arXiv subjects

Rafael Ferraro

Publications and source records attributed to Rafael Ferraro.

At least 55 records · Page 3Linked to original sources

arXiv2008

Luminosity distance for Born-Infeld electromagnetic waves propagating in a cosmological magnetic background

Born-Infeld electromagnetic waves interacting with a static magnetic background are studied in an expanding universe. The non-linear character of Born-Infeld electrodynamics modifies the relation between the energy flux and the distance to the source, which gains a new dependence on the redshift that is governed by the background field. We compute the luminosity distance as a function of the redshift and compare with Maxwellian curves for supernovae type Ia.

astro-ph↗

arXiv2008

Born-Infeld corrections to Coulombian interactions

Two-dimensional Born-Infeld electrostatic fields behaving as the superposition of two point-like charges in the linearized (Maxwellian) limit are worked out by means of a non-holomorphic mapping of the complex plane. The changes underwent by the Coulombian interaction between two charges in Born-Infeld theory are computed. Remarkably, the force between equal charges goes to zero as they approach each other.

hep-th↗

arXiv2007

Testing Born-Infeld electrodynamics in waveguides

Waveguides can be employed to test non-linear effects in electrodynamics. We solve Born-Infeld equations for TE waves in a rectangular waveguide. We show that the energy velocity acquires a dependence on the amplitude, and harmonic components appear as a consequence of the non-linear behavior.

hep-th↗

arXiv2007

From Newton to Einstein: the birth of Special Relativity

Physics was in crisis at the beginning of the twentieth century because the newborn Maxwell's electromagnetism defied mechanistic preconceptions. Albert Einstein understood that the solution to the crisis required an audacious reworking of the concepts of space and time. Special Relativity deeply modified our way of regarding space and time, in order to harmonize electromagnetism with the principle of relativity. As a consequence, lengths and elapsed times were stripped of the invariant character that classical Physics conferred them; in their place, the speed of light acquired that privileged status. Such revolutionary change forced Einstein to reformulate Newtonian mechanics, a step that led him to discover the mass-energy equivalence.

physics.hist-ph↗

arXiv2007

Modified teleparallel gravity: inflation without inflaton

Born-Infeld strategy to smooth theories having divergent solutions is applied to teleparallel equivalent of General Relativity. Differing from other theories of modified gravity, modified teleparallelism leads to second order equations, since teleparallel Lagrangian only contains first derivatives of the vierbein. We show that Born-Infeld-modified teleparallelism solves the particle horizon problem in a spatially flat FRW universe by providing an initial exponential expansion without resorting to an inflaton field.

gr-qc↗

arXiv2006

Anisotropic effects of background fields on Born-Infeld electromagnetic waves

We show exact solutions of Born-Infeld theory for electromagnetic plane waves propagating in the presence of static background fields. The non-linear character of Born-Infeld equations generates an interaction between background and wave that changes the speed of propagation and adds a longitudinal component to the wave. As a consequence, in a magnetic background the ray direction differs from the propagation direction --a behavior resembling the one of a wave in an anisotropic medium--. This feature could open up a way to experimental tests of Born-Infeld theory.

hep-th↗

arXiv2005

Hoffmann-Infeld Black Hole Solutions in Lovelock Gravity

Five-dimensional black holes are studied in Lovelock gravity coupled to Hoffmann-Infeld non-linear electrodynamics. It is shown that some of these solutions present a double peak behavior of the temperature as a function of the horizon radius. This feature implies that the evaporation process, though drastic for a period, leads to an eternal black hole remnant. Moreover, the form of the caloric curve corresponds to the existence of a plateau in the evaporation rate, which implies that black holes of intermediate scales turn out to be unstable. The geometrical aspects, such as the absence of conical singularity, the structure of horizons, etc. are also discussed. In particular, solutions that are asymptotically AdS arise for special choices of the parameters, corresponding to charged solutions of five-dimensional Chern-Simons gravity.

gr-qc↗

arXiv2004

Arago (1810): the first experimental result against the ether

95 years before Special Relativity was born, Arago attempted to detect the absolute motion of the Earth by measuring the deflection of starlight passing through a prism fixed to the Earth. The null result of this experiment gave rise to the Fresnel's hypothesis of an ether partly dragged by a moving substance. In the context of Einstein's Relativity, the sole frame which is privileged in Arago's experiment is the proper frame of the prism, and the null result only says that Snell's law is valid in that frame. We revisit the history of this premature first evidence against the ether theory and calculate the Fresnel's dragging coefficient by applying the Huygens' construction in the frame of the prism. We expose the dissimilar treatment received by the ray and the wave front as an unavoidable consequence of the classical notions of space and time.

physics.hist-ph↗

arXiv2004

Exact Solutions of Lovelock-Born-Infeld Black Holes

The exact five-dimensional charged black hole solution in Lovelock gravity coupled to Born-Infeld electrodynamics is presented. This solution interpolates between the Hoffmann black hole for the Einstein-Born-Infeld theory and other solutions in the Lovelock theory previously studied in the literature. The conical singularity of the metric around the origin can be removed by a proper choice of the black hole parameters. The thermodynamic properties of the solution are also analyzed and, in particular, it is shown that the behaviour of the specific heat indicates the existence of a stability transition point in the vacuum solutions. We discuss the similarities existing between this five-dimensional geometry and the three-dimensional black hole. Like BTZ black hole, the Lovelock black hole has an infinite lifetime.

gr-qc↗

arXiv2004

General relativity principle and uniqueness in Einstein equations

The issue of implementing the principle of general relativity in Einstein equations has been widely discussed, since Kretschmann's well-known criticism stated that general covariance of the Einstein equations is not suffice to express the principle of general relativity (the equivalence of all the coordinate systems). This failure is usually rooted in the fact that metric in Einstein equations is not univocally determined by the matter distribution. We show that the condition of univocal determination of the metric by the matter distribution is stronger than the requirement of equivalence of all coordinate systems. In order to separate the uniqueness problem in Einstein equations from the issue of the principle of general relativity, we define the "equivalence group" instead of the notion of covariance group which is empty of physical content. Moreover, we have complemented in a positive way Kretschmann's objection by supplementing Einstein equations with a sufficient condition for the equivalence of all the coordinate systems.

gr-qc↗

arXiv2003

2D Born-Infeld electrostatic fields

The electrostatic configurations of the Born-Infeld field in the 2-dimensional Euclidean plane are obtained by means of a non-analytical complex mapping which captures the structure of equipotential and field lines. The electrostatic field reaches the Born-Infeld limit value when the field lines become tangent to an epicycloid around the origin. The total energy by unit of length remains finite.

hep-th↗

arXiv2002

Generic composition of boosts: an elementary derivation of the Wigner rotation

Because of its apparent complexity, the discussion of Wigner rotation is usually reduced to the study of Thomas precession, which is too specific a case to allow a deep understanding of boost composition. However, by simple arguments and linear algebra, the result for the Wigner rotation is obtained straightforwardly, leading to a formula written in a manageable form, The result is exemplified in the context of the aberration of light.

physics.ed-ph↗

arXiv2002

The equivalence principle and the bending of light

The apparent discrepancy between the bending of light predicted by the equivalence principle and its corresponding value in general relativity is resolved by evaluating the deflection of light with respect to a direction that is parallel transported along the ray trajectory in 3-space. In this way the bending predicted by the equivalence principle is fulfilled in general relativity and other alternative metric theories of gravity.

gr-qc↗

arXiv2002

Time asymmetries in quantum cosmology and the searching for boundary conditions to the Wheeler-DeWitt equation

The paper addresses the quantization of minisuperspace cosmological models by studying a possible solution to the problem of time and time asymmetries in quantum cosmology. Since General Relativity does not have a privileged time variable of the newtonian type, it is necessary, in order to have a dynamical evolution, to select a physical clock. This choice yields, in the proposed approach, to the breaking of the so called clock-reversal invariance of the theory which is clearly distinguished from the well known motion-reversal invariance of both classical and quantum mechanics. In the light of this new perspective, the problem of imposing proper boundary conditions on the space of solutions of the Wheeler-DeWitt equation is reformulated. The symmetry-breaking formalism of previous papers is analyzed and a clarification of it is proposed in order to satisfy the requirements of the new interpretation.

gr-qc↗

arXiv2001

Quantization of a generally covariant gauge system with two super Hamiltonian constraints

The Becci-Rouet-Stora-Tyutin (BRST) operator quantization of a finite-dimensional gauge system featuring two quadratic super Hamiltonian and m linear supermomentum constraints is studied as a model for quantizing generally covariant gauge theories. The proposed model ``completely'' mimics the constraint algebra of General Relativity. The Dirac constraint operators are identified by realizing the BRST generator of the system as a Hermitian nilpotent operator, and a physical inner product is introduced to complete a consistent quantization procedure.

gr-qc↗

arXiv2000

Operator ordering for generally covariant systems

The constraint operators belonging to a generally covariant system are found out within the framework of the BRST formalism. The result embraces quadratic Hamiltonian constraints whose potential can be factorized as a never null function times a gauge invariant function. The building of the inner product between physical states is analyzed for systems featuring either intrinsic or extrinsic time.

gr-qc↗

arXiv2000

Quantization of the Taub cosmological model with extrinsic time

The paper addresses the quantization of minisuperspace cosmological models, with application to the Taub Model. By desparametrizing the model with an extrinsic time, a formalism is developed in order to define a conserved Schrödinger inner product in the space of solutions of the Wheeler-De Witt equation. A quantum version of classical canonical transformations is introduced for connecting the solutions of the Wheeler-De Witt equation with the wave functions of the desparametrized system. Once this correspondence is established, boundary conditions on the space of solutions of the Wheeler-De Witt equation are found to select the physical subspace. The question of defining boundary conditions on the space of solutions of the Wheeler-De Witt equation without having reduced the system is examined.

gr-qc↗

arXiv1999

Quantization of generally covariant systems with extrinsic time

A generally covariant system can be deparametrized by means of an ``extrinsic'' time, provided that the metric has a conformal ``temporal'' Killing vector and the potential exhibits a suitable behavior with respect to it. The quantization of the system is performed by giving the well ordered constraint operators which satisfy the algebra. The searching of these operators is enlightned by the methods of the BRST formalism.

gr-qc↗