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I introduce a straightforward technique for the filtering of extended astronomical images into components of different spatial scales. For a positive original image, each component is positive definite, and the sum of all components equals…

Astrophysics · Physics 2009-10-31 Lawrence Rudnick

Some considerations of long wavelength and broadband radiation sources based on the emission of the coherent radiation by a train of short relativistic electron bunches moving in an open resonator along an arc-like or undulator trajectories…

Classical Physics · Physics 2008-02-03 Yu. Shibata , E. G. Bessonov

Motivated by analogue models of classical and quantum field theory in curved spacetimes and their recent experimental realizations, we consider wave scattering processes of dispersive fields exhibiting two extra degrees of freedom. In…

General Relativity and Quantum Cosmology · Physics 2013-06-14 Maurício Richartz , Angus Prain , Silke Weinfurtner , Stefano Liberati

In this paper we study the application of a simplified method to solve the dynamic radiative transfer problem in expanding envelopes. The method, which requires a computational effort similar to that of the diffusion approximation, is based…

Astrophysics · Physics 2009-10-28 J. Gomez-Gomar , J. Isern

We continue our studies on stellar latitudinal differential rotation. The presented work is a sequel of the work of Reiners et al. who studied the spectral line broadening profile of hundreds of stars of spectral types A through G at high…

Solar and Stellar Astrophysics · Physics 2010-10-29 Matthias~Ammler von Eiff , Ansgar Reiners

Surface topography dictates the deterministic functionality of diffraction by a surface. In order to maximize the efficiency with which a diffractive optical component, such as a grating or a diffractive lens, directs light into a chosen…

In this paper, we present numerical and experimental evidence of directional wave behavior, i.e. beaming and diffraction, along high-order rotational symmetries of quasicrystalline elastic metamaterial plates. These structures are obtained…

Applied Physics · Physics 2022-01-31 Danilo Beli , Matheus Inguaggiato Nora Rosa , Carlos De Marqui , Massimo Ruzzene

This work describes a novel image analysis approach to characterize the uniformity of objects in agglomerates by using the propagation of normal wavefronts. The problem of width uniformity is discussed and its importance for the…

Disordered Systems and Neural Networks · Physics 2009-11-10 Luciano da F. Costa , Giancarlo Mutinari , David Schubert

We investigate travelling wave solutions in reaction-diffusion models of animal range expansion in the case that population diffusion is density-dependent. We find that the speed of the selected wave depends critically on the strength of…

Populations and Evolution · Quantitative Biology 2024-11-19 Beth M. Stokes , Tim Rogers , Richard James

We derive the scaling of differential rotation in both slowly- and rapidly-rotating convection zones using order of magnitude methods. Our calculations apply across stars and fluid planets and all rotation rates, as well as to both…

Solar and Stellar Astrophysics · Physics 2020-09-02 Adam S. Jermyn , Shashikumar M. Chitre , Pierre Lesaffre , Christopher A. Tout

We propose a new compressive imaging method for reconstructing 2D or 3D objects from their scattered wave-field measurements. Our method relies on a novel, nonlinear measurement model that can account for the multiple scattering phenomenon,…

Computer Vision and Pattern Recognition · Computer Science 2016-10-07 Hsiou-Yuan Liu , Ulugbek S. Kamilov , Dehong Liu , Hassan Mansour , Petros T. Boufounos

We give a detailed analysis of long range cumulative scattering effects from rough boundaries in waveguides. We assume small random fluctuations of the boundaries and obtain a quantitative statistical description of the wave field. The…

Analysis of PDEs · Mathematics 2011-11-07 Ricardo Alonso , Liliana Borcea , Josselin Garnier

Mutual dependencies of mass and orbital moment increase for rotating bodies of various configurations (a string with uniform mass distribution, a string with squared mass distribution or a sphere with uniform mass distribution, double…

Nuclear Theory · Physics 2007-05-23 S. V. Artemov , M. A. Belov , Yu. N. Koblik , G. A. Radyuk

We develop an all electrical experiment to perform the broadband phase-resolved spectroscopy of propagating spin waves in micrometer sized thin magnetic stripes. The magnetostatic surface spin waves are excited and detected by scaled down…

Mesoscale and Nanoscale Physics · Physics 2016-08-03 Florin Ciubotaru , Thibaut Devolder , Mauricio Manfrini , Christoph Adelmann , Iuliana Radu

Simple image rotations significantly reduce the accuracy of deep neural networks. Moreover, training with all possible rotations increases the data set, which also increases the training duration. In this work, we address trainable rotation…

Computer Vision and Pattern Recognition · Computer Science 2021-01-19 Wolfgang Fuhl , Enkelejda Kasneci

We discuss the conditions under which plane electromagnetic and gravitational waves can be amplified by a rotating black hole due to superradiant scattering. We show, in particular, that amplification can occur for low-frequency waves with…

General Relativity and Quantum Cosmology · Physics 2017-03-22 Joao G. Rosa

The study of planetary atmospheres is crucial for understanding the origin, evolution, and processes that shape celestial bodies like planets, moons and comets. The interpretation of planetary spectra requires a detailed understanding of…

Earth and Planetary Astrophysics · Physics 2023-10-31 Miriam Rengel , Jakob Adamczewski

We propose an algorithm for rotational sparse coding along with an efficient implementation using steerability. Sparse coding (also called dictionary learning) is an important technique in image processing, useful in inverse problems,…

Image and Video Processing · Electrical Eng. & Systems 2020-01-31 Michael T. McCann , Vincent Andrearczyk , Michael Unser , Adrien Depeursinge

Multipath propagation in the interstellar medium distorts radio pulses, an effect predominant for distant pulsars observed at low frequencies. Typically, broadened pulses are analyzed to determine the amount of propagation-induced pulse…

Astrophysics · Physics 2009-11-07 N. D. R. Bhat , J. M. Cordes , S. Chatterjee

Radiative heat transfer between uniform plates is bounded by the narrow range and limited contribution of surface waves. Using a combination of analytical calculations and numerical gradient-based optimization, we show that such a…

Mesoscale and Nanoscale Physics · Physics 2017-07-07 Weiliang Jin , Riccardo Messina , Alejandro W. Rodriguez