An Implication of "Gravity as the Weakest Force"

The negative specific heat of a radiating black hole is indicative of a cataclysmic endpoint to the evaporation process. In this letter, we suggest a simple mechanism for circumventing such a dramatic outcome. The basis for our argument is a conjecture that was recently proposed by Arkani-Hamed and collaborators. To put it another way, we use their notion of ``Gravity as the Weakest Force'' as a means of inhibiting the process of black hole evaporation.Comment: 7 pages; v2 some discussion clarifie

Canonical entropy of three-dimensional BTZ black hole

Recently, Hawking radiation of the black hole has been studied using the tunnel effect method. It is found that the radiation spectrum of the black hole is not a strictly pure thermal spectrum. How does the departure from pure thermal spectrum affect the entropy? This is a very interesting problem. In this paper, we calculate the partition function by energy spectrum obtained from tunnel effect. Using the partition function, we compute the black hole entropy and derive the expression of the black hole entropy after considering the radiation. And we derive the entropy of charged black hole. In our calculation, we consider not only the correction to the black hole entropy due to fluctuation of energy but also the effect of the change of the black hole charges on entropy. There is no other hypothesis. Our result is more reasonable.According to the fact that the black hole entropy is not divergent, we obtain the lower limit of Banados-Teitelboim-Zanelli black hole energy. That is, the least energy of Banados-Teitelboim-Zanelli black hole, which satisfies the stationary condition in thermodynamics.Comment: 10 page

Logarithmic correction to the Cardy-Verlinde formula in Topological Reissner-Nordstr\"om de Sitter Space

In this paper we compute leading order correction due to small statistical fluctuations around equilibrium, to the Cardy-Verlinde entropy formula (which is supposed to be an entropy formula of conformal field theory in any dimension) of a Topological Reissner-Nordstrom black hole in de Sitter space.Comment: 10 pages, no figure,LaTe

An AdS/dS duality for a scalar particle

The motion of a scalar particle in (d+1)-dimensional AdS space may be described in terms of the Cartesian coordinates that span the (d+2)-dimensional space in which the AdS space is embedded. Upon quantization, the mass hyperboloid defined in terms of the conjugate momenta turns into the wave equation in AdS space. By interchanging the roles of coordinates and conjugate momenta in the (d+2)-dimensional space we arrive at a dual description. For massive modes, the dual description is equivalent to the conventional formulation, as required by holography. For tachyonic modes, this interchange of coordinates and momenta establishes a duality between Euclidean AdS and dS spaces. We discuss its implications on Green functions for the various vacua.Comment: 13 pages, v2 contains expanded discussion to appear in Phys. Lett.

Logarithmic correction to the Cardy-Verlinde formula in Achucarro-Oritz Black Hole

In this paper we calculate leading order correction due to small statistical fluctuations around equilibrium, to the Bekenstein-Hawking entropy formula for the Achucarro-Oritz black hole, which is the most general two-dimensional black hole derived from the three-dimensional rotating Banados-Teitelboim-Zanelli black hole. Then we obtain the same correction to the Cardy-Verlinde entropy formula (which is supposed to be an entropy formula of conformal field theory in any dimension).Comment: 10 pages, no figure,LaTeX,,references added, typos corrected,clarifying comments added in Introduction, no physics changed, version to appear in Eur.Phys.J.C (2004

Dirac particles tunneling from BTZ black hole

We calculated the Dirac Particles' Hawking radiation from the outer horizon of BTZ black hole via tunneling formalism. Applying WKB approximation to the Dirac equation in (2+1) dimensional BTZ spacetime background, we obtain the radiation spectrum for fermions and Hawking temperature of BTZ black hole. The results obtained by taking the fermion tunneling into account is consistent with the previous literatures.Comment: 7 pages, no figure, accepted by PL

Hawking radiation as tunneling from charged black holes in 0A string theory

There has been much work on explaining Hawking radiation as a quantum tunneling process through horizons. Basically, this intuitive picture requires the calculation of the imaginary part of the action for outgoing particle. And two ways are known for achieving this goal: the null-geodesic method and the Hamilton-Jacobi method. We apply these methods to the charged black holes in 2D dilaton gravity which is originated from the low energy effective theory of type 0A string theory. We derive the correct Hawking temperature of the black holes including the effect of the back reaction of the radiation, and obtain the entropy by using the 1st law of black hole thermodynamics. For fixed-charge ensemble, the 0A black holes are free of phase transition and thermodynamically stable regardless of mass-charge ratio. We show this by interpreting the back reaction term as the inverse of the heat capacity of the black holes. Finally, the possibility of the phase transition in the fixed-potential ensemble is discussed.Comment: 12 pages; v2: references added, revised with some changes in formula and unaltered conclusions, to be published in Phys. Lett.

Weak gravity conjecture constraints on inflation

We consider the gravitational correction to the coupling of the scalar fields. Weak gravity conjecture says that the gravitational correction to the running of scalar coupling should be less than the contribution from scalar fields. For instance, a new scale $\Lambda=\lambda_4^{1/2}M_p$ sets a UV cutoff on the validity of the effective $\lambda_4 \phi^4$ theory. Furthermore, this conjecture implies a possible constraint on the inflation model, e.g. the chaotic inflation model might be in the swampland.Comment: 11 pages, 3 figs; monor corrections; some clarifying remarks added and the final version for publication in JHE

Hawking radiation of Dirac particles via tunnelling from rotating black holes in de Sitter spaces

Hawking radiation from black hole horizon can be viewed as a quantum tunnelling process, and fermions via tunnelling can successfully recover Hawking temperature. In this paper, considering the tunnelling particles with spin 1/2 (namely, Dirac particles), we further improve Kerner and Man's fermion tunnelling method to study Hawking radiation via tunnelling from rotating black holes in de Sitter spaces, specifically including that from Kerr de Sitter black hole and Kerr-Newman de Sitter black hole. As a result, Hawking temperatures at the event horizon (EH) and the cosmological horizon (CH) are well described via Dirac particles tunnelling.Comment: 13 page

Gravitational Correction and Weak Gravity Conjecture

We consider the gravitational correction to the running of gauge coupling. Weak gravity conjecture implies that the gauge theories break down when the gravitational correction becomes greater than the contribution from gauge theories. This observation can be generalized to non-Abelian gauge theories in diverse dimensions and the cases with large extra dimensions.Comment: 8 pages; minor correction and refs adde