Seminars and Colloquia by Series

Hypergraph Turán Problems

Series
Graph Theory Seminar
Time
Tuesday, September 23, 2025 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Bernard LidickýIowa State University

Hypergraph Turán Problems became more approachable due to flag algebras. In this talk we will first focus on tight cycles without an edge. A tight $k$-cycle minus an edge $C_k^-$ is the 3-graph on the vertex set $[k]$, where any three consecutive vertices in the string $123...k1$ form an edge. We show that for every $k \geq 5$, k not divisible by $3$, the extremal density is $1/4$. Moreover, we determine the extremal graph up to $O(n)$ edge edits. The proof is based on flag algebra calculations.

Then we describe new developments in solving large semidefinite programs that allows for improving several other bounds on Turán densities.

This talk is based on joint work with Connor Mattes, Florian Pfender and Jan Volec.

Quantum invariants from linear algebra with diagrams

Series
Geometry Topology Seminar
Time
Monday, September 22, 2025 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Anup PoudelGeorgia Tech

We will look at various instances of how working with skeins (diagrams) provides a way to describe the existence of various topological quantum invariants that were originally described using representation theory. This provides a very simple description of these invariants. Along the way we will look at how to describe the algebraic data (ribbon categories) topologically and also how one could observe instances of certain dualities that exist between certain categories using these diagrams. 

MacPhersonians and Pseudocircle Arrangements

Series
Algebra Seminar
Time
Monday, September 22, 2025 - 13:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Michael DobbinsBinghamton University

Please Note: There will be a pre-seminar 10:55-11:15 in Skiles 005.

MacPhersonians are a combinatorial analog of real Grassmannians defined by oriented matroids.  A long standing conjecture says that each MacPhersonian is homotopy equivalent to the corresponding Grassmannian.  Pseudolinear Grassmannians are spaces of topological representations of oriented matroids, and these are each homotopy equivalent to the corresponding Grassmannian in rank 3.  I will present a good cover of the rank 3 pseudolinear Grassmannian with nerve complex isomorphic to the order complex of the corresponding MacPhersonian, confirming the conjecture in rank 3.

Central limit theorem for non-stationary random products of SL(2, R) matrices

Series
CDSNS Colloquium
Time
Friday, September 19, 2025 - 15:00 for 1 hour (actually 50 minutes)
Location
Skiles 311
Speaker
Grigorii MonakovUC Irvine

Please Note: Zoom link: https://gatech.zoom.us/j/91390791493?pwd=QnpaWHNEOHZTVXlZSXFkYTJ0b0Q0UT09

Consider a sequence of independent and identically distributed SL(2, R) matrices. There are several classical results by Le Page, Tutubalin, Benoist, Quint, and others that establish various forms of the central limit theorem for the products of such matrices. I will talk about a recent joint work with Anton Gorodetski and Victor Kleptsyn, where we generalize these results to the non-stationary case. Specifically, we prove that the properly shifted and normalized logarithm of the norm of a product of independent (but not necessarily identically distributed) SL(2, R) matrices converges to the standard normal distribution under natural assumptions. A key component of our proof is the regularity of the distribution of the unstable vector associated with these products.

Lectures on Kahler Geometry I

Series
Geometry Topology Working Seminar
Time
Friday, September 19, 2025 - 14:00 for 1.5 hours (actually 80 minutes)
Location
Skiles 006
Speaker
Randy Van WhyGeorgia Tech

This series will tie together algebraic, complex analytic, symplectic, and contact geometries together in one coherent story. This will be done via the study of a series of couplets from different fields of geometry:

Algebraic manifolds:
Affine and quasi-projective varieties (non-compact models)
Projective varieties (compact models)

Complex manifolds:
Stein manifolds
Stein compactifications

Symplectic manifolds:
Liouville/ Weinstein geometry
Compact Kahler manifolds 

Depending on how long it takes to discuss these items, I will also attempt to include discussions on:

• Biran-Giroux decompositions of symplectic manifolds • Boothby-Wang bundles and contact plumbings of these • Milnor's fibration theorem for isolated singularities and connections to open book decompositions and Lefschetz fibrations • Open questions and interesting avenues of research

Most of our discussion will, as a side effect, outline the topological structure behind Type IIA String theory (the "topological A-model") which requires a 6-dimensional Calabi-Yau (Kahler) background.

Volume Polynomials

Series
School of Mathematics Colloquium
Time
Friday, September 19, 2025 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
June HuhPrinceton University

Volume polynomials constitute a distinguished class of log-concave polynomials with remarkable analytic and combinatorial properties arising from convex bodies and projective varieties. I will introduce new entropy inequalities satisfied by volume polynomials, discuss applications to the combinatorics of algebraic matroids, introduce the new class of analytic matroids, and pose several open questions (based on joint with Lukas Grund, Mateusz Michalek, Henrik Süss, and Botong Wang).

Surfaces associated to zeros of automorphic L-functions

Series
Number Theory
Time
Wednesday, September 17, 2025 - 15:30 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Cruz CastilloUniversity of Illinois Urbana-Champaign

Assuming the Riemann Hypothesis, Montgomery established results concerning the pair correlation of zeros of the Riemann zeta function. Rudnick and Sarnak extended these results for all level correlations of automorphic $L$-functions. We discover surfaces associated with the zeros of automorphic $L$-functions. In the case of pair correlation, the surface displays Gaussian behavior. For triple correlation, these structures exhibit characteristics of the Laplace and Chi-squared distributions, revealing an unexpected phase transition. This is joint work with Debmalya Basakand Alexandru Zaharescu.

The Fox Trapezoidal Conjecture for Special Alternating Links

Series
Geometry Topology Student Seminar
Time
Wednesday, September 17, 2025 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Jake GuyneeGeorgia Tech

The Fox trapezoidal conjecture is a longstanding open problem about the coefficients of the Alexander polynomial of alternating links. In this talk, we will discuss recent work which settled this conjecture for “special alternating links”. The first tool is a graph theoretic model of the Alexander polynomial of an alternating link discovered by Crowell in 1959. The second is the theory of Lorentzian polynomials, developed by Brändén and Huh in 2019 and a key part of Huh’s Fields medal work. We will show how a version of Crowell’s model produces a refinement of the Alexander polynomial of special alternating links that is Lorentzian, from which the result follows quickly.

Geometric Maximal Operators and Probabilistic Methods

Series
Analysis Seminar
Time
Wednesday, September 17, 2025 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Blanca Radillo MurguíaBaylor University

We will present advances on the boundedness of geometric maximal operators, focusing on a recent result from joint work with Paul Hagelstein and Alex Stokolos, which employs probabilistic techniques in the construction of Kakeya-type sets. The material presented extends ideas of M. Bateman and N. Katz.

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