blue
methane colours and their J-CH4off colours. We have also identified a sample of
7-8 Upper Sco member candidates bridging the gap between known cluster M-types
and our new T-type candidates. These candidates were selected based on their
positions in various colour-magnitude diagrams and they follow the sequence of
known Upper Sco members identified in the UKIRT Infrared Deep Sky Survey
(UKIDSS) Galactic Clusters Survey (GCS). We present additional membership
constraints using proper motion estimates from the multiple epochs available to
us. We also present optical and near-infrared spectra obtained with the
X--Shooter spectrograph on the Very Large Telescope for five L-type candidates
covering the 0.6 to 2.5 micron wavelength range, none of them being confirmed
as a young brown dwarf. We discuss the lack of detection of new candidate
members as well as the possible turn down in the USco mass function as we are
approaching the fragmentation limit.
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Today's cloud vendors are competing to provide various offerings to simplify
and accelerate AI service deployment. However, cloud users always have concerns
about the confidentiality of their runtime data, which are supposed to be
processed on third-party's compute infrastructures. Information disclosure of
user-supplied data may jeopardize users' privacy and breach increasingly
stringent data protection regulations. In this paper, we systematically
investigate the life cycles of inference inputs in deep learning image
classification pipelines and understand how the information could be leaked.
Based on the discovered insights, we develop a Ternary Model Partitioning
mechanism and bring trusted execution environments to mitigate the identified
information leakages. Our research prototype consists of two co-operative
components: (1) Model Assessment Framework, a local model evaluation and
partitioning tool that assists cloud users in deployment preparation; (2)
Infenclave, an enclave-based model serving system for online confidential
inference in the cloud. We have conducted comprehensive security and
performance evaluation on three representative ImageNet-level deep learning
models with different network depths and architectural complexity. Our results
demonstrate the feasibility of launching confidential inference services in the
cloud with maximized confidentiality guarantees and low performance costs.
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We prove that the property of a free group endomorphism being irreducible is
a group invariant of the ascending HNN extension it defines. This answers a
question posed by Dowdall-Kapovich-Leininger. We further prove that being
irreducible and atoroidal is a commensurability invariant. The invariance
follows from an algebraic characterization of ascending HNN extensions that
determines exactly when their defining endomorphisms are irreducible and
atoroidal; specifically, we show that the endomorphism is irreducible and
atoroidal if and only if the ascending HNN extension has no infinite index
subgroups that are ascending HNN extensions.
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Due to the recent advances in high-throughput sequencing technologies, it
becomes possible to directly analyze microbial communities in the human body
and in the environment. Knowledge of how microbes interact with each other and
form functional communities can provide a solid foundation to understand
microbiome related diseases; this can serve as a key step towards precision
medicine. In order to understand how microbes form communities, we propose a
two step approach: First, we infer the microbial co-occurrence network by
integrating a graph inference algorithm with phylogenetic information obtained
directly from metagenomic data. Next, we utilize a network-based community
detection algorithm to cluster microbes into functional groups where microbes
in each group are highly correlated. We also curate a "gold standard" network
based on the microbe-metabolic relationships which are extracted directly from
the metagenomic data. Utilizing community detection on the resulting microbial
metabolic pathway bipartite graph, the community membership for each microbe
can be viewed as the true label when evaluating against other existing methods.
Overall, our proposed framework Phylogenetic Graphical Lasso (PGLasso)
outperforms existing methods with gains larger than 100% in terms of Adjusted
Rand Index (ARI) which is commonly used to quantify the goodness of
clusterings.
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It is well accepted that 'hot Jupiters' did not form in situ, as the
temperature in the protoplanetary disc at the radius at which they now orbit
would have been too high for planet formation to have occurred. These planets,
instead, form at larger radii and then move into the region in which they now
orbit. The exact process that leads to the formation of these close-in planets
is, however, unclear and it seems that there may be more than one mechanism
that can produce these short-period systems. Dynamical interactions in
multiple-planet systems can scatter planets into highly eccentric orbits which,
if the pericentre is sufficiently close to the parent star, can be tidally
circularised by tidal interactions between the planet and star. Furthermore,
systems with distant planetary or stellar companions can undergo Kozai cycles
which can result in a planet orbiting very close to its parent star. However,
the most developed model for the origin of short period planets is one in which
the planet exchanges angular momentum with the surrounding protoplanetary disc
and spirals in towards the central star. In the case of 'hot Jupiters', the
planet is expected to open a gap in the disc and migrate through Type II
.migration. If this is the dominant mechanism for producing `hot Jupiters' then
we would expect the currect properties of observed close-in giant planets to be
consistent with an initial population resulting from Type II migration followed
by evolution due to tidal interactions with the central star. We consider
initial distributions that are consistent with Type II migration and find that
after tidal evolution, the final distributions can be consistent with that
observed. Our results suggest that a modest initial pile-up at a ~ 0.05 au is
required and that the initial eccentricity distribution must peak at e \sim 0.
|
The measurements of inclusive charm and beauty cross sections in
deep-inelastic scattering $ep$ collisions at HERA are compared with the
predictions of perturbative quantum chromodynamics from the CTEQ and MRST
fitting groups, employing a range of theoretical schemes. The differences in
the theoretical predictions are discussed and the theoretical uncertainties
investigated.
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We study the space-time distributions of intensity fluctuations in 2 - 3 hour
sequences of multi-spectral, high-resolution, high-cadence broad-band
filtergram images (BFI) made by the SOT-FG system aboard the Hinode spacecraft.
In the frequency range 5.5 < f < 8.0 mHz both G-band and Ca II H-line
oscillations are suppressed in the presence of magnetic fields, but the
suppression disappears for f > 10 mHz. By looking at G-band frequencies above
10 mHz we find that the oscillatory power, both at these frequencies and at
lower frequencies too, lies in a mesh pattern with cell scale 2 - 3 Mm, clearly
larger than normal granulation, and with correlation times on the order of
hours. The mesh pattern lies in the dark lanes between stable cells found in
time-integrated G-band intensity images. It also underlies part of the bright
pattern in time-integrated H-line emission. This discovery may reflect
dynamical constraints on the sizes of rising granular convection cells together
with the turbulence created in strong intercellular downflows.
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Recent Searchable Symmetric Encryption (SSE) schemes enable secure searching
over an encrypted database stored in a server while limiting the information
leaked to the server. These schemes focus on hiding the access pattern, which
refers to the set of documents that match the client's queries. This provides
protection against current attacks that largely depend on this leakage to
succeed. However, most SSE constructions also leak whether or not two queries
aim for the same keyword, also called the search pattern.
In this work, we show that search pattern leakage can severely undermine
current SSE defenses. We propose an attack that leverages both access and
search pattern leakage, as well as some background and query distribution
information, to recover the keywords of the queries performed by the client.
Our attack follows a maximum likelihood estimation approach, and is easy to
adapt against SSE defenses that obfuscate the access pattern. We empirically
show that our attack is efficient, it outperforms other proposed attacks, and
it completely thwarts two out of the three defenses we evaluate it against,
even when these defenses are set to high privacy regimes. These findings
highlight that hiding the search pattern, a feature that most constructions are
lacking, is key towards providing practical privacy guarantees in SSE.
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We have completed spectroscopic observations using LRIS on the Keck 1
telescope of 30 very high redshift quasars, 11 selected for the presence of
damped Ly-alpha absorption systems and 19 with redshifts z > 3.5 not previously
surveyed for absorption systems. We have surveyed an additional 10 QSOs with
the Lick 120'' and the Anglo-Australian Telescope. We have combined these with
previous data resulting in a statistical sample of 646 QSOs and 85 damped
Ly-alpha absorbers with column densities N(HI) >= 2 x 10^20 atoms/cm^2 covering
the redshift range 0.008 <= z <= 4.694. To make the data in our statistical
sample more readily available for comparison with scenarios from various
cosmological models, we provide tables that includes all 646 QSOs from our new
survey and previously published surveys. They list the minimum and maximum
redshift defining the redshift path along each line of sight, the QSO emission
redshift, and when an absorber is detected, the absorption redshift and
measured HI column density. [see the paper for the complete abstract]
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Objective. When a person listens to continuous speech, a corresponding
response is elicited in the brain and can be recorded using
electroencephalography (EEG). Linear models are presently used to relate the
EEG recording to the corresponding speech signal. The ability of linear models
to find a mapping between these two signals is used as a measure of neural
tracking of speech. Such models are limited as they assume linearity in the
EEG-speech relationship, which omits the nonlinear dynamics of the brain. As an
alternative, deep learning models have recently been used to relate EEG to
continuous speech. Approach. This paper reviews and comments on
deep-learning-based studies that relate EEG to continuous speech in single- or
multiple-speakers paradigms. We point out recurrent methodological pitfalls and
the need for a standard benchmark of model analysis. Main results. We gathered
29 studies. The main methodological issues we found are biased
cross-validations, data leakage leading to over-fitted models, or
disproportionate data size compared to the model's complexity. In addition, we
address requirements for a standard benchmark model analysis, such as public
datasets, common evaluation metrics, and good practices for the match-mismatch
task. Significance. We present a review paper summarizing the main
deep-learning-based studies that relate EEG to speech while addressing
methodological pitfalls and important considerations for this newly expanding
field. Our study is particularly relevant given the growing application of deep
learning in EEG-speech decoding.
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We consider a class of scalar field equations with anisotropic nonlocal
nonlinearities. We obtain a suitable extension of the well-known compactness
lemma of Benci and Cerami to this variable exponent setting, and use it to
prove that the Palais-Smale condition holds at all level below a certain
threshold. We deduce the existence of a ground state when the variable exponent
slowly approaches the limit at infinity from below.
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Rare-earth nickelates are strongly correlated oxides displaying a
metal-to-insulator transition at a temperature tunable by the rare-earth ionic
radius. In PrNiO$_3$ and NdNiO$_3$, the transition is very sharp and shows an
hysteretic behavior akin to a first-order transition. Both the temperature at
which the transition occurs and the associated resistivity change are extremely
sensitive to doping and therefore to off-stoichiometry issues that may arise
during thin film growth. Here we report that strong deviations in the transport
properties of NdNiO$_3$ films can arise in films grown consecutively under
nominally identical conditions by pulsed laser deposition; some samples show a
well-developed transition with a resistivity change of up to five orders of
magnitude while others are metallic down to low temperatures. Through a
detailed analysis of \textit{in-situ} X-ray photoelectron spectroscopy data, we
relate this behavior to large levels of cationic off-stoichoimetry that also
translate in changes in the Ni valence and bandwidth. Finally, we demonstrate
that this lack of reproducibility can be remarkably alleviated by using
single-phase NdNiO$_3$ targets.
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In this paper we determine extensions of higher degree between indecomposable
modules over gentle algebras. In particular, our results show how such
extensions either eventually vanish or become periodic. We give a geometric
interpretation of vanishing and periodicity of higher extensions in terms of
the surface underlying the gentle algebra. For gentle algebras arising from
triangulations of surfaces, we give an explicit basis of higher extension
spaces between indecomposable modules.
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We study a version of the BGG category O for Dynkin Borel subalgebras of
root-reductive Lie algebras g, such as gl(\infty). We prove results about
extension fullness and compute the higher extensions of simple modules by Verma
modules. In addition, we show that our category O is Ringel self-dual and
initiate the study of Koszul duality. An important tool in obtaining these
results is an equivalence we establish between appropriate Serre subquotients
of category O for g and category O for finite dimensional reductive subalgebras
of g.
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Most studies that consider the problem of estimating the location of a point
source in wireless sensor networks assume that the source location is estimated
by a set of spatially distributed sensors, whose locations are fixed. Motivated
by the fact that the observation quality and performance of the localization
algorithm depend on the location of the sensors, which could be randomly
distributed, this paper investigates the performance of a recently proposed
energy-based source-localization algorithm under the assumption that the
sensors are positioned according to a uniform clustering process. Practical
considerations such as the existence and size of the exclusion zones around
each sensor and the source will be studied. By introducing a novel performance
measure called the estimation outage, it will be shown how parameters related
to the network geometry such as the distance between the source and the closest
sensor to it as well as the number of sensors within a region surrounding the
source affect the localization performance.
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Inspired by neuronal diversity in the biological neural system, a plethora of
studies proposed to design novel types of artificial neurons and introduce
neuronal diversity into artificial neural networks. Recently proposed quadratic
neuron, which replaces the inner-product operation in conventional neurons with
a quadratic one, have achieved great success in many essential tasks. Despite
the promising results of quadratic neurons, there is still an unresolved issue:
\textit{Is the superior performance of quadratic networks simply due to the
increased parameters or due to the intrinsic expressive capability?} Without
clarifying this issue, the performance of quadratic networks is always
suspicious. Additionally, resolving this issue is reduced to finding killer
applications of quadratic networks. In this paper, with theoretical and
empirical studies, we show that quadratic networks enjoy parametric efficiency,
thereby confirming that the superior performance of quadratic networks is due
to the intrinsic expressive capability. This intrinsic expressive ability comes
from that quadratic neurons can easily represent nonlinear interaction, while
it is hard for conventional neurons. Theoretically, we derive the approximation
efficiency of the quadratic network over conventional ones in terms of real
space and manifolds. Moreover, from the perspective of the Barron space, we
demonstrate that there exists a functional space whose functions can be
approximated by quadratic networks in a dimension-free error, but the
approximation error of conventional networks is dependent on dimensions.
Empirically, experimental results on synthetic data, classic benchmarks, and
real-world applications show that quadratic models broadly enjoy parametric
efficiency, and the gain of efficiency depends on the task.
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Our ability to optically interrogate nanoscopic objects is controlled by the
difference between their extinction cross sections and the diffraction limited
area to which light can be confined in the far field. We show that a partially
transmissive spatial mask placed near the back focal plane of a high numerical
aperture microscope objective enhances the extinction contrast of a scatterer
near an interface by approximately $T^{-1/2}$, where T is the transmissivity of
the mask. Numerical aperture based differentiation of background from scattered
light represents a general approach to increasing extinction contrast and
enables routine label free imaging down to the single molecule level.
|
We argue that diffraction (Pomeron) contribution is present in the pp
spin-flip amplitude. RHIC polarization will be able to prove (or disprove) this
conjecture.
|
Most exact algorithms for general partially observable Markov decision
processes (POMDPs) use a form of dynamic programming in which a
piecewise-linear and convex representation of one value function is transformed
into another. We examine variations of the "incremental pruning" method for
solving this problem and compare them to earlier algorithms from theoretical
and empirical perspectives. We find that incremental pruning is presently the
most efficient exact method for solving POMDPs.
|
We present the calculation of the electroweak corrections for
squark-antisquark pair production at the LHC within the Minimal Supersymmetric
Standard Model. Taking into account all possible chirality and light-flavor
configurations, we evaluate the NLO EW corrections, which are of O(a_s^2 a), as
well as the subleading tree-level contributions of O(a_s a) and O(a^2).
Numerical results are presented for several scans in the SUSY parameter space
and relevant differential distributions are investigated. The impact of the
electroweak corrections is nonnegligible and strongly depends on the chirality
configuration of the produced squarks. Our analysis includes a discussion of
photon-gluon initiated processes with a focus on the impact of the
corresponding large PDF uncertainties.
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We report on the measurement of the equation of state of a two-component
Fermi gas of $^6$Li atoms with resonant interactions. By analyzing the
\textit{in situ} density distributions of a population-imbalanced Fermi mixture
reported in the recent experiment [Y. Shin \textit{et al.}, Nature
\textbf{451}, 689 (2008)], we determine the energy density of a resonantly
interacting Fermi gas as a function of the densities of the two components. We
present a method to determine the equation of state directly from the shape of
the trapped cloud, where the fully-polarized, non-interacting ideal Fermi gas
in the outer region provides the absolute calibration of particle density. From
the density profiles obtained at the lowest temperature, we estimate the
zero-temperature equation of state.
|
We employ a silicon dielectric waveguide to confine and concentrate terahertz
pulses, and observe that the absorption saturates under strong terahertz
fields. By comparing the response between lightly-doped and intrinsic silicon
waveguides, we confirm the role of hot carriers in this saturable absorption.
We introduce a nonlinear dynamical model of Drude conductivity that, when
incorporated into a wave propagation equation, accurately reproduces the
observations and elucidates the physical mechanisms underlying this nonlinear
effect. The results are numerically confirmed by Monte Carlo simulations of the
Boltzmann transport equation, coupled with split-step nonlinear wave
propagation.
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In cell membranes, proteins and lipids diffuse in a highly crowded and
heterogeneous landscape, where aggregates and dense domains of proteins or
lipids obstruct the path of diffusing molecules. In general, hindered motion
gives rise to anomalous transport, though the nature of the onset of this
behavior is still under debate and difficult to investigate experimentally.
Here, we present a systematic study where proteins bound to supported lipid
membranes diffuse freely in two dimensions, but are increasingly hindered by
the presence of other like proteins. In our model system, the surface coverage
of the protein avidin on the lipid bilayer is well controlled by varying the
concentration of biotinylated lipid anchors. Using fluorescence correlation
spectroscopy (FCS), we measure the time correlation function over long times
and convert it to the mean-square displacement of the diffusing proteins. Our
approach allows for high precision data and a clear distinction between
anomalous and normal diffusion. It enables us to investigate the onset of
anomalous diffusion, which takes place when the area coverage of membrane
proteins increases beyond approximately 5%. This transition region exhibits
pronounced spatial heterogeneities. Increasing the packing fraction further,
transport becomes more and more anomalous, manifested in a decrease of the
exponent of subdiffusion.
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We study reaction zones in three different versions of the A+B->0 system. For
a steady state formed by opposing currents of A and B particles we derive
scaling behavior via renormalization group analysis. By use of a previously
developed analogy, these results are extended to the time-dependent case of an
initially segregated system. We also consider an initially mixed system, which
forms reaction zones for dimension d<4. In this case an extension of the
steady-state analogy gives scaling results characterized by new exponents.
|
Let $W$ be a nonorientable $4$-dimensional handlebody without $3$- and
$4$-handles. We show that $W$ admits a Lefschetz fibration over the $2$-disk,
whose regular fiber is a nonorientable surface with nonempty boundary. This is
an analogue of a result of Harer obtained in the orientable case. As a
corollary, we obtain a $4$-dimensional proof of the fact that every
nonorientable closed $3$-manifold admits an open book decomposition, which was
first proved by Berstein and Edmonds using branched coverings. Moreover, the
monodromy of the open book we obtain for a given $3$-manifold belongs to the
twist subgroup of the mapping class group of the page. In particular, we
construct an explicit minimal open book for the connected sum of arbitrarily
many copies of the product of the circle with the real projective plane.
We also obtain a relative trisection diagram for $W$, based on the
nonorientable Lefschetz fibration we construct, similar to the orientable case
first studied by Castro. As a corollary, we get trisection diagrams for some
closed $4$-manifolds, e.g. the product of the $2$-sphere with the real
projective plane, by doubling $W$. Moreover, if $X$ is a closed nonorientable
$4$-manifold which admits a Lefschetz fibration over the $2$-sphere, equipped
with a section of square $\pm 1$, then we construct a trisection diagram of
$X$, which is determined by the vanishing cycles of the Lefschetz fibration.
Finally, we include some simple observations about low-genus Lefschetz
fibrations on closed nonorientable $4$-manifolds.
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In this paper we examine the subset of Farey fractions of order Q consisting
of those fractions whose denominators are odd. In particular, we consider the
frequencies of values of numerators of differences of consecutive elements in
this set. After proving an asymptotic result for these frequencies, we use
estimates coming from incomplete Kloosterman sums to generalize our result to
subintervals of [0,1].
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The association between light and psychological states has a long history and
permeates our language. LIVEIA (Light-based Immersive Visualization Environment
for Imaginative Actualization) is a new immersive, interactive technology that
uses physical light as a metaphor for visualizing peoples' inner lives and
relationships. This paper outlines its educational value, as a tool for
understanding and explaining aspects of how people think and interact, and its
potential therapeutic value as a form of art therapy in which the artwork has
straightforwardly interpretable symbolic meanings.
|
In gauge theories with fundamental matter there is typically no sharp way to
distinguish confining and Higgs regimes, e.g. using generalized global
symmetries acting on loop order parameters. It is standard lore that these two
regimes are continuously connected, as has been explicitly demonstrated in
certain lattice and continuum models. We point out that Higgsing and
confinement sometimes lead to distinct symmetry protected topological (SPT)
phases -- necessarily separated by a phase transition -- for ordinary global
symmetries. We present explicit examples in 3+1 dimensions, obtained by adding
elementary Higgs fields and Yukawa couplings to QCD while preserving parity P
and time reversal T. In a suitable scheme, the confining phases of these
theories are trivial SPTs, while their Higgs phases are characterized by
non-trivial P- and T-invariant theta-angles $\theta_f, \theta_g = \pi$ for
flavor or gravity background gauge fields, i.e. they are topological insulators
or superconductors. Finally, we consider conventional three-flavor QCD (without
elementary Higgs fields) at finite $U(1)_B$ baryon-number chemical potential
$\mu_B$, which preserves P and T. At very large $\mu_B$, three-flavor QCD is
known to be a completely Higgsed color superconductor that also spontaneously
breaks $U(1)_B$. We argue that this high-density phase is in fact a gapless
SPT, with a gravitational theta-angle $\theta_g = \pi$ that safely co-exists
with the $U(1)_B$ Nambu-Goldstone boson. We explain why this SPT motivates
unexpected transitions in the QCD phase diagram, as well as anomalous surface
modes at the boundary of quark-matter cores inside neutron stars.
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In this paper, we address the problem of autonomous exploration of unknown
environments with an aerial robot equipped with a sensory set that produces
large point clouds, such as LiDARs. The main goal is to gradually explore an
area while planning paths and calculating information gain in short computation
time, suitable for implementation on an on-board computer. To this end, we
present a planner that randomly samples viewpoints in the environment map. It
relies on a novel and efficient gain calculation based on the Recursive
Shadowcasting algorithm. To determine the Next-Best-View (NBV), our planner
uses a cuboid-based evaluation method that results in an enviably short
computation time. To reduce the overall exploration time, we also use a dead
end resolving strategy that allows us to quickly recover from dead ends in a
challenging environment. Comparative experiments in simulation have shown that
our approach outperforms the current state-of-the-art in terms of computational
efficiency and total exploration time. The video of our approach can be found
at https://www.youtube.com/playlist?list=PLC0C6uwoEQ8ZDhny1VdmFXLeTQOSBibQl.
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Transport phenomena still stand as one of the most challenging problems in
computational physics. By exploiting the analogies between Dirac and lattice
Boltzmann equations, we develop a quantum simulator based on pseudospin-boson
quantum systems, which is suitable for encoding fluid dynamics transport
phenomena within a lattice kinetic formalism. It is shown that both the
streaming and collision processes of lattice Boltzmann dynamics can be
implemented with controlled quantum operations, using a heralded quantum
protocol to encode non-unitary scattering processes. The proposed simulator is
amenable to realization in controlled quantum platforms, such as ion-trap
quantum computers or circuit quantum electrodynamics processors.
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The congruences for Jacobi sums of some lower orders has been treated by many
authors in the literature. In this paper we establish the congruences for
Jacobi sums of order 2l^2 with odd prime l. These congruences are useful to
obtain algebraic and arithmetic characterizations for Jacobi sums of order 2l^2 .
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The stability of the hard-sphere icosahedral quasilattice is analyzed using
the differential formulation of the generalized effective liquid approximation.
We find that the icosahedral quasilattice is metastable with respect to the
hard-sphere crystal structures. Our results agree with recent findings by
McCarley and Ashcroft [Phys. Rev. B {\bf 49}, 15600 (1994)] carried out using
the modified weighted density approximation.
|
Good local features improve the robustness of many 3D re-localization and
multi-view reconstruction pipelines. The problem is that viewing angle and
distance severely impact the recognizability of a local feature. Attempts to
improve appearance invariance by choosing better local feature points or by
leveraging outside information, have come with pre-requisites that made some of
them impractical. In this paper, we propose a surprisingly effective
enhancement to local feature extraction, which improves matching. We show that
CNN-based depths inferred from single RGB images are quite helpful, despite
their flaws. They allow us to pre-warp images and rectify perspective
distortions, to significantly enhance SIFT and BRISK features, enabling more
good matches, even when cameras are looking at the same scene but in opposite
directions.
|
This paper advances theory on the process of collaboration between entities
and its implications on the quality of services, information, and/or products
(SIPs) that the collaborating entities provide to each other. It investigates
the scenario of outsourced IS projects (such as custom software development)
where the extent of collaboration between a client and vendor is high. Using
the social exchange theory, the proposed conceptual model tries to establish
the "bidirectional" nature of SIP quality in a collaborative environment, where
the SIPs exchanged are possibly "dependent" on each other, and if any entity
wishes to receive high SIP quality then it should make efforts to provide high
SIP quality in return too. Furthermore, it advocates increasing efforts to link
financial stakes (tangible or intangible monetary benefits or risks) to the
quality of SIP being continuously exchanged throughout the project lifecycle.
|
In the context of electromagnetism and nonlinear optical interactions damping
is generally introduced as a phenomenological, viscous term that dissipates
energy, proportional to the temporal derivative of the polarization. Here, we
follow the radiation reaction method presented in [G. W. Ford and R. F.
O'Connell, Phys. Lett. A, 157, 217 (1991)], which applies to non-relativistic
electrons of finite size, to introduce an explicit reaction force in the
Newtonian equation of motion, and derive a hydrodynamic equation that offers
new insight on the influence of damping in generic plasmas, metal-based and/or
dielectric structures. In these settings, we find new damping-dependent linear
and nonlinear source terms that suggest the damping coefficient is proportional
to the local charge density, and nonlocal contributions that stem from the
spatial derivative of the magnetic field and discuss the conditions that could
modify both linear and nonlinear electromagnetic responses.
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In this paper, we discuss the interaction of non-Abelian SU(2) Yang-Mills
progressive waves with gravitational waves. We solve and obtain some
interesting solutions to pure Yang-Mills equations in different backgrounds,
and perturbative solutions induced due to gravitational waves. These
perturbations show `beat patterns' and depending on boundary conditions,
changes in frequency. In flat space-time, when the Yang-Mills fields and the
gravitational waves are in the same direction there is no interaction, unless
there is self interaction of the Yang-Mills fields. In the system with non-zero
self interaction the amplitudes of the perturbation are inversely proportional
to the Yang-Mills coupling constant. In a cosmological background, the
Yang-Mills fields and the gravitational wave interact when they are in the same
direction even without self interaction of the Yang-Mills progressive fields.
We find that in the electroweak symmetry broken phase of the gauge fields, the
interactions are perturbative only for an infinitesimal time.
|
The paper deals with the theoretical analysis of a logistic system composed
of at least two elements with distributed parameters. It has been shown that
such a system may generate specific oscillations in spite of the fact that the
solutions of the mathematical method are characterized by no dynamic
bifurcations. It has also been shown that the time series of the state
variables of such a system may behave in a semi-chaotic way. This means that
they have then predictable and unpredictable fragments. The analysis has been
illustrated by two examples, viz. of a simple logistic model and of a reactor
with feedback.
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The centers of stellar spheroids are often marked by the presence of
nucleated central regions, called nuclear star clusters (NSCs). The origin of
NSCs is still unclear. Here we investigate the possibility that NSCs originate
from the migration and merger of stellar clusters at the center of galaxies
where a massive black hole (MBH) may sit. We show that the observed relation
between NSC masses and the velocity dispersion of their host spheroids cannot
be reconciled with a purely in-situ formation scenario. On the other hand, the
observed relation appears to be in agreement with the predictions of the
cluster merger model which also reproduces the observed relation between the
size of NSCs and their total luminosity. We evolve through dynamical friction a
population of stellar clusters in a model of a galactic bulge taking into
account dynamical dissolution, starting from a power-law cluster initial mass
function and a total mass in stellar clusters consistent with the cluster
formation efficiency of the Milky Way (MW). The most massive clusters reach the
center of the galaxy and merge to form a compact nucleus; after 10 Gyr, the
resulting NSC has properties that are consistent with the observed distribution
of stars in the MW NSC. When a MBH is included at the center of a galaxy,
globular clusters are tidally disrupted during inspiral, resulting in NSCs with
lower densities than those of NSCs forming in galaxies with no MBHs. We suggest
this as a possible explanation for the lack of NSCs in galaxies containing MBHs
more massive than ~10^8M_Sun. Finally, we investigate the orbital evolution of
globular clusters in giant elliptical galaxies which are believed to always
host a MBH at their center rather than a NSC. In these systems an additional
mechanism can prevent a NSC from forming: the time for globular clusters to
reach the center of the galaxy is much longer than the Hubble time.
|
In this write-up we focus on fast data links that read out particle
detectors. This includes developments of ASICs, optical modules, identifying
passive components such as fiber and connector, and a link system design. A
review of the current status is provided. The goal of R\&D is to double (near
term) and quadruple (longer term) the present data transmission rate for
particle detectors, enabling a wide range of physics exploration and
measurements.
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We show that for fields that are of characteristic 0 or algebraically closed
of characteristic greater than 5, that certain classes of Leibniz algebras are
2-recognizeable. These classes are solvable, strongly solvable and super
solvable. These results hold in Lie algebras and in general for groups.
|
The residual interaction between composite fermions (CFs) can express itself
through higher order fractional Hall effect. With the help of diagonalization
in a truncated composite fermion basis of low-energy many-body states, we
predict that quantum Hall effect with partial spin polarization is possible at
several fractions between $\nu=1/3$ and $\nu=2/5$. The estimated excitation
gaps are approximately two orders of magnitude smaller than the gap at
$\nu=1/3$, confirming that the inter-CF interaction is extremely weak in higher
CF levels.
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We describe a maximum-likelihood method for determining the mass distribution
in spherical stellar systems from the radial velocities of a population of
discrete test particles. The method assumes a parametric form for the mass
distribution and a non-parametric two-integral distribution function. We apply
the method to a sample of 161 globular clusters in M87. We find that the mass
within 32 kpc is $(2.4\pm0.6)\times 10^{12} $M${_\odot}$, and the exponent of
the density profile $\rho\propto r^{-\alpha}$ in the range 10-100 kpc is
$\alpha=1.6\pm0.4$.The energy distribution suggests a few kinematically
distinct groups of globular clusters. The anisotropy of the globular-cluster
velocity distribution cannot be determined reliably with the present data.
Models fitted to an NFW potential yield similar mass estimates but cannot
constrain the concentration radius $r_c$ in the range 10-500 kpc.
|
Jolie is a service-oriented programming language which comes with the formal
specification of its type system. However, there is no tool to ensure that
programs in Jolie are well-typed. In this paper we provide the results of
building a type checker for Jolie as a part of its syntax and semantics formal
model. We express the type checker as a program with dependent types in Agda
proof assistant which helps to ascertain that the type checker is correct.
|
In this paper, we show that every measure-preserving ergodic equivalence
relation of cost less than m comes from a "rich" faithful invariant random
subgroup of the free group on m generators, strengthening a result of Bowen
which had been obtained by a Baire category argument. Our proof is completely
explicit: we use our previous construction of topological generators for full
groups and observe that these generators induce a totally non free action. We
then twist this construction so that the action is moreover amenable onto
almost every orbit and highly faithful.
|
We review recent theoretical developments, which suggest that a set of shared
principles underpin macroscopic quantum phenomena observed in high temperature
super conducting materials, room temperature coherence in photosynthetic
processes and the emergence of long range order in biological structures. These
systems are driven by dissipative systems, which lead to fractal assembly and a
fractal network of charges (with associated quantum potentials) at the
molecular scale. At critical levels of charge density and fractal dimension,
individual quantum potentials merge to form a charged induced macroscopic
quantum potential, which act as a structuring force dictating long range order.
Whilst the system is only partially coherent (i.e. only the bosonic fields are
coherent), within these processes many of the phenomena associated with
standard quantum theory are recovered, with macroscopic quantum potentials and
associated forces having their equivalence in standard quantum mechanics. We
establish a testable hypothesis that the development of structures analogous to
those found in biological systems, which exhibit macroscopic quantum
properties, should lead to increased critical temperatures in high temperature
superconducting materials. If the theory is confirmed it opens up a new,
systematic, ab initio approach to the structural development of these types of
materials.
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We present the first detailed hydrodynamic simulation of a superoutburst to
incorporate the full tidal potential of a binary system. A two-dimensional
smoothed particle hydrodynamics code is used to simulate a superoutburst in a
binary with the parameters of the SU UMa system Z Chamaeleontis. The simulated
light curves shows all the features observed in such systems. Analysis of the
mass flux through the disc and the growth rate of the superhumps and disc
eccentricity show that the superoutburst-superhump phenomenon is a direct
result of tidal instability. No enhanced mass transfer from the secondary is
required to initiate or sustain these phenomena. Comparisons of superoutbursts
with normal outbursts are made and we show that the model can be reconciled
with the behavior of U Geminorum type dwarf novae, which show no
superoutbursts.
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Detecting clinically relevant objects in medical images is a challenge
despite large datasets due to the lack of detailed labels. To address the label
issue, we utilize the scene-level labels with a detection architecture that
incorporates natural language information. We present a challenging new set of
radiologist paired bounding box and natural language annotations on the
publicly available MIMIC-CXR dataset especially focussed on pneumonia and
pneumothorax. Along with the dataset, we present a joint vision language weakly
supervised transformer layer-selected one-stage dual head detection
architecture (LITERATI) alongside strong baseline comparisons with class
activation mapping (CAM), gradient CAM, and relevant implementations on the NIH
ChestXray-14 and MIMIC-CXR dataset. Borrowing from advances in vision language
architectures, the LITERATI method demonstrates joint image and referring
expression (objects localized in the image using natural language) input for
detection that scales in a purely weakly supervised fashion. The architectural
modifications address three obstacles -- implementing a supervised vision and
language detection method in a weakly supervised fashion, incorporating
clinical referring expression natural language information, and generating high
fidelity detections with map probabilities. Nevertheless, the challenging
clinical nature of the radiologist annotations including subtle references,
multi-instance specifications, and relatively verbose underlying medical
reports, ensures the vision language detection task at scale remains
stimulating for future investigation.
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We are interested in a WKB analysis of the Logarithmic Non-Linear
Schr\"odinger Equation with "Riemann-like" variables in an analytic framework
in semiclassical regime. We show that the Cauchy problem is locally well posed
uniformly in the semiclassical constant and that the semiclassical limit can be
performed. In particular, our framework is not only compatible with the
Gross-Pitaevskii equation with logarithmic nonlinearity, but also allows
initial data (and solutions) which can converge to $0$ at infinity.
|
We describe a new method for determining proper motions of extended objects,
and a pipeline developed for the application of this method. We then apply this
method to an analysis of four epochs of [S~II] HST images of the HH~1 jet
(covering a period of $\sim 20$~yr).
We determine the proper motions of the knots along the jet, and make a
reconstruction of the past ejection velocity time-variability (assuming
ballistic knot motions). This reconstruction shows an "acceleration" of the
ejection velocities of the jet knots, with higher velocities at more recent
times. This acceleration will result in an eventual merging of the knots in
$\sim 450$~yr and at a distance of $\sim 80"$ from the outflow source, close to
the present-day position of HH~1.
|
Synaptic plasticity is vital for learning and memory in the brain. It
consists of long-term potentiation (LTP) and long-term depression (LTD). Spike
frequency is one of the major components of synaptic plasticity in the brain, a
noisy environment. Recently, we mathematically analysed the frequency-dependent
synaptic plasticity (FDP) in vivo and found that LTP is more likely to occur
with an increase in the frequency of background synaptic activity. Previous
studies suggest fluctuation in the amplitude of background synaptic activity.
However, little is understood about the relationship between synaptic
plasticity and the fluctuation in the background synaptic activity. To address
this issue, we performed numerical simulations of a calcium-based synapse
model. Then, we found attenuation of the tendency to become LTD due to an
increase in the fluctuation of background synaptic activity, leading to an
enhancement of synaptic weight. Our result suggests that the fluctuation affect
synaptic plasticity in the brain.
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A class of classical affine W-algebras are shown to be isomorphic as
differential algebras to the coordinate rings of double coset spaces of certain
prounipotent proalgebraic groups. As an application, integrable Hamiltonian
hierarchies associated with them are constructed geometrically, generalizing
the corresponding result of Feigin-Frenkel and Enriquez-Frenkel for the
principal cases.
|
The main challenges that arise when adopting Gaussian Process priors in
probabilistic modeling are how to carry out exact Bayesian inference and how to
account for uncertainty on model parameters when making model-based predictions
on out-of-sample data. Using probit regression as an illustrative working
example, this paper presents a general and effective methodology based on the
pseudo-marginal approach to Markov chain Monte Carlo that efficiently addresses
both of these issues. The results presented in this paper show improvements
over existing sampling methods to simulate from the posterior distribution over
the parameters defining the covariance function of the Gaussian Process prior.
This is particularly important as it offers a powerful tool to carry out full
Bayesian inference of Gaussian Process based hierarchic statistical models in
general. The results also demonstrate that Monte Carlo based integration of all
model parameters is actually feasible in this class of models providing a
superior quantification of uncertainty in predictions. Extensive comparisons
with respect to state-of-the-art probabilistic classifiers confirm this
assertion.
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An unbiased shift of the two-sided Brownian motion $(B_t \colon t\in{\mathbb
R})$ is a random time $T$ such that $(B_{T+t} \colon t\in{\mathbb R})$ is still
a two-sided Brownian motion. Given a pair $\mu, \nu$ of orthogonal probability
measures, an unbiased shift $T$ solves the embedding problem, if $B_0\sim\mu$
implies $B_{T}\sim\nu$. A solution to this problem was given by Last et al.
(2014), based on earlier work of Bertoin and Le Jan (1992), and Holroyd and
Liggett (2001). In this note we show that this solution minimises ${\mathbb E}
\psi(T)$ over all nonnegative unbiased solutions $T$, simultaneously for all
nonnegative, concave functions $\psi$. Our proof is based on a discrete
concavity inequality that may be of independent interest.
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We propose a discretization of classical confocal coordinates. It is based on
a novel characterization thereof as factorizable orthogonal coordinate systems.
Our geometric discretization leads to factorizable discrete nets with a novel
discrete analog of the orthogonality property. A discrete confocal coordinate
system may be constructed geometrically via polarity with respect to a sequence
of classical confocal quadrics. Various sequences correspond to various
discrete parametrizations. The coordinate functions of discrete confocal
quadrics are computed explicitly. The theory is illustrated with a variety of
examples in two and three dimensions. These include confocal coordinate systems
parametrized in terms of Jacobi elliptic functions. Connections with incircular
(IC) nets and a generalized Euler-Poisson-Darboux system are established.
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We establish bounds on expected values of various geometric quantities that
describe the size of the convex hull spanned by a path of the standard planar
Brownian motion. Expected values of the perimeter and the area of the Brownian
convex hull are known explicitly, and satisfactory bounds on the expected value
of its diameter can be found in the literature as well. In this work we
investigate circumradius and inradius of the Brownian convex hull and obtain
lower and upper bounds on their expected values. Our other goal is to find
bounds on the related inverse processes (that correspond to the perimeter,
area, diameter, circumradius and inradius of the convex hull) which provide us
with some information on the speed of growth of the size of the Brownian convex
hull.
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This paper proposes an extensive overview of safety applications and
approaches as it relates to automated driving from the prospectives of sensor
configurations, vehicle dynamics modelling, tyre modeling, and estimation
approaches. First, different Advanced-Driver Assistance Systems (ADAS) are
introduced along with the main sensing components and technologies. Then,
different kinematics modelling of vehicles and tyres are discussed. Finally,
various communicational technologies and architectures along with self-driving
modules are presented. Moreover, some interesting perspectives for future
research are listed based on the extensive experience of the authors. The
objective of this study is to teach and guide the beginner and expert for
choosing the most suitable approach for autonomous driving applications in
safety and stability targeted issues.
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Time crystals are proposed states of matter which spontaneously break time
translation symmetry. There is no settled definition of such states. We offer a
new definition which follows the traditional recipe for Wigner symmetries and
order parameters. Supplementing our definition with a few plausible assumptions
we find that a) systems with time independent Hamiltonians should not exhibit
TTSB while b) the recently studied $\pi$ spin glass/Floquet time crystal can be
viewed as breaking a global internal symmetry and as breaking time translation
symmetry as befits its two names.
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The Liverpool Telescope has been in fully autonomous operation since 2004.
The supporting data archive facility has largely been untouched. The data
provision service has not been an issue although some modernisation of the
system is desirable. This project is timely. Not only does it suit the upgrade
of the current LT data archive, it is in line with the design phase of the New
Robotic Telescope which will be online in the early-2020s; and with the
development of a new data archive facility for a range of telescopes at the
National Astronomical Research Institute of Thailand. The Newton Fund enabled
us to collaborate in designing a new versatile generic system that serves all
purposes. In the end, we conclude that a single system would not meet the needs
of all parties and only adopt similar front-ends while the back-ends are
bespoke to our respective systems and data-flows.
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We use inelastic neutron scattering to probe magnetic excitations of an
optimally electron-doped superconductor Nd$_{1.85}$Ce$_{0.15}$CuO$_{4-\delta}$
above and below its superconducting transition temperature $T_c=25$ K. In
addition to gradually opening a spin pseudo gap at the antiferromagnetic
ordering wavevector ${\bf Q}=(1/2,1/2,0)$, the effect of superconductivity is
to form a resonance centered also at ${\bf Q}=(1/2,1/2,0)$ but at energies
above the spin pseudo gap. The intensity of the resonance develops like a
superconducting order parameter, similar to those for hole-doped
superconductors and electron-doped Pr$_{0.88}$LaCe$_{0.12}$CuO$_4$. The
resonance is therefore a general phenomenon of cuprate superconductors, and
must be fundamental to the mechanism of high-$T_c$ superconductivity.
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Computing is at a moment of profound opportunity. Emerging applications --
such as capable artificial intelligence, immersive virtual realities, and
pervasive sensor systems -- drive unprecedented demand for computer. Despite
recent advances toward net zero carbon emissions, the computing industry's
gross energy usage continues to rise at an alarming rate, outpacing the growth
of new energy installations and renewable energy deployments. A shift towards
sustainability is needed to spark a transformation in how computer systems are
manufactured, allocated, and consumed.
Carbon Connect envisions coordinated research thrusts that produce design and
management strategies for sustainable, next-generation computer systems. These
strategies must flatten and then reverse growth trajectories for computing
power and carbon for society's most rapidly growing applications such as
artificial intelligence and virtual spaces. We will require accurate models for
carbon accounting in computing technology. For embodied carbon, we must
re-think conventional design strategies -- over-provisioned monolithic servers,
frequent hardware refresh cycles, custom silicon -- and adopt life-cycle design
strategies that more effectively reduce, reuse and recycle hardware at scale.
For operational carbon, we must not only embrace renewable energy but also
design systems to use that energy more efficiently. Finally, new hardware
design and management strategies must be cognizant of economic policy and
regulatory landscape, aligning private initiatives with societal goals. Many of
these broader goals will require computer scientists to develop deep, enduring
collaborations with researchers in economics, law, and industrial ecology to
spark change in broader practice.
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Spectral methods, thanks to their high accuracy and the possibility to use
fast algorithms, represent an effective way to approximate the collisional
kinetic equations of Boltzmann type, such as the Boltzmann-Nordheim equation.
This equation, modeled on the seminal Boltzmann equation, describes using a
statistical physics formalism the time evolution of a gas composed of bosons or
fermions. Using the spectral-Galerkin algorithm introduced in [F. Filbet, J.
Hu, and S. Jin, ESAIM: Math. Model. Numer. Anal., 2011], together with some
novel parallelization techniques, we investigate some of the conjectured
properties of the large time behavior of the solutions to this equation. In
particular, we are able to observe numerically both Bose-Einstein condensation
and Fermi-Dirac relaxation.
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A simple general theorem is used as a tool that generates nonlocal constants
of motion for Lagrangian systems. We review some cases where the constants that
we find are useful in the study of the systems: the homogeneous potentials of
degree~$-2$, the mechanical systems with viscous fluid resistance and the
conservative and dissipative Maxwell-Bloch equations of laser dynamics. We also
prove a new result on explosion in the past for mechanical system with
hydraulic (quadratic) fluid resistance and bounded potential.
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We analyze from a general perspective all possible supersymmetric
generalizations of symplectic and metric structures on smooth manifolds. There
are two different types of structures according to the even/odd character of
the corresponding quadratic tensors. In general we can have even/odd symplectic
supermanifolds, Fedosov supermanifolds and Riemannian supermanifolds. The
geometry of even Fedosov supermanifolds is strongly constrained and has to be
flat. In the odd case, the scalar curvature is only constrained by Bianchi
identities. However, we show that odd Riemannian supermanifolds can only have
constant scalar curvature. We also point out that the supersymmetric
generalizations of AdS space do not exist in the odd case.
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Control systems over networks with a finite data rate can be conveniently
modeled as hybrid (impulsive) systems. For the class of nonlinear systems in
feedfoward form, we design a hybrid controller which guarantees stability, in
spite of the measurement noise due to the quantization, and of an arbitrarily
large delay which affects the communication channel. The rate at which feedback
packets are transmitted from the sensors to the actuators is shown to be
arbitrarily close to the infimal one.
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The Gaia DR3 parallax approach was used to estimate the absolute parameters
of 2375 Delta Scuti stars from the ASAS catalog. The selected stars have a
variety of observational characteristics, with a higher than 80% probability of
being Delta Scuti stars. We have displayed all the stars in the
Hertzsprung-Russell (H-R) diagram along with the Delta Scuti instability strip,
the Zero Age Main Sequence (ZAMS), and the Terminal-Age Main Sequence (TAMS).
Then, we determined which fundamental and overtone modes each star belongs to
using pulsation constant (Q) calculations. In addition, we evaluated the
parameters in the Q calculation equation using three machine learning methods,
which showed that surface gravity and temperature have the greatest effect on
its calculation. The Period-Luminosity (P-L) relationship of the Delta Scuti
stars was also revisited. Eventually, using least squares linear regression, we
made four linear fits for fundamental and overtone modes and updated their
relationships.
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In this paper we introduce the word "fresco" to denote a \
$[\lambda]-$primitive monogenic geometric (a,b)-module. The study of this
"basic object" (generalized Brieskorn module with one generator) which
corresponds to the minimal filtered (regular) differential equation satisfied
by a relative de Rham cohomology class, began in [B.09] where the first
structure theorems are proved. Then in [B.10] we introduced the notion of theme
which corresponds in the \ $[\lambda]-$primitive case to frescos having a
unique Jordan-H{\"o}lder sequence. Themes correspond to asymptotic expansion of
a given vanishing period, so to the image of a fresco in the module of
asymptotic expansions. For a fixed relative de Rham cohomology class (for
instance given by a smooth differential form $d-$closed and $df-$closed) each
choice of a vanishing cycle in the spectral eigenspace of the monodromy for the
eigenvalue \ $exp(2i\pi.\lambda)$ \ produces a \ $[\lambda]-$primitive theme,
which is a quotient of the fresco associated to the given relative de Rham
class itself. The first part of this paper shows that, for any \
$[\lambda]-$primitive fresco there exists an unique Jordan-H{\"o}lder sequence
(called the principal J-H. sequence) with corresponding quotients giving the
opposite of the roots of the Bernstein polynomial in a non decreasing order.
Then we introduce and study the semi-simple part of a given fresco and we
characterize the semi-simplicity of a fresco by the fact for any given order of
the roots of its Bernstein polynomial we may find a J-H. sequence making them
appear with this order. Then, using the parameter associated to a rank \ 2 \ \
$[\lambda]-$primitive theme, we introduce inductiveley a numerical invariant,
that we call the \ $\alpha-$invariant, which depends polynomially on the
isomorphism class of a fresco (in a sens which has to be defined) and which
allows to give an inductive way to produce a sub-quotient rank \ 2 \ theme of a
given \ $[\lambda]-$primitive fresco assuming non semi-simplicity. In the last
section we prove a general existence result which naturally associate a fresco
to any relative de Rham cohomology class of a proper holomorphic function of a
complex manifold onto a disc. This is, of course, the motivation for the study
of frescos.
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The optical and vibrational properties of nanocrystalline thin films of MoS2,
comprised of a mixture of edge terminated vertically aligned (ETVA) and
(001)-oriented regions, on large insulating substrates are reported. From high
resolution transmission electron microscopy (HRTEM), the average size of ETVA
nanocrystals were ~5 nm and each nanocrystal consisted of only 3 to 5
monolayers of MoS2. The films were highly transparent (~80%) but the percent of
transmittance decreased as the energy of the incident light approached to the
band gap. Additionally, weak excitonic peaks were observed both in the
absorption and transmission spectra. The room temperature Raman study showed
that both the E12g and A1g modes were significantly broader, and a few
additional Raman modes were observed when compared to bulk MoS2. The broadening
of the A1g mode was analyzed using the phonon-confinement model and the
calculated particle size was in good agreement with TEM observations. Moreover,
the temperature coefficient of the A1g mode was estimated from the temperature
dependent Raman studies.
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Rejoinder: Struggles with Survey Weighting and Regression Modeling
[arXiv:0710.5005]
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A search is performed for the as yet unobserved baryonic $\Lambda_b
\rightarrow \Lambda \eta^\prime$ and $\Lambda_b \rightarrow \Lambda \eta$
decays with 3$fb^{-1}$ of proton-proton collision data recorded by the LHCb
experiment. The $B^0 \rightarrow K_S^0 \eta^\prime$ decay is used as a
normalisation channel. No significant signal is observed for the $\Lambda_b
\rightarrow \Lambda \eta^\prime$ decay. An upper limit is found on the
branching fraction of $\mathcal{B}(\Lambda_b \rightarrow \Lambda
\eta^\prime)<3.1\times10^{-6}$} at 90\% confidence level. Evidence is seen for
the presence of the $\Lambda_b \rightarrow \Lambda \eta$ decay at the level of
$3\sigma$ significance, with a branching fraction $\mathcal{B}(\Lambda_b
\rightarrow \Lambda \eta)=(9.3^{+7.3}_{-5.3})\times10^{-6}$}.
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Similar to Poisson's effect, mechanical coupling is a directional indirect
response by a directional input loading. With the advance in manufacturing
techniques of 3D complex geometry, architected materials with unit cells of
finite volume rather than a point yield more degrees of freedom and foster
exotic mechanical couplings such as axial-shear, axial-rotation, axial-bending,
and axial-twisting. However, most structural materials have been built by the
ad hoc design of mechanical couplings without theoretical support of
elasticity, which does not provide general guidelines for mechanical couplings.
Moreover, no comprehensive study of all the mechanical couplings of 3D lattices
with symmetry operations has been undertaken. Therefore, we construct the
decoupled micropolar elasticity tensor of 3D lattices to identify individual
mechanical couplings correlated with the point groups. The decoupled micropolar
elasticity tensors, classified with 32 point groups, provide 15 mechanical
couplings for 3D lattices. Our findings help provide solid theoretical
guidelines for the mechanical couplings of 3D structural materials with
potential applications in various areas, including active metamaterials,
sensors, actuators, elastic waveguides, and acoustics.
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It is shown how the linear method of the Yosida-approximation of the
derivative applies to solve possibly nonlinear abstract functional differential
equations in both, the finite and infinite delay case. A generalization of the
integral solution will provide regularity results. Moreover, this method
applies to derive uniform convergence on the halfline, and therefore general
results on boundedness and various types of asymptotic almost periodicity.
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In this paper we study the global exponential stability in the $L^{2}$ norm
of semilinear $1$-$d$ hyperbolic systems on a bounded domain, when the source
term and the nonlinear boundary conditions are Lipschitz. We exhibit two
sufficient stability conditions: an internal condition and a boundary
condition. This result holds also when the source term is nonlocal. Finally, we
show its robustness by extending it to global Input-to State Stability in the
$L^{2}$ norm with respect to both interior and boundary disturbances.
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The decay of extremal charged black holes has been a useful guidance to
derive consistency conditions in quantum gravity. In de Sitter space it has
been argued that requiring (extremal) charged Nariai black holes to decay
without forming a big crunch singularity yields the Festina Lente (FL) bound:
particles with mass $m_s$ and charge $q$ should satisfy $m_s^2 \gg M_pHq$,
where $M_p$ is the Planck mass and $H$ the Hubble parameter. Using a tunneling
approach we show that the decay probability of charged black holes in de Sitter
space in the s-wave sector is $P\sim \exp(\Delta S_b)$, where $\Delta S_b$ is
the change in the black hole entropy. We find that the FL bound corresponds to
$\Delta S_b \leq -1$ in the Nariai and probe limit. However, taking into
account backreaction we identify unsuppressed decays that violate this bound
but nonetheless do not result in a big crunch for every observer.
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Most physics theories are deterministic, with the notable exception of
quantum mechanics which, however, comes plagued by the so-called measurement
problem. This state of affairs might well be due to the inability of standard
mathematics to "speak" of indeterminism, its inability to present us a
worldview in which new information is created as time passes. In such a case,
scientific determinism would only be an illusion due to the timeless
mathematical language scientists use. To investigate this possibility it is
necessary to develop an alternative mathematical language that is both powerful
enough to allow scientists to compute predictions and compatible with
indeterminism and the passage of time. We argue that intuitionistic mathematics
provides such a language and we illustrate it in simple terms.
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Continuously Variable Series Reactor (CVSR) can regulate its reactance on the
ac side using the nonlinear ferromagnetic core, shared by an ac and a dc
winding for applications like power flow control, oscillation damping, load
balancing and others. In order to use a CVSR in the power grid, it is essential
to know its operating characteristics. The Gyrator-Capacitor approach has been
applied to model the magnetic circuit coupled with the electrical circuit. In
the paper, we investigate the CVSR behavior in terms of induced voltages across
the dc winding, flux densities (B) through the core legs, and power exchange
between the ac controlled and the dc control circuit.
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The system of a quarkonium confined by an impenetrable spherical cavity
filled with a hot quantum chromodynamics (QCD) medium is studied by solving the
Schr\"{o}dinger equation. This is the first time this issue has been raised for
discussion. The Schr\"{o}dinger equation with an appropriate boundary condition
of a quarkonium in an impenetrable cavity filled with a hot medium is derived.
The numerical results are obtained with the help of Gaussian Expansion Method.
Binding energies and radii of the ground and low-excited states are obtained as
a function of the medium temperature and the cavity radius. We find the
behaviour of quarkonium in this cavity is different from that in infinite
space. Our results show that the quarkonium dissociation temperature decreases
as the cavity radius decreases and the finite volume effects on the ground
state are more obvious than on the excited states. We also find that the less
mass of the constituents and the bigger radius of the quarkonium lead the
finite volume effects to become more obvious.
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Subsets and Splits