Interview: Suvrat Raju

This is a conversation between myself and Suvrat Raju, who works in the fields of quantum gravity and quantum field theory. He has given various lectures on AdS/CFT and the black hole information paradox. His arXiv published articles can be read here: https://arxiv.org/a/raju_s_1.html 

Nolan Fitzpatrick: What, in your view, is the current position of the field of quantum gravity, and where do you think it is going?

Suvrat Raju: I think quantum gravity is in an interesting position. On the one hand, experimental data looks like it will be very hard to come by. But there are significant theoretical questions about black hole interiors and cosmology. These questions are bringing us face to face with some fundamental questions about quantum mechanics and how it applies to cosmological settings. People have thought about these questions for long, but I think that in the context of gravity, we are (a) forced to confront these questions and (b) may have tools to address them.

Nolan Fitzpatrick: How do gravitons fit into a theory of quantum gravity, such as perturbative string theory?

Suvrat Raju: Perturbative string theory describes gravitons very well. It describes their classical aspects (given by general relativity) and it can also describe the scattering of gravitons beyond general relativity. This is a basic criterion that any theory of quantum gravity has to satisfy.

Nolan Fitzpatrick: How do we reconcile black hole evaporation with quantum mechanics and reversibility?

Suvrat Raju: In principle, the answer is that information is stored in fine-correlations in the outgoing Hawking quanta. However, the challenge is to consistently describe the evolution of the black hole interior as the black hole evaporates. This brings me back to point (1) above.

Nolan Fitzpatrick: How can AdS/CFT help to answer some of these questions?

Suvrat Raju: AdS/CFT gives us well defined toy models of quantum gravity. So its the best setting to answer questions that are raised in (3) above and presumably then also questions in (1).