Weekly Bulletin (it)

Notiziario dei seminari di carattere matematico
a cura del Dipartimento di Matematica G. Castelnuovo, Sapienza Università di Roma

Settimana dal 22-07-2019 al 28-07-2019

Martedì 23 luglio 2019
Ore 14:00, Aula Dal Passo, Dipartimento di Matematica di Tor Vergata
Seminario
Florin Radulescu (Dipartimento di Matematica di Tor Vergata)
Transferring unitary representations from PSL(2,R) to PSL(2,Q_p)- an operator algebra approach
We use an operator algebra approach in transferring unitary representations in the discrete series of PSL(2,R) to PSL(2,Q_p). This is related to finite Murray von Neumann dimension of the von Neumann algebra obtained by restriction to PSL(2,Z). In the case of infinite dimension, we construct a "double representation" (by left and right multiplication operators) that we can control modulo compact operators.


Martedì 23 luglio 2019
Ore 15:00, Aula 14 (via Scarpa), Dip. SBAI (Scienze di Base e Applicate per l'Ingegneria), Sapienza Università di Roma
Incontri di Algebra e Geometria allo SBAI
Daniel Labardini-Fragoso (National Autonomous University of Mexico)
Cluster algebras and hyperbolic geometry
Sergey Fomin and Andrei Zelevinsky invented cluster algebras almost 20 years ago. In less than two decades, cluster algebras have found connections with many areas of Mathematics, e.g. Hyperbolic geometry and Teichmüller theory. I will start this talk by giving a brief overview of what a cluster algebra is (a ring whose generators are produced recursively by applying a very simple combinatorial operation, called mutation, on oriented graphs). Then I will present a beautiful identity discovered to hold in the hyperbolic plane by Robert Penner, and describe how this identity allows cluster algebras to appear as coordinate rings of Teichmüller spaces of punctured surfaces, as discovered by Sergey Fomin, Michael Shapiro and Dylan Thurston, and Vladimir Fock and Alexander Goncharov. Finally, I will present 'Hyperbolic GeometPy', a program which, motivated by the above, I am writing to be able to interact with the hyperbolic plane and visualize things like orbits and invariant curves of Möbius transformations, hyperbolic convex hulls, hyperbolic geodesics with constant rapidity, circular motion with constant angular rapidity, and tessellations of the hyperbolic plane by Fuchsian group actions.


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