Thermodynamics with Pressure and Volume under Charged Particle Absorption

We investigate the variation of the charged anti-de Sitter black hole under charged particle absorption by considering thermodynamic volume. The variation exactly corresponds to that expected as the first law of thermodynamics. Nevertheless, we find the decrease of the Bekenstein-Hawking entropy for extremal and near-extremal black holes under the absorption to be an irreversible process. This violation of the second law of thermodynamics is only found in the case considering thermodynamic volume. We test the weak cosmic censorship conjecture affected by the violation. Fortunately, the conjecture is still valid. However, extremal and near-extremal black holes do not change their configurations under the absorption. This is quite different from the case without thermodynamic volume.Comment: 14 pages, 5 figure

Thermodynamics Inducing Massive Particles' Tunneling and Cosmic Censorship

By calculating the change of entropy, we prove that the first law of black hole thermodynamics leads to the tunneling probability of massive particles through the horizon, including the tunneling probability of massive charged particles from the Reissner-Nordstr\"om black hole and the Kerr-Newman black hole. Novelly, we find the trajectories of massive particles are close to that of massless particles near the horizon, although the trajectories of massive charged particles may be affected by electromagnetic forces. We show that Hawking radiation as massive particles tunneling does not lead to violation of the weak cosmic-censorship conjecture

Thermodynamics of string black hole with hyperscaling violation

In this paper, we start with black brane and construct specific space-time which violates hyperscaling. In order to obtain the string solution we apply Null-Melvin-Twist and $KK$-reduction. By using the difference action method we study thermodynamics of system to obtain Hawking-Page phase transition. In order to have hyperscaling violation we need to consider $\theta=\frac{d}{2}.$ In that case the free energy $F$ is always negative and our solution is thermal radiation without a black hole. Therefore we find that there is not any Hawking-Page transition. Also, we discuss the stability of system and all thermodynamical quantities.Comment: 12 pages. Accepted for publication in EPJ

Second Law Violations in Lovelock Gravity for Black Hole Mergers

We study the classical second law of black hole thermodynamics, for Lovelock theories (other than General Relativity), in arbitrary dimensions. Using the standard formula for black hole entropy, we construct scenarios involving the merger of two black holes in which the entropy instantaneously decreases. Our construction involves a Kaluza-Klein compactification down to a dimension in which one of the Lovelock terms is topological. We discuss some open issues in the definition of the second law which might be used to compensate this entropy decrease.Comment: 15 pages, 1 figure, v2 Title change & minor revisions to match published version, v3 fixed accidental deletion of author name