arXiv subjects

Cheng-Yong Zhang

Publications and source records attributed to Cheng-Yong Zhang.

75 records · Page 5Linked to original sources

arXiv2014

Entropy of isolated horizon from surface term of gravitational action

Starting from the surface term of gravitational action, one can construct a Virasoro algebra with central extension, with which the horizon entropy can be derived by using Cardy formula. This approach gives a new routine to calculate and interpret the horizon entropy. In this paper, we generalize this approach to a more general case, the isolated horizon, which contains non-stationary spacetimes beyond stationary ones. By imposing appropriate boundary conditions near the horizon, the full set of diffeomorphism is restricted to a subset where the corresponding Noether charges form a Virasoro algebra with central extension. Then by using the Cardy formula, we can derive the entropy of the isolated horizon.

gr-qc↗

arXiv2013

Generalized Kerr/CFT correspondence with electromagnetic field

The electrovac axisymmetric extreme isolated horizon/CFT correspondence is considered. By expansion techniques under the Bondi-like coordinates, it is proved that the near horizon geometry of electrovac axisymmetric extreme isolated horizon is unique. Furthermore, explicit coordinate transformation between the Bondi-like coordinates and the Poincare-type coordinates for the near horizon metric of the extreme Kerr-Newmann spacetime is found. Based on these analyses and the thermodynamics of the isolated horizon, then, the Kerr/CFT correspondence is generalized to nonstationary extreme black holes with electromagnetic fields.

gr-qc↗

arXiv2012

Magnetohydrodynamics from gravity

Imposing the Petrov-like boundary condition on the hypersurface at finite cutoff, we derive the hydrodynamic equation on the hypersurface from the bulk Einstein equation with electromagnetic field in the near horizon limit. We first get the general framework for spacetime with matter field, and then derive the incompressible Navier-Stokes equations for black holes with electric charge and magnetic charge respectively. Especially, in the magnetic case, the standard magnetohydrodynamic equations will arise due to the existence of the background electromagnetic field on the hypersurface.

hep-th↗