Violation of unitarity by Hawking radiation does not violate energymomentum conservation
Abstract
An argument by Banks, Susskind and Peskin (BSP), according to which violation of unitarity would violate either locality or energymomentum conservation, is widely believed to be a strong argument against nonunitarity of Hawking radiation. We find that the whole BSP argument rests on the crucial assumption that the Hamiltonian is not highly degenerate, and point out that this assumption is not satisfied for systems with many degrees of freedom. Using Lindblad equation, we show that high degeneracy of the Hamiltonian allows local nonunitary evolution without violating energymomentum conservation. Moreover, since energymomentum is the source of gravity, we argue that energymomentum is necessarily conserved for a large class of nonunitary systems with gravity. Finally, we explicitly calculate the Lindblad operators for nonunitary Hawking radiation and show that they conserve energymomentum.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 April 2015
 DOI:
 10.1088/14757516/2015/04/002
 arXiv:
 arXiv:1502.04324
 Bibcode:
 2015JCAP...04..002N
 Keywords:

 High Energy Physics  Theory;
 General Relativity and Quantum Cosmology;
 Quantum Physics
 EPrint:
 18 pages, abstract sharpened, two references added, accepted for publication in JCAP