2,513 research outputs found
On the Number of Zeros of Abelian Integrals: A Constructive Solution of the Infinitesimal Hilbert Sixteenth Problem
We prove that the number of limit cycles generated by a small
non-conservative perturbation of a Hamiltonian polynomial vector field on the
plane, is bounded by a double exponential of the degree of the fields. This
solves the long-standing tangential Hilbert 16th problem. The proof uses only
the fact that Abelian integrals of a given degree are horizontal sections of a
regular flat meromorphic connection (Gauss-Manin connection) with a
quasiunipotent monodromy group.Comment: Final revisio
Machine Learning for Fluid Mechanics
The field of fluid mechanics is rapidly advancing, driven by unprecedented
volumes of data from field measurements, experiments and large-scale
simulations at multiple spatiotemporal scales. Machine learning offers a wealth
of techniques to extract information from data that could be translated into
knowledge about the underlying fluid mechanics. Moreover, machine learning
algorithms can augment domain knowledge and automate tasks related to flow
control and optimization. This article presents an overview of past history,
current developments, and emerging opportunities of machine learning for fluid
mechanics. It outlines fundamental machine learning methodologies and discusses
their uses for understanding, modeling, optimizing, and controlling fluid
flows. The strengths and limitations of these methods are addressed from the
perspective of scientific inquiry that considers data as an inherent part of
modeling, experimentation, and simulation. Machine learning provides a powerful
information processing framework that can enrich, and possibly even transform,
current lines of fluid mechanics research and industrial applications.Comment: To appear in the Annual Reviews of Fluid Mechanics, 202
A BPS Skyrme model and baryons at large Nc
Within the class of field theories with the field contents of the Skyrme
model, one submodel can be found which consists of the square of the baryon
current and a potential term only. For this submodel, a Bogomolny bound exists
and the static soliton solutions saturate this bound. Further, already on the
classical level, this BPS Skyrme model reproduces some features of the liquid
drop model of nuclei. Here, we investigate the model in more detail and,
besides, we perform the rigid rotor quantization of the simplest Skyrmion (the
nucleon). In addition, we discuss indications that the viability of the model
as a low energy effective field theory for QCD is further improved in the limit
of a large number of colors N_c.Comment: latex, 23 pages, 1 figure, a numerical error in section 3.2
corrected; matches published versio
An anthology of non-local QFT and QFT on noncommutative spacetime
Ever since the appearance of renormalization theory there have been several
differently motivated attempts at non-localized (in the sense of not generated
by point-like fields) relativistic particle theories, the most recent one being
at QFT on non-commutative Minkowski spacetime. The often conceptually
uncritical and historically forgetful contemporary approach to these problems
calls for a critical review the light of previous results on this subject.Comment: 33 pages tci-latex, improvements of formulations, shortening of
sentences, addition of some reference
Application of the Kalman Filter in Functional Magnetic Resonance Image Data
The Kalman-Bucy filter was applied on the preprocessing of the functional magnetic resonance image-fMRI. Numerical simulations of hemodynamic response added Gaussian noise were performed to evaluate the performance of the filter. After the proceeding was applied in auditory real data. The Kohonen’s self-organized map was employed as tools to compare the performance of the Kalman’s filter with another type of pre-processing. The results of the application of Kalman-Bucy filter for simulated data and real auditory data showed that it can be used as a tool in the temporal filtering step in fMRI data
Expectation values of twist fields and universal entanglement saturation of the free massive boson
The evaluation of vacuum expectation values (VEVs) in massive integrable
quantum field theory (QFT) is a nontrivial renormalization-group "connection
problem" -- relating large and short distance asymptotics -- and is in general
unsolved. This is particularly relevant in the context of entanglement entropy,
where VEVs of branch-point twist fields give universal saturation predictions.
We propose a new method to compute VEVs of twist fields associated to
continuous symmetries in QFT. The method is based on a differential equation in
the continuous symmetry parameter, and gives VEVs as infinite form-factor
series which truncate at two-particle level in free QFT. We verify the method
by studying U(1) twist fields in free models, which are simply related to the
branch-point twist fields. We provide the first exact formulae for the VEVs of
such fields in the massive uncompactified free boson model, checking against an
independent calculation based on angular quantization. We show that logarithmic
terms, overlooked in the original work of Callan and Wilczek [Phys. Lett. B333
(1994)], appear both in the massless and in the massive situations. This
implies that, in agreement with numerical form-factor observations by Bianchini
and Castro-Alvaredo [Nucl. Phys. B913 (2016)], the standard power-law
short-distance behavior is corrected by a logarithmic factor. We discuss how
this gives universal formulae for the saturation of entanglement entropy of a
single interval in near-critical harmonic chains, including log log
corrections.Comment: V2: 37 pages, explications and references adde
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