Events

Spiro Karigiannis, University of Waterloo

Schwarz Lemma for Smith maps

I will discuss a generalized Schwarz Lemma for Smith maps, proved recently by Broder-Iliashenko-Madnick, and explain how it generalizes the classical Schwarz Lemma from complex analysis.

MC 5403

Noé de Rancourt , Université de Lille

Big Ramsey degrees of metric structures

Distortion problems, from Banach space geometry, ask about the possibility of distorting the norm of a Banach space in a significant way on all of its subspaces. Big Ramsey degree problems, from combinatorics, are about proving weak analogues of the infinite Ramsey theorem in structures such as hypergraphs, partially ordered sets, etc. Those two topics, coming back to the seventies, have quite disjoint motivations but share a surprisingly similar flavour. In a ongoing work with Tristan Bice, Jan Hubička and Matěj Konečný, as a step towards the unification of those two topics, we developped an analogue of big Ramsey degrees adapted to the study of metric structures (metric spaces, Banach spaces...). Our theory allows us to associate to certain metric structures a sequence of compact metric spaces quantifying their default of Ramseyness. In this talk, I'll present our theory and its motivations and illustrate it on the examples of the Banach space $\ell_\infty$ and the Urysohn sphere. If time permits, links with topological dynamics will also be discussed.

QNC 1507 or Join on Zoom

Jon Cheah, University of Hong Kong

An advertisement of cluster algebras

Cluster algebras have had many surprising links with many areas of mathematics beyond their original purpose in studying total positivity. In this expository talk, we consider two discrete dynamical systems, namely Markov triples and Coxeter--Conway friezes. While the study of these examples predated that of cluster theory, we will see how the latter provides a conceptual explanation for the intergrality and positivity phenomena.

MC 5479

(snacks at 16:00)

Alex Pawelko, University of Waterloo

Riemannian Geometry of Knot Spaces

We will review the construction of knot spaces of manifolds, specifically over G2 and Spin(7) manifolds. We will then see an explicit construction of the Levi-Civita connection of the knot space, and see what this can tell us about the torsion of the induced special geometric structures on knot spaces of G2 and Spin(7) manifolds.

MC 5403

Joaco Prandi, University of Waterloo

When the weak separation condition implies the generalize finite type in R^d

Let S be an iterated function system with full support. Under some restrictions on the allowable rotations, we will show that S satisfies the weak separation condition if and only if it satisfies the generalized finite-type condition. To do this, we will extend the notion of net intervals from R to R^d. If time allows, we will also use net intervals to calculate the local dimension of a self-similar measure with the finite-type condition and full support.

QNC 1507 or Join on Zoom

Sergey Grigorian, University of Texas Rio Grande Valley

Geometric structures determined by the 7-sphere

The 7-sphere is remarkable not only for its rich topological and algebraic properties but also for the special geometric structures it encodes. In this talk, we explore how the symmetries and stabilizer subgroups of Spin(7) acting on the 7-sphere, regarded as the set of unit octonions, give rise to G2​-structures on 7-manifolds, SU(3)-structures on 6-manifolds, and SU(2)-structures on 5-manifolds. We will trace how these structures arise naturally via the inclusions of Lie groups and are reflected in the geometry of sphere fibrations. This perspective highlights the role of the 7-sphere as a unifying object in special geometry in dimensions from 5 to 8.

MC 5417