L6

The critical Fortuin–Kasteleyn random planar map with parameter q>0 is a model of random (discretised) surfaces decorated by loops, related to the q-state Potts model. For q<4, Sheffield established a scaling limit result for these discretised surfaces, where the limit is described by a so-called Liouville quantum gravity surface decorated by a conformal loop ensemble. At q=4 a phase transition occurs, and the correct rescaling needed to obtain a limit has so far remained unclear. I will talk about joint work with William Da Silva, XinJiang Hu, and Mo Dick Wong, where we identify the right rescaling at this critical value and prove a number of convergence results.

 I will talk about recent progress on (a) a conjecture of Fyodorov and Keating on supercritical asymptotics of moments of moments of characteristic polynomials of the circular beta ensemble and (b) on the correlation functions of the sine beta point process. This is joint work with Joseph Najnudel.

The question is this:  can one effectively decide whether two given groups have isomorphic profinite completions? Thanks to Bridson and Wilton, it is known that the answer is `no' in general, even for finitely presented residually finite groups. However, if the groups are (and are given to be) virtually polycyclic, then the answer is 'yes'. This is not really surprising, as a lot is known both about the profinite completions of such groups and about how they are determined up to isomorphism; but it may be instructive to see how it is done.

This talk will provide an overview of the landscape of bicommutant categories, these are tensor categories with a strong functional-analytic flavour. I will discuss the evolution of the definition (and give the current version of the definition) and explain precisely how they categorify von Neumann algebras, in the same way a tensor category can be viewed as a categorification of an algebra. We will also introduce the string-calculus that renders the coherences in the definition transparent and workable. 

The necessary background from functional analysis (in particular, operator theory) will be reviewed, and I will conclude with open questions (if waiting for the end of talk is not your style, there are 75 Open problems on André’s website). 

A 3-manifold is a space which locally looks like R^3. A major theme in 3-manifold Topology is to understand and classify 3-manifolds. Given two compact 3-manifolds M_1,M_2 we can form another 3-manifold by taking what’s called the “connect sum” of M_1 and M_2. Under this operation, 3-manifolds can be decomposed uniquely into prime pieces just like the integers can be decomposed uniquely as a product of primes. We will discuss this prime decomposition theorem for 3-manifolds while also giving a wide variety of examples.