## An ideal convergence: an example in noncommutative metric geometry (Prof. Konrad Aguilar)

### March 31 @ 4:15 pm - 5:30 pm

Title: An ideal convergence: an example in noncommutative metric geometry

Abstract:

The ability to calculate the distance between sets (rather than just distance between points) has found applications in geometry and group theory as well as various branches of applied mathematics. The Hausdorff distance and the Gromov-Hausdorff distance are standard distances used in these applications. Moreover, a certain generalization of the Gromov-Hausdorff distance called the quantum Gromov-Hausdorff distance was built by M. A. Rieffel to answer some questions from physics about operator algebras, which are generalizations of algebras of complex-valued square matrices. In another direction, J.M.G. Fell introduced a notion of convergence of ideals of a given operator algebra. Can the quantum Gromov-Hausdorff distance also be used to establish convergence of the associated quotient algebras? We discuss this for certain operator algebras called approximately finite-dimensional (AF) C*-algebras, which can be represented by infinite graphs called Bratteli diagrams where the ideals and quotients are represented by subgraphs. It is the movement of the quotient graphs with respect to the ideal graphs that motivates our question and its answer. The main example we discuss will be given by graph representations of irrational numbers built by their associated continued fractions. (This talk contains joint work with Samantha Brooker, Frédéric Latrémolière, and Alejandra López).

Professor Konrad Aguilar is Assistant Professor at Pomona College.