"Randomness and the Emergence of Spacetime" by Pratik Rath (TIFR, Mumbai)

Date: 2026-04-15 Why does spacetime admit a simple semiclassical description, and what role does randomness play in its emergence from quantum mechanics? In this talk, I will argue that randomness plays a crucial role in several recent advances in quantum gravity, while also leading to some of its sharpest open puzzles. I will begin with random tensor networks, which serve as tractable models of the AdS/CFT dictionary. I will explain how these models can be related quantitatively to the gravitational path integral through fixed-area states, allowing tensor network calculations to illuminate the entanglement structure of gravitational systems. I will also discuss Jackiw–Teitelboim gravity and the PSSY model of black hole evaporation, where randomness appears through ensemble averaging and replica wormholes, leading to a semiclassical computation of the Page curve. Taken together, these examples suggest that coarse-graining and randomness are deeply tied to the emergence of spacetime. At the same time, they raise a basic question: how can such a picture be reconciled with exact factorization in holography? I will conclude by discussing this tension and its relation to recent puzzles involving closed universes, which may offer a useful window into the limits of our current understanding of emergent spacetime. https://scitalks.tifr.res.in/event/9323/