J. M. Salim

Geometrical aspects of light propagation in nonlinear electrodynamics

We analyze the propagation of light in the context of nonlinear electrodynamics, as it occurs in modified QED vacua. We show that the corresponding characteristic equation can be described in terms of a modification of the effective geometry of the underlying spacetime structure. We present the general form for this effective geometry and exhibit some new consequences that result from such an approach.

Nonlinear electrodynamics and the acceleration of the Universe

It is shown that the addition of a non-linear term to the Lagrangian of the electromagnetic field yields a fluid with an asymptotically super-negative equation of state, causing an accelerated expansion of the universe. Some general properties of nonlinear electromagnetism in cosmology are also discussed.

Light propagation in non-linear electrodynamics

Working on the approximation of low frequency, we present the light cone conditions for a class of theories constructed with the two gauge invariants of the Maxwell field without making use of average over polarization states. Different polarization states are thus identified describing birefringence phenomena. We make an application of the formalism to the case of Euler-Heisenberg effective Lagrangian and well know results are obtained.

Cosmological effects of nonlinear electrodynamics

It will be shown that a given realization of nonlinear electrodynamics, used as a source of Einsteins equations, generates a cosmological model with interesting features, namely a phase of current cosmic acceleration, and the absence of an initial singularity, thus pointing to a way of solving two important problems in cosmology.

Analogue black holes in flowing dielectrics

We show that a flowing dielectric medium with a linear response to an external electric field can be used to generate an analogue geometry that has many of the formal properties of a Schwarzschild black hole for light rays, in spite of birefringence. The surface gravity of this analogue black hole has a contribution that depends only on the dielectric properties of the fluid (in addition to the usual term dependent on the acceleration). This term may give a hint at a new mechanism to increase the temperature of Hawking radiation.

Creation of cosmological magnetic fields in a bouncing cosmology

We show (in a completely analytical and exact manner) that an efficient magnetic field amplification method is operative during the bounce in a time-dependent gauge coupling model. The cosmological magnetic fields so generated have particular spectral features, and may be observed by future cosmic microwave background measurements and by direct cluster measurements.

The radiation era in scalar-tensor cosmology

Abstract An action inspired on the low-energy effective action for heterotic string and Weyl integrable space-time theory is used to describe the radiation era in scalar-tensor cosmology. The resulting field equations for a Friedmann–Robertson–Walker geometry are written and the general solution for this system is obtained and its main properties are discussed.

Analogue black holes for light rays in static dielectrics

Propagation of light in nonlinear materials is here studied in the regime of the geometrical optics. It is shown that a spherically symmetric medium at rest with some specific dielectric properties can be used to produce an exact analogue model for a class of space-times which includes spherically symmetric and static black hole solutions. The optical model here presented can be a useful tool to reproduce in laboratory the behavior of optical null geodesics near a compact object with an observable gravitational Schwarzschild radius.

Production of photons in a bouncing universe

Using a new non-singular solution, it is shown that the production of photons in dilaton electrodynamics in a cosmological setting is greatly increased if the effect of matter creation on the geometry is taken into account. We show that this increment can be related to the problem of the origin of magnetic fields in the universe.

The light rays analogue of a static black hole1)

The propagation of light pulses inside nonlinear static media is described in the limit of geometrical optics. A spherically symmetric dielectric model for a nonlinear medium at rest is obtained, with the help of which an exact analogue model of static black holes can be built. Such an optical model may improve the feasibility in laboratory of the null geodesics near a compact object with an observable gravitational Schwarzschild radius.