27 July 2023, 13:15 (EET), ЧЕТВЪРТЪК, ЗАЛА 300 НА ИЯИЯЕ

• Prof. Changrim Ahn (Ewha Womans University, Seoul, Korea)
• Title: Classification of UV complete CFTs via TTbar
• Abstract: It is well understood that 2d conformal field theory (CFT) deformed by an irrelevant TT perturbation of dimension 4 has universal properties. In particular, for the most interesting cases, the theory develops a singularity in the ultra-violet (UV), signifying a shortest possible distance, with a Hagedorn transition in applications to string theory. We show that by adding an infinite number of higher [TT]s>1 irrelevant operators of positive integer scaling dimension 2(s+1) with tuned couplings, this singularity can be resolved and the theory becomes UV complete with a Virasoro central charge cUV > cIR consistent with the c-theorem. We propose an approach to classifying the possible UV completions of a given CFT perturbed by [TT]s that are integrable. The main tool utilized is the thermodynamic Bethe ansatz. We study this classification for theories with scalar (diagonal) factorizable S-matrices. For the Ising model with cIR = 1/2 we find 3 UV completions based on a single massless Majorana fermion description with cUV =7/10 and 3/3, which both have N = 1 SUSY and were previously known, and we argue that these are the only solutions to our classification problem based on this spectrum of particles. We find 3 additional ones with a spectrum of 8 massless particles related to the Lie group E8 appropriate to a magnetic perturbation with cUV =21/22,15/2 and 31/2.