A kinetic interpretation of thermomechanical restrictions of continua
 Farrell, P Málek, J Souček, O Zerbinati, U International Journal of Engineering Science volume 225 (05 May 2026)
Tue, 16 Jun 2026
15:00
L6

Dehn functions of Solvable Lie groups

Ido Grayevsky
(Dept of Maths University of Bristol)
Abstract

In the 2010s, Cornulier and Tessera presented an algorithm deciding whether a Lie group has exponential or polynomially bounded Dehn function. I will discuss the highlights of their work, and then focus on the following question: in case the Dehn function is polynomially bounded, what is the degree of the bounding polynomials? The heart of the matter in this context is the geometric relation between a (completely) solvable group and its largest nilpotent quotient. I will outline the basics of this geometry, and present a new method that exploits it to give (in some cases) better bounds on the degree of the bounding polynomials.

Joint with Gabriel Pallier.

Tue, 09 Jun 2026
15:00
L6

Simplicity and Selflessness of Reduced Group C*-Algebras

Greg Patchell
((Mathematical Institute University of Oxford))
Abstract
There are numerous sufficient conditions for the reduced group C*-algebra of a discrete group to be simple, including growth conditions, paradoxical decompositions, and existence of boundary actions. Recently, an important strengthening of C*-simplicity, namely C*-selflessness, has been described and there is a substantial overlap between the techniques used to prove C*-simplicity and C*-selflessness. However, although a characterization of C*-simplicity was found by Kalantar-Kennedy in 2014, no such characterization of C*-selflessness is yet known. I will survey three different approaches taken to prove C*-selflessness and the limitations of each approach.
Tue, 02 Jun 2026
15:00
L4

Marking graphs and finite-type Artin groups

Kaitlin Ragosta
(University of the Basque Country (UPV/EHU))
Abstract

Clean markings on surfaces were a key component in Masur and Minsky's hierarchy machinery, which proved to be a powerful tool in the study of mapping class groups. In this talk, I will briefly discuss the connection between clean markings and hierarchies, and I will explain how a natural analogue can be constructed for finite-type Artin groups.

Tue, 26 May 2026
15:00
L6

Groethendieck pairs from iterated Dehn filling

Francesco Fournier-Facio
(Cambridge)
Abstract

A Groethendieck pair consists of a finitely generated residually finite group G, with a finitely generated subgroup N such that the inclusion N -> G induces an isomorphism of profinite completions. I will present a new method to produce Groethendieck pairs with peculiar properties, using iterated group theoretic Dehn filling on hyperbolic virtually special groups. Such pairs witness the profinite non-invariance of quasimorphisms, stable commutator length, and actions on hyperbolic spaces and finite-dimensional CAT(0) cube complexes.

Tue, 19 May 2026
15:00
L6

A virtual fibering criterion for amalgamated free products

Ashot Minasyan
(University of Southampton)
Abstract

Let G be a group acting on a tree. I will discuss necessary conditions for G to have a finitely generated infinite normal subgroup of infinite index. When the edge stabilisers are virtually cyclic this naturally leads to considering (virtual) fibering of G. I will give an “if and only if” criterion for (virtual) fibering in the special case of amalgamated free products over virtually cyclic subgroups. The talk will be based on joint work with Jon Merladet.

Tue, 12 May 2026
15:00
L6

Median metric groups

Pénélope Azuelos
(Dept of Maths University of Bristol)
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.
Physics potential of the IceCube Upgrade for atmospheric neutrino oscillations
 Abbasi, R Ackermann, M Adams, J Agarwalla, S Aguilar, J Ahlers, M Alameddine, J Ali, S Amin, N Andeen, K Argüelles, C Ashida, Y Athanasiadou, S Axani, S Babu, R Bai, X Baines-Holmes, J V., A Barwick, S Bash, S Basu, V Bay, R Beatty, J Tjus, J Behrens, P Beise, J Bellenghi, C Benkel, B BenZvi, S Berley, D Bernardini, E Besson, D Blaufuss, E Bloom, L Blot, S Bodo, I Bontempo, F Motzkin, J Meneguolo, C Böser, S Botner, O Böttcher, J Braun, J Brinson, B Brisson-Tsavoussis, Z Burley, R Butterfield, D Campana, M Carloni, K Carpio, J Chattopadhyay, S Chau, N Chen, Z Chirkin, D Choi, S Clark, B Coleman, A Coleman, P Collin, G Borja, D Connolly, A Conrad, J Corley, R Cowen, D De Clercq, C DeLaunay, J Delgado, D Delmeulle, T Deng, S Desiati, P de Vries, K de Wasseige, G DeYoung, T Díaz-Vélez, J DiKerby, S Dittmer, M Domi, A Draper, L Dueser, L Durnford, D Dutta, K DuVernois, M Ehrhardt, T Eidenschink, L Eimer, A Eller, P Ellinger, E Elsässer, D Engel, R Erpenbeck, H Esmail, W Eulig, S Evans, J Evenson, P Fan, K Fang, K Farrag, K Fazely, A Fedynitch, A Feigl, N Finley, C Fischer, L Fox, D Franckowiak, A Fukami, S Fürst, P Gallagher, J Ganster, E Garcia, A Garcia, M Garg, G Genton, E Gerhardt, L Ghadimi, A Glaser, C Glüsenkamp, T Gonzalez, J Goswami, S Granados, A Grant, D Gray, S Griffin, S Griswold, S Groth, K Guevel, D Günther, C Gutjahr, P Ha, C Haack, C Hallgren, A Halve, L Halzen, F Hamacher, L Minh, M Handt, M Hanson, K Hardin, J Harnisch, A Hatch, P Haungs, A Häußler, J Helbing, K Hellrung, J Henke, B Hennig, L Henningsen, F Heuermann, L Hewett, R Heyer, N Hickford, S Hidvegi, A Hill, C Hill, G Hmaid, R Hoffman, K Hooper, D Hori, S Hoshina, K Hostert, M Hou, W Huber, T Hultqvist, K Hymon, K Ishihara, A Iwakiri, W Jacquart, M Jain, S Janik, O Jansson, M Jeong, M Jin, M Kamp, N Kang, D Kang, W Kang, X Kappes, A Kardum, L Karg, T Karl, M Karle, A Katil, A Katori, T Kauer, M Kelley, J Khanal, M Zathul, A Kheirandish, A Kimku, H Kiryluk, J Klein, C Klein, S Kobayashi, Y Kochocki, A Koirala, R Kolanoski, H Kontrimas, T Köpke, L Kopper, C Koskinen, D Koundal, P Kowalski, M Kozynets, T Krieger, N Krishnamoorthi, J Krishnan, T Kruiswijk, K Krupczak, E Kumar, A Kun, E Kurahashi, N Lad, N Gualda, C Arnaud, L Lamoureux, M Larson, M Lauber, F Lazar, J DeHolton, K Leszczyńska, A Liao, J Lin, C Liu, Y Liubarska, M Love, C Lu, L Lucarelli, F Luszczak, W Lyu, Y Madsen, J Magnus, E Makino, Y Manao, E Mancina, S Mand, A Mariş, I Marka, S Marka, Z Marten, L Martinez-Soler, I Maruyama, R Mauro, J Mayhew, F McNally, F Mead, J Meagher, K Mechbal, S Medina, A Meier, M Merckx, Y Merten, L Millsop, A Mitchell, J Molchany, L Montaruli, T Moore, R Morii, Y Mosbrugger, A Moulai, M Mousadi, D Moyaux, E Mukherjee, T Naab, R Nakos, M Naumann, U Necker, J Neste, L Neumann, M Niederhausen, H Nisa, M Noda, K Noell, A Novikov, A Pollmann, A O’Dell, V Olivas, A Orsoe, R Osborn, J O’Sullivan, E Palusova, V Pandya, H Parenti, A Park, N Parrish, V Paudel, E Paul, L de los Heros, C Pernice, T Peterson, J Plum, M Pontén, A Poojyam, V Popovych, Y González, J Rodriguez, M Pries, B Procter-Murphy, R Przybylski, G Pyras, L Raab, C Rack-Helleis, J Rad, N Ravn, M Rawlins, K Rechav, Z Rehman, A Reistroffer, I Resconi, E Reusch, S Rho, C Rhode, W Ricca, L Riedel, B Rifaie, A Roberts, E Robertson, S Rongen, M Rosted, A Rott, C Ruhe, T Ruohan, L Ryckbosch, D Saffer, J Salazar-Gallegos, D Sampathkumar, P Sandrock, A Sanger-Johnson, G Santander, M Sarkar, S Savelberg, J Scarnera, M Schaile, P Schaufel, M Schieler, H Schindler, S Schlickmann, L Schlüter, B Schlüter, F Schmeisser, N Schmidt, T Schröder, F Schumacher, L Schwirn, S Sclafani, S Seckel, D Seen, L Seikh, M Seunarine, S Myhr, P Shah, R Shefali, S Shimizu, N Skrzypek, B Snihur, R Soedingrekso, J Søgaard, A Soldin, D Soldin, P Sommani, G Spannfellner, C Spiczak, G Spiering, C Stachurska, J Stamatikos, M Stanev, T Stezelberger, T Stürwald, T Stuttard, T Sullivan, G Taboada, I Ter-Antonyan, S Terliuk, A Thakuri, A Thiesmeyer, M Thompson, W Thwaites, J Tilav, S Tollefson, K Toscano, S Tosi, D Trettin, A Upadhyay, A Upshaw, K Vaidyanathan, A Valtonen-Mattila, N Valverde, J Vandenbroucke, J Van Eeden, T van Eijndhoven, N Van Rootselaar, L van Santen, J Vara, J Varsi, F Venugopal, M Vereecken, M Carrasco, S Verpoest, S Veske, D Vijai, A Villarreal, J Walck, C Wang, A Warrick, E Weaver, C Weigel, P Weindl, A Weldert, J Wen, A Wendt, C Werthebach, J Weyrauch, M Whitehorn, N Wiebusch, C Williams, D Witthaus, L Wolf, M Wrede, G Xu, X Yanez, J Yao, Y Yildizci, E Yoshida, S Young, R Yu, F Yu, S Yuan, T Zegarelli, A Zhang, S Zhang, Z Zhelnin, P Zilberman, P Physical Review D volume 113 issue 7 072009 (01 Apr 2026)
Tue, 28 Apr 2026
15:00
L6

Realising quasi-isometry groups

Lawk Mineh
(University of Bonn)
Abstract

The quasi-isometry group QI(X) of a metric space X is a natural group of automorphisms of the space that preserve its large-scale structure. The quasi-isometry groups of most familiar spaces are usually enormous and quite wild. Spaces X for which QI(X) is understood tend to exhibit a sort of rigidity phenomenon: every quasi-isometry of such spaces is close to an isometry. We exploit this phenomenon to address the question of which abstract groups arise as the quasi-isometry groups of metric spaces. This talk is based on joint work with Paula Heim and Joe MacManus.

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