Events items teaser

Ergodic Theory Learning Seminar
2026-05-29 11:30 - 12:30 (America/Toronto)
JULIUS FRIZZELL, UNIVERSITY OF WATERLOO

_Multiple recurrence for weakly-mixing transformations._

We will cover some basic facts about weakly mixing transformations and
work towards proving a version of the multiple recurrence theorem for
measure-preserving systems with all of the transformations being
weakly mixing.

MC 5417

Algebraic Geometry Working Seminar
2026-05-28 11:00 - 12:00
ANNE JOHNSON, UNIVERSITY OF WATERLOO

_Twisted arcs on root stacks_

We briefly introduce the theory of stacks via the stack of triangles
using Kai Behrend’s exposition as a guide. We move on to Yasuda’s
notion of the twisted arc space of a DM stack. As time permits, we
take up the special case of twisted arcs on a root stack.

MC 5403

Computability Learning Seminar
2026-05-28 13:30 - 15:00
BARBARA CSIMA, UNIVERSITY OF WATERLOO

_Priority Arguments in Computability Theory_

This term, Computability Learning Seminar will focus on Priority
Arguments. Priority Arguments are a common proof technique used in
Computability Theory. A theorem is broken down to being equivalent to
a list of requirements. These requirements are given a priority order,
and a strategy is devised to meet all the requirements, making use of
the priority order. In the early days of the subject, a big question
(Post’s Problem -1944) was whether there were any non-computable
computably enumerable (c.e.) sets that were not Turing equivalent to
the halting set. The solution, from Friedberg (1957) and Muchnik
(1956), was to construct a pair of Turing incomparable c.e. sets,
using a finite injury priority argument. In this first talk, we will
begin our examination of priority arguments by going through the proof
of this theorem, introducing definitions and reviewing notions from
Computability Theory as needed along the way.

MC 5403

Differential Geometry Working Seminar
2026-05-27 14:00 - 15:30
SPENCER KELLY, UNIVERSITY OF WATERLOO

_Sobolev Spaces Over Compact Manifolds_

The space of smooth sections of a vector bundle over a manifold is an
infinite dimensional Fréchet Space, and thus many of the tools used
in finite-dimensional geometry are rendered useless on this space.
However, taking the completion of this space with respect to the
Sobolev norm, we obtain a Banach space. What's even better is that in
the $L^2$ case we obtain a Hilbert space. In this talk we will walk
through different constructions of the$L^2$-Sobolev spaces of sections
of a vector bundle over a compact manifold, and discuss the Sobolev
embedding theorem. We will also work through some of the properties of
differential operators on this space and, time permitting, we will
finish with the Berger-Ebin decomposition for differential operators
with injective symbol.

MC 5417

Ergodic Theory Learning Seminar
2026-05-22 11:30 - 12:30
JULIUS FRIZZELL, UNIVERSITY OF WATERLOO

_Szemerédi's Theorem and Multiple Recurrence_

We will cover Szemerédi's Theorem and its equivalence to
Furstenberg's multiple recurrence theorem, we will then begin to look
at weak-mixing transformations in more detail.

MC 5417

Differential Geometry Working Seminar
2026-05-20 14:00 - 15:30
BENOIT CHARBONNEAU, UNIVERSITY OF WATERLOO

_Some homogeneous geometry on the manifold of full flags_

I will be using the manifold of full flags of complex three-space
(seen as the quotient of $\mathrm{SU(3)}$ byits torus) to illustrate
how much geometry one can do with homogenous objects.

MC 5417

Differential Geometry Working Seminar
2026-05-20 15:30 - 17:00
FACUNDO CAMANO, UNIVERSITY OF WATERLOO

_Boundary Conditions for Non-Euclidean Monopoles_

In this talk, I will discuss the heuristic behind defining asymptotics
for monopoles. Specifically, the asymptoticsshould be abelian
solutions embedded into the gauge group. I will first go over this
heuristic for Euclideanmonopoles and then move on to non-Euclidean
situations such as hyperbolic and singly periodic.

MC 5417

Pure Math Graduate Student Colloquia
2026-05-22 15:30 - 17:00
BORIS LI, UNIVERSITY OF WATERLOO, PURE MATHEMATICS

_On the physics of bells_

We shall discuss the acoustics and resonance of bells from the
perspective of physics. After a short review ofnormal modes in musical
instruments, we shall compare bells with one-dimensional systems such
as strings andwinds. In contrast to these systems, bells exhibit
strongly inharmonic partials due to its curved geometry. Wediscuss
some consequences of this structure, including some prominent partials
and the psychoacousticphenomenon of the strike note. Time permitting,
we shall examine how bell geometry and thickness profilesaffect
tuning.

Refreshments at 3:30pm. Talk starts at 4:00pm.

MC 5403

Ergodic Theory Learning Seminar
2026-05-15 11:30 - 12:30
JULIUS FRIZZELL, University of Waterloo

_A Quick Introduction to Ergodic Theory_

I will introduce the basic definitions and theorems (without proof) of
ergodic theory that are needed to discuss Furstenberg's multiple
recurrence theorem. The development will follow that in Chapter 1 of
"An Introduction to Ergodic Theory" by Peter Walters and Chapter 3 of
"Multiple Recurrence in Ergodic Theory and Combinatorial Number
Theory" by Harry Furstenberg. Time allowing, I will also cover the
statement of the Multiple recurrence theorem itself and its
relationship to Szemerédi's theorem.

MC 5417

Algebraic Geometry Working Seminar
2026-05-14 11:00 - 12:00
KALEB RUSCITTI, University of Waterloo

_Building Kronecker Moduli Spaces_

Kronecker moduli spaces are quiver moduli spaces and a generalization
of Grassmannians. They parameterize n-tuples of matrices between two
vector spaces, up to change of basis on both sides. In this seminar, I
will describe how to construct them as GIT quotients and what
properties we can prove about them from this construction.

MC 5417
