Thursday 10 July 2025 from 10:30 am, as part of the Al@Bicocca seminar cycle, Arnaud Brothier (University of Trieste and UNSW Sydney) and Ryan Seelig (UNSW Sydney) will give the following talks
Speaker: Arnaud Brothier
Title: Vaughan Jones’ reconstruction program and infinite groups
Abstract: In his quest in constructing conformal field theories (CFT) from subfactors Vaughan Jones found an unexpected connection with Richard Thompson’s group T. This led to Jones’ technology: a powerful method for constructing actions of certain groups. I will present the great lines of Jones’ fascinating connection and will mention various applications of it in group theory, (operator) algebras and so on. I will end by introducing forest-skein groups which sit at the intersection of all these areas and ideas.
Speaker: Ryan Seelig
Title: Finitely presented simple groups with no piecewise projective actions
Abstract: Following on from the previous talk, we investigate an explicit class of examples of forest-skein (FS) groups. We show they act naturally on the circle by orientation-preserving homeomorphisms, are finitely presented, and are simple. Surprisingly, we will show these examples admit no piecewise projective, and hence no piecewise affine, actions on the circle. This is in stark contrast to previous examples of such simple groups in the literature. Finally, using powerful dynamical techniques of Rubin and McCleary, we are able to distinguish infinitely many isomorphism classes in our class of examples. This is joint work with Arnaud Brothier.
Information to attend
The seminars will be held in Room 3014 (3rd Floor - U5 Building), Department of Mathematics and Applications and will also be available online by this link
For more information, visit the website