Speakers: Stefan Hohenegger (Université Claude Bernard Lyon 1)
In this talk, I discuss so-called Little String Theories (LSTs), which are a type of interacting quantum theories whose UV-completion contains string-like (i.e. extended) degrees of freedom without gravitation. I focus on the so-called A-type LSTs with eight supercharges, which can be described in M-theory through N M5-branes probing a transverse Z_M orbifold. These M-brane configurations compactified on a circle are dual to F-theory compactified on a toric Calabi-Yau threefold X_{N,M}. I argue that the Kähler cone of the latter admits three regions associated with weakly coupled quiver gauge theories with gauge groups [U(N)]^M, [U(M)]^N and [U(NM/k)]^k where k=gcd(N,M), which provide low-energy descriptions of different LSTs. This triality is an extension of the well known T-duality of the LSTs. For the case M=1, I argue that it implies a dihedral symmetry for any individual theory, which acts intrinsically non-perturbative from a gauge theory perspective. Exploiting this symmetry I provide evidence for a decomposition of the free energy at leading instanton order, which is reminiscent of (effective) Feynman diagrams. The effective coupling functions appearing in this fashion show certain similarities with so-called modular graph functions, which have appeared in the study of Feynman amplitudes in string- and field theory.
https://indico.math.cnrs.fr/event/5434/