The International Center for Mathematical Sciences – Sofia (ICMS-Sofia)
at the
Bulgarian Academy of Sciences


ICMS Seminar

September 14, 2021, 4:30-5:30 pm

ICMS-Sofia, Room 403 and via Zoom

Vesselin Dimitrov

University of Toronto

The congruence property in two-dimensional rational conformal field theory, revisited

In a joint work with Frank Calegari and Yunqing Tang, we use methods from transcendental number theory to prove a conjecture that goes back to Atkin and
Swinnerton-Dyer, in a special case, and generalized by Mason to the following form:

A vector-valued modular form on SL(2,Z) whose components have q-expansions with bounded denominators are exactly the ones for which the underlying representation of SL(2,Z) has a finite image with kernel containing the congruence subgroup of matrices reducing to the identity modulo some positive integer N.

In this talk, I will outline the basic ideas of the proof of the conjecture, describe the relation to mathematical physics and the representation theory of vertex algebras, and explain how our result in particular recovers a completely new proof of the so-called “congruence property” in rational conformal field theory.

Тhe lectures will be held in hall 403 of the Institute of Mathematics and Informatics and via Zoom.

Download Seminar poster