**The Black Hole Information Loss Problem** - Saurya Das

Abstract: Black holes, which are one of the most intriguing predictions of general relativity, are not entirely black. Quantum mechanics predicts that a black hole radiates like an almost perfect black body (Hawking radiation) at a characteristic temperature (Hawking temperature). Moreover, it has entropy proportional to its horizon area. Its mass, temperature and entropy satisfy laws analogous to the laws of thermodynamics. If a black hole radiates completely due to Hawking radiation, then all information which went inside it during its formation would be lost forever (since thermal radiation carries no information about its interior). This suggests that the evolution of the black hole is non-unitary, in which pure states evolve to mixed states. All proposed fundamental theories of quantum gravity (including string theory and loop quantum gravity), which should describe the microscopic details of this evaporation, are however unitary. This apparent paradox, known as the `Black Hole Information Loss Problem\\\\\\\', will be reviewed in this talk, along with some proposed resolutions.
Reference: S. Das, hep-th/0403202