March 2024

2:30 PM - 4 PM

Room 113, School of Arts and Sciences
Ahmedabad University


A Smooth Horizon without a Smooth Horizon

Seminar and Lecture Series
Chethan Krishnan | Speaker at Ahmedabad University

Chethan Krishnan

Centre for High Energy Physics
Indian Institute of Science (Bengaluru)

The nature of the black hole horizon and whether spacetime ends there has been a puzzling question ever since the discovery of the first black hole solutions of Einstein's general relativity. Principle of equivalence suggests that the horizon should be smoothly traversible. Smoothness of the horizon is also directly responsible for the thermal properties of black holes discovered by Hawking. But a smooth horizon, at very long time scales, leads to the breakdown of quantum mechanics, our most experimentally successful theory. We will discuss some of these questions from the vantage point of recent puzzles about the black hole information paradox in quantum gravity. There is evidence from very recent results that suggest that the black hole interior is an emergent feature that arises in the weak-gravity limit, in a manner similar to how magnetism arises from spins in the large-volume limit of metals. This will mean that just as magnetism is not to be found in the metal atoms, smoothness is not to be found in the full ``UV-complete" description of quantum gravity, but only only in its effective description in terms of general relativity and quantum field theory at low energies.


Chethan Krishnan

Upon discovering that he has a Bachelor's degree in electronics from the Indian Institute of Technology Chennai, Chethan Krishnan quickly course-corrected himself. He received his PhD In theoretical high energy physics from the University of Texas at Austin in 2006. After postdoctoral fellowships at the Solvay Institute in Brussels and SISSA, Trieste, he is currently a permanent faculty member at the Center for High Energy Physics in the Indian Institute of Science, Bangalore. His research interests are broad, but centered around string theory. He has written highly cited papers on cosmological supersymmetry breaking, membranes in M-theory, integrability in the AdS/CFT correspondence and more recently, on various aspects of cosmology, black holes and holography.