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We explore the dynamics of the simplest worm algorithm for a class of two-dimensional dimer models and argue that the dynamics of the worm head represents an example of fractional Brownian motion whenever dimer correlations in equilibrium have power-law character. Numerical estimates of the corresponding Hurst exponent and persistence exponent are obtained, and it is further argued that the Hurst exponent is completely determined by equilibrium dimer correlations, while the persistence exponent is additionally influenced by equilibrium correlations between test monomers.

The Weil representation zeta function of a group G is a generating function counting the absolutely irreducible representations of G over all finite fields. It is reminiscent of the Hasse-Weil zeta function of algebraic varieties and converges for the large class of UBERG groups. We give a short introduction, discuss the abscissa of convergence and present some examples. Even for procyclic groups it can be difficult to determine the abscissa of convergence due to close relations to open problems in number theory. We will explain how to calculate the Weil abscissa for random procyclic groups. (based on joint work with Ged Corob Cook and Matteo Vannacci)

We study a variant of the Iwahori-Hecke algebra of a Coxeter group, whose generators T_i satisfy the braid relations but are assumed to be nilpotent (in parallel to Coxeter groups where the T_i are involutions, and 0-Hecke algebras where they are idempotent). Motivated by Coxeter (1957) and Broue-Malle-Rouquier (1998), we classify the finite-dimensional among these "generalized nil-Coxeter algebras". These turn out to be the usual nil-Coxeter algebras, and exactly one other type-A family of algebras, which have a finite "word basis" in the T_i and a unique longest word.

In the remaining time I will present joint work with Sutanay Bhattacharyya, in which we explore the "Temperley-Lieb" variant of the above, wherein all sufficiently long braid words are also killed. Now the finite-dimensional algebras obtained include ones with bases indexed by:
(a) words with a unique reduced expression (any Coxeter type),
(b) fully commutative words (counted by Stembridge),
(c) Catalan numbers (via the XYX algebras of Postnikov), and
(d) the \bar{12} avoiding signed permutations (in type B=C).

Let G be a nice (connected reductive) Lie group. An irreducible representation of G, when restricted to a maximal torus, decomposes into weights with multiplicity. We outline a procedure to compute symmetric polynomials (e.g., power sums) of this multiset of weights in terms of the highest weight. This is joint work with Rohit Joshi.

Similar to standard growth of (finitely generated) groups, one can define conjugacy growth of groups which, informally, counts the number of conjugacy classes in a ball of radius n in a Cayley graph. This was first studied by Riven for free groups, and techniques from geometry, combinatorics and formal language theory have proven to be useful for determining information about the conjugacy growth series for a variety of groups.
This talk will provide a survey on the key tools and results about conjugacy growth. Time permitting, I’ll also discuss joint work with Laura Ciobanu, where we studied conjugacy growth in dihedral Artin groups.

In this talk, I will discuss zeta functions that count the number of twisted conjugacy classes of a fixed group.

Twisted conjugacy is a generalisation of the usual conjugacy, where we introduce a twist by an endomorphism. Specifically, given a group G and an automorphism f, we consider the action gx = gx f(g)^{-1}. The orbits of this action are known as twisted conjugacy classes, or Reidemeister classes.

Recent years have seen intensive investigation into the sizes of these classes. A major goal in this area is to classify groups where all classes are infinite. For groups that do not possess this property, the focus shifts to understanding the possible sizes of the classes, among all automorphisms.

In this talk, we will see that, as typical, these zeta functions admit Euler product decompositions with rational local factors, and we will explore how these zeta functions can be utilised to understand twisted conjugacy classes of certain nilpotent groups.

Let F be a non-Archimedean local field F with ring of integers O and a finite residue field k of characteristic greater than three. While the representations of finite groups of Lie type GL_n(k) and of the p-adic groups GL_n(F) are well studied, the representations of GL_n(O) remain far less understood.

In this talk, we will explore the challenges involved in constructing the complex irreducible representations of GL_n(O), highlighting key differences from the case of GL_n(k). We will then present a method for constructing irreducible representations of GL_3(O). This is based on a recent joint work with Uri Onn and Amritanshu Prasad.

In the symmetric group S_n, there are n^{n-2} ways to write each n-cycle as a product of the minimum number of transpositions. This theorem has numerous extensions: in the symmetric group, such questions are tied to the enumeration of embedded maps on surfaces and moduli spaces of curves, while in real and complex reflection groups the analogous theorem is one ingredient in the Catalan--Coxeter theory and the study of the lattice of W-noncrossing partitions.

About a decade ago, with Vic Reiner and Dennis Stanton, we studied the analogue of this result for the general linear group over a finite field F_q. In this setting, the role of the n-cycle is taken by a Singer cycle, and that of the transpositions by the reflections; we showed that the number of factorizations is (q^n - 1)^{n - 1}. In this talk, I will discuss ongoing work, joint with C. Ryan Vinroot, that extends this work to a larger family of linear and unitary groups over a finite field.

This is an expository talk on some combinatorial aspects of matrix groups over rings. We first discuss results on different types of bounded factorizations of elementary Chevalley groups over certain commutative rings. These rings include local rings, finite fields, rings of matrix-valued holomorphic maps on Stein spaces as well as number rings. The results are intimately related to deep properties such as the congruence subgroup property and Kazhdan’s property T among other things. We also briefly mention growth functions which arise naturally, whose analytic information encodes group theoretic information.

Over the three lectures and the tutorial, I want to explore some problems in enumerative algebra that can be understood by associating lattices to semistandard Young tableaux. I will introduce a family of rational functions called Hall--Littlewood--Schubert series (HLS series), which was recently introduced by Christopher Voll and myself. The enumerative problems we discuss will be solved by judicious substitutions of the variables of the HLS series.

Over the three lectures and the tutorial, I want to explore some problems in enumerative algebra that can be understood by associating lattices to semistandard Young tableaux. I will introduce a family of rational functions called Hall--Littlewood--Schubert series (HLS series), which was recently introduced by Christopher Voll and myself. The enumerative problems we discuss will be solved by judicious substitutions of the variables of the HLS series.