Papers by Renato Klippert
The Fourteenth Marcel Grossmann Meeting, 2017
Wave propagation in nonlinear theories of the electromagnetism described by Lagrangian densities ... more Wave propagation in nonlinear theories of the electromagnetism described by Lagrangian densities dependent upon its two local invariants L(F, G) is revisited. On the light of the recent findings in metamaterials, it is here shown that trirefringence is also a possible phenomenon to occur in the realm of such nonlinear theories. A specific model exhibiting this effect is investigated both in terms of phase and group velocities. It is claimed that wave propagation in some well known nonlinear models for spin-one fields, like QED and QCD in certain regimes, may exhibit trirefringence.
The barotropic indices and the corresponding FRW scale factors of the so-called Darboux cosmologi... more The barotropic indices and the corresponding FRW scale factors of the so-called Darboux cosmological fluids are presented in the comoving time axis, which is the natural one for the phenomenology related to the cosmological data. Some useful comments on the features of the plots are included. In a previous work, an interesting class of Darboux cosmological fluids in closed and open FRW models of the Λ = 0 cosmology has been introduced by one of the authors. 1 However, the results have been displayed in the conformal time axis, whereas for comparison with definite cosmological data the comoving time axis is usually needed. The purpose of this letter is to present the cosmological comoving evolution of that class of fluids and add several heuristic comments on the obtained results. We plot here the comoving time dependent barotropic indices and the corresponding scale factors for open FRW universes, 2 respectively. Our general conclusions are presented in the following. (i) For the op...
Physical Review A
Nonmagnetic and spherically symmetric dielectric material media are investigated in their general... more Nonmagnetic and spherically symmetric dielectric material media are investigated in their generality as analog models, in the domains of geometrical optics, for a few relevant static and spherically symmetric solutions of gravitation, including black holes and wormholes. Typical and desirable gravitational features are systematically linked to the nonlinear properties of the phenomenological dielectric permittivity of the medium. From this, the limitations of such analogies are explored in terms of their corresponding geometric flexibility, dielectric configurations, and causal structure.
Classical and Quantum Gravity
Crude comparison between four alternative proposals for the very definition of a wormhole is prov... more Crude comparison between four alternative proposals for the very definition of a wormhole is provided, all of which were intended to apply to the dynamical cases. An interesting dynamical solution, based upon large scale magnetic fields, is used for the comparisons. Such solution goes beyond the perfect fluid approximation due to an anisotropic pressure component, bringing to the fore some unsuspected features of those definitions. Certain notions as reversible traversability are claimed as a way to select among those definitions the best suited one to represent our intuition of what a wormhole solution is expected to be. 1 Also, as noted in , the attempt of using embedding techniques usually applied in the static case for the dynamical one, as done in , can be misleading when checking the flare-out condition.
Int J Theor Phys, 2002
The strictly nonrelativistic isospectral scheme based on the general Riccati solution and Darboux... more The strictly nonrelativistic isospectral scheme based on the general Riccati solution and Darboux transformation function corresponding to excited states is presented on the following examples: the harmonic oscillator, the square well, and the hydrogen atom.
The dominant contribution for the renormalized stress tensor of a massless scalar field around a ... more The dominant contribution for the renormalized stress tensor of a massless scalar field around a cosmic string with a dislocation was presented recently. By considering this energy-momentum distribution as source of the linearized semiclassical Einstein equations, the first order perturbative solution for the approximated spacetime geometry is derived. The non trivial motion of test particles is discussed, showing that a helical motion is quantum mechanically induced by the presence of the defect.
We show that a flowing dielectric medium with a linear response to an external electric field can... more We show that a flowing dielectric medium with a linear response to an external electric field can be used to generate an analog geometry that has many of the formal properties of a Schwarzschild black hole for light rays, in spite of birefringence. We also discuss the possibility of generating these analog black holes in the laboratory.
On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (In 3 Volumes), 2002
ABSTRACT From standard results of gravitational collapse of a thin shell of charged dust matter w... more ABSTRACT From standard results of gravitational collapse of a thin shell of charged dust matter we obtain that no naked singularities can be dinamically formed from conventional initial data. The electromagnetic energy of the system (stored in the electric field) when the shell crosses the event horizon coincides with the maximum amount of extractable energy (Mtot - Mir)c2.
On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (In 3 Volumes), 2002
Recently 2 we have developed the Quasi-Maxwellian (QM) treatment for dealing with gauge-invariant... more Recently 2 we have developed the Quasi-Maxwellian (QM) treatment for dealing with gauge-invariant cosmological perturbations in Friedman-Robertson-Walker model, providing their Hamiltonian description from a complete minimal set of gauge independent variables. The QM framework has been used since the early seventies to analyze perturbations of conformally at geometries uniquely. In this work we show that this approach may go beyond such restricted use. We apply it in order to describe linear perturbations of Schwarzschild vacuum solution, obtaining a simpler formulation than that provided by the usual method which deals with perturbations of the metric tensor (see Chandrasekhar, 3 for instance). For simplicity we will limit ourselves here to the more relevant tensorial case (which should encompass that of gravitational waves). In this vein we construct a convenient frame suggested by the background symmetries, such that the associated congruence has, besides a non null expansion, tensorial kinematic quantities (viz., the shear). The immediate consequence of introducing this property into the realm of the perturbation scheme is that additional constraints arise on the fundamental tensor basis. These new constraints, however, do not concern to eventual perturbations, but are linked with the very existence of a tensor basis referred to the chosen frame, and we exhibit them in order to obtain a gauge independent dynamical system, therefore avoiding the use of the explicit point dependence of such a basis. The resulting perturbations seem to be highly unstable due to cosmological considerations.
Working with electrodynamics in the geometrical optics approximation we derive the expression rep... more Working with electrodynamics in the geometrical optics approximation we derive the expression representing an eectively curved geometry which guides the propagation of electromagnetic waves in material media whose physical properties depend on an external electric eld. The issue of birefringence is addressed, and the trajectory of the extraordinary ray is explicitly worked out. Quite general curves are obtained for the
On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories (In 3 Volumes), 2002
ABSTRACT The observation for near one hour of the conjunction of Jupiter and Venus at less than 1... more ABSTRACT The observation for near one hour of the conjunction of Jupiter and Venus at less than 1 arcminute on May 17th, 2000 (about 10 U.T.), has evidenced the possibility to measure the distances from the Sun of the Earth, Jupiter and Venus with a measurement of the speed of the relative motion of Venus with respect to Jupiter. The Kepler laws for the orbital velocity of the planets and the particular geometrical configuration occurred are required for this derivation.
The Tenth Marcel Grossmann Meeting, On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories - Proceedings of the MG10 Meeting, 2005
The Tenth Marcel Grossmann Meeting, On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories - Proceedings of the MG10 Meeting, 2005
The dominant contribution for the renormalized stress tensor of a massless scalar field around a ... more The dominant contribution for the renormalized stress tensor of a massless scalar field around a cosmic string with a dislocation was presented recently. By considering this energy-momentum distribution as source of the linearized semiclassical Einstein equations, the first order perturbative solution for the approximated spacetime geometry is derived. The non trivial motion of test particles is discussed, showing that a helical motion is quantum mechanically induced by the presence of the defect.
The Twelfth Marcel Grossmann Meeting - On Recent Developments in Theoretical and Experimental General Relativity Astrophysics and Relativistic Field Theories - Proceedings of the MG12 Meeting on General Relativity, 2012
ABSTRACT The one-loop semi-classical description of quantum electrodynamics is taken as a source ... more ABSTRACT The one-loop semi-classical description of quantum electrodynamics is taken as a source of the Einstein field equations for a homogeneous and isotropic universe, in the limit of high conductivity which is expected to hold in the early era of our Universe. It is shown that a cosmic singularity (the standard big-bang scenario) is either present or not according with an arbitrary choice of accuracy.
International Journal of Theoretical Physics, 2002
The strictly nonrelativistic isospectral scheme based on the general Riccati solution and Darboux... more The strictly nonrelativistic isospectral scheme based on the general Riccati solution and Darboux transformation function corresponding to excited states is presented on the following examples: the harmonic oscillator, the square well, and the hydrogen atom.
The Eleventh Marcel Grossmann Meeting - On Recent Developments in Theoretical and Experimental General Relativity, Gravitation and Relativistic Field Theories - Proceedings of the MG11 Meeting on General Relativity, 2008
An approach to deal with the limit of geometrical optics of electromagnetic waves which propagate... more An approach to deal with the limit of geometrical optics of electromagnetic waves which propagate in moving nonlinear local dielectric media in the context of Maxwellian electrodynamics is here developed in order to apply to quite general material media. Fresnel equations for the light rays are generically found, and its solutions are intrinsically obtained. The multi-refringence problem is addressed, and no more than four monochromatic polarization modes are found to propagate there. This work does not provide an analog model of General Relativity, but instead relies in the fundamentals for an analog model to be built in geometrical optics.
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Papers by Renato Klippert