No talk on July 2

Date: July 9

Time: 10:00 IST (UTC + 5:30)

Speaker: Geoffrey Penington (Stanford University)

Title: Leading order corrections to the quantum extremal surface prescription

• Abstract: The QES prescription is a rule for computing entanglement entropies in quantum gravity that has become one of the central tools in holography. In particular, it was crucial to recent progress on understanding the Page curve for evaporating black holes. However, as I will show, a naïve application of the QES prescription for arbitrary bulk states is paradoxical, even at leading order. Instead, it needs to be replaced by a more refined prescription based on tools from one-shot quantum Shannon theory. I will show how the failure of the QES prescription come from a failure of the assumptions in the Lewkowycz-Maldacena derivation, and how a more careful replica trick derivation correctly computes the leading order corrections.

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Date: July 16

Time: 17:30 IST (UTC + 5:30)

Speaker: Rakibur Rahman (MPI Potsdam and Univ of Dhaka)

Title: Fragmentation Equation, Stochastic Fractal and Noether's Theorem

• Abstract: We study the binary fragmentation problem where, at each fragmentation event, one of the daughter segments may disappear with certain probability. Described by a stochastic dyadic Cantor set, the system evolves in time to become a fractal. With the generalized product kernel (for which segments undergo fragmentation at a breakup point given by the beta distribution, with a rate proportional to length-to-some-power), we demonstrate the existence of a fractal dimension and self-similarity, thereby establishing the fractal nature of the system. We also show that there appear certain conserved quantities, and that they could be understood as Noether charges of the corresponding Euclidean quantum-mechanical system that describes an infinitely-heavy particle in a non-local non-Hermitian potential.

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Date: July 23

Time: 17:30 IST (UTC + 5:30)

Speaker: Chethan Krishnan (IISc Bangalore)

Title: Islands Beyond AdS

• Abstract: I will discuss some aspects of recent (what feels like) progress on the information paradox.

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Date: July 30

Time: 17:30 IST (UTC + 5:30)

Speaker: Suresh Govindarajan (IIT Madras)

Title: Mathieu Moonshine

• Abstract: I plan to discuss the mysterious and not well-understood appearance of Mathieu's largest sporadic finite simple group, M_24, in the counting of BPS states in N=4 supersymmetric string theory in four dimensions. We show connections that relate modular forms, Jacobi forms & mock modular forms and Siegel modular forms to every conjugacy class of M_24. This talk will be at an elementary level and no knowledge of modular forms will be assumed.

VIDEO LINK: Click here