Violation of Unitarity in Gravitational Subregions
arXiv:2104.03253 · doi:10.1142/S0218271821420141
Abstract
This essay contends that in quantum gravity, some spatial regions do not admit a unitary Hilbert space. Because the gravitational path integral spontaneously breaks CPT symmetry, "states" with negative probability can be identified on either side of trapped surfaces. I argue that these negative norm states are tolerable, by analogy to quantum mechanics. This viewpoint suggests a resolution of the firewall paradox, similar to black hole complementarity. Implications for cosmology are briefly discussed.
8 pages, 3 figs. Submitted to the Gravity Research Foundation 2021 Essay Competition