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1609.03041 | We present an algorithm for solving inverse problems on graphs analogous to
those arising in diffuse optical tomography for continuous media. In
particular, we formulate and analyze a discrete version of the inverse Born
series, proving estimates characterizing the domain of convergence,
approximation errors, and stability of our approach. We also present a
modification which allows additional information on the structure of the
potential to be incorporated, facilitating recovery for a broader class of
problems.
| [
"math.CO"
] | math.CO | Combinatorics | 1,014Combinatorics
|
|
2205.07426 | The Matrix-based Renyi's entropy enables us to directly measure information
quantities from given data without the costly probability density estimation of
underlying distributions, thus has been widely adopted in numerous statistical
learning and inference tasks. However, exactly calculating this new information
quantity requires access to the eigenspectrum of a semi-positive definite (SPD)
matrix $A$ which grows linearly with the number of samples $n$, resulting in a
$O(n^3)$ time complexity that is prohibitive for large-scale applications. To
address this issue, this paper takes advantage of stochastic trace
approximations for matrix-based Renyi's entropy with arbitrary $\alpha \in R^+$
orders, lowering the complexity by converting the entropy approximation to a
matrix-vector multiplication problem. Specifically, we develop random
approximations for integer order $\alpha$ cases and polynomial series
approximations (Taylor and Chebyshev) for non-integer $\alpha$ cases, leading
to a $O(n^2sm)$ overall time complexity, where $s,m \ll n$ denote the number of
vector queries and the polynomial order respectively. We theoretically
establish statistical guarantees for all approximation algorithms and give
explicit order of s and m with respect to the approximation error
$\varepsilon$, showing optimal convergence rate for both parameters up to a
logarithmic factor. Large-scale simulations and real-world applications
validate the effectiveness of the developed approximations, demonstrating
remarkable speedup with negligible loss in accuracy.
| [
"stat.ML",
"cs.LG"
] | stat.ML | cs.LG | Machine Learning;Machine Learning | 4,163Machine Learning;Machine Learning
|
2205.10872 | This paper introduces {\em fusion subspace clustering}, a novel method to
learn low-dimensional structures that approximate large scale yet highly
incomplete data. The main idea is to assign each datum to a subspace of its
own, and minimize the distance between the subspaces of all data, so that
subspaces of the same cluster get {\em fused} together. Our method allows low,
high, and even full-rank data; it directly accounts for noise, and its sample
complexity approaches the information-theoretic limit. In addition, our
approach provides a natural model selection {\em clusterpath}, and a direct
completion method. We give convergence guarantees, analyze computational
complexity, and show through extensive experiments on real and synthetic data
that our approach performs comparably to the state-of-the-art with complete
data, and dramatically better if data is missing.
| [
"cs.LG",
"stat.ML"
] | cs.LG | stat.ML | Machine Learning;Machine Learning | 4,163Machine Learning;Machine Learning
|
2005.04974 | Robust localization of organs in computed tomography scans is a constant
pre-processing requirement for organ-specific image retrieval, radiotherapy
planning, and interventional image analysis. In contrast to current solutions
based on exhaustive search or region proposals, which require large amounts of
annotated data, we propose a deep reinforcement learning approach for organ
localization in CT. In this work, an artificial agent is actively self-taught
to localize organs in CT by learning from its asserts and mistakes. Within the
context of reinforcement learning, we propose a novel set of actions tailored
for organ localization in CT. Our method can use as a plug-and-play module for
localizing any organ of interest. We evaluate the proposed solution on the
public VISCERAL dataset containing CT scans with varying fields of view and
multiple organs. We achieved an overall intersection over union of 0.63, an
absolute median wall distance of 2.25 mm, and a median distance between
centroids of 3.65 mm.
| [
"eess.IV",
"cs.CV",
"cs.LG"
] | eess.IV | cs.CV | Image and Video Processing;Computer Vision and Pattern Recognition;Machine Learning | 3,535Image and Video Processing;Computer Vision and Pattern Recognition;Machine Learning
|
2110.05783 | In a decade, the adaptive quality control of video streaming and the
super-resolution (SR) technique have been deeply explored. As edge devices
improved to have exceptional processing capability than ever before, streaming
users can enhance the received image quality to allow the transmitter to
compress the images to save its power or pursue network efficiency. In this
sense, this paper proposes a novel dynamic video streaming algorithm that
adaptively compresses video chunks at the transmitter and separately enhances
the quality at the receiver using SR. In order to allow transmission of video
chunks with different compression levels and control of the computation burden,
we present the adaptive SR network which is optimized by minimizing the
weighted sum of losses extracted from different layer outputs. for dynamic
video streaming. In addition, we jointly orchestrate video delivery and
resource usage, and the proposed video delivery scheme balances the tradeoff
well among the average video quality, the queuing delay, buffering time,
transmit power, and computation power. Simulation results show that the
proposed scheme pursues the quality-of-services (QoS) of the video streaming
better than the adaptive quality control without the cooperation of the
transmitter and the receiver and the non-adaptive SR network.
| [
"cs.MM",
"cs.DC"
] | cs.MM | cs.DC | Multimedia;Distributed, Parallel, and Cluster Computing | 7,267longtail
|
2307.03764 | In this paper, we present a computational analysis of the Persian language
Twitter discourse with the aim to estimate the shift in stance toward gender
equality following the death of Mahsa Amini in police custody. We present an
ensemble active learning pipeline to train a stance classifier. Our novelty
lies in the involvement of Iranian women in an active role as annotators in
building this AI system. Our annotators not only provide labels, but they also
suggest valuable keywords for more meaningful corpus creation as well as
provide short example documents for a guided sampling step. Our analyses
indicate that Mahsa Amini's death triggered polarized Persian language
discourse where both fractions of negative and positive tweets toward gender
equality increased. The increase in positive tweets was slightly greater than
the increase in negative tweets. We also observe that with respect to account
creation time, between the state-aligned Twitter accounts and pro-protest
Twitter accounts, pro-protest accounts are more similar to baseline Persian
Twitter activity.
| [
"cs.CY",
"cs.AI",
"cs.CL",
"cs.LG"
] | cs.CY | cs.AI | Computers and Society;Artificial Intelligence;Computation and Language;Machine Learning | 1,650Computers and Society;Artificial Intelligence;Computation and Language;Machine Learning
|
2311.16668 | Existing real-time RGB-D reconstruction approaches, like Kinect Fusion, lack
real-time photo-realistic visualization. This is due to noisy, oversmoothed or
incomplete geometry and blurry textures which are fused from imperfect depth
maps and camera poses. Recent neural rendering methods can overcome many of
such artifacts but are mostly optimized for offline usage, hindering the
integration into a live reconstruction pipeline.
In this paper, we present LiveNVS, a system that allows for neural novel view
synthesis on a live RGB-D input stream with very low latency and real-time
rendering. Based on the RGB-D input stream, novel views are rendered by
projecting neural features into the target view via a densely fused depth map
and aggregating the features in image-space to a target feature map. A
generalizable neural network then translates the target feature map into a
high-quality RGB image. LiveNVS achieves state-of-the-art neural rendering
quality of unknown scenes during capturing, allowing users to virtually explore
the scene and assess reconstruction quality in real-time.
| [
"cs.CV",
"cs.GR"
] | cs.CV | cs.GR | Computer Vision and Pattern Recognition;Graphics | 1,568Computer Vision and Pattern Recognition;Graphics
|
1712.07167 | We give a constructive, computer-assisted proof that
$\operatorname{Aut}(\mathbb{F}_5)$, the automorphism group of the free group on
$5$ generators, has Kazhdan's property $(T)$.
| [
"math.GR",
"math.FA",
"math.OA"
] | math.GR | math.FA | Group Theory;Functional Analysis;Operator Algebras | 2,948Group Theory;Functional Analysis;Operator Algebras
|
1310.2865 | We consider a potential pathology in the derivation of plate theories as
Gamma-limits of 3-dimensional nonlinear elasticity by Friesecke James and
Muller (Comm. Pure Appl. Math., 55:1461-1506 and Arch. Ration. Mech. Anal.,
180:183-236), which consists in recovery sequences of invertible maps that
converge to a non-invertible limit. These pathologies have been noted by Muller
and Spector (Arch. Ration. Mech. Anal. 131:1-66) in a different context. Using
a combination of degree theory, the approximation of Sobolev functions by
Lipschitz functions and geometric rigidity we show that the potentially
pathological situation in the derivation of plate theories provides sufficient
conditions for the self-intersection of the graph of the recovery sequence
element, and thus the pathology is excluded.
| [
"math.AP"
] | math.AP | Analysis of PDEs | 205Analysis of PDEs
|
|
2005.11764 | We consider the problem of recovering the divergence-free velocity field
${\mathbf U}\in\mathbf{L}^2(\Omega)$ of a given vorticity ${\mathbf
F}=\mathrm{curl}\,{\mathbf U}$ on a bounded Lipschitz domain
$\Omega\subset\mathbb{R}^3$. To that end, we solve the "div-curl problem" for a
given ${\mathbf F}\in{\mathbf H}^{-1}(\Omega)$. The solution is expressed in
terms of a vector potential (or stream function) ${\mathbf A}\in{\mathbf
H}^1(\Omega)$ such that ${\mathbf U}=\mathrm{curl}\,{\mathbf A}$. After
discussing existence and uniqueness of solutions and associated vector
potentials, we propose a well-posed construction for the stream function. A
numerical method based on this construction is presented, and experiments
confirm that the resulting approximations display higher regularity than those
of another common approach.
| [
"math.AP"
] | math.AP | Analysis of PDEs | 205Analysis of PDEs
|
|
1004.4160 | The fundamental properties of the lepton sector include the neutrino masses
and flavor mixings. Both are difficult to observe because of the extremely
small neutrino masses and neutrino-matter cross sections. In these lectures, we
focus on the basic concepts for the determination of neutrino properties. We
introduce neutrino oscillations as standard mechanism for neutrino flavor
changes, and we discuss methods to measure the neutrino mass. Furthermore, we
illustrate how precision measurements in neutrino oscillations will be
performed in the future, and may even open a window to new physics properties,
such as motivated by LHC physics. Finally, we discuss some applications of
neutrinos in astrophysics, such as neutrino oscillations in the Sun. We also
illustrate how neutrinos from extragalactic cosmic accelerators may be used for
the determination of neutrino properties.
| [
"hep-ph",
"hep-ex"
] | hep-ph | hep-ex | High Energy Physics - Phenomenology;High Energy Physics - Experiment | 3,198High Energy Physics - Phenomenology;High Energy Physics - Experiment
|
1801.04958 | Topic modeling enables exploration and compact representation of a corpus.
The CaringBridge (CB) dataset is a massive collection of journals written by
patients and caregivers during a health crisis. Topic modeling on the CB
dataset, however, is challenging due to the asynchronous nature of multiple
authors writing about their health journeys. To overcome this challenge we
introduce the Dynamic Author-Persona topic model (DAP), a probabilistic
graphical model designed for temporal corpora with multiple authors. The
novelty of the DAP model lies in its representation of authors by a persona ---
where personas capture the propensity to write about certain topics over time.
Further, we present a regularized variational inference algorithm, which we use
to encourage the DAP model's personas to be distinct. Our results show
significant improvements over competing topic models --- particularly after
regularization, and highlight the DAP model's unique ability to capture common
journeys shared by different authors.
| [
"cs.CL",
"cs.LG",
"stat.ML"
] | cs.CL | cs.LG | Computation and Language;Machine Learning;Machine Learning | 1,239Computation and Language;Machine Learning;Machine Learning
|
cs/0102002 | In this paper we discuss several issues related to automated text
classification of web sites. We analyze the nature of web content and metadata
in relation to requirements for text features. We find that HTML metatags are a
good source of text features, but are not in wide use despite their role in
search engine rankings. We present an approach for targeted spidering including
metadata extraction and opportunistic crawling of specific semantic hyperlinks.
We describe a system for automatically classifying web sites into industry
categories and present performance results based on different combinations of
text features and training data. This system can serve as the basis for a
generalized framework for automated metadata creation.
| [
"cs.IR"
] | cs.IR | Information Retrieval | 3,577Information Retrieval
|
|
2310.02629 | Mixture-of-experts based models, which use language experts to extract
language-specific representations effectively, have been well applied in
code-switching automatic speech recognition. However, there is still
substantial space to improve as similar pronunciation across languages may
result in ineffective multi-language modeling and inaccurate language boundary
estimation. To eliminate these drawbacks, we propose a cross-layer language
adapter and a boundary-aware training method, namely Boundary-Aware
Mixture-of-Experts (BA-MoE). Specifically, we introduce language-specific
adapters to separate language-specific representations and a unified gating
layer to fuse representations within each encoder layer. Second, we compute
language adaptation loss of the mean output of each language-specific adapter
to improve the adapter module's language-specific representation learning.
Besides, we utilize a boundary-aware predictor to learn boundary
representations for dealing with language boundary confusion. Our approach
achieves significant performance improvement, reducing the mixture error rate
by 16.55\% compared to the baseline on the ASRU 2019 Mandarin-English
code-switching challenge dataset.
| [
"cs.SD",
"eess.AS"
] | cs.SD | eess.AS | Sound;Audio and Speech Processing | 6,734Sound;Audio and Speech Processing
|
1610.06303 | This paper studies a fourth-order, nonlinear, doubly-degenerate parabolic
equation derived from the thin film equation in spherical geometry. A
regularization method is used to study the equation and several useful
estimates are obtained. The main result of this paper is to prove the existence
of a weak solution of the equation in a weighted Sobolev space.
| [
"math.AP"
] | math.AP | Analysis of PDEs | 205Analysis of PDEs
|
|
1910.01018 | Let $G$ be a Cayley graph of a nonamenable group with spectral radius $\rho <
1$. It is known that branching random walk on $G$ with offspring distribution
$\mu$ is transient, i.e., visits the origin at most finitely often almost
surely, if and only if the expected number of offspring $\bar \mu$ satisfies
$\bar \mu \leq \rho^{-1}$. Benjamini and M\"uller (2010) conjectured that
throughout the transient supercritical phase $1<\bar{\mu} \leq \rho^{-1}$, and
in particular at the recurrence threshold $\bar \mu = \rho^{-1}$, the trace of
the branching random walk is tree-like in the sense that it is infinitely-ended
almost surely on the event that the walk survives forever. This is essentially
equivalent to the assertion that two independent copies of the branching random
walk intersect at most finitely often almost surely. We prove this conjecture,
along with several other related conjectures made by the same authors.
A central contribution of this work is the introduction of the notion of
local unimodularity, which we expect to have several further applications in
the future.
| [
"math.PR",
"math.GR"
] | math.PR | math.GR | Probability;Group Theory | 5,756Probability;Group Theory
|
1701.01793 | In this paper, we present CrowdTone, a system designed to help people set the
appropriate tone in their email communication. CrowdTone utilizes the context
and content of an email message to identify and set the appropriate tone
through a consensus-building process executed by crowd workers. We evaluated
CrowdTone with 22 participants, who provided a total of 29 emails that they had
received in the past, and ran them through CrowdTone. Participants and
professional writers assessed the quality of improvements finding a substantial
increase in the percentage of emails deemed "appropriate" or "very appropriate"
- from 25% to more than 90% by recipients, and from 45% to 90% by professional
writers. Additionally, the recipients' feedback indicated that more than 90% of
the CrowdTone processed emails showed improvement.
| [
"cs.HC"
] | cs.HC | Human-Computer Interaction | 3,474Human-Computer Interaction
|
|
2103.00457 | Data collected in criminal investigations may suffer from: (i)
incompleteness, due to the covert nature of criminal organisations; (ii)
incorrectness, caused by either unintentional data collection errors and
intentional deception by criminals; (iii) inconsistency, when the same
information is collected into law enforcement databases multiple times, or in
different formats. In this paper we analyse nine real criminal networks of
different nature (i.e., Mafia networks, criminal street gangs and terrorist
organizations) in order to quantify the impact of incomplete data and to
determine which network type is most affected by it. The networks are firstly
pruned following two specific methods: (i) random edges removal, simulating the
scenario in which the Law Enforcement Agencies (LEAs) fail to intercept some
calls, or to spot sporadic meetings among suspects; (ii) nodes removal, that
catches the hypothesis in which some suspects cannot be intercepted or
investigated. Finally we compute spectral (i.e., Adjacency, Laplacian and
Normalised Laplacian Spectral Distances) and matrix (i.e., Root Euclidean
Distance) distances between the complete and pruned networks, which we compare
using statistical analysis. Our investigation identified two main features:
first, the overall understanding of the criminal networks remains high even
with incomplete data on criminal interactions (i.e., 10% removed edges);
second, removing even a small fraction of suspects not investigated (i.e., 2%
removed nodes) may lead to significant misinterpretation of the overall
network.
| [
"cs.SI",
"cs.CY"
] | cs.SI | cs.CY | Social and Information Networks;Computers and Society | 6,486Social and Information Networks;Computers and Society
|
2312.00944 | While perspective is a well-studied topic in art, it is generally taken for
granted in images. However, for the recent wave of high-quality image synthesis
methods such as latent diffusion models, perspective accuracy is not an
explicit requirement. Since these methods are capable of outputting a wide
gamut of possible images, it is difficult for these synthesized images to
adhere to the principles of linear perspective. We introduce a novel geometric
constraint in the training process of generative models to enforce perspective
accuracy. We show that outputs of models trained with this constraint both
appear more realistic and improve performance of downstream models trained on
generated images. Subjective human trials show that images generated with
latent diffusion models trained with our constraint are preferred over images
from the Stable Diffusion V2 model 70% of the time. SOTA monocular depth
estimation models such as DPT and PixelFormer, fine-tuned on our images,
outperform the original models trained on real images by up to 7.03% in RMSE
and 19.3% in SqRel on the KITTI test set for zero-shot transfer.
| [
"cs.CV",
"cs.GR"
] | cs.CV | cs.GR | Computer Vision and Pattern Recognition;Graphics | 1,568Computer Vision and Pattern Recognition;Graphics
|
cond-mat/9511040 | We investigate coarsening and persistence in the voter model by introducing
the quantity $P_n(t)$, defined as the fraction of voters who changed their
opinion n times up to time t. We show that $P_n(t)$ exhibits scaling behavior
that strongly depends on the dimension as well as on the initial opinion
concentrations. Exact results are obtained for the average number of opinion
changes, <n>, and the autocorrelation function, $A(t)\equiv \sum (-1)^n P_n\sim
t^{-d/2}$ in arbitrary dimension d. These exact results are complemented by a
mean-field theory, heuristic arguments and numerical simulations. For
dimensions d>2, the system does not coarsen, and the opinion changes follow a
nearly Poissonian distribution, in agreement with mean-field theory. For
dimensions d<=2, the distribution is given by a different scaling form, which
is characterized by nontrivial scaling exponents. For unequal opinion
concentrations, an unusual situation occurs where different scaling functions
correspond to the majority and the minority, as well as for even and odd n.
| [
"cond-mat"
] | cond-mat | Condensed Matter | 1,697Condensed Matter
|
|
2109.08010 | We introduce WildWood (WW), a new ensemble algorithm for supervised learning
of Random Forest (RF) type. While standard RF algorithms use bootstrap
out-of-bag samples to compute out-of-bag scores, WW uses these samples to
produce improved predictions given by an aggregation of the predictions of all
possible subtrees of each fully grown tree in the forest. This is achieved by
aggregation with exponential weights computed over out-of-bag samples, that are
computed exactly and very efficiently thanks to an algorithm called context
tree weighting. This improvement, combined with a histogram strategy to
accelerate split finding, makes WW fast and competitive compared with other
well-established ensemble methods, such as standard RF and extreme gradient
boosting algorithms.
| [
"cs.LG",
"stat.ML"
] | cs.LG | stat.ML | Machine Learning;Machine Learning | 4,163Machine Learning;Machine Learning
|
1006.0385 | Brain-Like Stochastic Search (BLiSS) refers to this task: given a family of
utility functions U(u,A), where u is a vector of parameters or task
descriptors, maximize or minimize U with respect to u, using networks (Option
Nets) which input A and learn to generate good options u stochastically. This
paper discusses why this is crucial to brain-like intelligence (an area funded
by NSF) and to many applications, and discusses various possibilities for
network design and training. The appendix discusses recent research, relations
to work on stochastic optimization in operations research, and relations to
engineering-based approaches to understanding neocortex.
| [
"cs.AI"
] | cs.AI | Artificial Intelligence | 361Artificial Intelligence
|
|
1611.04976 | Context: For many years, we have observed industry struggling in defining a
high quality requirements engineering (RE) and researchers trying to understand
industrial expectations and problems. Although we are investigating the
discipline with a plethora of empirical studies, those studies either
concentrate on validating specific methods or on single companies or countries.
Therefore, they allow only for limited empirical generalisations. Objective: To
lay an empirical and generalisable foundation about the state of the practice
in RE, we aim at a series of open and reproducible surveys that allow us to
steer future research in a problem-driven manner. Method: We designed a
globally distributed family of surveys in joint collaborations with different
researchers from different countries. The instrument is based on an initial
theory inferred from available studies. As a long-term goal, the survey will be
regularly replicated to manifest a clear understanding on the status quo and
practical needs in RE. In this paper, we present the design of the family of
surveys and first results of its start in Germany. Results: Our first results
contain responses from 30 German companies. The results are not yet
generalisable, but already indicate several trends and problems. For instance,
a commonly stated problem respondents see in their company standards are
artefacts being underrepresented, and important problems they experience in
their projects are incomplete and inconsistent requirements. Conclusion: The
results suggest that the survey design and instrument are well-suited to be
replicated and, thereby, to create a generalisable empirical basis of RE in
practice.
| [
"cs.SE"
] | cs.SE | Software Engineering | 6,626Software Engineering
|
|
1705.02305 | Community structure describes the organization of a network into subgraphs
that contain a prevalence of edges within each subgraph and relatively few
edges across boundaries between subgraphs. The development of
community-detection methods has occurred across disciplines, with numerous and
varied algorithms proposed to find communities. As we present in this Chapter
via several case studies, community detection is not just an "end game" unto
itself, but rather a step in the analysis of network data which is then useful
for furthering research in the disciplinary domain of interest. These
case-study examples arise from diverse applications, ranging from social and
political science to neuroscience and genetics, and we have chosen them to
demonstrate key aspects of community detection and to highlight that community
detection, in practice, should be directed by the application at hand.
| [
"physics.soc-ph",
"cs.SI",
"physics.data-an"
] | physics.soc-ph | cs.SI | Physics and Society;Social and Information Networks;Data Analysis, Statistics and Probability | 5,532Physics and Society;Social and Information Networks;Data Analysis, Statistics and Probability
|
mtrl-th/9607010 | Six-dimensional quantum dynamical calculations of the scattering of H_2 from
a Pd(100) surface using a potential energy surface derived from
density-functional theory calculations are presented. Due to the corrugation
and anisotropy of the PES strong off-specular and rotationally inelastic
diffraction is found. The dependence of the diffraction intensitities on the
incident kinetic energy is closely examined. In particular we focus on the
quantum oscillations for normal and off-normal incidence.
| [
"mtrl-th",
"cond-mat.mtrl-sci"
] | mtrl-th | cond-mat.mtrl-sci | Materials Science;Materials Science | 4,329Materials Science;Materials Science
|
1209.5308 | We study the dynamical evolution of the gravitational-wave driven instability
of the f-mode in rapidly rotating relativistic stars. With an approach based on
linear perturbation theory we describe the evolution of the mode amplitude and
follow the trajectory of a newborn neutron star through its instability window.
The influence on the f-mode instability of the magnetic field and the presence
of an unstable r-mode is also considered. Two different configurations are
studied in more detail; an N = 1 polytrope with a typical mass and radius and a
more massive polytropic N = 0.62 model with gravitational mass M = 1.98 Msun.
We study several evolutions with different initial rotation rates and
temperature and determine the gravitational waves radiated during the
instability. In more massive models, an unstable f-mode with a saturation
energy of about 1e-6 Msun c^2 may generate a gravitational-wave signal which
can be detected by the Advanced LIGO/Virgo detector from the Virgo cluster. The
magnetic field affects the evolution and then the detectability of the
gravitational radiation when its strength is higher than 1e12 G, while the
effects of an unstable r-mode become dominant when this mode reaches the
maximum saturation value allowed by non-linear mode couplings. However, the
relative saturation amplitude of the f- and r-modes must be known more
accurately in order to provide a definitive answer to this issue. From the
thermal evolution we find also that the heat generated by shear viscosity
during the saturation phase completely balances the neutrinos' cooling and
prevents the star from entering the regime of mutual friction. The evolution
time of the instability is therefore longer and the star loses significantly
larger amounts of angular momentum via gravitational waves.
| [
"astro-ph.SR",
"gr-qc"
] | astro-ph.SR | gr-qc | Solar and Stellar Astrophysics;General Relativity and Quantum Cosmology | 6,696Solar and Stellar Astrophysics;General Relativity and Quantum Cosmology
|
1809.05266 | We study the dissipative preparation of pure non-Gaussian states of a target
mode which is coupled both linearly and quadratically to an auxiliary damped
mode. We show that any pure state achieved independently of the initial
condition is either (i) a cubic phase state, namely a state given by the action
of a non-Gaussian (cubic) unitary on a squeezed vacuum or (ii) a (squeezed and
displaced) finite superposition of Fock states. Which of the two states is
realized depends on whether the transformation induced by the engineered
reservoir on the target mode is canonical (i) or not (ii). We discuss how to
prepare these states in an optomechanical cavity driven with multiple control
lasers, by tuning the relative strengths and phases of the drives. Relevant
examples in (ii) include the stabilization of mechanical Schr\"odinger cat-like
states or Fock-like states of any order. Our analysis is entirely analytical,
it extends reservoir engineering to the non-Gaussian regime and enables the
preparation of novel mechanical states with negative Wigner function.
| [
"quant-ph"
] | quant-ph | Quantum Physics | 5,985Quantum Physics
|
|
1511.08161 | Boson Sampling represents a promising witness of the supremacy of quantum
systems as a resource for the solution of computational problems. The classical
hardness of Boson Sampling has been related to the so called
Permanent-of-Gaussians Conjecture and has been extended to some generalizations
such as scattershot Boson Sampling, approximate and lossy sampling under some
reasonable constraints. However, it is still unclear how demanding these bounds
are for a quantum experimental sampler. Starting from a state of the art
analysis and focusing on the foreseeable practical conditions needed to reach
quantum supremacy, we look at different techniques and present a more general
and effective solution. We apply our approach to both the experimental
suggestions presented to date and we eventually find in both cases a new
threshold that is less error sensitive and experimentally more feasible.
| [
"quant-ph",
"physics.chem-ph"
] | quant-ph | physics.chem-ph | Quantum Physics;Chemical Physics | 6,011Quantum Physics;Chemical Physics
|
hep-ph/0006333 | For quantum theories with a classical limit (which includes the large N
limits of typical field theories), we derive a hierarchy of evolution equations
for equal time correlators which systematically incorporate corrections to the
limiting classical evolution. Explicit expressions are given for
next-to-leading order, and next-to-next-to-leading order time evolution. The
large N limit of N-component vector models, and the usual semiclassical limit
of point particle quantum mechanics are used as concrete examples. Our
formulation directly exploits the appropriate group structure which underlies
the construction of suitable coherent states and generates the classical phase
space. We discuss the growth of truncation error with time, and argue that
truncations of the large-N evolution equations are generically expected to be
useful only for times short compared to a ``decoherence'' time which scales
like N^{1/2}.
| [
"hep-ph",
"hep-th"
] | hep-ph | hep-th | High Energy Physics - Phenomenology;High Energy Physics - Theory | 3,223High Energy Physics - Phenomenology;High Energy Physics - Theory
|
1107.0446 | This paper introduces and studies a particular subclass of the class of
commutative rings with finite Gorenstein global dimension.
| [
"math.AC"
] | math.AC | Commutative Algebra | 1,107Commutative Algebra
|
|
2005.05176 | The H.E.S.S. Galactic Plane Survey (HGPS) represents one of the most
sensitive surveys of the Galactic Plane at very high energies (VHE, 0.1-100
TeV). However the source detection algorithm of the HGPS pipeline is not
well-suited for complex regions, including sources with shell-like
morphologies. As an alternative and complementary approach, we have
investigated blind search methods for VHE gamma-ray source detection based on
well-known and widely used image processing and pattern recognition techniques.
Our goal is to build in a short amount of computational time a list of
potentially valuable objects without prior case-specific morphological
assumptions. We aim to classify and rank the detected objects in order to
identify only the most promising source candidates for further
multi-wavelength-association searches, dedicated analyses, or deeper
observations. In the approach proposed, we extract sparse and pertinent
structural information from the significance maps using a edge detection
operator. We then apply a Hough circle transform and detect a collection of
objects as local maxima in the Hough space. On the basis of morphological
parameters we can characterize different object classes. Classification can be
used to identify valuable source candidates sharing the characteristics of
well-known sources. We show that using these pattern recognition techniques we
can detect objects with partial circular symmetry irrespective of a
morphological template (e.g. point-like, Gaussian-like, or shell-like). All the
shell-type supernova remnants (SNRs) catalogued in the HGPS are associated with
at least one detected object. Catalogue cross-matches indicate that several
detected objects not catalogued in the HGPS are spatially coincident with
multi-wavelength counterparts. Further investigation on the most promising
candidates will be conducted in dedicated follow-up analyses.
| [
"astro-ph.HE",
"astro-ph.IM"
] | astro-ph.HE | astro-ph.IM | High Energy Astrophysical Phenomena;Instrumentation and Methods for Astrophysics | 3,035High Energy Astrophysical Phenomena;Instrumentation and Methods for Astrophysics
|
2009.06230 | We show that the layered-structure BaCuS$_2$ is a moderately correlated
electron system in which the electronic structure of the CuS layer bears a
resemblance to those in both cuprates and iron-based superconductors.
Theoretical calculations reveal that the in-plane $d$-$p$ $\sigma^*$-bonding
bands are isolated near the Fermi level. As the energy separation between the
$d$ and $p$ orbitals are much smaller than those in cuprates and iron-based
superconductors, BaCuS$_2$ is expected to be moderately correlated. We suggest
that this material is an ideal system to study the competitive/collaborative
nature between two distinct superconducting pairing mechanisms, namely the
conventional BCS electron-phonon interaction and the electron-electron
correlation, which may be helpful to establish the elusive mechanism of
unconventional high-temperature superconductivity.
| [
"cond-mat.supr-con"
] | cond-mat.supr-con | Superconductivity | 7,066Superconductivity
|
|
1502.00944 | The depth-bounded fragment of the pi-calculus is an expressive class of
systems enjoying decidability of some important verification problems.
Unfortunately membership of the fragment is undecidable. We propose a novel
type system, parameterised over a finite forest, that formalises name usage by
pi-terms in a manner that respects the forest. Type checking is decidable and
type inference is computable; furthermore typable pi-terms are guaranteed to be
depth bounded.
The second contribution of the paper is a proof of equivalence between the
semantics of typable terms and nested data class memory automata, a class of
automata over data words. We believe this connection can help to establish new
links between the rich theory of infinite-alphabet automata and nominal
calculi.
| [
"cs.LO",
"cs.PL"
] | cs.LO | cs.PL | Logic in Computer Science;Programming Languages | 3,842Logic in Computer Science;Programming Languages
|
astro-ph/9503058 | We recently reported strong evidence for solar-like oscillations in the G0 IV
star eta Boo (Kjeldsen et al. 1995, AJ 109, 1313). We measured small
temperature fluctuations produced by oscillations through their effect on the
equivalent widths of the Balmer lines. Here we address several issues that were
raised at this conference. In particular, we show a power spectrum made without
applying a high-pass filter to the observations. This spectrum shows increased
noise at low frequencies, as expected, and the oscillation signature is still
clearly visible.
| [
"astro-ph"
] | astro-ph | Astrophysics | 463Astrophysics
|
|
1511.07082 | We provide several constructions for problems in Ramsey theory. First, we
prove a superexponential lower bound for the classical 4-uniform Ramsey number
$r_4(5,n)$, and the same for the iterated $(k-4)$-fold logarithm of the
$k$-uniform version $r_k(k+1,n)$. This is the first improvement of the original
exponential lower bound for $r_4(5,n)$ implicit in work of Erd\H os and Hajnal
from 1972 and also improves the current best known bounds for larger $k$ due to
the authors. Second, we prove an upper bound for the hypergraph Erd\H os-Rogers
function $f^k_{k+1, k+2}(N)$ that is an iterated $(k-13)$-fold logarithm in
$N$. This improves the previous upper bounds that were only logarithmic and
addresses a question of Dudek and the first author that was reiterated by
Conlon, Fox and Sudakov. Third, we generalize the results of Erd\H os and
Hajnal about the 3-uniform Ramsey number of $K_4$ minus an edge versus a clique
to $k$-uniform hypergraphs.
| [
"math.CO"
] | math.CO | Combinatorics | 1,014Combinatorics
|
|
1904.09905 | In this article, we consider fractional stochastic wave equations on $\mathbb
R$ driven by a multiplicative Gaussian noise which is white/colored in time and
has the covariance of a fractional Brownian motion with Hurst parameter
$H\in(\frac14, \frac12)$ in space. We prove the existence and uniqueness of the
mild Skorohod solution, establish lower and upper bounds for the $p$-th moment
of the solution for all $p\ge2$, and obtain the H\"older continuity in time and
space variables for the solution.
| [
"math.PR"
] | math.PR | Probability | 5,709Probability
|
|
1808.06300 | Let $v_n$ be the maximum expected length of an increasing subsequence, which
can be selected by an online nonanticipating policy from a random sample of
size $n$. Refining known estimates, we obtain an asymptotic expansion of $v_n$
up to a $O(1)$ term. The method we use is based on detailed analysis of the
dynamic programming equation, and is also applicable to the online selection
problem with observations occurring at times of a Poisson process.
| [
"math.OC"
] | math.OC | Optimization and Control | 5,234Optimization and Control
|
|
2312.07811 | This investigation explores the asymptotic shape for subadditive processes on
finitely generated groups with polynomial growth, commonly referred to as
virtually nilpotent groups. By shedding light on the algebraic structures
inherent in a specific class of subadditive processes, the study presents a
generalization beyond the fundamental settings of previously explored models.
The findings not only contribute to our understanding of mathematical
structures but also have the potential to deepen insights into various
mathematical phenomena. The article concludes by highlighting potential
applications arising from the derived results, supported by illustrative
examples.
| [
"math.PR",
"math.GR"
] | math.PR | math.GR | Probability;Group Theory | 5,756Probability;Group Theory
|
1404.3579 | Forecasting the in situ properties of coronal mass ejections (CMEs) from
remote images is expected to strongly enhance predictions of space weather, and
is of general interest for studying the interaction of CMEs with planetary
environments. We study the feasibility of using a single heliospheric imager
(HI) instrument, imaging the solar wind density from the Sun to 1 AU, for
connecting remote images to in situ observations of CMEs. We compare the
predictions of speed and arrival time for 22 CMEs (in 2008-2012) to the
corresponding interplanetary coronal mass ejection (ICME) parameters at in situ
observatories (STEREO PLASTIC/IMPACT, Wind SWE/MFI). The list consists of
front- and backsided, slow and fast CMEs (up to $2700 \: km \: s^{-1}$). We
track the CMEs to $34.9 \pm 7.1$ degrees elongation from the Sun with J-maps
constructed using the SATPLOT tool, resulting in prediction lead times of
$-26.4 \pm 15.3$ hours. The geometrical models we use assume different CME
front shapes (Fixed-$\Phi$, Harmonic Mean, Self-Similar Expansion), and
constant CME speed and direction. We find no significant superiority in the
predictive capability of any of the three methods. The absolute difference
between predicted and observed ICME arrival times is $8.1 \pm 6.3$ hours ($rms$
value of 10.9h). Speeds are consistent to within $284 \pm 288 \: km \: s^{-1}$.
Empirical corrections to the predictions enhance their performance for the
arrival times to $6.1 \pm 5.0$ hours ($rms$ value of 7.9h), and for the speeds
to $53 \pm 50 \: km \: s^{-1}$. These results are important for Solar Orbiter
and a space weather mission positioned away from the Sun-Earth line.
| [
"astro-ph.SR",
"astro-ph.EP"
] | astro-ph.SR | astro-ph.EP | Solar and Stellar Astrophysics;Earth and Planetary Astrophysics | 6,684Solar and Stellar Astrophysics;Earth and Planetary Astrophysics
|
hep-ph/0111329 | Results are reviewed, which provide relations between the response (and
eventual instability) of the chiral QCD vacuum to an increase of the number of
massless quarks in the theory and the observed violations of the large $N_c$
expansion in the scalar meson sector, by combining chiral perturbation theory
expansions in $m_s$ with sum rule methods. An approach based on the
construction of scalar form-factors was recently confirmed by an independent
approach which uses the $\pi K$ scattering amplitudes.
| [
"hep-ph"
] | hep-ph | High Energy Physics - Phenomenology | 3,129High Energy Physics - Phenomenology
|
|
2201.12762 | Effect of interfacial disturbances on instabilities of
buoyant/thermocapillary convective flows in rectangular cavities is studied in
a series of numerical experiments. The computations are carried out for several
two-liquid two-layer systems taking into account properties of liquids used in
previously published experiments. Relation between the interface deformations
and the Boussinesq approximation is discussed. It is shown that in some
systems, including the interface disturbances in the model can alter the
critical temperature difference by approximately 10%, producing either
destabilizing, or stabilizing effect. The interface oscillations appear as
standing or travelling waves whose wavelength can vary from short wave lengths
to a single wave occupying all the available space. Rough estimations show that
in some liquid-liquid systems the interface oscillations amplitude can reach
several tens of microns. Patterns of the most unstable disturbances are
presented and discussed. It is argued that instabilities in some two layer
systems develop similarly to the Holmboe instabilities in stratified mixing
layers.
| [
"physics.flu-dyn"
] | physics.flu-dyn | Fluid Dynamics | 2,452Fluid Dynamics
|
|
2006.01260 | In this paper we demonstrate that it is possible to generate more meaningful
electroencephalography (EEG) features from raw EEG features using generative
adversarial networks (GAN) to improve the performance of EEG based continuous
speech recognition systems. We improve the results demonstrated by authors in
[1] using their data sets for for some of the test time experiments and for
other cases our results were comparable with theirs. Our proposed approach can
be implemented without using any additional sensor information, whereas in [1]
authors used additional features like acoustic or articulatory information to
improve the performance of EEG based continuous speech recognition systems.
| [
"eess.AS",
"cs.LG",
"cs.SD"
] | eess.AS | cs.LG | Audio and Speech Processing;Machine Learning;Sound | 661Audio and Speech Processing;Machine Learning;Sound
|
1412.0695 | The DUSTiNGS survey (DUST in Nearby Galaxies with Spitzer) is a 3.6 and 4.5
micron imaging survey of 50 nearby dwarf galaxies designed to identify
dust-producing Asymptotic Giant Branch (AGB) stars and massive stars. Using two
epochs, spaced approximately six months apart, we identify a total of 526 dusty
variable AGB stars (sometimes called "extreme" or x-AGB stars; [3.6]-[4.5]>0.1
mag). Of these, 111 are in galaxies with [Fe/H] < -1.5 and 12 are in galaxies
with [Fe/H] < -2.0, making them the most metal-poor dust-producing AGB stars
known. We compare these identifications to those in the literature and find
that most are newly discovered large-amplitude variables, with the exception of
approximately 30 stars in NGC 185 and NGC 147, one star in IC 1613, and one
star in Phoenix. The chemical abundances of the x-AGB variables are unknown,
but the low metallicities suggest that they are more likely to be carbon-rich
than oxygen-rich and comparisons with existing optical and near-IR photometry
confirms that 70 of the x-AGB variables are confirmed or likely carbon stars.
We see an increase in the pulsation amplitude with increased dust production,
supporting previous studies suggesting that dust production and pulsation are
linked. We find no strong evidence linking dust production with metallicity,
indicating that dust can form in very metal-poor environments.
| [
"astro-ph.GA"
] | astro-ph.GA | Astrophysics of Galaxies | 464Astrophysics of Galaxies
|
|
1909.08704 | We introduce the Balsam service to manage high-throughput task scheduling and
execution on supercomputing systems. Balsam allows users to populate a task
database with a variety of tasks ranging from simple independent tasks to
dynamic multi-task workflows. With abstractions for the local resource
scheduler and MPI environment, Balsam dynamically packages tasks into ensemble
jobs and manages their scheduling lifecycle. The ensembles execute in a pilot
"launcher" which (i) ensures concurrent, load-balanced execution of arbitrary
serial and parallel programs with heterogeneous processor requirements, (ii)
requires no modification of user applications, (iii) is tolerant of task-level
faults and provides several options for error recovery, (iv) stores provenance
data (e.g task history, error logs) in the database, (v) supports dynamic
workflows, in which tasks are created or killed at runtime. Here, we present
the design and Python implementation of the Balsam service and launcher. The
efficacy of this system is illustrated using two case studies: hyperparameter
optimization of deep neural networks, and high-throughput single-point quantum
chemistry calculations. We find that the unique combination of flexible
job-packing and automated scheduling with dynamic (pilot-managed) execution
facilitates excellent resource utilization. The scripting overheads typically
needed to manage resources and launch workflows on supercomputers are
substantially reduced, accelerating workflow development and execution.
| [
"cs.DC"
] | cs.DC | Distributed, Parallel, and Cluster Computing | 2,194Distributed, Parallel, and Cluster Computing
|
|
0708.2854 | We give a survey of algorithms for computing topological invariants of
semi-algebraic sets with special emphasis on the more recent developments in
designing algorithms for computing the Betti numbers of semi-algebraic sets.
Aside from describing these results, we discuss briefly the background as well
as the importance of these problems, and also describe the main tools from
algorithmic semi-algebraic geometry, as well as algebraic topology, which make
these advances possible. We end with a list of open problems.
| [
"math.GT",
"cs.CC",
"cs.CG",
"math.AG",
"math.AT"
] | math.GT | cs.CC | Geometric Topology;Computational Complexity;Computational Geometry;Algebraic Geometry;Algebraic Topology | 7,267longtail
|
1602.03078 | For open sets $\Omega\subset \mathbb{R}^d$ we study Hadamard operators on
$\mathscr{D}'(\Omega)$, that is, continuous linear operators which admit all
monomials as eigenvectors. We characterize them as operators of the form
$L(S)=S\star T$ where $T$ is a distribution and $\star$ the multiplicative
convolution. This extends previous results for the case of
$\Omega=\mathbb{R}^d$ but requires essentially different methods.
| [
"math.FA"
] | math.FA | Functional Analysis | 2,549Functional Analysis
|
|
cond-mat/0603792 | In this short review we present our recent results concerning the rotation of
atomic Bose-Einstein condensates confined in quadratic or quartic potentials,
and give an overview of the field. We first describe the procedure used to set
an atomic gas in rotation and briefly discuss the physics of condensates
containing a single vortex line. We then address the regime of fast rotation in
harmonic traps, where the rotation frequency is close to the trapping
frequency. In this limit the Landau Level formalism is well suited to describe
the system. The problem of the condensation temperature of a fast rotating gas
is discussed, as well as the equilibrium shape of the cloud and the structure
of the vortex lattice. Finally we review results obtained with a quadratic +
quartic potential, which allows to study a regime where the rotation frequency
is equal to or larger than the harmonic trapping frequency.
| [
"cond-mat.mes-hall"
] | cond-mat.mes-hall | Mesoscale and Nanoscale Physics | 4,450Mesoscale and Nanoscale Physics
|
|
1006.4482 | A factorization formula for wave functions, which is basic in the inverse
spectral transform approach to initial-boundary value problems, is proved in
greater generality than before. Applications follow. Related compatibility
questions for the GBDT version of B\"acklund-Darboux transformation are treated
too.
| [
"math.FA",
"math.AP",
"math.SP",
"nlin.SI"
] | math.FA | math.AP | Functional Analysis;Analysis of PDEs;Spectral Theory;Exactly Solvable and Integrable Systems | 7,267longtail
|
1109.0140 | We analyze the effect of Proca mass and orbital angular momentum of photons
imposed by a structured plasma in Kerr-Newman and Reissner-Nordstrom-de Sitter
spacetimes. The presence of characteristic lengths in a turbulent plasma
converts the virtual Proca photon mass on orbital angular momentum, with the
result of decreasing the virtual photon mass. The combination of this plasma
effect and that of the gravitational field leads to a new astrophysical
phenomenon that imprints a specific distribution of orbital angular momentum
into different frequencies of the light emitted from the neighborhood of such a
black hole. The determination of the orbital angular momentum spectrum of the
radiation in different frequency bands leads to a complete characterization of
the electrostatic and gravitational field of the black hole and of the plasma
turbulence, with fundamental astrophysical and cosmological implications.
| [
"gr-qc",
"astro-ph.HE",
"quant-ph"
] | gr-qc | astro-ph.HE | General Relativity and Quantum Cosmology;High Energy Astrophysical Phenomena;Quantum Physics | 2,737General Relativity and Quantum Cosmology;High Energy Astrophysical Phenomena;Quantum Physics
|
1709.03168 | We consider two types of fractional integral moduli of smoothness, which are
widely used in theory of functions and approximation theory. In particular, we
obtain new equivalences between these moduli of smoothness and the classical
moduli of smoothness. It turns out that for fractional integral moduli of
smoothness some pathological effects arise.
| [
"math.CA"
] | math.CA | Classical Analysis and ODEs | 934Classical Analysis and ODEs
|
|
2104.14999 | In an oscillatory medium, a region which oscillates faster than its
surroundings can act as a source of outgoing waves. Such pacemaker-generated
waves can synchronize the whole medium and are present in many chemical and
biological systems, where they are a means of transmitting information at a
fixed speed over large distances. In this paper, we apply analytical tools to
investigate the factors that determine the speed of these waves. More
precisely, we apply singular perturbation and phase reduction methods to two
types of negative-feedback oscillators, one built on underlying bistability and
one including a time delay in the negative feedback. In both systems, we
investigate the influence of timescale separation on the resulting wave speed,
as well as the effect of size and frequency of the pacemaker region. We compare
our analytical estimates to numerical simulations which we described previously
[1].
| [
"nlin.PS",
"physics.bio-ph"
] | nlin.PS | physics.bio-ph | Pattern Formation and Solitons;Biological Physics | 5,411Pattern Formation and Solitons;Biological Physics
|
astro-ph/0104115 | We use data on the local 3-dimensional galaxy distribution for studying the
statistics of the detection rates of gravitational waves (GW) coming from
supernova explosions. We consider both tensor and scalar gravitational waves
which are possible in a wide range of relativistic and quantum gravity
theories. We show that statistics of GW events as a function of sidereal time
can be used for distinction between scalar and tensor gravitational waves
because of the anisotropy of spatial galaxy distribution. For calculation of
the expected amplitudes of GW signals we use the values of the released GW
energy, frequency and duration of GW pulse which are consistent with existing
scenarios of SN core collapse. The amplitudes of the signals produced by Virgo
and the Great Attractor clusters of galaxies is expressed as a function of the
sidereal time for resonant bar detectors operating now (IGEC) and for
forthcoming laser interferometric detectors (VIRGO).Then, we calculate the
expected number of GW events as a function of sidereal time produced by all the
galaxies within 100 Mpc. In the case of axisymmetric rotational core collapse
which radiates a GW energy of $10^{-9}M_{\odot}c^2$, only the closest
explosions can be detected. However, in the case of nonaxisymmetric supernova
explosion, due to such phenomena as centrifugal hangup, bar and lump formation,
the GW radiation could be as strong as that from a coalescing neutron-star
binary. For radiated GW energy higher than $10^{-6}M_{\odot}c^2$ and
sensitivity of detectors at the level $h \approx 10^{-23}$ it is possible to
detect Virgo cluster and Great Attractor, and hence to use the statistics of GW
events for testing gravity theories.
| [
"astro-ph"
] | astro-ph | Astrophysics | 463Astrophysics
|
|
2005.01419 | Computer science class enrollments have rapidly risen in the past decade.
With current class sizes, standard approaches to grading and providing
personalized feedback are no longer possible and new techniques become both
feasible and necessary. In this paper, we present the third version of Automata
Tutor, a tool for helping teachers and students in large courses on automata
and formal languages. The second version of Automata Tutor supported automatic
grading and feedback for finite-automata constructions and has already been
used by thousands of users in dozens of countries. This new version of Automata
Tutor supports automated grading and feedback generation for a greatly extended
variety of new problems, including problems that ask students to create regular
expressions, context-free grammars, pushdown automata and Turing machines
corresponding to a given description, and problems about converting between
equivalent models - e.g., from regular expressions to nondeterministic finite
automata. Moreover, for several problems, this new version also enables
teachers and students to automatically generate new problem instances. We also
present the results of a survey run on a class of 950 students, which shows
very positive results about the usability and usefulness of the tool.
| [
"cs.FL"
] | cs.FL | Formal Languages and Automata Theory | 2,525Formal Languages and Automata Theory
|
|
1605.01766 | For a subgroup of a free product of finite groups, we obtain necessary
conditions (on its Kurosh decomposition) to be verbally closed.
| [
"math.GR"
] | math.GR | Group Theory | 2,913Group Theory
|
|
1409.7638 | The study of the graph diameter of polytopes is a classical open problem in
polyhedral geometry and the theory of linear optimization. In this paper we
continue the investigation initiated in [4] by introducing a vast hierarchy of
generalizations to the notion of graph diameter. This hierarchy provides some
interesting lower bounds for the usual graph diameter. After explaining the
structure of the hierarchy and discussing these bounds, we focus on clearly
explaining the differences and similarities among the many diameter notions of
our hierarchy. Finally, we fully characterize the hierarchy in dimension two.
It collapses into fewer categories, for which we exhibit the ranges of values
that can be realized as diameters.
| [
"math.CO",
"math.OC"
] | math.CO | math.OC | Combinatorics;Optimization and Control | 1,092Combinatorics;Optimization and Control
|
1711.04519 | In this paper we study symmetry properties of the Hilbert transformation of
several real variables in the Clifford algebra setting. In order to describe
the symmetry properties we introduce the group $r\mathrm{Spin}(n)+\mathbb{R}^n,
r>0,$ which is essentially an extension of the ax+b group. The study concludes
that the Hilbert transformation has certain characteristic symmetry properties
in terms of $r\mathrm{Spin}(n)+\mathbb{R}^n.$ In the present paper, for $n=2$
and $3$ we obtain, explicitly, the induced spinor representations of the
$r\mathrm{Spin}(n)+\mathbb{R}^n$ group. Then we decompose the natural
representation of $r\mathrm{Spin}(n)+\mathbb{R}^n$ into the direct sum of some
two irreducible spinor representations, by which we characterize the Hilbert
transformation in $\mathbb{R}^3$ and $\mathbb{R}^2.$ Precisely, we show that a
nontrivial skew operator is the Hilbert transformation if and only if it is
invariant under the action of the $r\mathrm{Spin}(n)+\mathbb{R}^n, n=2,3,$
group.
| [
"math.CV",
"math.RT"
] | math.CV | math.RT | Complex Variables;Representation Theory | 1,163Complex Variables;Representation Theory
|
0807.2092 | Here we address the question regarding the nature of quark gluon plasma
(QGP), whether it is a liquid or strongly coupled plasma (SCP), using two
different phenomenological models, namely quasi-particle model (qQGP) and
strongly coupled quark gluon plasma (SCQGP). First we compare these two models,
both of which explains the results of lattice simulation of quantum
chromodynamics, as a function of plasma parameter and conclude that the QGP is
largely ($T > 1.5 T_c$) SCQGP and only for $T < 1.5 T_c$ it may be a liquid.
| [
"hep-ph"
] | hep-ph | High Energy Physics - Phenomenology | 3,129High Energy Physics - Phenomenology
|
|
1104.2807 | The aim of this article is to give explicit formulae for various generating
functions, including the generating function of torus-invariant primitive
ideals in the big cell of the quantum minuscule grassmannian of type B_n.
| [
"math.QA",
"math.CO",
"math.RT"
] | math.QA | math.CO | Quantum Algebra;Combinatorics;Representation Theory | 5,887Quantum Algebra;Combinatorics;Representation Theory
|
1810.07706 | The final ringdown phase in a coalescence process is a valuable laboratory to
test General Relativity and potentially constrain additional degrees of freedom
in the gravitational sector. We introduce here an effective description for
perturbations around spherically symmetric spacetimes in the context of
scalar-tensor theories, which we apply to study quasi-normal modes for black
holes with scalar hair. We derive the equations of motion governing the
dynamics of both the polar and the axial modes in terms of the coefficients of
the effective theory. Assuming the deviation of the background from
Schwarzschild is small, we use the WKB method to introduce the notion of "light
ring expansion". This approximation is analogous to the slow-roll expansion
used for inflation, and it allows us to express the quasinormal mode spectrum
in terms of a small number of parameters. This work is a first step in
describing, in a model independent way, how the scalar hair can affect the
ringdown stage and leave signatures on the emitted gravitational wave signal.
Potential signatures include the shifting of the quasi-normal spectrum, the
breaking of isospectrality between polar and axial modes, and the existence of
scalar radiation.
| [
"hep-th",
"astro-ph.CO",
"gr-qc"
] | hep-th | astro-ph.CO | High Energy Physics - Theory;Cosmology and Nongalactic Astrophysics;General Relativity and Quantum Cosmology | 3,306High Energy Physics - Theory;Cosmology and Nongalactic Astrophysics;General Relativity and Quantum Cosmology
|
1801.02877 | Consecutive stochastic 90{\deg} polarization switching events, clearly
resolved in recent experiments, are described by a new nucleation and growth
multi-step model. It extends the classical Kolmogorov-Avrami-Ishibashi approach
and includes possible consecutive 90{\deg}- and parallel 180{\deg}-switching
events. The model predicts the results of simultaneous time-resolved
macroscopic measurements of polarization and strain, performed on a tetragonal
Pb(Zr,Ti)O3 ceramic in a wide range of electric fields over a time domain of
five orders of the magnitude. It allows the determination of the fractions of
individual switching processes, their characteristic switching times,
activation fields, and respective Avrami indices.
| [
"cond-mat.mtrl-sci"
] | cond-mat.mtrl-sci | Materials Science | 4,287Materials Science
|
|
math/9905109 | Given a lattice polytope $P$ (with underlying lattice $\lo$), the universal
counting function $\uu_P(\lo')=|P\cap \lo'|$ is defined on all lattices $\lo'$
containing $\lo$. Motivated by questions concerning lattice polytopes and the
Ehrhart polynomial, we study the equation $\uu_P=\uu_Q$.
| [
"math.CO",
"math.AG"
] | math.CO | math.AG | Combinatorics;Algebraic Geometry | 1,015Combinatorics;Algebraic Geometry
|
2308.15830 | Highly magnetized neutron stars have magnetic fields of order of the critical
field and can lead to measurable QED effects. We consider the Goldreich-Julian
pulsar model with supercritical magnetic fields, induced subcritical electric
fields, and a period of milliseconds. We then study the strong field physics,
such as Schwinger pair production and the vacuum birefringence including the
wrench effect, whose X-ray polarimetry will be observed in future space
missions.
| [
"astro-ph.HE",
"hep-ph"
] | astro-ph.HE | hep-ph | High Energy Astrophysical Phenomena;High Energy Physics - Phenomenology | 3,031High Energy Astrophysical Phenomena;High Energy Physics - Phenomenology
|
1811.01032 | We propose a novel method to measure flavor-oscillations and charge-parity
(CP) violation in charm mixing. The approach uses multibody charm decays, such
as $D^0\to K_S^0\pi^+\pi^-$, and avoids the need for a fit of the decay
amplitudes while suppressing biases due to nonuniform signal-reconstruction
efficiencies as functions of phase space and decay time. Data are partitioned
in decay-time and Dalitz-plot regions (bins). The Dalitz-plot bins are
symmetric with respect to the principal bisector and chosen to ensure nearly
constant values of the strong-interaction phases in each. The ratios of signal
yields observed in each symmetric bin pair are fit as functions of decay time,
using independent auxiliary measurements of the strong-interaction phases as
constraints, to determine the relevant physics parameters. Simulation shows
that this approach improves the sensitivity to the normalized charm-eigenstate
mass difference by 35% with respect to existing model-independent methods. In
addition, we introduce a parametrization of oscillation and CP-violation
effects in charm mixing that has attractive statistical properties and may find
wider applicability.
| [
"hep-ex",
"hep-ph"
] | hep-ex | hep-ph | High Energy Physics - Experiment;High Energy Physics - Phenomenology | 3,075High Energy Physics - Experiment;High Energy Physics - Phenomenology
|
1705.03728 | We test numerically the recently proposed linear relationship between the
scale-invariant period $T_{\rm s.i.} = T |E|^{3/2}$, and the topology of an
orbit, on several hundred planar Newtonian periodic three-body orbits. Here $T$
is the period of an orbit, $E$ is its energy, so that $T_{\rm s.i.}$ is the
scale-invariant (s.i.) period, or, equivalently, the period at unit energy $|E|
= 1$. All of these orbits have vanishing angular momentum and pass through a
linear, equidistant configuration at least once. Such orbits are classified in
ten algebraically well-defined sequences. Orbits in each sequence follow an
approximate linear dependence of $T_{\rm s.i.}$, albeit with slightly different
slopes and intercepts. The orbit with the shortest period in its sequence is
called the "progenitor": six distinct orbits are the progenitors of these ten
sequences. We have studied linear stability of these orbits, with the result
that 21 orbits are linearly stable, which includes all of the progenitors. This
is consistent with the Birkhoff-Lewis theorem, which implies existence of
infinitely many periodic orbits for each stable progenitor, and in this way
explains the existence and ensures infinite extension of each sequence.
| [
"physics.class-ph",
"physics.comp-ph"
] | physics.class-ph | physics.comp-ph | Classical Physics;Computational Physics | 989Classical Physics;Computational Physics
|
2208.10652 | Estimating 3D human pose and shape from 2D images is a crucial yet
challenging task. While prior methods with model-based representations can
perform reasonably well on whole-body images, they often fail when parts of the
body are occluded or outside the frame. Moreover, these results usually do not
faithfully capture the human silhouettes due to their limited representation
power of deformable models (e.g., representing only the naked body). An
alternative approach is to estimate dense vertices of a predefined template
body in the image space. Such representations are effective in localizing
vertices within an image but cannot handle out-of-frame body parts. In this
work, we learn dense human body estimation that is robust to partial
observations. We explicitly model the visibility of human joints and vertices
in the x, y, and z axes separately. The visibility in x and y axes help
distinguishing out-of-frame cases, and the visibility in depth axis corresponds
to occlusions (either self-occlusions or occlusions by other objects). We
obtain pseudo ground-truths of visibility labels from dense UV correspondences
and train a neural network to predict visibility along with 3D coordinates. We
show that visibility can serve as 1) an additional signal to resolve depth
ordering ambiguities of self-occluded vertices and 2) a regularization term
when fitting a human body model to the predictions. Extensive experiments on
multiple 3D human datasets demonstrate that visibility modeling significantly
improves the accuracy of human body estimation, especially for partial-body
cases. Our project page with code is at: https://github.com/chhankyao/visdb.
| [
"cs.CV"
] | cs.CV | Computer Vision and Pattern Recognition | 1,498Computer Vision and Pattern Recognition
|
|
1407.3718 | We extend the Z. Gajda's result concerning the stability threshold for
additive mappings to the n-additive and symmetric functions.
| [
"math.FA"
] | math.FA | Functional Analysis | 2,549Functional Analysis
|
|
1809.02472 | Multicopters are becoming increasingly important in both civil and military
fields. Currently, most multicopter propulsion systems are designed by
experience and trial-and-error experiments, which are costly and ineffective.
This paper proposes a simple and practical method to help designers find the
optimal propulsion system according to the given design requirements. First,
the modeling methods for four basic components of the propulsion system
including propellers, motors, electric speed controls, and batteries are
studied respectively. Secondly, the whole optimization design problem is
simplified and decoupled into several sub-problems. By solving these
sub-problems, the optimal parameters of each component can be obtained
respectively. Finally, based on the obtained optimal component parameters, the
optimal product of each component can be quickly located and determined from
the corresponding database. Experiments and statistical analyses demonstrate
the effectiveness of the proposed method.
| [
"cs.SY",
"cs.RO"
] | cs.SY | cs.RO | Systems and Control;Robotics | 7,210Systems and Control;Robotics
|
2006.15263 | The Sun exhibits a well-observed modulation in the number of spots on its
disk over a period of about 11 years. From the dawn of modern observational
astronomy sunspots have presented a challenge to understanding -- their
quasi-periodic variation in number, first noted 175 years ago, stimulates
community-wide interest to this day. A large number of techniques are able to
explain the temporal landmarks, (geometric) shape, and amplitude of sunspot
"cycles," however forecasting these features accurately in advance remains
elusive. Recent observationally-motivated studies have illustrated a
relationship between the Sun's 22-year (Hale) magnetic cycle and the production
of the sunspot cycle landmarks and patterns, but not the amplitude of the
sunspot cycle. Using (discrete) Hilbert transforms on more than 270 years of
(monthly) sunspot numbers we robustly identify the so-called "termination"
events that mark the end of the previous 11-yr sunspot cycle, the
enhancement/acceleration of the present cycle, and the end of 22-yr magnetic
activity cycles. Using these we extract a relationship between the temporal
spacing of terminators and the magnitude of sunspot cycles. Given this
relationship and our prediction of a terminator event in 2020, we deduce that
Sunspot Cycle 25 could have a magnitude that rivals the top few since records
began. This outcome would be in stark contrast to the community consensus
estimate of sunspot cycle 25 magnitude.
| [
"astro-ph.SR",
"physics.ao-ph",
"physics.space-ph"
] | astro-ph.SR | physics.ao-ph | Solar and Stellar Astrophysics;Atmospheric and Oceanic Physics;Space Physics | 7,267longtail
|
2312.11750 | Transformers have revolutionized deep learning and generative modeling,
enabling unprecedented advancements in natural language processing tasks.
However, the size of transformer models is increasing continuously, driven by
enhanced capabilities across various deep-learning tasks. This trend of
ever-increasing model size has given rise to new challenges in terms of memory
and computing requirements. Conventional computing platforms, including GPUs,
suffer from suboptimal performance due to the memory demands imposed by models
with millions/billions of parameters. The emerging chiplet-based platforms
provide a new avenue for compute- and data-intensive machine learning (ML)
applications enabled by a Network-on-Interposer (NoI). However, designing
suitable hardware accelerators for executing Transformer inference workloads is
challenging due to a wide variety of complex computing kernels in the
Transformer architecture. In this paper, we leverage chiplet-based
heterogeneous integration (HI) to design a high-performance and
energy-efficient multi-chiplet platform to accelerate transformer workloads. We
demonstrate that the proposed NoI architecture caters to the data access
patterns inherent in a transformer model. The optimized placement of the
chiplets and the associated NoI links and routers enable superior performance
compared to the state-of-the-art hardware accelerators. The proposed NoI-based
architecture demonstrates scalability across varying transformer models and
improves latency and energy efficiency by up to 22.8x and 5.36x respectively.
| [
"cs.AR",
"cs.DC"
] | cs.AR | cs.DC | Hardware Architecture;Distributed, Parallel, and Cluster Computing | 2,975Hardware Architecture;Distributed, Parallel, and Cluster Computing
|
2012.14234 | The proliferation of massive open online courses (MOOCs) demands an effective
way of course recommendation for jobs posted in recruitment websites,
especially for the people who take MOOCs to find new jobs. Despite the advances
of supervised ranking models, the lack of enough supervised signals prevents us
from directly learning a supervised ranking model. This paper proposes a
general automated weak supervision framework AutoWeakS via reinforcement
learning to solve the problem. On the one hand, the framework enables training
multiple supervised ranking models upon the pseudo labels produced by multiple
unsupervised ranking models. On the other hand, the framework enables
automatically searching the optimal combination of these supervised and
unsupervised models. Systematically, we evaluate the proposed model on several
datasets of jobs from different recruitment websites and courses from a MOOCs
platform. Experiments show that our model significantly outperforms the
classical unsupervised, supervised and weak supervision baselines.
| [
"cs.DB",
"cs.IR"
] | cs.DB | cs.IR | Databases;Information Retrieval | 2,000Databases;Information Retrieval
|
2309.15586 | We prove that if $G$ is a finite irreducible solvable subgroup of an
orthogonal group $O(V,Q)$ with $\dim V$ odd, then $G$ preserves an orthogonal
decomposition of $V$ into $1$-spaces. In particular $G$ is monomial. This
generalizes a theorem of Rod Gow.
| [
"math.GR",
"math.RT"
] | math.GR | math.RT | Group Theory;Representation Theory | 2,966Group Theory;Representation Theory
|
1305.1691 | The main result of this paper is a bi-parameter T(b) theorem for the case
that b is a tensor product of two pseudo-accretive functions. In the proof, we
also discuss the L^2 boundedness of different types of the b-adapted
bi-parameter paraproducts.
| [
"math.CA"
] | math.CA | Classical Analysis and ODEs | 934Classical Analysis and ODEs
|
|
1506.06964 | The present work deals with the resolution of the Poisson equation in a
bounded domain made of a thin and periodic layer of finite length placed into a
homogeneous medium. We provide and justify a high order asymptotic expansion
which takes into account the boundary layer effect occurring in the vicinity of
the periodic layer as well as the corner singularities appearing in the
neighborhood of the extremities of the layer. Our approach combines the method
of matched asymptotic expansions and the method of periodic surface
homogenization, and a complete justification is included in the paper or its
appendix.
| [
"math.AP"
] | math.AP | Analysis of PDEs | 205Analysis of PDEs
|
|
1903.04727 | Let G be a locally compact group. In this note, we characterise
non-degenerate *-representations of A_\Phi(G) and B_\Phi(G). We also study
spectral subspaces associated to a non-degenerate Banach space representation
of A_\Phi(G).
| [
"math.FA"
] | math.FA | Functional Analysis | 2,549Functional Analysis
|
|
1710.05745 | An empirical 2-hit hypothesis is presented to account for premature and
unilateral ripening in Euonymus alatus.
| [
"q-bio.TO"
] | q-bio.TO | Tissues and Organs | 7,243Tissues and Organs
|
|
hep-th/0009185 | We show that two-dimensional (2D) AdS gravity induces on the spacetime
boundary a conformally invariant dynamics that can be described in terms of a
de Alfaro-Fubini-Furlan model coupled to an external source with conformal
dimension two. The external source encodes the information about the gauge
symmetries of the 2D gravity system. Alternatively, there exists a description
in terms of a mechanical system with anholonomic constraints. The considered
systems are invariant under the action of the conformal group generated by a
Virasoro algebra, which occurs also as asymptotic symmetry algebra of
two-dimensional anti-de Sitter space. We calculate the central charge of the
algebra and find perfect agreement between statistical and thermodynamical
entropy of AdS_2 black holes.
| [
"hep-th",
"gr-qc"
] | hep-th | gr-qc | High Energy Physics - Theory;General Relativity and Quantum Cosmology | 3,321High Energy Physics - Theory;General Relativity and Quantum Cosmology
|
1409.1915 | Quantum effects in material systems are often pronounced at low energies and
become insignificant at high temperatures. We find that, perhaps
counterintuitively, certain quantum effects may follow the opposite route and
become sharp when extrapolated to high temperature within a "classical" liquid
phase. In the current work, we suggest basic quantum bounds on relaxation (and
thermalization) times, examine kinetic theory by taking into account such
possible fundamental quantum time scales, find new general equalities
connecting semi-classical dynamics and thermodynamics to Planck's constant, and
compute current correlation functions. Our analysis suggests that, on average,
the extrapolated high temperature dynamical viscosity of general liquids may
tend to a value set by the product of the particle number density ${\sf n}$ and
Planck's constant $h$. We compare this theoretical result with experimental
measurements of an ensemble of 23 metallic fluids where this seems to indeed be
the case. The extrapolated high temperature viscosity of each of these liquids
$\eta$ divided (for each respective fluid by its value of ${\sf n} h$) veers
towards a Gaussian with an ensemble average value that is close to unity up to
an error of size $0.6 \%$. Inspired by the Eigenstate Thermalization
Hypothesis, we suggest a relation between the lowest equilibration temperature
to the melting or liquidus temperature and discuss a possible corollary
concerning the absence of finite temperature "ideal glass" transitions. We
suggest a general quantum mechanical derivation for the viscosity of glasses at
general temperatures. We invoke similar ideas to discuss other transport
properties and demonstrate how simple behaviors including resistivity
saturation and linear $T$ resistivity may appear very naturally. Our approach
suggests that minimal time lags may be present in fluid dynamics.
| [
"cond-mat.stat-mech",
"hep-ph",
"hep-th",
"quant-ph"
] | cond-mat.stat-mech | hep-ph | Statistical Mechanics;High Energy Physics - Phenomenology;High Energy Physics - Theory;Quantum Physics | 7,267longtail
|
1802.06594 | We provide a combinatorial characterization of monomial linear systems on
toric varieties whose general member is quasismooth. This is given both in
terms of the Newton polytope and in terms of the matrix of exponents of a
monomial basis.
| [
"math.AG"
] | math.AG | Algebraic Geometry | 47Algebraic Geometry
|
|
1009.6036 | This thesis is concerned with distributed control and coordination of
networks consisting of multiple, potentially mobile, agents. This is motivated
mainly by the emergence of large scale networks characterized by the lack of
centralized access to information and time-varying connectivity. Control and
optimization algorithms deployed in such networks should be completely
distributed, relying only on local observations and information, and robust
against unexpected changes in topology such as link failures. We will describe
protocols to solve certain control and signal processing problems in this
setting. We will demonstrate that a key challenge for such systems is the
problem of computing averages in a decentralized way. Namely, we will show that
a number of distributed control and signal processing problems can be solved
straightforwardly if solutions to the averaging problem are available. The rest
of the thesis will be concerned with algorithms for the averaging problem and
its generalizations. We will (i) derive the fastest known averaging algorithms
in a variety of settings and subject to a variety of communication and storage
constraints (ii) prove a lower bound identifying a fundamental barrier for
averaging algorithms (iii) propose a new model for distributed function
computation which reflects the constraints facing many large-scale networks,
and nearly characterize the general class of functions which can be computed in
this model.
| [
"math.OC"
] | math.OC | Optimization and Control | 5,234Optimization and Control
|
|
2011.10037 | We show that (i) the standard fine structural properties for premice follow
from normal iterability (whereas the classical proof relies on iterability for
stacks of normal trees), and (ii) every mouse which is finitely generated above
its projectum, is an iterate of its core.
That is, let $m$ be an integer and let $M$ be an $m$-sound,
$(m,\omega_1+1)$-iterable premouse. Then (i) $M$ is $(m+1)$-solid and
$(m+1)$-universal, $(m+1)$ condensation holds for $M$, and if $m\geq 1$ then
$M$ is super-Dodd-sound, a slight strengthening of Dodd-soundness. And (ii) if
there is $x\in M$ such that $M$ is the $\mathrm{r}\Sigma_{m+1}$-hull of
parameters in $\rho_{m+1}^M\cup\{x\}$, then $M$ is a normal iterate of its
$(m+1)$-core $C=\mathfrak{C}_{m+1}(M)$; in fact, there is an $m$-maximal
iteration tree $\mathcal{T}$ on $C$, of finite length, such that
$M=M^{\mathcal{T}}_\infty$, and $i^{\mathcal{T}}_{0\infty}$ is just the core
embedding.
Applying fact (ii), we prove that if $M\models\mathrm{ZFC}$ is a mouse and
$W\subseteq M$ is a ground of $M$ via a strategically $\sigma$-closed forcing
$\mathbb{P}\in W$, and if $M|\aleph_1^M\in W$ (that is, the initial segment of
$M$ of height $\aleph_1^M$ is in $W$), then the forcing is trivial; that is,
$M\subseteq W$.
And if there is a measurable cardinal, then there is a non-solid premouse.
The results hold for premice with Mitchell-Steel indexing, allowing extenders
of superstrong type to appear on the extender sequence.
| [
"math.LO"
] | math.LO | Logic | 3,800Logic
|
|
astro-ph/0401105 | Using steady, axisymmetric, ideal magnetohydrodynamics (MHD) we analyze
relativistic outflows by means of examining the momentum equation along the
flow and in the transfield direction. We argue that the asymptotic Lorentz
factor is ~ mu-sigma_M, and the asymptotic value of the Poynting-to-matter
energy flux ratio - the so-called sigma function - is given by sigma/(1+sigma)
\~ sigma_M / mu, where sigma_M is the Michel's magnetization parameter and mu
c^2 the total energy-to-mass flux ratio. We discuss how these values depend on
the conditions near the origin of the flow. By employing self-similar solutions
we verify the above result, and show that a Poynting-dominated flow near the
source reaches equipartition between Poynting and matter energy fluxes, or even
becomes matter-dominated, depending on the value of sigma_M / mu.
| [
"astro-ph"
] | astro-ph | Astrophysics | 463Astrophysics
|
|
1709.07230 | We use the new catalogue by Laigle et al. (2016) to provide a full census of
VLA-COSMOS radio sources. We identify 90% of such sources and sub-divide them
into AGN and star-forming galaxies on the basis of their radio luminosity. The
AGN sample is COMPLETE with respect to radio selection at all z<3.5. Out of 704
AGN, 272 have a counterpart in the Herschel maps. By exploiting the better
statistics of the new sample, we confirm the results of Magliocchetti et al.
(2014): the probability for a radio-selected AGN to be detected at FIR
wavelengths is both a function of radio luminosity and redshift, whereby
powerful sources are more likely FIR emitters at earlier epochs. Such an
emission is due to star-forming processes within the host galaxy. FIR emitters
and non-FIR emitters only differentiate in the z<1 universe. At higher
redshifts they are indistinguishable from each other, as there is no difference
between FIR-emitting AGN and star-forming galaxies. Lastly, we focus on radio
AGN which show AGN emission at other wavelengths. We find that MIR emission is
mainly associated with ongoing star-formation and with sources which are
smaller, younger and more radio luminous than the average parent population.
X-ray emitters instead preferentially appear in more massive and older
galaxies. We can therefore envisage an evolutionary track whereby the first
phase of a radio-active AGN and of its host galaxy is associated with MIR
emission, while at later stages the source becomes only active at radio
wavelengths and possibly also in the X-ray.
| [
"astro-ph.GA",
"astro-ph.CO"
] | astro-ph.GA | astro-ph.CO | Astrophysics of Galaxies;Cosmology and Nongalactic Astrophysics | 470Astrophysics of Galaxies;Cosmology and Nongalactic Astrophysics
|
2302.05629 | Differentiable Architecture Search (DARTS) is a simple yet efficient Neural
Architecture Search (NAS) method. During the search stage, DARTS trains a
supernet by jointly optimizing architecture parameters and network parameters.
During the evaluation stage, DARTS discretizes the supernet to derive the
optimal architecture based on architecture parameters. However, recent research
has shown that during the training process, the supernet tends to converge
towards sharp minima rather than flat minima. This is evidenced by the higher
sharpness of the loss landscape of the supernet, which ultimately leads to a
performance gap between the supernet and the optimal architecture. In this
paper, we propose Self-Distillation Differentiable Neural Architecture Search
(SD-DARTS) to alleviate the discretization gap. We utilize self-distillation to
distill knowledge from previous steps of the supernet to guide its training in
the current step, effectively reducing the sharpness of the supernet's loss and
bridging the performance gap between the supernet and the optimal architecture.
Furthermore, we introduce the concept of voting teachers, where multiple
previous supernets are selected as teachers, and their output probabilities are
aggregated through voting to obtain the final teacher prediction. Experimental
results on real datasets demonstrate the advantages of our novel
self-distillation-based NAS method compared to state-of-the-art alternatives.
| [
"cs.CV",
"cs.AI",
"cs.LG"
] | cs.CV | cs.AI | Computer Vision and Pattern Recognition;Artificial Intelligence;Machine Learning | 1,521Computer Vision and Pattern Recognition;Artificial Intelligence;Machine Learning
|
1402.5342 | Our primary goal is to provide a rigorous treatment of scattering nonlocality
in semiconductor nanostructures. On the one hand, starting from the
conventional density-matrix formulation and employing as ideal instrument for
the study of the semiclassical limit the well-known Wigner-function picture, we
shall perform a fully quantum-mechanical derivation of the space-dependent
Boltzmann equation. On the other hand, we shall examine the validity limits of
such semiclassical framework, pointing out, in particular, regimes where
scattering-nonlocality effects may play a relevant role; to this end we shall
supplement our analytical investigation with a number of simulated experiments,
discussing and further expanding preliminary studies of scattering-induced
quantum diffusion in GaN-based nanomaterials. As for the case of
carrier-carrier relaxation in photoexcited semiconductors, our analysis will
show the failure of simplified dephasing models in describing phonon-induced
scattering nonlocality, pointing out that such limitation is particularly
severe for the case of quasielastic dissipation processes.
| [
"cond-mat.mes-hall"
] | cond-mat.mes-hall | Mesoscale and Nanoscale Physics | 4,450Mesoscale and Nanoscale Physics
|
|
1610.05444 | We present a detailed analysis of the interstellar medium towards the TeV
$\gamma$-ray sources HESS J1640$-$465 and HESS J1641$-$463 using results from
the Mopra Southern Galactic Plane CO Survey and from a Mopra 7 mm-wavelength
study. The $\gamma$-ray sources are positionally coincident with two supernova
remnants G338.3$-$0.0 and G338.5+0.1 respectively. A bright complex of HII
regions connect the two SNRs and TeV objects. Observations in the CO(1-0)
transition lines reveal substantial amounts of diffuse gas positionally
coincident with the $\gamma$-ray sources at multiple velocities along the line
of sight, while 7 mm observations in CS, SiO, HC$_{3}$N and CH$_{3}$OH
transition lines reveal regions of dense, shocked gas. Archival HI data from
the Southern Galactic Plane Survey was used to account for the diffuse atomic
gas. Physical parameters of the gas towards the TeV sources were calculated
from the data. We find that for a hadronic origin for the $\gamma$-ray
emission, the cosmic-ray enhancement rates are $\sim 10^{3}$ and $10^{2}$ times
the local solar value for HESS J1640$-$465 and HESS J1641$-$463 respectively.
| [
"astro-ph.HE"
] | astro-ph.HE | High Energy Astrophysical Phenomena | 2,990High Energy Astrophysical Phenomena
|
|
1210.0229 | In 2009 Lurie published an expository article outlining a proof for a higher
version of the cobordism hypothesis conjectured by Baez and Dolan in 1995. In
this note we give a proof for the 1-dimensional case of this conjecture. The
proof follows most of the outline given in Lurie's paper, but differs in a few
crucial details. In particular, the proof makes use of the theory of
quasi-unital $\infty$-categories as developed by the author in a previous note.
| [
"math.AT"
] | math.AT | Algebraic Topology | 156Algebraic Topology
|
|
hep-lat/0010063 | We present results for the light quark masses in lattice QCD with two
degenerate flavours of dynamical fermions. We used configurations generated by
the UKQCD and QCDSF collaborations at six different combinations of beta and
kappa_sea.
| [
"hep-lat"
] | hep-lat | High Energy Physics - Lattice | 3,092High Energy Physics - Lattice
|
|
1507.03283 | A nonanticipative analog method is used for the long-term forecast of air
temperature extremes. The data to be used for prediction include average daily
air temperature, mean visibility, mean wind speed, mean dew point, maximum and
minimum temperatures reported during the day from 66 places around the world,
as well as sea level, average monthly Darwin and Tahiti sea level pressures,
SOI, equatorial SOI, sea surface temperature, and multivariate ENSO index.
Every dataset is split into two samples - learning (1973-2010) and validation
(2011-2013). Initially, the sum of variables in datasets for two locations,
minus corresponding climatological values, is calculated over a summation
interval of length from 1 to 365 days. A "quality criterion" selects datasets
for two locations with appropriate lead-time and summation interval, which have
maximum (or minimum) sum compared with the rest of data four times at least,
when extreme events occur later within the learning sample. Up to 18.2% of all
extremes are specifically predicted. The methodology has 100% accuracy with
respect to the sign of predicted and actual values. It is more useful than
current methods for predicting extreme values because it does not require the
estimation of a probability distribution from scarce observations.
| [
"stat.AP"
] | stat.AP | Applications | 276Applications
|
|
1710.00155 | We report the first principle investigations on the structural, electronic,
magnetic and ferroelectric properties of a Pb free double perovskite
multiferroic Bi2NiTiO6 using density functional theory within the general
gradient approximation (GGA) and GGA+U method. Our results show that Bi2NiTiO6
will be an insulator with G-type magnetic ordering in its ground state with
Ni2+ in a high spin state and a spin moment of 1.74\mu_B. The paraelectric
phase stabilizes in nonmagnetic state with Ni2+ in low spin configuration
showing that spin state transition plays an important role in strong
magnetoelectric coupling in Bi2NiTiO6. The bonding characteristics of the
constituents are analyzed with the help of partial density of states and Born
effective charges. The presence of Ti ions at Ni sites suppresses the
disproportionation observed in case of BiNiO3 and results in a
noncentrosymmetric crystal structure. The coexistence of Bi 6s lone pair and
Ti4+ d0 ions which brings covalency produces a polarization of 32 \muCcm-2.
| [
"physics.comp-ph",
"cond-mat.mtrl-sci"
] | physics.comp-ph | cond-mat.mtrl-sci | Computational Physics;Materials Science | 1,416Computational Physics;Materials Science
|
2109.13612 | In ducts with varying cross-sectional area and sustaining a subsonic
non-isentropic mean flow, the axially varying flow conditions affect the
acoustic energy balance of the system. This is significant in understanding and
controlling thermo-acoustic phenomena, particularly in combustors. This work
aims at quantifying the acoustic energy change in such configurations, using
the acoustic absorption coefficient, $\Delta$. The acoustic response of the
duct to acoustic forcing is determined using an analytical model, neglecting
the effect of entropy fluctuations on the acoustic field, and subsequently,
$\Delta$ is estimated. The model predictions of $\Delta$ are validated using a
linearised Euler equations (LEEs) solver. The model was found to be accurate
for Mach numbers below $0.25$, provided the lower frequency limit set by the
analytical solution is satisfied. For conically varying area ducts with linear
mean temperature gradient, it was observed that $\Delta$ showed very little
dependence on frequency, and that the absolute value of $\Delta$ tended to be
maximised when the upstream boundary was anechoic rather than non-anechoic.
More importantly, $\Delta$ was also observed to show stronger dependence on the
mean temperature gradient than area gradient variation for such configurations.
Further parametric and optimisation studies for $\Delta$ revealed a crucial
finding that a positive mean temperature gradient, representing a heated duct
caused acoustic energy absorption. Similarly, a negative mean temperature
gradient, representing a cooled duct caused acoustic energy generation -- a key
result of this analysis. This behaviour was shown to be consistent with a
simplified analysis of the acoustic energy balance. Based on this finding, a
linearly proportional reduction in acoustic energy generation was achieved by
changing the mean temperature gradient.
| [
"physics.flu-dyn"
] | physics.flu-dyn | Fluid Dynamics | 2,452Fluid Dynamics
|
|
0903.4268 | We investigate the use of a non-degenerate parametric oscillator (NDPO) as a
source for quantum lithography, for which the light can have high-flux and
strong non-classical features. This builds on the proposal of Boto, et al. [A.
N. Boto, et al., PRL (85), 2733 (2000)], for etching simple patterns on
multi-photon absorbing materials with sub-Rayleigh resolution, using special
two-mode entangled states of light. An NDPO has two outgoing modes
differentiated by polarization or direction of propagation, but sharing the
same optical frequency. We derive analytical expressions for the multi-photon
absorption rates when the NDPO is operated below, near, and above its
threshold. The resulting interference patterns are characterized by an
effective wavelength half that for the illuminating modes. We compare our
results with those for the case of a high-gain optical amplifier source, and
discuss the relative merit of the NDPO.
| [
"quant-ph"
] | quant-ph | Quantum Physics | 5,985Quantum Physics
|
|
2306.06017 | We study a version of the lights out game played on directed graphs. For a
digraph $D$, we begin with a labeling of $V(D)$ with elements of $\mathbb{Z}_k$
for $k \ge 2$. When a vertex $v$ is toggled, the labels of $v$ and any vertex
that $v$ dominates are increased by 1 mod $k$. The game is won when each vertex
has label 0. We say that $D$ is $k$-Always Winnable (also written $k$-AW) if
the game can be won for every initial labeling with elements of $\mathbb{Z}_k$.
We prove that all acyclic digraphs are $k$-AW for all $k$, and we reduce the
problem of determining whether a graph is $k$-AW to the case of strongly
connected digraphs. We then determine winnability for tournaments with a
minimum feedback arc set that arc-induces a directed path or directed star
digraph.
| [
"math.CO"
] | math.CO | Combinatorics | 1,014Combinatorics
|
|
2308.08062 | This work aims at constraining the size, shape, and geometric albedo of the
dwarf planet candidate 2002 MS4 through the analysis of nine stellar
occultation events. Using multichord detection, we also studied the object's
topography by analyzing the obtained limb and the residuals between observed
chords and the best-fitted ellipse. We predicted and organized the
observational campaigns of nine stellar occultations by 2002 MS4 between 2019
and 2022, resulting in two single-chord events, four double-chord detections,
and three events with three to up to sixty-one positive chords. Using 13
selected chords from the 8 August 2020 event, we determined the global
elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the
object's rotational information from the literature, constrains the object's
size, shape, and albedo. Additionally, we developed a new method to
characterize topography features on the object's limb. The global limb has a
semi-major axis of 412 $\pm$ 10 km, a semi-minor axis of 385 $\pm$ 17 km, and
the position angle of the minor axis is 121 $^\circ$ $\pm$ 16$^\circ$. From
this instantaneous limb, we obtained 2002 MS4's geometric albedo and the
projected area-equivalent diameter. Significant deviations from the fitted
ellipse in the northernmost limb are detected from multiple sites highlighting
three distinct topographic features: one 11 km depth depression followed by a
25$^{+4}_{-5}$ km height elevation next to a crater-like depression with an
extension of 322 $\pm$ 39 km and 45.1 $\pm$ 1.5 km deep. Our results present an
object that is $\approx$138 km smaller in diameter than derived from thermal
data, possibly indicating the presence of a so-far unknown satellite. However,
within the error bars, the geometric albedo in the V-band agrees with the
results published in the literature, even with the radiometric-derived albedo.
| [
"astro-ph.EP"
] | astro-ph.EP | Earth and Planetary Astrophysics | 2,351Earth and Planetary Astrophysics
|
|
2101.09395 | Volatility of financial stock is referring to the degree of uncertainty or
risk embedded within a stock's dynamics. Such risk has been received huge
amounts of attention from diverse financial researchers. By following the
concept of regime-switching model, we proposed a non-parametric approach, named
encoding-and-decoding, to discover multiple volatility states embedded within a
discrete time series of stock returns. The encoding is performed across the
entire span of temporal time points for relatively extreme events with respect
to a chosen quantile-based threshold. As such the return time series is
transformed into Bernoulli-variable processes. In the decoding phase, we
computationally seek for locations of change points via estimations based on a
new searching algorithm in conjunction with the information criterion applied
on the observed collection of recurrence times upon the binary process. Besides
the independence required for building the Geometric distributional likelihood
function, the proposed approach can functionally partition the entire return
time series into a collection of homogeneous segments without any assumptions
of dynamic structure and underlying distributions. In the numerical
experiments, our approach is found favorably compared with parametric models
like Hidden Markov Model. In the real data applications, we introduce the
application of our approach in forecasting stock returns. Finally, volatility
dynamic of every single stock of S&P500 is revealed, and a stock network is
consequently established to represent dependency relations derived through
concurrent volatility states among S&P500.
| [
"q-fin.ST",
"stat.AP"
] | q-fin.ST | stat.AP | Statistical Finance;Applications | 6,801Statistical Finance;Applications
|
2008.06179 | The cataloging of product listings is a fundamental problem for most
e-commerce platforms. Despite promising results obtained by unimodal-based
methods, it can be expected that their performance can be further boosted by
the consideration of multimodal product information. In this study, we
investigated a multimodal late fusion approach based on text and image
modalities to categorize e-commerce products on Rakuten. Specifically, we
developed modal specific state-of-the-art deep neural networks for each input
modal, and then fused them at the decision level. Experimental results on
Multimodal Product Classification Task of SIGIR 2020 E-Commerce Workshop Data
Challenge demonstrate the superiority and effectiveness of our proposed method
compared with unimodal and other multimodal methods. Our team named pa_curis
won the 1st place with a macro-F1 of 0.9144 on the final leaderboard.
| [
"cs.CV",
"cs.IR"
] | cs.CV | cs.IR | Computer Vision and Pattern Recognition;Information Retrieval | 1,588Computer Vision and Pattern Recognition;Information Retrieval
|
2203.03509 | Light-driven electronic excitation is a cornerstone for energy and
information transfer. In the interaction of intense and ultrafast light fields
with solids, electrons may be excited irreversibly, or transiently during
illumination only. As the transient electron population cannot be observed
after the light pulse is gone it is referred to as virtual, while the
population remaining excited is called real. Virtual charge carriers have
recently been associated with high-harmonic generation and transient
absorption, while photocurrent generation may stem from real as well as virtual
charge carriers. Yet, a link between the carrier types in their generation and
importance for observables up to technological relevance is missing. Here we
show that real and virtual carriers can be excited and disentangled in the
optical generation of currents in a gold-graphene-gold heterostructure using
few-cycle laser pulses. Depending on the waveform used for photoexcitation,
real carriers receive net momentum and propagate to the gold electrodes, while
virtual carriers generate a polarization response read out at the gold-graphene
interfaces. Based on these insights, we further demonstrate a proof of concept
of a logic gate for future lightwave electronics. Our results offer a direct
means to monitor and excite real and virtual charge carriers. Individual
control over each type will dramatically increase the integrated circuit design
space and bring closer to reality petahertz signal processing.
| [
"physics.optics",
"cond-mat.mes-hall"
] | physics.optics | cond-mat.mes-hall | Optics;Mesoscale and Nanoscale Physics | 5,201Optics;Mesoscale and Nanoscale Physics
|
1501.03415 | IceTop, the surface component of the IceCube detector, has been used to
measure the energy spectrum of cosmic ray primaries in the range between 1.58
PeV and 1.26 EeV. It can also be used to study the low energy muons in air
showers by looking at large distances (> 300m) from the shower axis. We will
show the muon lateral distribution function at large lateral distances as
measured with IceTop and discuss the implications of this measurement. We also
discuss the prospects for low energy muon studies with IceTop.
| [
"astro-ph.HE",
"astro-ph.IM"
] | astro-ph.HE | astro-ph.IM | High Energy Astrophysical Phenomena;Instrumentation and Methods for Astrophysics | 3,035High Energy Astrophysical Phenomena;Instrumentation and Methods for Astrophysics
|
1411.2821 | We have added a simplified neuromorphic model of Spike Time Dependent
Plasticity (STDP) to the Synapto-dendritic Kernel Adapting Neuron (SKAN). The
resulting neuron model is the first to show synaptic encoding of afferent
signal to noise ratio in addition to the unsupervised learning of spatio
temporal spike patterns. The neuron model is particularly suitable for
implementation in digital neuromorphic hardware as it does not use any complex
mathematical operations and uses a novel approach to achieve synaptic
homeostasis. The neurons noise compensation properties are characterized and
tested on noise corrupted zeros digits of the MNIST handwritten dataset.
Results show the simultaneously learning common patterns in its input data
while dynamically weighing individual afferent channels based on their signal
to noise ratio. Despite its simplicity the interesting behaviors of the neuron
model and the resulting computational power may offer insights into biological
systems.
| [
"cs.NE",
"q-bio.NC"
] | cs.NE | q-bio.NC | Neural and Evolutionary Computing;Neurons and Cognition | 4,797Neural and Evolutionary Computing;Neurons and Cognition
|
1308.2775 | We consider generalized inverses of linear operators on arbitrary vector
spaces and study the question when their product in reverse order is again a
generalized inverse. This problem is equivalent to the question when the
product of two projectors is again a projector, and we discuss necessary and
sufficient conditions in terms of their kernels and images alone. We give a new
representation of the product of generalized inverses that does not require
explicit knowledge of the factors. Our approach is based on implicit
representations of subspaces via their orthogonals in the dual space. For
Fredholm operators, the corresponding computations reduce to finite-dimensional
problems. We illustrate our results with examples for matrices and linear
ordinary boundary problems.
| [
"math.FA",
"math.CA"
] | math.FA | math.CA | Functional Analysis;Classical Analysis and ODEs | 2,560Functional Analysis;Classical Analysis and ODEs
|
cond-mat/0701341 | We study Si:P donor electron spin decoherence due to anisotropic hyperfine
(AHF) interaction with the surrounding nuclear spin bath. In particular, we
clarify the electron spin echo envelope modulation (ESEEM) in the Si:P system
and the resonancelike contributions from nuclear spins in various shells away
from the P atoms. We suggest an approach to minimize AHF-induced decoherence by
avoiding the resonances and orienting an applied magnetic field along
directions that can periodically eliminate contributions from the dominant
nearest neighbor atoms. Our remarkable agreement with experiment demonstrates
nearly complete understanding of electron spin decoherence in Si:P when
combining ESEEM, spectral diffusion, instantaneous diffusion, and spin-lattice
relaxation.
| [
"cond-mat.mes-hall",
"quant-ph"
] | cond-mat.mes-hall | quant-ph | Mesoscale and Nanoscale Physics;Quantum Physics | 4,536Mesoscale and Nanoscale Physics;Quantum Physics
|