# Seminars and colloquia

E.g., Sep. 25, 2022

### Jim Bryan

UBC
A theory of Gopakumar-Vafa invariants for orbifold Calabi-Yau threefolds

September 26, 2022

We define integer valued invariants of an orbifold Calabi-Yau threefold $X$ with transverse ADE orbifold points. These invariants contain equivalent information to the Gromov-Witten invariants of $X$ and are related by a Gopakumar-Vafa like formula which may be regarded as a ... Read more
• Intercontinental Moduli and Algebraic Geometry Seminar

### Alexia Yavicoli

Thickness and a Gap Lemma in $\mathbb{R}^d$

September 26, 2022

UBC

A general problem that comes up repeatedly in geometric measure theory, dynamics and analysis is understanding when two or more (fractal) compact sets intersect. In the real line, the classical Gap Lemma of S. Newhouse, based on the notion of thickness, gives an easily ... Read more

### Tim Hoheisel

McGill University Dept. of Mathematics and Statistics
The Maximum Entropy on the Mean Method for Linear Inverse Problems (and Beyond)

September 26, 2022

LSK 306

The principle of maximum entropy states that the probability distribution that best represents the current state of knowledge about a system is the one with largest entropy with respect to a given prior (data) distribution. It was first formulated in the context of statistical ... Read more

### Kalle Karu

UBC
Effective cones of blowups

September 26, 2022

The cone of effective divisors in a general algebraic variety is usually not polyhedral. It may have infinitely many extremal rays, and it may even be round. For toric varieties, however, the effective cone is always polyhedral. In this talk I will discuss the effective cone ... Read more
• Algebra and Algebraic geometry

### Alexia Yavicoli

Patterns, Games and Thickness

September 27, 2022

UBC

An highly active research area is concerned with finding conditions on sparse sets that ensure the existence of many geometric patterns. I will present some results in this direction connecting Newhouse thickness and its generalizations to higher dimensions, games of Schmidt ... Read more
• Harmonic Analysis and Fractal Geometry

### Karim Johannes Becher

University of Antwerp
Fields with bounded Brauer 2-torsion index

September 28, 2022

Alexander Merkurjev’s groundbreaking results from the 1980ies showed that the u-invariant (maximal dimension of an anisotropic quadratic form) of a field is related to the degrees of division algebras of exponent 2. This led Bruno Kahn to conjecture that the u-invariant is ... Read more
• Algebra and Algebraic geometry

### Charlie Peskin

Courant Institute of Mathematical Sciences, New York University
Rotary Molecular Motors Driven by Transmembrane Ionic Currents

September 28, 2022

Zoom - contact Katie Faulkner for link

There are two rotary motors in biology, ATP synthase and the bacterial flagellar motor. Both are driven by transmembrane ionic currents. We consider an idealized model of such a motor, essentially an electrostatic turbine. The model has a rotor and a stator, which are closely ... Read more
• Mathematical Biology

### Andrew Granville

Universite de Montreal
K-rational points on curves

September 28, 2022

1984 Mathematics Rd

Mazur and Rubin's Diophantine stability'' program suggests asking, for a given curve $C$, over what fields $K$ does $C$ have rational points, or at least to study the degrees of such $K$. We study this question for planar curves $C$ from various perspectives and relate ... Read more
• Number Theory

### Andrew Granville

Université de Montréal
Primes, postdocs and pretentiousness

September 28, 2022

ESB 1013

Reflections on the research developments that have contributed to this award, mostly to do with the distribution of primes and multiplicative functions, discussing my research team's contributions, and the possible future for several of these questions. 2021 Award ... Read more

### Emilio Corso

UBC
Ergodic properties of large circles: from Euclidean to hyperbolic geometry

September 29, 2022

ESB 4133

What happens to a progressively dilating body when folding the space in which it lives? For a start, we shall examine the problem in a Euclidean context, surveying results of Randol and Strichartz through the quantitative, fractal-geometric viewpoint of Fourier dimension