The categorical p-adic local Langlands correspondence has been established for the group GL_2(Q_p) in joint work of the speaker with Andrea Dotto and Toby Gee. In this talk I will describe some aspects of this categorical correspondence. I hope to indicate the relationship to existing ideas in the subject: particularly to Taylor--Wiles--Kisin patching, but also to the work of Colmez and Paskunas, and to recent work of Johansson--Newton--Wang-Erickson. But more than this, I hope to indicate some of the underlying philosophy of the correspondence: what it means to represent the category of representations of a group geometrically, and why stacks (rather than just varieties) play a key role.

Homogenization is the approximation of a complex, “disordered” system by a simpler, “ordered” one. Picture a walker on a grid. In each step, the walker chooses to walk along a neighboring edge with equal probability. At large scales, the walker approximates Brownian motion. But what if some edges are more likely to be traversed than others? I will discuss recent advances in the theory of quantitative homogenization which make it possible to analyze random walk with drift and other models in probability. Joint work with Scott Armstrong and Tuomo Kuusi.