Mathematical Physics

Let G be a complex reductive group, and X be any smooth projective G-variety. In this talk, we will construct an algebra homomorphism from the G-equivariant homology of the affine Grassmannian Gr_G to the G-equivariant quantum cohomology of X. The construction uses shift operators in quantum cohomologies. We will also discuss the possible extension to the loop rotation equivariant setting and the relation with the Peterson isomorphism when X is the flag variety associated with G. This is based on joint work with Alexander Braverman.

There has long been interest in Beilinson-Bernstein localization for the affine Grassmannian (or affine flag variety). First, Kashiwara-Tanisaki treated the so-called negative level case in the 90's. Some ten years later, Frenkel-Gaitsgory (following work of Beilinson-Drinfeld and Feigin-Frenkel) formulated a conjecture at the critical level and made some progress on it. Their conjecture is more subtle than its negative level counterpart, but also more satisfying. We will review the necessary background from representation theory of Kac-Moody algebras at critical level, formulate the Frenkel-Gaitsgory conjecture, and outline a proof for GL_2. Time permitting, we will discuss how our result provides a test of the Frenkel-Gaitsgory proposal for local geometric Langlands.

Classical work by Thurston in the theory of surfaces gives symplectic co-ordinate charts on Teichmüller space, associated to quadratic differentials. Motivated by wall crossing in 4d field theories Gaiotto, Moore and Neitzke defined a generalization of these; giving maps from the moduli of one dimensional local systems on a spectral curve to the moduli space of n-dimensional local systems on a non-compact Riemann surface. I will describe joint work with M. Ionita which extends this construction to arbitrary reductive algebraic groups G. Time permitting I will describe the interpretation of this construction in terms of the wild Riemann--Hilbert Correspondence in the closely related setting of Frobenius manifolds.

From a probabilistic perspective, 2D quantum gravity is the study of natural probability measures on the space of all possible geometries on a topological surface. One natural approach is to take scaling limits of discrete random surfaces. Another approach, known as Liouville quantum gravity (LQG), is via a direct description of the random metric under its conformal coordinate. In this talk, we review both approaches, featuring a joint work with N. Holden proving that uniformly sampled triangulations converge to the so called pure LQG under a certain discrete conformal embedding.

In this talk we describe a systematic way of producing stochastic solutions to the Yang-Baxter equation from a “base solution” that is not necessarily stochastic. This gives rise to a wide class of new families of stochastic (Markovian) vertex models with integrable weights. In various cases, these models are more amenable to algebraic analysis than are their non-stochastic counterparts, sometimes leading to new (and at times unexpected) refined asymptotic results for them. In other cases, these stochastic systems are amenable to probabilistic analysis, yielding results that seem less transparent to access algebraically and that can occasionally shed new light on the original (non-stochastic) model. This is partially based on joint work with Alexei Borodin and Alexey Bufetov.