Seminar 09.16.21 Ferre Moragues

Title: Polynomial ergodic averages for certain countable ring actions

Speaker: Andreu Ferre Moragues – Nicolaus Copernicus University, Torun, Poland

Abstract: Inspired by a recent result of Frantzikinakis that allows one to establish joint ergodicity of general integer valued sequences, we will take a look at the ring actions setup. I will present new joint ergodicity results for families of independent polynomials when the acting ring is a field of characteristic zero, their corollaries in combinatorics and topological dynamics, and the methods of proof. Based on joint work with Andrew Best.

Zoom link: https://osu.zoom.us/j/91638927725

Meeting ID: 916 3892 7725

Password: Mixing

Recorded Talk: https://osu.zoom.us/rec/play/h2IKj8dcab78XnCag1DHQ_Qu76CrivFtY5TDxnco_vDe0SuH6LaFQILKy0omyhG8yRAD_WU_461XYiMT.p3_TVFm36rLaZ-KS?continueMode=true&_x_zm_rtaid=y6kPXldWSOq2BEH7eY2rrQ.1631863073516.46b8b6ed0ca4481f5aa60be2f193e0be&_x_zm_rhtaid=291

Seminar 09.09.21 Wolf

Title: Computability of topological pressure on compact shift spaces beyond finite type

Speaker: Christian Wolf – CUNY

Abstract: In this talk we discuss the computability (in the sense of computable analysis) of the topological pressure $P_{\rm top}(\phi)$ on compact shift spaces $X$ for continuous potentials $\phi:X\to\bR$. This question has recently been studied for subshifts of finite type (SFTs) and their factors (Sofic shifts). We develop a framework to address the computability of the topological pressure on general shift spaces and apply this framework to coded shifts. In particular, we prove the computability of the topological pressure for all continuous potentials on S-gap shifts, generalized gap shifts, and Beta shifts. We also construct shift spaces which, depending on the potential, exhibit computability and non-computability of the topological pressure. We further show that the generalized pressure function $(X,\phi)\mapsto P_{\rm top}(X,\phi\vert_{X})$ is not computable for a large set of shift spaces $X$ and potentials $\phi$. Along the way of developing these computability results, we derive several ergodic-theoretical properties of coded shifts which are of independent interest beyond the realm of computability. The topic of the talk is joint work with Michael Burr (Clemson U.), Shuddho Das (NYU) and Yun Yang (Virginia Tech).

Zoom link: https://osu.zoom.us/j/91638927725

Meeting ID: 916 3892 7725

Password: Mixing

Recorded Talk: https://osu.zoom.us/rec/share/dIchmAETAILph7uojccOdxliuEeNlsH4SfDUEzzVuFwqKQiQi3brEW6GvX_Hpj_4.onMqP6LjZX6OSA6_

Seminar 08.26.21 Dymek

Title: Topological dynamics of (multidimensional) B-free systems

Speaker: Aurelia Dymek – Nicolaus Copernicus University, Torun, Poland

Abstract: Sarnak turned attention to B-free systems. In particular, he investigated the squarefree subshift. Two multidimensional generalizations of B-free systems have been dealt with by Cellarosi, Vinogradov, Baake and Huck. My talk will be concerned with some similarities and differences between B-free systems in the one- and multidimensional case. This is a part of my doctoral dissertation.

Zoom link: https://osu.zoom.us/j/91638927725

Meeting ID: 916 3892 7725

Password: Mixing

Recorded Talk: https://osu.zoom.us/rec/play/HkONQZ2ALv6bbdnUaWmJcn0MZj-S2OkT4MOQlHkqmC9IJkZee0I2vxnpHxdGXqxsF-ARe9GuE50A8pJi.8ZNn6D_A7PGsRwPl?continueMode=true

Seminar program for Fall 2021

This year, our seminar will be a mixture of in person and virtual seminars, with the mix anticipated to trend towards in person later in the year, and virtual early in the year. As usual, we meet on Thursdays at 3.00pm EST unless otherwise noted. In person talks will be in MW154.

For virtual talks, the Zoom link can be obtained from the organizers, Andreas Koutsogianis and Dan Thompson. For most virtual talks, video will be posted afterwards, and will remain viewable on Zoom for 120 days after the talk.

The following is our current schedule, and more talks will be announced soon.

Aug 17th: In person –  Federico Rodriguez Hertz (Penn State)

Aug 26: Virtual – Aurelia Dymek (Nicolaus Copernicus University, Torun, Poland)

Sept 9: Virtual – Christian Wolf (City College of New York)

Sept 16: Virtual – Andreu Ferre Moragues (Nicolaus Copernicus University, Torun, Poland)

Sept 30: Virtual – Pablo Shmerkin (UBC, Canada)

Oct 8 (Friday, 12.00pm, note unusual day): Virtual – Ryokichi Tanaka (Tohoku University, Sendai, Japan)

Oct 19 (Tues, note unusual day): In Person – Keith Burns (Northwestern)

Oct 21: Virtual – Alejandro Maass (University of Chile, Chile)

Oct 28: Virtual – Wenbo Sun (Virginia Tech)

Nov 18: Virtual – Rigo Zelada Cifuentes (University of Maryland)

Dec 9: Virtual – Giulio Tiozzo (University of Toronto, Canada)