55 research outputs found

### Nonlinear Electrodynamics: Alternative Field Theory for Featuring Photon Propagation Over Weak Background Electromagnetic Fields and what Earth Receivers Read off Radio Signals from Interplanetary Spacecraft Transponders

A few observational and/or experimental results have dramatically pushed
forward the research program on gravity as those from the radio-metric Doppler
tracking received from the Pioneer 10 and 11 spacecrafts when the space
vehicles were at heliocentric distances between 20 and 70 Astronomical Units
(AU). These data have conclusively demonstrated the presence of an anomalous,
tiny and blue-shifted frequency drift that changes smoothly at a rate of $\sim
6 \times 10^{-9}$ Hz s$^{-1}$. Those signals, if interpreted as a gravitational
pull of the Sun on each Pioneer vehicle, translates into a deceleration of $a_P
= (8.74\pm 1.33) \times 10^{-10}$ m s$^{-2}$. This Sunward acceleration appears
to be a violation of Newton's inverse-square law of gravitation, and is
referred to as the Pioneer anomaly, the nature of which remains still elusive
to unveil.
Within the theoretical framework of nonlinear electrodynamics (NLED) in what
follows we will address this astrodynamics puzzle, which over the last fifteen
years has challenged in a fundamental basis our understanding of gravitational
physics. To this goal we will first, and briefly, review the history of the
Pioneers 10 and 11 missions. Then a synopsis of currently available Lagrangian
formulations of NLED is given. And finally, we present our solution of this
enigma by invoking a special class of NLED theories featuring a proper
description of electromagnetic phenomena taking place in environments where the
strength of the (electro)magnetic fields in the background is decidedly low.Comment: 24, pages, 3 figures. Source of the first publication of this
article: InTech Publisher: http://www.intechweb.or

### A spherically symmetric and stationary universe from a weak modification of general relativity

It is shown that a weak modification of general relativity, in the linearized
approach, renders a spherically symmetric and stationary model of the universe.
This is due to the presence of a third mode of polarization in the linearized
gravity in which a "curvature" energy term is present. Such an energy can, in
principle, be identified as the Dark Energy. The model can also help to a
better understanding of the framework of the Einstein-Vlasov system.Comment: Accepted for publication by Europhysics Letter

### Primordial magnetic fields and gravitational baryogenesis in nonlinear electrodynamics

The amplification of the primordial magnetic fields and the gravitational
baryogenesis, a mechanism that allows to generate the baryon asymmetry in the
Universe by means of the coupling between the Ricci scalar curvature and the
baryon current, are reviewed in the framework of the nonlinear electrodynamics.
To study the amplification of the primordial magnetic field strength, we write
down the gauge invariant wave equations and then solve them (in the long
wavelength approximation) for three different eras of the Universe: de Sitter,
the reheating and the radiation dominated era. Constraints on parameters
entering the nonlinear electrodynamics are obtained by using the amplitude of
the observed galactic magnetic fields and the baryon asymmetry, which are
characterized by the dimensionless parameters $r\sim 10^{-37}$ and
$\eta_B\lesssim 9\times 10^{-11}$, respectively.Comment: 10 pages, 3 tables, 6 figures. Accepted for publication in Physical
Review

### Weak-Scale Hidden Sector and Energy Transport in Fireball Models of Gamma-Ray Bursts

The annihilation of pairs of very weakly interacting particles in the
neibourghood of gamma-ray sources is introduced here as a plausible mechanism
to overcome the baryon load problem. This way we can explain how these very
high energy gamma-ray bursts can be powered at the onset of very energetic
events like supernovae (collapsars) explosions or coalescences of binary
neutron stars. Our approach uses the weak-scale hidden sector models in which
the Higgs sector of the standard model is extended to include a gauge singlet
that only interacts with the Higgs particle. These particles would be produced
either during the implosion of the red supergiant star core or at the aftermath
of a neutron star binary merger. The whole energetics and timescales of the
relativistic blast wave, the fireball, are reproduced.Comment: 4 pp, 1 ps fig, text revised and improve

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