Past Events

Primitive integral Apollonian circle packings are fractal arrangements of tangent circles with integer curvatures. The curvatures form an orbit of a 'thin group,' a subgroup of an arithmetic group having infinite index in its Zariski closure. The...

In this talk, I introduce several first- and second-order models for self-collective behaviour on general manifolds and discuss their emergent behaviors. For the first-order model, we consider attractive-repulsive and purely attractive interaction...

This talk requires no prior knowledge and will be a gentle introduction to colouring graphs. It will be suitable for a broad audience including undergraduates. We will start with some historical tales, including the four colour map problem and the...

On a few examples, such as the permanent of a matrix, (partition function for a system of bosons), matching polynomial of a graph (partition function in a monomer-dimer system), and the independence polynomial of a graph (partition function in the...

From a directed graph $Q$, called a quiver, one can construct what is known as a quiver variety $Y_Q$, an algebraic variety defined as a quotient of a vector space by a group defined in terms of $Q$. A mutation of a quiver is an operation that...

In this talk I will explain how to obtain a local to global principle for expected values over free ℤ-modules of finite rank. We use the same philosophy as Ekedhal’s Sieve for densities, later extended and improved by Poonen and Stoll in their local...

The backtracking line-search is an effective technique to automatically tune the step-size in smooth optimization. It guarantees similar performance to using the theoretically optimal step-size. Many approaches have been developed to instead tune per...

Zero forcing is a type of graph propagation based on the color-change rule: Given graph $G$, if each vertex of $G$ is colored either white or blue, and vertex $v$ is a blue vertex with only one white neighbor $w$, then change the color of $w$ to blue...

I will try to present an overview of some results of unbalanced optimal transport for positive measures with different total masses, showing the crucial role of the so-called cone representation and of the corresponding homogeneous marginals. The...

The problem of finding minimizers of functions on graphs arises naturally in many different domains, for example, exponential random graphs and extremal combinatorics. In Euclidean setting, there are two widely used approaches for minimizing a given...