Ji-Rong Ren

Corrections to Hawking-like radiation for a Friedmann–Robertson–Walker universe

Recently, a Hamilton–Jacobi method beyond the semiclassical approximation in black hole physics was developed by Banerjee and Majhi. We generalize their analysis of black holes to the case of a Friedmann–Robertson–Walker (FRW) universe. It is shown that all the higher order quantum corrections in the single particle action are proportional to the usual semiclassical contribution. The corrections to the Hawking-like temperature and entropy of the apparent horizon for the FRW universe are also obtained. In the corrected entropy, the area law involves a logarithmic area correction together with the standard term with the inverse power of the area.

Entropy of Kaluza–Klein black hole from Kerr/CFT correspondence

We extend the recently proposed Kerr/CFT correspondence to examine the dual conformal field theory of four-dimensional Kaluza-Klein black hole in Einstein-Maxwell-Dilaton theory. For the extremal Kaluza-Klein black hole, the central charge and temperature of the dual conformal field are calculated following the approach of Guica, Hartman, Song and Strominger. Meanwhile, we show that the microscopic entropy given by the Cardy formula agrees with Bekenstein-Hawking entropy of extremal Kaluza-Klein black hole. For the non-extremal case, by studying the near-region wave equation of a neutral massless scalar field, we investigate the hidden conformal symmetry of Kaluza-Klein black hole, and find the left and right temperatures of the dual conformal field theory. Furthermore, we find that the entropy of non-extremal Kaluza-Klein black hole is reproduced by Cardy formula

Fermion Resonances on Multi-field Thick Branes

Motivated by the recent work on the fermion resonances on scalar-constructed thick branes (arXiv:0901.3543 and arXiv:0904.1785), we extend the idea to multi-scalar generated thick branes and complete previous work. The fermion localization and reso- nances on the three-field and two-field thick branes are investigated. With the Numerov method, our numerical results show that the resonance states also exist in the brane be- sides the single-field thick branes and the two-field thick branes in the former cases. This interesting phenomenon is related to the internal structure of the brane and the coupling of fermions and scalars. We find that the Kaluza-Klein chiral decomposition of massive fermion resonances is the parity-chiral decomposition. For the couplings ��� k ��� and ��� k �� for three-field and two-field models with odd positive k, respectively, the number of the resonant states decreases with k. This result is opposite to the one obtained in the single-field de Sitter thick brane (arXiv:0904.1785).

Quantization of black hole entropy from quasinormal modes

Using the new physical interpretation of quasinormal modes proposed by Maggiore, we calculate the quantum spectra of entropy for various types of non-rotating black holes with no charge. The spectrum is obtained by imposing Bohr-Sommerfeld quantization condition to the adiabatic invariant quantity. We conjecture that the spacing of entropy spectrum is equidistant and is independent of the dimension of spacetime. However, the spacing of area spectrum depends on gravity theory. In Einsteins gravity, it is equally spaced, otherwise it is non-equidistant.

Localization of matters on Anti-de Sitter thick branes

By presenting the mass-independent potentials of the Kaluza-Klein (KK) modes in the corresponding Schrödinger equations, we investigate the localization and mass spectra of various bulk matter fields on an AdS thick brane. For a spin 0 scalar Φ coupled with itself and the domain-wall-forming field ϕ via a coupling potential V = (λϕ2−u2)Φ2 + τΦ4, the localization and spectrum are decided by a critical coupling constant λ0. When λ > λ0, the potential of the scalar KK modes in the corresponding Schrödinger equation tends to infinite when far away from the brane, which results in that there exist infinite discrete scalar bound KK states, and the massless modes could be trapped on the AdS brane by fine-tuning of parameters. When λ < λ0, the potential of the scalar KK modes tends to negative infinite when far away from the brane, hence there does not exist any scalar bound KK state. For a spin 1 vector, the situation is same like the scalar with a coupling constant λ > λ0, but the zero mode can not be localized on the brane. For a spin 1/2 fermion, we introduce the usual Yukawa coupling

Holographic dual of linear dilaton black hole in Einstein-Maxwell-dilaton-axion gravity

\eta \bar \Psi \phi \Psi

Anomaly analysis of Hawking radiation from Kaluza–Klein black hole with squashed horizon

, and find that the localization of the fermion is decided by a critical coupling constant η0. For η > η0, the four-dimensional massless left chiral fermion and massive Dirac fermions consisted of the pairs of coupled left-hand and right-hand KK modes could be localized on the AdS brane, and the massive Dirac fermions have a set of discrete mass spectrum. While for the case 0 < η < η0, no four-dimensional Dirac fermion can be localized on the AdS brane.

Quasinormal modes of self-dual warped AdS{sub 3} black hole in topological massive gravity

Motivated by the recently proposed Kerr/CFT correspondence, we investigate the holographic dual of the extremal and non-extremal rotating linear dilaton black hole in Einstein-Maxwell-Dilaton-Axion Gravity. For the case of extremal black hole, by imposing the appropriate boundary condition at spatial infinity of the near horizon extremal geometry, the Virasoro algebra of conserved charges associated with the asymptotic symmetry group is obtained. It is shown that the microscopic entropy of the dual conformal field given by Cardy formula exactly agrees with Bekenstein-Hawking entropy of extremal black hole. Then, by rewriting the wave equation of massless scalar field with sufficient low energy as the SLL(2, R) × SLR(2, R) Casimir operator, we find the hidden conformal symmetry of the non-extremal linear dilaton black hole, which implies that the non-extremal rotating linear dilaton black hole is holographically dual to a two dimensional conformal field theory with the non-zero left and right temperatures. Furthermore, it is shown that the entropy of non-extremal black hole can be reproduced by using Cardy formula.

Acceleration of particles in Einstein-Maxwell-dilaton black holes

Considering gravitational and gauge anomalies at the horizon, a new method to derive Hawking radiation from black holes has been developed by Wilczek et al. In this paper, we apply this method to non-rotating and rotating Kaluza–Klein black holes with squashed horizon, respectively. For the rotating case, we found that, after dimensional reduction, an effective U(1) gauge field is generated by an angular isometry. The results show that the gauge current and energy-momentum tensor fluxes are exactly equivalent to Hawking radiation from the event horizon.

Ghost field realizations of the spinor W2,s strings based on the linear W1,2,s algebras

We consider the scalar, vector and spinor field perturbations in the background of self-dual warped AdS{sub 3} black hole of topological massive gravity. The corresponding exact expressions for quasinormal modes are obtained by analytically solving the perturbation equations and imposing the vanishing Dirichlet boundary condition at asymptotic infinity. It is expected that the quasinormal modes agree with the poles of retarded Greens functions of the CFT dual to self-dual warped AdS{sub 3} black hole. Our results provide a quantitative test of the warped AdS/CFT correspondence.