Black Holes, Quantum Mechanics and the Reversibility of Time by Suvrat Raju

Kaapi with Kuriosity

Black Holes, Quantum Mechanics and the Reversibility of Time

Speaker: Suvrat Raju (International Centre for Theoretical Sciences)

When: 4:00 pm to 5:30 pm Saturday, 14 January 2023

Where: Jawaharlal Nehru Planetarium, Bengaluru


Abstract:

Black Holes are enigmatic objects that pepper the Universe around us. Their existence was predicted theoretically by the modern theory of gravity and has been confirmed by a wide variety of observations. Quantum Mechanics is one of the most successful theories known to humanity. Although it was originally developed to study atoms, it is believed that quantum mechanics underpins the dynamics of all physical systems. However, paradoxes arise when one attempts to apply quantum mechanics to black holes. The most famous of these - called the "information paradox" - has to do with the nature of time. This talk will describe these ideas and paradoxes, and the recent progress that has been made towards their resolution.

About the Speaker:

Suvrat Raju is a theoretical physicist at the International Centre for Theoretical Sciences of the Tata Institute of Fundamental Research. He works on string theory, quantum gravity and quantum field theory. He obtained his PhD in 2008 at Harvard University. His work on quantum aspects of black holes has been recognized by the Swarnajayanti Fellowship (2017), the ICTP Prize (2019), and the Nishina-Asia award (2022).

Table of Contents (powered by https://videoken.com)
0:00:00 Introduction
0:02:24 Black Holes, Quantum Mechanics and the Reversibility of Time
0:03:51 Projectile motion
0:04:49 Projectile motion: scales
0:09:17 Projectile motion: reversibility
0:12:49 Reversibility
0:16:39 Escape velocity
0:23:16 Newtonian gravity
0:25:26 Scope of Newtonian gravity
0:26:28 Nonlocality in Newtonian gravity
0:29:39 The fabric of spacetime
0:31:40 Locality in general relativity
0:35:45 A black hole
0:39:12 Theorists and black holes!
0:41:01 Datt-Oppenheimer-Snyder collapse
0:45:16 Penrose diagrams
0:46:25 Journey through physics
0:55:37 Schrodinger's cat
0:58:43 Superpositions
1:00:19 Entanglement
1:01:50 Consequences of entanglement
1:04:07 Fluctuations of spacetime
1:19:34 Pair creation
1:22:17 Hawking radiation
1:23:18 Spectrum of Hawking radiation
1:25:52 Black-hole evaporation
1:27:09 Lifetime!
1:29:55 The life of a dead star
1:30:12 Information paradox
1:31:36 Reversibility of time evolution
1:31:42 Solution: delicate correlations
1:33:55 Formation of correlations?
1:35:07 Holography of information
1:36:46 Recovery of information
1:38:35 Energy Eigenstates in Quantum Mechanics
1:39:26 Localization via superposition
1:40:45 Energy in Gravity
1:42:03 Gravitational tails
1:42:52 Failure of localization in gravity
1:43:43 No split states in gravity
1:45:44 Errors in Hawking's argument
1:47:44 Thank You
1:47:52 Q&A