The Black Hole Interior

Fabio Sanches, University of California, Berkeley

Photo of Fabio Sanches

The study of black holes is one of our best methods of exploring physics where quantum mechanical effects of gravity become important, relevant at very high energies significantly beyond current collider capabilities. Our current theoretical framework – quantum field theory, incredibly successful at describing matter and radiation around us – fails to provide an adequate picture when applied to black holes.

Stephen Hawking first put forth the issue almost 40 years ago, shortly after his discovery that black holes can emit particles and radiate away mass. His discovery contradicted one of the most fundamental principles of quantum mechanics: unitarity, which essentially states that the information in a closed system is never lost. Information loss in black holes, if true, would actually spread throughout all energy scales through quantum effects.

While there is significant evidence that the evolution should indeed be unitary, another issue associated with cloning information in quantum mechanics poses an extra challenge. In the 1990s, a remarkable suggestion called complementarity was made to address this. Recently, however, the information paradox was sharpened, and it was shown that complementarity is insufficient. Furthermore, the argument showed that if we require information to come out, space-time itself breaks down at the horizon. The black hole interior would thus not exist.

In our study, we present a coherent picture for black hole evaporation that successfully avoids the new paradox mentioned above. We achieve this by correctly interpreting the origin of black hole entropy and the emergence of low-energy descriptions from a fundamental theory. Our picture allows for the recovery of information and also suggests that an observer who falls into the black hole does not see deviations from the predictions of general relativity. This provides an important step towards reconciling quantum mechanics and gravity, the longstanding issue in theoretical physics.

Abstract Author(s): Yasunori Nomura, Fabio Sanches, Sean Weinberg