Time: 10:00-12:00, Apr. 28, 2026

Location: Seminar Room of KITS, UCAS

Speaker: Yunfeng Jiang (Southeast Univ.)

Abstract:

The torus partition function of a TTbar-deformed conformal field theory (CFT) plays an important role in the study of TTbar deformation. This function is modular invariant, enabling a harmonic analysis on the Poincaré upper half-plane. Such an analysis provides a natural and powerful framework for computing and analyzing this quantity. In this talk, I will first review the TTbar-deformed partition function and the basics of harmonic analysis on the Poincaré upper half-plane. I will then explain how to expand the CFT partition function in terms of Maass waveforms, which are functions that are modular invariant and transform in a particularly simple manner under TTbar deformation. Next, I will discuss how this approach allows us to compute the deformed partition function at finite values of the deformation parameter, thereby revealing its analytic structure. Finally, I will show that harmonic analysis offers a natural analytic continuation that defines the partition function beyond the Hagedorn singularity.