Thermodynamics and gravitational collapse

Journal of High Energy Physics, 2011

We consider the generalized laws of thermodynamics in massive gravity. Making use of explicit black hole solutions, we devise black hole merger processes in which i) total entropy of the system decreases ii) the zero-temperature extremal black hole is created. Thus, both second and third laws of thermodynamics are violated. In both cases, the violation can be traced back to the presence of negative-mass black holes, which, in turn, is related to the violation of the null energy condition. The violation of the third law of thermodynamics implies, in particular, that a naked singularity may be created as a result of the evolution of a singularity-free state. This may signal a problem in the model, unless the creation of the negative-mass black holes from positive-mass states can be forbidden dynamically or the naked singularity may somehow be resolved in a full quantum theory.

The conventional view of gravitational collapse predicts the formation of a classical event horizon (EH), followed by an inevitable singularity. However, this scenario does not fully account for the thermodynamic properties of self-gravitating systems, particularly their negative heat capacity. In this work, we investigate how thermodynamic constraints may influence the late stages of collapse and propose that a non-singular, thermodynamically stabilized intermediate state may emerge at Planck-scale temperatures. By analyzing the temperature evolution driven by gravitational compression and energy-momentum effects, we show that the system can reach the Planck temperature well before the classical free-fall time completes. This rapid heating phase naturally leads to a transition into a stabilized state supported by an Anti-de Sitter (AdS)-like interior with a negative cosmological constant. While an event horizon still forms as an observerindependent boundary, the singularity is avoided due to this internal stabilization. We further examine the holographic implications of this scenario. The event horizon acts not as a classical one-way membrane, but as a quantumclassical interface that stores and gradually releases information. This provides a thermodynamically motivated framework for resolving the black hole information paradox. Rather than contradicting standard black hole physics, this model extends it by incorporating thermodynamic and quantum gravitational principles. The results suggest new avenues for theoretical and observational exploration of non-singular gravitational collapse.

Communications in Theoretical Physics, 2020

Gravity and thermal energy are universal phenomena which compete over the stabilization of astrophysical systems. The former induces an inward pressure driving collapse and the latter a stabilizing outward pressure generated by random motion and energy dispersion. Since a contracting self-gravitating system is heated up one may wonder why is gravitational collapse not halted in all cases at a sufficient high temperature establishing either a gravo-thermal equilibrium or explosion. Here, based on the equivalence between mass and energy, we show that there always exists a temperature threshold beyond which the gravitation of thermal energy overcomes its stabilizing pressure and the system collapses under the weight of its own heat.

Astrophysics and Space Science, 2010

International Journal of Theoretical Physics, 2010

Classical and Quantum Gravity, 2010

We investigate the validity of the generalized second law of gravitational thermodynamics on the apparent and event horizons in a non-flat FRW universe containing the interacting dark energy with dark matter. We show that for the dynamical apparent horizon, the generalized second law is always satisfied throughout the history of the universe for any spatial curvature and it is independent of the equation of state parameter of the interacting dark energy model. Whereas for the cosmological event horizon, the validity of the generalized second law depends on the equation of state parameter of the model.

Physics Letters B, 2017

2012

Here we investigate the genericity and stability aspects for naked singularities and black holes that arise as the final states for a complete gravitational collapse of a spherical massive matter cloud. The form of the matter considered is a general Type I matter field, which includes most of the physically reasonable matter fields such as dust, perfect fluids and such other physically interesting forms of matter widely used in gravitation theory. Here, we first study in some detail the effects of small pressure perturbations in an otherwise pressure-free collapse scenario, and examine how a collapse evolution that was going to the black hole endstate would be modified and go to a naked singularity, once small pressures are introduced in the initial data. This allows us to understand the distribution of black holes and naked singularities in the initial data space. Collapse is examined in terms of the evolutions allowed by Einstein equations, under suitable physical conditions and as evolving from a regular initial data. We then show that both black holes and naked singularities are generic outcomes of a complete collapse, when genericity is defined in a suitable sense in an appropriate space.

Physical Review D, 1998

We analyze black hole thermodynamics in a generalized theory of gravity whose Lagrangian is an arbitrary function of the metric, the Ricci tensor and a scalar field. We can convert the theory into the Einstein frame via a "Legendre" transformation or a conformal transformation. We calculate thermodynamical variables both in the original frame and in the Einstein frame, following the Iyer-Wald definition which satisfies the first law of thermodynamics. We show that all thermodynamical variables defined in the original frame are the same as those in the Einstein frame, if the spacetimes in both frames are asymptotically flat, regular and possess event horizons with non-zero temperatures. This result may be useful to study whether the second law is still valid in the generalized theory of gravity.