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L. Herrera

Publications and source records attributed to L. Herrera.

At least 145 records · Page 8Linked to original sources
arXiv2000

The static cylinder, gyroscopes, the C metric, and all that

The physical meaning of the Levi-Civita spacetime for some "critical" values of the parameter sigma, is discussed in the light of gedanken experiments performed with gyroscopes circumventing the axis of symmetry. The fact that sigma=1/2 corresponds to flat space described from the point of view of an accelerated frame of reference, led us to incorporate the C metric into discussion. The interpretation of phi as an angle variable for any value of sigma, appears to be at the origen of difficulties.

gr-qc↗
arXiv2000

Measuring multipole moments of Weyl metrics by means of gyroscopes

Using the technique of Rindler and Perlick we calculate the total precession per revolution of a gyroscope circumventing the source of Weyl metrics. We establish thereby a link between the multipole moments of the source and an ``observable'' quantity. Special attention deserves the case of the gamma-metric. As an extension of this result we also present the corresponding expressions for some stationary space-times.

gr-qc↗
arXiv2000

On the influence of gravitational radiation on a gyroscope

We calculate the precession of a gyroscope at rest in a Bondi spacetime. It is shown that, far from the source, the leading term in the rate of precession of the gyroscope is simply expressed through the news function of the system, and vanishes if and only if there is no news. Rough estimates are presented, illustrating the order of magnitude of the expected effect for different scenarios. It is also shown from the next order term that non-radiative (but time dependent) spacetimes will produce a gyroscope precession of that order, providing thereby ``observational'' evidence for the violation of the Huygens's principle.

gr-qc↗
arXiv2000

Gyroscope precession in cylindrically symmetric spacetimes

We present calculations of gyroscope precession in spacetimes described by Levi-Civita and Lewis metrics, under different circumstances. By doing so we are able to establish a link between the parameters of the metrics and observable quantities, providing thereby a physical interpretation for those parameters, without specifying the source of the field.

gr-qc↗
arXiv1999

Measuring the strength of dissipative inflation

We comment on recently proposed dissipative inflationary models. It is shown that the strength of the inflationary expansion is related to a specific combination of thermodynamic variables which is known to measure the instability of self-gravitating dissipative systems.

gr-qc↗
arXiv1999

The Relativistic Transformation to Rotating Frames

We present a critical review of the relativistic rotation transformation of Trocheris and Takeno. A new transformation is proposed which is free from the drawbacks of the former. Some applications are presented.

gr-qc↗
arXiv1998

Geodesics in the Gamma spacetime

Circular and radial geodesics are studied in the spacetime described by the $γ$ metric. Their behaviour is compared with the spherically symmetric situation, bringing out the sensitivity of the trajectories to deviations from spherical symmetry.

gr-qc↗
arXiv1998

The Levi-Civita spacetime as a limiting case of the Gamma spacetime

It is shown that the Levi-Civita metric can be obtained from a family of the Weyl metric, the Gamma metric, by taking the limit when the length of its Newtonian image source tends to infinity. In this process a relationship appears between two fundamental parameters of both metrics.

gr-qc↗
arXiv1998

The Active Gravitational Mass of a Heat Conducting Sphere Out of Hydrostatic Equilibrium

We obtain an expression for the active gravitational mass of a relativistic heat conducting fluid, just after its departure from hydrostatic equilibrium, on a time scale of the order of relaxation time. It is shown that an increase of a characteristic parameter leads to larger (smaller) values of active gravitational mass of collapsing (expanding) spheres, enhacing thereby the instability of the system.

gr-qc↗
arXiv1998

Dissipative Collapse Through the Critical Point

A relativistic model of a heat conducting collapsing star, which includes thermal pre-relaxation processes, is presented. Particular attention is paid to the influence of a given parameter defined in terms of thermodynamic variables, on the outcome of evolution. Evaluation of the system when passing through a critical value of the aforesaid parameter, does not yield evidence of anomalous behaviour.

gr-qc↗
arXiv1998

Thermal conduction before relaxation in slowly rotating fluids

For slowly rotating fluids, we establish the existence of a critical point similar to the one found for non-rotating systems. As the fluid approaches the critical point, the effective inertial mass of any fluid element decreases, vanishing at that point and changing of sign beyond it. This result implies that first order perturbative method is not always reliable to study dissipative processes ocurring before relaxation. Physical consequences that might follow from this effect are commented.

gr-qc↗
arXiv1998

Breakdown of the linear approximation in the perturbative analysis of heat conduction in relativistic systems

We analyze the effects of thermal conduction in a relativistic fluid just after its departure from spherical symmetry, on a time scale of the order of relaxation time. Using first order perturbation theory, it is shown that, as in spherical systems, at a critical point the effective inertial mass density of a fluid element vanishes and becomes negative beyond that point. The impact of this effect on the reliability of causality conditions is discussed.

gr-qc↗
arXiv1997

Gravitational collapse: A case for thermal relaxation

Two relativistic models for collapsing spheres at different stages of evolution, which include pre-relaxation processes, are presented. The influence of relaxation time on the outcome of evolution in both cases is exhibited and established. It is shown that relaxation processes can drastically change the final state of the collapsing system. In particular, there are cases in which the value of the relaxation time determines the bounce or the collapse of the sphere.

gr-qc↗
arXiv1997

Dissipative fluids out of hydrostatic equilibrium

In the context of the Müller-Israel-Stewart second order phenomenological theory for dissipative fluids, we analyze the effects of thermal conduction and viscosity in a relativistic fluid, just after its departure from hydrostatic equilibrium, on a time scale of the order of relaxation times. Stability and causality conditions are contrasted with conditions for which the ''effective inertial mass'' vanishes.

gr-qc↗
arXiv1997

Geodesics in Lewis Spacetime

The geodesic equations are integrated for the Lewis metric and the effects of the different parameters appearing in the Weyl class on the motion of test particles are brought out. Particular attention deserves the appearance of a force parallel to the axial axis and without Newtonian analogue.

gr-qc↗