Radiation from the LTB black hole

¹ Department of Physics, Sharif University of Technology - Tehran, Iran
² School of Astronomy, Institute for Research in Fundamental Sciences (IPM) - Tehran, Iran

^a firouzjaee@physics.sharif.edu
^b taghizade.javad@gmail.com
^c mansouri@ipm.ir

Received: 2 October 2011
Accepted: 2 December 2011

Abstract

Does a dynamical black hole embedded in a cosmological FRW background emit the Hawking radiation where a globally defined event horizon does not exist? What are the differences to the Schwarzschild black hole? What about the first law of black-hole mechanics? We face these questions using the LTB cosmological black-hole model recently published. Using the Hamilton-Jacobi and radial null geodesic methods suitable for dynamical cases, we show that it is the apparent horizon which contributes to the Hawking radiation and not the event horizon. The Hawking temperature is calculated using the two different methods giving the same result. The first law of LTB black-hole dynamics and the thermal character of the radiation is also dealt with.