R. Klippert

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.

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.

Analogue gravity from electrodynamics in nonlinear media

Working with electrodynamics in the geometrical optics approximation we derive an expression representing effectively curved geometries which guide the propagation of electromagnetic waves in material media whose physical properties depend on an external electric field. The issue of birefringence is addressed, and the trajectory of the extraordinary ray is explicitly worked out. Quite general curves are obtained for the path of the light ray by suitably setting the electric field.

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.

Birefringence in nonlinear anisotropic dielectric media

Light propagation is investigated in the context of local anisotropic nonlinear dielectric media at rest with the dielectric coefficients {epsilon}{sup {mu}}{sub {nu}}={epsilon}{sup {mu}}{sub {nu}}(E{yields},B{yields}) and constant {mu}, in the limit of geometrical optics. Birefringence was examined and the general conditions for its occurrence were presented. A toy model is exhibited, in which uniaxial birefringent media with nonlinear dielectric properties could be driven by external fields in such way that birefringence may be artificially controlled. The effective geometry interpretation is also addressed.

Non gravitational black holes

Analogue models of general relativity have recently been considered with great interest by the scientific community. They connect branches of physics as different as gravitation, condensed matter physics, electrodynamics, acoustics, and quantum field theory. One of the main expectations about such models lies on the possibility of testing in laboratory some aspects of quantum field theory in curved spacetimes. For instance, it seems to be possible to probe the existence of Hawking radiation by means of analogue models in the context of certain condensed matter systems. We briefly report the present day status of this topic of research. Some specific models are considered, particularly those presenting analogue event horizons as solutions. The issue of thermal emission (analogue Hawking radiation) is also discussed.

Semiclassical backreaction around a cosmic dislocation

The energy-momentum vacuum average of a conformally coupled massless scalar field vibrating around a cosmic dislocation--a cosmic string with a dislocation along its axis--is taken as source of the linearized semiclassical Einstein equations. The solution up to first order in the Planck constant is derived. Motion of a test particle is then discussed, showing that under certain circumstances a helical-like dragging effect, with no classical analogue around the cosmic dislocation, is induced by backreaction.

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.

Multirefringence phenomena in nonlinear electrodynamics

Universite´ de Nice Sophia Antipolis, 06103 Nice Cedex 2, Franceand Dipartimento di Fisica and ICRA, Sapienza Universita` di Roma, I-00185 Rome, Italy(Received 19 April 2013; published 13 September 2013)Wave propagation in nonlinear theories of the electromagnetism described by Lagrangian densitiesdependent upon its two local invariants LðF;GÞ is revisited. On the light of the recent findings inmetamaterials, it is here shown that trirefringence is also a possible phenomenon to occur in the realm ofsuch nonlinear theories. A specific model exhibiting this effect is investigated in terms of both phase andgroup velocities. It is claimed that wave propagation in some well known nonlinear models for spin-onefields, like QED and QCD in certain regimes, may exhibit trirefringence.