20,545 research outputs found
Image Augmentation using Radial Transform for Training Deep Neural Networks
Deep learning models have a large number of free parameters that must be
estimated by efficient training of the models on a large number of training
data samples to increase their generalization performance. In real-world
applications, the data available to train these networks is often limited or
imbalanced. We propose a sampling method based on the radial transform in a
polar coordinate system for image augmentation to facilitate the training of
deep learning models from limited source data. This pixel-wise transform
provides representations of the original image in the polar coordinate system
by generating a new image from each pixel. This technique can generate radial
transformed images up to the number of pixels in the original image to increase
the diversity of poorly represented image classes. Our experiments show
improved generalization performance in training deep convolutional neural
networks with radial transformed images.Comment: This paper is accepted for presentation at IEEE International
Conference on Acoustics, Speech and Signal Processing (IEEE ICASSP), 201
A hybrid approach to black hole perturbations from extended matter sources
We present a new method for the calculation of black hole perturbations
induced by extended sources in which the solution of the nonlinear
hydrodynamics equations is coupled to a perturbative method based on
Regge-Wheeler/Zerilli and Bardeen-Press-Teukolsky equations when these are
solved in the frequency domain. In contrast to alternative methods in the time
domain which may be unstable for rotating black-hole spacetimes, this approach
is expected to be stable as long as an accurate evolution of the matter sources
is possible. Hence, it could be used under generic conditions and also with
sources coming from three-dimensional numerical relativity codes. As an
application of this method we compute the gravitational radiation from an
oscillating high-density torus orbiting around a Schwarzschild black hole and
show that our method is remarkably accurate, capturing both the basic
quadrupolar emission of the torus and the excited emission of the black hole.Comment: 12 pages, 4 figures. Phys. Rev. D, in pres
An Itzykson-Zuber-like Integral and Diffusion for Complex Ordinary and Supermatrices
We compute an analogue of the Itzykson-Zuber integral for the case of
arbitrary complex matrices. The calculation is done for both ordinary and
supermatrices by transferring the Itzykson-Zuber diffusion equation method to
the space of arbitrary complex matrices. The integral is of interest for
applications in Quantum Chromodynamics and the theory of two-dimensional
Quantum Gravity.Comment: 20 pages, RevTeX, no figures, agrees with published version,
including "Note added in proof" with an additional result for rectangular
supermatrice
Noneuclidean Tessellations and their relation to Reggie Trajectories
The coefficients in the confluent hypergeometric equation specify the Regge
trajectories and the degeneracy of the angular momentum states. Bound states
are associated with real angular momenta while resonances are characterized by
complex angular momenta. With a centrifugal potential, the half-plane is
tessellated by crescents. The addition of an electrostatic potential converts
it into a hydrogen atom, and the crescents into triangles which may have
complex conjugate angles; the angle through which a rotation takes place is
accompanied by a stretching. Rather than studying the properties of the wave
functions themselves, we study their symmetry groups. A complex angle indicates
that the group contains loxodromic elements. Since the domain of such groups is
not the disc, hyperbolic plane geometry cannot be used. Rather, the theory of
the isometric circle is adapted since it treats all groups symmetrically. The
pairing of circles and their inverses is likened to pairing particles with
their antiparticles which then go one to produce nested circles, or a
proliferation of particles. A corollary to Laguerre's theorem, which states
that the euclidean angle is represented by a pure imaginary projective
invariant, represents the imaginary angle in the form of a real projective
invariant.Comment: 27 pages, 4 figure
Classical dynamics on curved Snyder space
We study the classical dynamics of a particle in nonrelativistic Snyder-de
Sitter space. We show that for spherically symmetric systems, parametrizing the
solutions in terms of an auxiliary time variable, which is a function only of
the physical time and of the energy and angular momentum of the particles, one
can reduce the problem to the equivalent one in classical mechanics. We also
discuss a relativistic extension of these results, and a generalization to the
case in which the algebra is realized in flat space.Comment: 12 pages, LaTeX, version published on CQ
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