arXiv subjects

J. T. Mendonca

Publications and source records attributed to J. T. Mendonca.

26 records · Page 2Linked to original sources

arXiv2005

Dipolar radiation from spinning dust grains coupled to an electromagnetic wave

In this letter we investigate how the complex rotation and quivering motion of an elongated polarized dust grain in the presence of a monochromatic electromagnetic wave can originate dipolar emission with two distinct spectral components. We present a model for the emission of radiation by elongated polarized dust grains under the influence of both an external electromagnetic wave and a constant background magnetic field. The dust, exhibiting rotational motion at the external electromagnetic field frequency w0 as well as quivering motion at frequency W0, proportional to the em field amplitude, will radiate with frequencies that will depend on the external field wavelength and amplitude. The radiated spectra exibits a frequency around w0, and sidebands at w0+-W0 and w0+-2W0. Since the amplitude and the frequency of the background electromagnetic field are independent parameters, this model establishes a correlation between different spectral components of galactic dipolar emission, which may help to explain the correlation between a component of the Galactic microwave emission and the 100micons thermal emission from interstellar dust, that has been recently measured.

physics.plasm-ph↗

arXiv2005

A kinetic approach to Bose-Einstein condensates: self-phase modulation and Bogoliubov oscillations

A kinetic approach to the Bose-Einstein condensates (BECs) is proposed, based on the Wigner-Moyal equation (WME). In the quasi-classical limit, the WME reduces to the particle number conservation equation. Two examples of application are: i) a self-phase modulation of a BE condensate beam where we show that part of the beam is decelerated and eventually stops as a result of the gradient of the effective self-potential; ii) the derivation of a kinetic dispersion relation for sound waves in the BECs, including a collisionless Landau damping.

nlin.PS↗

arXiv2003

Self-phase modulation of spherical gravitational waves

Self-phase modulation of spherical gravitational wavepackets propagating in a flat space-time in the presence of a tenuous distribution of matter is considered. Analogies with respect to similar effects in nonlinear optics are explored. Self phase modulation of waves emitted from a single source can eventually lead to an efficient energy dilution of the gravitational wave energy over an increasingly large spectral range. An explicit criterium for the occurrence of a significant spectral energy dilution is established.

gr-qc↗

arXiv2003

Nonlinear self-interaction of plane gravitational waves

Recently Mendonca and Cardoso [Phys. Rev. D, vol. 66, 104009 (2002)] considered nonlinear gravitational wave packets propagating in flat space-time. They concluded that the evolution equation - to third order in amplitude - takes a similar form to what arises in nonlinear optics. Based on this equation, the authors found that nonlinear gravitational waves exhibit self-phase modulation and high harmonic generation leading to frequency up-shifting and spectral energy dilution of the gravitational wave energy. In this Brief Report we point out the fact - a possibility that seems to have been overlooked by Mendonca and Cardoso - that the nonlinear terms in the evolution equation cancels and, hence, that there is no amplitude evolution of the pulse. Finally we discuss scenarios where these nonlinearities may play a role.

astro-ph↗

arXiv2002

Gravitational Optics: Self-phase modulation and harmonic cascades

Nonlinear wave interaction of low amplitude gravitational waves in flat space-time is considered. Analogy with optics is established. It is shown that the flat metric space-time is equivalent to a centro-symmetric optical medium, with no second order susceptibility. The lowest order nonlinear effects are those due to the third order nonlinearity and include self-phase modulation and high harmonic generation. These processes lead to an efficient energy dilution of the gravitational wave energy over an increasingly large spectral range.

gr-qc↗

arXiv2001

Moving boundary effects in Quark Gluon Plasma

We analyze the known moving boundary effects in plasma and briefly review a mechanism for particle acceleration through a plasma front. We then show how this mechanism may affect particles crossing the boundary of an expanding quark gluon plasma.

hep-ph↗

arXiv2000

Explosion Implosion Duality and the Laboratory Simulation of Astrophysical Systems

The Euler equations of ideal gas dynamics posess a remarkable nonlinear involutional symmetry which allows one to factor out an arbitrary uniform expansion or contraction of the system. The nature of this symmetry (called by cosmologists the transformation to supercomoving variables) is discussed and its origin clarified. It is pointed out that this symmetry allows one to map an explosion problem to a dual implosion problem and vice versa. The application to laboratory simulations of supernova remnants is considered; in principle this duality allows the complete three-dimensional evolution of highly structured explosion ejecta to be modelled using a static target in an implosion facility.

astro-ph↗

arXiv1998

Comment on "Ponderomotive force due to neutrinos"

The derivation of the ponderomotive force due to neutrinos by Hardy and Melrose, Phys.Rev.D v.54, p.6491 (1996) is based on a flawed analysis of the ponderomotive force concept. Their conclusions also contain an erroneous physical assumption related to the neutrino emission in supernovae. A correct analysis shows the importance of the ponderomotive force due to neutrinos in type II supernovae explosions.

physics.plasm-ph↗