- Series
- School of Mathematics Colloquium
- Time
- Thursday, February 25, 2021 - 11:00am for 1 hour (actually 50 minutes)
- Location
- https://us02web.zoom.us/j/87011170680?pwd=ektPOWtkN1U0TW5ETFcrVDNTL1V1QT09
- Speaker
- Matthew Foreman – University of California, Irvine – mforeman@math.uci.edu – https://www.math.uci.edu/people/matthew-foreman
- Organizer
- Anton Bernshteyn
The talk considers the equivalence relations of topological conjugacy and measure isomorphism on diffeomorphisms of compact manifolds of small dimension. It is shown that neither is a Borel equivalence relation. As a consequence, there is no inherently countable method that, for general diffeomorphisms $S$ and $T$, determines whether $S\sim T$. It is also shown that the Time Forward/Time Backward problem for diffeomorphisms of the 2-torus encodes most mathematical questions, such as the Riemann Hypothesis.
This work is joint with B Weiss and A Gorodetski.