801 research outputs found
A Monte-Carlo simulation of the equilibrium beam polarization in ultra-high energy electron (positron) storage rings
With the recently emerging global interest in building a next generation of
circular electron-positron colliders to study the properties of the Higgs
boson, and other important topics in particle physics at ultra-high beam
energies, it is also important to pursue the possibility of implementing
polarized beams at this energy scale. It is therefore necessary to set up
simulation tools to evaluate the beam polarization at these ultra-high beam
energies. In this paper, a Monte-Carlo simulation of the equilibrium beam
polarization based on the Polymorphic Tracking Code(PTC) (Schmidt et al., 2002
[1]) is described. The simulations are for a model storage ring with parameters
similar to those of proposed circular colliders in this energy range, and they
are compared with the suggestion (Derbenev et al., 1978 [2]) that there are
different regimes for the spin dynamics underlying the polarization of a beam
in the presence of synchrotron radiation at ultra-high beam energies. In
particular, it has been suggested that the so-called "correlated" crossing of
spin resonances during synchrotron oscillations at current energies, evolves
into "uncorrelated" crossing of spin resonances at ultra-high energies.Comment: submitted to and accepted by Nucl. Instrum. Meth.
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Dynamic Mode Decomposition for Compressive System Identification
Dynamic mode decomposition has emerged as a leading technique to identify
spatiotemporal coherent structures from high-dimensional data, benefiting from
a strong connection to nonlinear dynamical systems via the Koopman operator. In
this work, we integrate and unify two recent innovations that extend DMD to
systems with actuation [Proctor et al., 2016] and systems with heavily
subsampled measurements [Brunton et al., 2015]. When combined, these methods
yield a novel framework for compressive system identification [code is publicly
available at: https://github.com/zhbai/cDMDc]. It is possible to identify a
low-order model from limited input-output data and reconstruct the associated
full-state dynamic modes with compressed sensing, adding interpretability to
the state of the reduced-order model. Moreover, when full-state data is
available, it is possible to dramatically accelerate downstream computations by
first compressing the data. We demonstrate this unified framework on two model
systems, investigating the effects of sensor noise, different types of
measurements (e.g., point sensors, Gaussian random projections, etc.),
compression ratios, and different choices of actuation (e.g., localized,
broadband, etc.). In the first example, we explore this architecture on a test
system with known low-rank dynamics and an artificially inflated state
dimension. The second example consists of a real-world engineering application
given by the fluid flow past a pitching airfoil at low Reynolds number. This
example provides a challenging and realistic test-case for the proposed method,
and results demonstrate that the dominant coherent structures are well
characterized despite actuation and heavily subsampled data
MythQA: Query-Based Large-Scale Check-Worthy Claim Detection through Multi-Answer Open-Domain Question Answering
Check-worthy claim detection aims at providing plausible misinformation to
downstream fact-checking systems or human experts to check. This is a crucial
step toward accelerating the fact-checking process. Many efforts have been put
into how to identify check-worthy claims from a small scale of pre-collected
claims, but how to efficiently detect check-worthy claims directly from a
large-scale information source, such as Twitter, remains underexplored. To fill
this gap, we introduce MythQA, a new multi-answer open-domain question
answering(QA) task that involves contradictory stance mining for query-based
large-scale check-worthy claim detection. The idea behind this is that
contradictory claims are a strong indicator of misinformation that merits
scrutiny by the appropriate authorities. To study this task, we construct
TweetMythQA, an evaluation dataset containing 522 factoid multi-answer
questions based on controversial topics. Each question is annotated with
multiple answers. Moreover, we collect relevant tweets for each distinct
answer, then classify them into three categories: "Supporting", "Refuting", and
"Neutral". In total, we annotated 5.3K tweets. Contradictory evidence is
collected for all answers in the dataset. Finally, we present a baseline system
for MythQA and evaluate existing NLP models for each system component using the
TweetMythQA dataset. We provide initial benchmarks and identify key challenges
for future models to improve upon. Code and data are available at:
https://github.com/TonyBY/Myth-QAComment: Accepted by SIGIR 202
Mode-locking Theory for Long-Range Interaction in Artificial Neural Networks
Visual long-range interaction refers to modeling dependencies between distant
feature points or blocks within an image, which can significantly enhance the
model's robustness. Both CNN and Transformer can establish long-range
interactions through layering and patch calculations. However, the underlying
mechanism of long-range interaction in visual space remains unclear. We propose
the mode-locking theory as the underlying mechanism, which constrains the phase
and wavelength relationship between waves to achieve mode-locked interference
waveform. We verify this theory through simulation experiments and demonstrate
the mode-locking pattern in real-world scene models. Our proposed theory of
long-range interaction provides a comprehensive understanding of the mechanism
behind this phenomenon in artificial neural networks. This theory can inspire
the integration of the mode-locking pattern into models to enhance their
robustness.Comment: 10 pages, 6 figure
gCAPjoint, A Software Package for Full Moment Tensor Inversion of Moderately Strong Earthquakes with Local and Teleseismic Waveforms
Earthquake moment tensors and focal depths are crucial to assessing seismic hazards and studying active tectonic and volcanic processes. Although less powerful than strong earthquakes (M 7+), moderately strong earthquakes (M 5ā6.5) occur more frequently and extensively, which can cause severe damages in populated areas. The inversion of moment tensors is usually affected by insufficient local waveform data (epicentral distance <5Ā°ā ) in sparse seismic networks. It would be necessary to combine local and teleseismic data (epicentral distance 30Ā°ā90Ā°) for a joint inversion. In this study, we present the generalized cutāandāpaste joint (gCAPjoint) algorithm to jointly invert full moment tensor and centroid depth with local and teleseismic broadband waveforms. To demonstrate the effectiveness and explore the limitations of this algorithm, we perform case studies on three earthquakes with different tectonic settings and source properties. Comparison of our results with global centroid moment tensor and other catalog solutions illustrates that both nonādoubleācouple compositions of the focal mechanisms and centroid depths can be reliably recovered for very shallow (ā <10āākmā ) earthquakes and intermediateādepth events with this software package
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