Optical geometry for gravitational collapse and Hawking radiation - art. no. 064010

The notion of optical geometry, introduced more than 20 years ago as a form al tool in quantum field theory on a static background, has recently found several applications to the study of physical processes around compact obje cts. In this paper we define optical geometry for spherically symmetric gra vitational collapse, with the purpose of extending the current formalism to physically interesting spacetimes which are not conformally static. The tr eatment is fully general but, as an example, we also discuss the special ca se of the Oppenheimer-Snyder model. The analysis of the late-time behavior shows a close correspondence between the structure of optical spacetime for gravitational collapse and that of flat spacetime with an accelerating bou ndary. Thus, optical geometry provides a natural physical interpretation fo r derivations of the Hawking effect based on the "moving mirror analogy." F inally, we briefly discuss the issue of back reaction in black hole evapora tion and the information paradox from the perspective of optical geometry.