题 目：Infrared Divergences in de Sitter: wavefunction, density matrix and stochastic inflation
报告人：王东刚(香港科技大学，研究助理教授)
时 间：2026年1月9号(星期五)14:00
地 点：LE201
邀请人：孙冠豪
报告摘要：Interacting light scalars in de Sitter space (dS) normally lead to infrared divergences. I shall revisit this topic with recent developments of the cosmological bootstrap. After reviewing simple tree-level examples, at the loop level, we apply the wavefunction method, and identify that the leading contributions to IR-divergent correlators always come from classical loops from tree-level wavefunction coefficients. This significantly simplifies the problem and indicates the importance of the saddle-point approximation when we go beyond perturbation theory. With this insight, we present a non-perturbative derivation of the stochastic formalism. Using the semi-classical wavefunction, we find that the Fokker-Planck equation follows from a combination of the Schroedinger equation and the Polchinski equation for the exact renormalization group flow.
Dr. Dong-Gang Wang is a Research Assistant Professor and an IAS Junior Fellow at HKUST. He received his Master degree from University of Science and Technology of China in 2016, and Doctoral degree from Leiden University in 2020. After that he joined the University of Cambridge as a Research Associate, and later became a Rubicon Senior Fellow in the Department of Applied Mathematics and Theoretical Physics. His research focuses on Primordial Cosmology, and in particular possible connections with high energy physics theories and astronomical observations.