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A. Di Prisco

Publications and source records attributed to A. Di Prisco.

62 records · Page 4Linked to original sources
arXiv2000

Non spherical sources of strong gravitational fields out of hydrostatic equilibrium

We describe the departure from equilibrium of matter distributions representing sources for a class of Weyl metric. It is shown that, for extremely high gravitational fields, slight deviations from spherical symmetry may enhance the stability of the system weakening thereby its tendency to a catastrophic collapse. For critical values of surface gravitational potential, in contrast with the exactly spherically symmetric case, the speed of entering the collapse regime decreases substantially, at least for specific cases.

gr-qc↗
arXiv2000

Qualitative analysis of dissipative cosmologies

The evolution of an homogeneous and isotropic dissipative fluid is analyzed using dynamical systems techniques. The dissipation is driven by bulk viscous pressure and the truncated Israel-Stewart theory is used. Although almost all solutions inflate, we show that only few of them can be considered as physical solutions since the dominant energy condition is not satisfied.

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↗
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

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

Thermal Conduction in Systems out of Hydrostatic Equilibrium

We analyse the effects of thermal conduction in a relativistic fluid, just after its departure from hydrostatic equilibrium, on a time scale of the order of thermal relaxation time. It is obtained that the resulting evolution will critically depend on a parameter defined in terms of thermodynamic variables, which is constrained by causality requirements.

gr-qc↗