Sphere partition function and Polchinski's phase

by Dr Zimo Sun (Princeton IAS)

Friday 27 Feb 2026, 12:00 → 14:00 America/Chicago

The round sphere is the leading saddle point of Euclidean Einstein gravity with a positive cosmological constant. The sphere partition function is directly related to de Sitter entropy. In the first half of the talk, I will discuss the structure of one-loop sphere partition functions, including the presence of Harish-Chandra characters, their relation to the quasinormal mode spectrum, and a bulk-edge decomposition. In the second half, I will focus on a complex phase arising in the gravitational path integral on the sphere, first identified by Polchinski. I will review and clarify Polchinski’s calculation and present recent developments concerning similar phases associated with other saddle points.