Feb 2  Ofir Schnabel, Classifying crossed products up to several graded equivalence relations 
A graded algebra is a crossed product if every homogeneous component admits an invertible element. Hence, natural examples of crossed products are group algebras, twisted group algebras, skew group algebras and graded division algebras. We will define some natural equivalence relations on graded algebras and we will illustrate how to classify crossed products up to these equivalence relations in terms of orbits with respect to certain group actions on crossed products. No prior knowledge is required. This is joint work with Yuval Ginosar.  
Feb 11  Ilaria Colazzo, The algebraic structure of bracelike semitrusses 
To study settheoretic solutions of the YangBaxter equation, several authors introduced algebraic structures. Rump, and Cedó, Jespers and Okniński introduced braces, Guarnieri and Vendramin introduced skew braces and Catino, Colazzo and Stefanelli, and Jespers and Van Antwerpen introduced semibraces. All these objects are subclasses of (semi)trusses, an algebraic structure introduced by Brzeziński to study the distributive law of (semi)braces. In this talk, we focus on a subclass of left semitrusses, the class of bracelike semitrusses. First, we prove that in the finite case, the additive structure is a completely regular semigroup. Secondly, we apply this result on a specific instance of a left semitruss called an almost left semibrace, introduced by Miccoli to study its algebraic structure. In particular, we show that one can associate a left semibrace to any almost left semibrace. Furthermore, we show that the settheoretic solutions of the YangBaxter equation originating from almost left semibraces arise from this correspondence. This talk is based on joint work with Arne Van Antwerpen (arXiv:1908.11744)  
Feb 18  Charlotte Verwimp, Structure monoids of settheoretic solutions of the YangBaxter equation 
Given a settheoretic solution (X, r) of the YangBaxter equation, GatevaIvanova and Majid [2] showed that this solution can be extended to a solution (M(X, r), rM) on the so called structure monoid M(X, r), such that rM restricts to r on XxX. At the group level, this is no longer true. This shows the importance of looking at the structure monoid instead of the structure group. For (finite, bijective) left nondegenerate solutions, there is an important link between the structure monoid and another “richer” associative structure, called the derived structure monoid. Using this richer structure, one has been able to study algebraic properties of the structure monoid. In this talk, we take a better look at how GatevaIvanova and Majid extend an arbitrary settheoretic solution of the YangBaxter equation to a solution on the structure monoid. Next, we generalize the link between the structure monoid and the derived structure monoids for arbitrary settheoretic solutions of the YangBaxter equation. The latter is based on some new results of a joint work with Ferran Cedó and Eric Jespers [1]. Finally, we pose questions and discuss recent results on nondegenerate and bijective solutions. [1] F. Cedó, E. Jespers, C. Verwimp, Structure monoids of set theoretic solutions of the YangBaxter equation, arXiv:1912.09710 [math.RA]. [2] T. GatevaIvanova and S. Majid, Matched pairs approach to set theoretic solutions of the YangBaxter equation, J. Algebra 319 (2008), no. 4, 1462–1529.  
Feb 25  Réamonn Ó Buachalla, 
 
Mar 3  Abel Lacabanne, An asymptotic cellular category for G(e,e,n) 
Given a Coxeter system (W,S), one can associate a Hecke algebra which is a deformation of the group algebra of W. Kazhdan and Lusztig have constructed another basis of this algebra, which is then used to develop a cell theory for Coxeter groups. Bonnafé and Rouquier developed a theory of cells for complex reflection groups which is conjectured to be a generalization of the KazhdanLusztig theory.
 
Mar 10  Leandro Vendramin, On the classification of Nichols algebras 
Nichols algebras appear in several branches of mathematics going from Hopf algebras and quantum groups, to Schubert calculus and conformal field theories. In this talk, we review the main problems related to Nichols algebras and we discuss some classification theorems. The talk is mainly based on joints works with I. Heckenberger.  
Mima Stanojkovski, Automorphism groups, elliptic curves, and the PORC conjecture  
In 1960, Graham Higman formulated his famous PORC conjecture in relation to the function f(p,n) counting the isomorphism classes of pgroups of order p^n . By means of explicit formulas, the PORC conjecture has been verified for n < 8. Despite that, it is still open and has in recent years been questioned. I will discuss (generalizations of) an example of du Sautoy and VaughanLee (2012), together with a conceptualization of the phenomena they observe. Hidden heroes of this story turn out to be Hessian matrices and torsion points of elliptic curves. This is joint work with Christopher Voll.  
Mar 17  Seminar Cancelled, 
 
Mar 24  Seminar Cancelled, 
 
Mar 31  Seminar Cancelled, 
 
Avr 7  Seminar Cancelled, 
 
Avr 14  Seminar Cancelled, 
 
Avr 21  Theo Raedschelders, 
 
Avr 24  Marco Bonatto, 
 
Avr 28  free slot, 
 
May 5  Eugenio Gianelli + Carolina Vallejo, 
 
May 12  free slot, 
 
May 19  free slot, 
 
May 26  Martina Lanini, 
 
Jun 2  Mandi SchaefferFry, 
 
Jun 3  Tomasz Brzezinski, 
11h 

Jun 9  free slot, 
 
Jun 16  free slot, 
 
Jun 23  free slot, 
 
Jun 30  free slot, 
