## Seminars and Colloquia by Series

### TBA by Adrien Saumard

Series
Stochastics Seminar
Time
Thursday, April 6, 2023 - 15:30 for 1 hour (actually 50 minutes)
Location
ONLINE
Speaker
Adrien SaumardENSAI and CREST

### Journey to the Center of the Earth

Series
Colloquia
Time
Thursday, April 6, 2023 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Gunther UhlmannUniversity of Washington

We will consider the inverse problem of determining the sound
speed or index of refraction of a medium by measuring the travel times of
waves going through the medium. This problem arises in global seismology
in an attempt to determine the inner structure of the Earth by measuring
travel times of earthquakes. It also has several applications in optics
and medical imaging among others.

The problem can be recast as a geometric problem: Can one determine
the Riemannian metric of a Riemannian manifold with boundary by
measuring the distance function between boundary points? This is the
boundary rigidity problem.

We will also describe some recent results, joint with Plamen Stefanov
and Andras Vasy, on the partial data case, where you are making
measurements on a subset of the boundary.

### Combinatorial moment sequences

Series
Analysis Seminar
Time
Wednesday, April 5, 2023 - 14:00 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Natasha BlitvicQueen Mary University of London

We will look at a number of interesting examples — some proven, others merely conjectured — of Hamburger moment sequences in combinatorics. We will consider ways in which this positivity may be expected, for instance in different types of combinatorial statistics on perfect matchings that turn out to encode moments in noncommutative analogues of the classical Central Limit Theorem. We will also consider situations in which this positivity may be surprising, and where proving it would open up new approaches to a class of very hard open problems in combinatorics.

### Thresholds for edge colorings

Series
Graph Theory Seminar
Time
Tuesday, April 4, 2023 - 15:45 for 1 hour (actually 50 minutes)
Location
Skiles 005
Speaker
Vishesh JainUniversity of Illinois at Chicago

We show that if each edge of the complete bipartite graph $K_{n,n}$ is given a random list of $C(\log n)$ colors from $[n]$, then with high probability, there is a proper edge coloring where the color of each edge comes from the corresponding list. We also prove analogous results for Latin squares and Steiner triple systems. This resolves several related conjectures of Johansson, Luria-Simkin, Casselgren-Häggkvist, Simkin, and Kang-Kelly-Kühn-Methuku-Osthus. I will discuss some of the main ingredients which go into the proof: the Kahn-Kalai conjecture, absorption, and the Lovasz Local Lemma distribution. Based on joint work with Huy Tuan Pham.

### TBA by Ben Seeger

Series
PDE Seminar
Time
Tuesday, April 4, 2023 - 15:00 for 1 hour (actually 50 minutes)
Location
Skiles 006
Speaker
Ben SeegerUniversity of Texas at Austin

TBA

### TBD

Series
Algebra Seminar
Time
Monday, April 3, 2023 - 10:20 for 1.5 hours (actually 80 minutes)
Location
Skiles 005
Speaker
Thuy-Duong VuongStandford University

TBD

### TBA by Zachary Hamaker

Series
Combinatorics Seminar
Time
Friday, March 31, 2023 - 15:00 for 1 hour (actually 50 minutes)
Location
Skiles 249
Speaker
Zachary HamakerUniversity of Florida

TBA

### Stability for symmetric groups, and beyond

Series
Colloquia
Time
Friday, March 31, 2023 - 11:00 for 1 hour (actually 50 minutes)
Location
Skiles 249
Speaker
Weiqiang WangUniversity of Virginia

Please Note: Special date and special room

We shall explain a simple remarkable stability phenomenon regarding the centers of the group algebras of the symmetric groups in n letters, as n goes to infinity. The same type of stability phenomenon extends to a wide class of finite groups including wreath products and finite general linear groups. Such stability has connections and applications to the cohomology rings of Hilbert schemes of n points on algebraic surfaces.