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V. A. De Lorenci

Publications and source records attributed to V. A. De Lorenci.

54 records · Page 3Linked to original sources
arXiv2002

On the self-consistence of electrodynamics in the early universe

The issue of a self-consistent solution of Maxwell-Einstein equations achieves a very simple form when all quantum effects are neglected but a weak vacuum polarization due to an external magnetic field is taken into account. From a semi-classical point of view this means to deal with an appropriate limit of the one-loop effective Lagrangian for electrodynamics. When the corresponding stress-energy tensor is considered as a source of the gravitational field a surprisingly bouncing behavior is obtained. The present toy model leads to important new features which should have taken place in the early universe.

gr-qc↗
arXiv2001

Classical self-forces in a space with a dispiration

We derive the gravitational and electrostatic self-energies of a particle at rest in the background of a cosmic dispiration (topological defect), finding that the particle may experience potential steps, well potentials or potential barriers depending on the nature of the interaction and also on certain properties of the defect. The results may turn out to be useful in cosmology and condensed matter physics.

gr-qc↗
arXiv2001

Analog gravity from electrodynamics in non-linear media

Working with electrodynamics in the geometrical optics approximation we derive the expression representing an effectively curved geometry which guides 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 an electric field.

gr-qc↗
arXiv2001

Electromagnetic wave propagation inside a material medium: an effective geometry interpretation

We present a method developed to deal with electromagnetic wave propagation inside a material medium that reacts, in general, non-linearly to the field strength. We work in the context of Maxwell' s theory in the low frequency limit and obtain a geometrical representation of light paths for each case presented. The isotropic case and artificial birefringence caused by an external electric field are analyzed as an application of the formalism and the effective geometry associated to the wave propagation is exhibited.

gr-qc↗
arXiv2001

Dyadosphere bending of light

In the context of the static and spherically symmetric solution of a charged compact object, we present the expression for the bending of light in the region just outside the event horizon (the dyadosphere) where vacuum polarization effects are taken into account.

astro-ph↗
arXiv2000

Remarks on vacuum fluctuations around a spinning cosmic string

We apply the point-splitting method to investigate vacuum fluctuations in the nonglobally hyperbolic background of a spinning cosmic string. Implementing renormalization by removing the Minkowski contribution it is shown that although the Green function in the literature satisfies the usual Green function equation, it leads to pathological physical results.

gr-qc↗
arXiv2000

The Rotating Detector and Vacuum Fluctuations

In this work we compare the quantization of a massless scalar field in an inertial frame with the quantization in a rotating frame. We used the Trocheries-Takeno mapping to relate measurements in the inertial and the rotating frames. An exact solution of the Klein-Gordon equation in the rotating coordinate system is found and the Bogolubov transformation between the inertial and rotating modes is calculated, showing that the rotating observer defines a vacuum state different from the Minkowski one. We also obtain the response function of an Unruh-De Witt detector coupled with the scalar field travelling in a uniformly rotating world-line. The response function is obtained for two different situations: when the quantum field is prepared in the usual Minkowski vacuum state and when it is prepared in the Trocheries-Takeno vacuum state. We also consider the case of an inertial detector interacting with the field in the rotating vacuum.

hep-th↗
arXiv2000

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.

gr-qc↗
arXiv2000

The Velocity of Gravitational Waves

We examine the propagation of gravitational waves in the new field theory of gravitation recently proposed by Novello-De Lorenci-Luciane (NDL). This examination is done on a solvable case corresponding to a spherically symmetric static configuration. We show that in NDL theory the velocity of gravitational waves is lower than light velocity. We point out some consequences of this result and suggest a possible scenario for its verification.

gr-qc↗
arXiv1999

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 approach.

gr-qc↗
arXiv1999

From spinning to non-spinning cosmic string spacetimes

We analyse the properties of a fluid generating a spinning cosmic string spacetime with flat limiting cases corresponding to a constant angular momentum in the infinite past and static configuration in the infinite future. The spontaneous loss of angular momentum of a spinning cosmic string due to particle emission is discussed. The rate of particle production between the spinning and non-spinning cosmic string spacetimes is calculated.

gr-qc↗
arXiv1998

A Rotating Quantum Vacuum

We investigate how a uniformly rotating frame is defined as the rest frame of an observer rotating with constant angular velocity $Ω$ around the $z$ axis of an inertial frame. Assuming that this frame is a Lorentz one, we second quantize a free massless scalar field in this rotating frame and obtain that creation-anihilation operators of the field are not the same as those of an inertial frame. This leads to a new vacuum state --- a rotating vacuum --- which is a superposition of positive and negative frequency Minkowski particles. After this, introducing an apparatus device coupled linearly with the field we obtain that there is a strong correlation between number of rotating particles (in a given state) obtained via canonical quantization and via response function of the rotating detector. Finally, we analyse polarization effects in circular accelerators in the proper frame of the electron making a connection with the inertial frame point of view.

hep-th↗
arXiv1997

Can Non Gravitational Black Holes Exists?

We claim that the existence of a mechanism such that photons may be trapped in a compact domain is not an exclusive property of gravitational forces. We show the case in which a non-linear electrodynamics allows such effect. In this latter case we should call this region an Electromagnetic Black Hole (EBH).

gr-qc↗
arXiv1997

Gluon Confinement

In this paper we present a new model for a gauge field theory such that self-interacting spin-one particles can be confined in a compact domain. The necessary conditions to produce the confinement appear already in the properties of the eikonal structure generated by the particular choice of the dynamics. The gluons do not follow along Minkowski null cone and thus can be equivalently interpreted as if they were massive.

hep-ph↗
arXiv1997

Gravitational Particle Production in Spinning Cosmic String Spacetimes

The spontaneous loss of angular momentum of a spinning cosmic string due to particle emission is discussed. The rate of particle production between two assymptotic spacetimes: the spinning cosmic string spacetime in the infinite past and a non-spinning cosmic string spacetime in the infinite future is calculated.

gr-qc↗
arXiv1997

The Binary Pulsar Is Not the Ultimate Test for the Theory of Gravity

General relativity can be formulated either as in its original geometrical version (Einstein, 1915) or as a field theory (Feynman, 1962). In the Feynman presentation of Einstein theory an hypothesis concerning the interaction of gravity to gravity, which was hidden in the original version, becomes explicit. This is nothing but the assumed extension of the validity of the equivalence principle not only for matter-gravity interaction, but also for gravity-gravity. Recently we have presented a field theory of gravity (from here on called the NDL theory) which does not contain such a hypothesis. We have shown that, for this theory, both the cosmological structure and the PPN approximation for the solar tests are satisfied. The proposal of this paper is to go one step further and to show that NDL theory is able to solve the problem of radiation emission by a binary pulsar in the same degree of accuracy as it was done in the GR theory. In the post-Newtonian order of approximation we show that the quadrupole formula of this theory is equal to the corresponding one in general relativity. Thus, the unique actual observable distinction of these theories concerns the velocity of gravitational waves, which becomes then the true ultimate test for gravity theory.

gr-qc↗
arXiv1995

The Static Gravitational Field of a Spherically Symmetric Body

We continue here the exam \cite{LuMa} of a theory of gravity that satisfies the Einstein Equivalence Principle (EEP) for any kind of matter/energy, except for the gravitational energy. This is part of a research program that intends to re-examine the standard Feynman-Deser approach of field theoretical derivation of Einstein\rq s General Relativity. The hypothesis implicit in such precedent derivations \cite{Feynman} \cite{Deser} concerns the universality of gravity interaction. Although there is a strong observational basis supporting the universality of matter to gravity interaction, there is not an equivalent situation that supports the hypothesis that gravity interacts with gravity as any other form of non-gravitational energy. We analyse here a kind of gravity-gravity interaction distinct from GR but, as we shall see, that conforms with the actual status of observation. We exhibit the gravitational field produced by a spherically symmetric static configuration as described in this field theory of gravity. The values that we obtain for the standard PPN parameters ($α= β= γ= 1$) coincide with those of General Relativity. Thus, as we pointed out in a previous paper, the main different aspect of our theory and GR concerns the velocity of the gravitational waves. Since there is a large expectation that the detection of gravitational waves will occur in the near future, the question of which theory describes Nature better will probably be settled soon.

gr-qc↗