Odeljenje za matematiku, 15. decembar 2023.

Naredni sastanak Seminara biće održan u petak, 15. decembra 2023, u sali 301f Matematičkog instituta SANU sa početkom u 14.15. U pitanju je zajednički sastanak sa Logičkim seminarom.

Predavač: Ilijas Farah, York University, Toronto
 
Naslov predavanja: CORONA RIGIDITY
 
Apstrakt: This talk will be about a story that started with Weyl’s work on compact perturbations of pseudodifferential operators. The Weyl-von Neumann theorem asserts that two self-adjoint operators on a complex Hilbert space are unitarily equivalent modulo the compacts if and only if their essential spectra coincide. Later on, this was extended to normal operators by Berg and Sikonia. New impetus to this study was given in the work of Brown, Douglas, and Fillmore, who replaced single operators with (separable) C*-algebras and compact perturbations with extensions by K(H). After passing to the quotient (the Calkin algebra, Q) and identifies an extension with a *-homomorhism into Q analytic methods have to be supplemented by methods coming from algebraic topology, homological algebra, and (more recently) logic.After briefly introducing the BDF theory, I will move to coronas of separable C*-algebras (of which Q is the simplest example) and question of their rigidity. Much attention will be given to the (still half-open) question of Brown-Douglas-Fillmore, whether Q has an automorphism that flips the Fredholm index. This talk will be partially based on the preprint Farah, I., Ghasemi, S., Vaccaro, A., and Vignati, A. (2022). Corona rigidity. arXiv preprint arXiv:2201.11618.
 
Napomena: Predavanja se mogu pratiti na daljinu preko linka:
https://miteam.mi.sanu.ac.rs/call/T9XDGChhq8aDcNqmz/qw7wIwci2jv2rdg9I9CrXkm7OJhF_LB8DfjXZp4jTFV
 
Registraciona forma je dostupna na:
https://miteam.mi.sanu.ac.rs/asset/tz97w4Hu4c3unsJ7N


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