Tue, 28 Apr 2026
16:00
L6

Refining Mirzakhani

Elba Garcia-Felide
Abstract

I will present a generalisation of Mirzakhani’s recursion for the volumes of moduli spaces of bordered Klein surfaces, including non-orientable surfaces. On these moduli spaces, the top form introduced by Norbury diverges as the lengths of one-sided geodesics approach zero. However, integrating this form over Gendulphe’s regularised moduli space—where the systole of one-sided geodesics is bounded below by epsilon—yields a finite volume. Using Norbury’s extension of the Mirzakhani–McShane identities to the non-orientable setting, we derive an explicit formula for the volume of the moduli space of one-bordered Klein bottles, as well as a recursion for arbitrary topologies that fully captures the dependence on the geometric regularisation parameter epsilon. I will conclude with remarks on the relation to refined topological recursion, which leads us to a refinement of the Witten–Kontsevich recursion and of the Harer–Zagier formula for the orbifold Euler characteristic of the moduli space of curves of genus g with n marked points. Based on joint work with P. Gregori and K. Osuga; the final part reflects ongoing work with N. Chidambaram, A. Giacchetto, and K. Osuga.

A kinetic interpretation of thermomechanical restrictions of continua
Farrell, P Zerbinati, U Málek, J Souček, O International Journal of Engineering Science
Tue, 26 May 2026
15:00
L6

TBD

Francesco Fournier-Facio
Abstract

to follow

Tue, 12 May 2026
15:00
L6

Median metric groups

Pénélope Azuelos
Abstract
Median spaces form a broad and increasingly important class of metric spaces, encompassing both CAT(0) cube complexes and real trees. Finitely generated groups which admit free transitive (or proper cocompact) actions on discrete median spaces — equivalently, on the 0-skeletons of CAT(0) cube complexes — are reasonably well understood.  In contrast, much less is known about their continuous analogue: groups acting freely and transitively on connected median spaces. I will present some methods for constructing such actions, focusing on actions on real trees and their products, and discuss some of the surprising behaviours that show up. Even when considering real trees, the class of groups acting on such spaces is vastly more diverse than in the discrete setting: while any simplicial tree admits at most one free vertex transitive action, we will see that there are 2^{2^{\aleph_0}} pairwise non-isomorphic groups which admit a free transitive action on the universal real tree with continuum valence.
Tue, 05 May 2026
15:00
L6

Tangles in random covering of orbifolds

Adam Klukowski
Abstract
A surface is called tangle-free when it has no complicated topology on a small scale. This property is useful in applications such as Benjamini-Schramm convergence, strong covergence of representations, and spectral gaps. Consequently, there was much recent interest in tangle-freeness of random surfaces, primarily in random models induced by the Weil-Petersson measure, counting finite coverings, and Brooks-Makover model of Belyi surfaces. I will review these results, and discuss the ongoing work to extend them to branched coverings of surfaces with cone points.
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