Seminars and Colloquia by Series

A Journey of Balanced Separators: From Graph Minors to Induced Minors to Fat Minors

Series
Graph Theory Seminar
Time
Tuesday, December 8, 2026 - 15:45 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Hung Le – University of Massachusetts Amherst

Separator theorems are cornerstones of modern structural and algorithmic graph theory. Over the last few decades, researchers have developed various separator theorems for many different classes of graphs. The techniques underlying these results reveal deep and unexpected connections between different areas of math and computer science. In this talk, I will discuss a (biased) sample of a few separator theorems and sketch the techniques behind them.

Data-driven hyperbolic conservation laws

Series
Applied and Computational Mathematics Seminar
Time
Monday, November 30, 2026 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005 and https://gatech.zoom.us/j/94954654170
Speaker
Lu Zhang – Rice University –
Hyperbolic conservation laws are fundamental to modeling wave propagation, fluid dynamics, and collective behavior across science and engineering. Despite their universal importance, traditional numerical solvers rely on explicitly known flux functions and parameters, which are often unavailable in realistic scenarios where only trajectory or observation data are accessible. In this talk, I will discuss our recent work in data-driven approaches for learning hyperbolic conservation laws that preserve their intrinsic physical and mathematical structures. These developments combine principles from numerical analysis, partial differential equations, and machine learning to construct models that are both predictive and faithful to the underlying conservation and stability properties of the governing equations.

Random graph processes

Series
Atlanta Combinatorics Colloquium
Time
Friday, November 20, 2026 - 16:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Felix Joos – Heidelberg University –

Fix a graph or uniform hypergraph $F$ and consider the following simple 
process. Start with the complete (hyper)graph $K_n$ on $n$ vertices and 
repeatedly remove the edge set of a copy of $F$, chosen uniformly at 
random among all copies present at that time. Stop when no copy of $F$ 
is left. This is the $F$-removal process, and the key question is when 
it ends, that is, how many edges are left at the end.

This question has proven to be very hard. In 2015, Bohman, Frieze and 
Lubetzky famously proved that the triangle-removal process typically 
ends with $n^{3/2+o(1)}$ edges. Until now, the answer was not known for 
any other $F$.

We determine when the $F$-removal process ends for many choices of $F$. 
This includes cliques, where it confirms a well-known conjecture of 
Bennett and Bohman on the final number of edges. This is joint work with 
Kühn.

On the bow lemma and higher dimensional analogs.

Series
Dissertation Defense
Time
Thursday, November 19, 2026 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 168
Speaker
John Stavroulakis – Georgia Institute of Technology –

We discuss the bow lemma or Schur comparison theorem, and in particular its higher dimensional analogs. We first investigate isoperimetry under upper and lower curvature bounds, including the Cartan-Hadamard conjecture. We then discuss Fenchel's theorem for CAT(0) spaces and its higher dimensional versions concerning tight (hyper)surfaces in Cartan-Hadamard manifolds. We also develop a rigidity mechanism for flat hypersurfaces in Alexandrov ambient spaces, which is applied to completely characterize surfaces which optimize total Gauss curvature in 3-folds with upper or lower curvature bounds.

Teams link: https://teams.microsoft.com/meet/2172100941812051?p=0YimD0FGzxQfer6TrD

Alex Divoux, TBA

Series
Graph Theory Seminar
Time
Tuesday, November 17, 2026 - 15:45 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Alex Divoux – Princeton University

TBA

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