Previous Conferences & Workshops

Nov
09
2020

Members’ Seminar

Some analogies between arithmetic and topology
2:00pm|Simonyi Hall 101 and Remote Access

There are striking analogies between topology and arithmetic algebraic geometry, which studies the behavior of solutions to polynomial equations in arithmetic rings. One expression of these analogies is through the theory of etale cohomology, which...

Nov
09
2020

Computer Science/Discrete Mathematics Seminar I

Associativity testing
Ben Green
11:15am|Simonyi Hall 101 and Remote Access - see Zoom link below

Suppose we have a cancellative binary associative operation * on a finite set X. We say that it is delta-associative if the proportion of triples x, y, z such that x*(y*z) = (x*y)*z is at least delta.

Gowers and Long studied somewhat associative...

Nov
06
2020

Workshop on Topology: Identifying Order in Complex Systems

Algebraic and topological models for DNA recombination
Nataša Jonoska
2:00pm|Remote Access Only

DNA rearrangement is observed at developmental and evolutionary scale. The recombination process can be directly modeled by 4-regular graphs and Gauss codes, also called double occurrence words. We discuss properties of these graphs, their spatial...

Nov
05
2020

Joint IAS/Princeton University Number Theory Seminar

Strong approximation for the Markoff equation via nonabelian level structures on elliptic curves
William Chen
4:30pm|Remote Access

Following Bourgain, Gamburd, and Sarnak, we say that the Markoff equation $x^2 + y^2 + z^2 - 3xyz = 0$ satisfies strong approximation at a prime $p$ if its integral points surject onto its $F_p$ points. In 2016, Bourgain, Gamburd, and Sarnak were...

Nov
04
2020

Mathematical Conversations

Three-term arithmetic progressions in sets of integers
Olof Sisask
5:30pm|Remote Access

It turns out that certain additive patterns in the integers are very hard to get rid of. An instance of this is captured in a conjecture of Erdős, which states that as long as a set of natural numbers is 'somewhat dense' -- namely the sum of the...

Nov
04
2020

Geometric and Modular Representation Theory Seminar

The Derived Geometric Satake Equivalence of Bezrukavnikov and Finkelberg
3:00pm|Simonyi Hall 101 and Remote Access

This is the last talk towards understanding Bezrukavnikov-Finkelberg's derived geometric Satake equivalence. With the preparations from previous talks, we will introduce two filtrations: a topological filtration on the equivariant cohomology and an...

Nov
04
2020

Stability and Testability

Stability and sofic approximations for product groups and property (tau)
Adrian Ioana
11:00am|Remote Access

A countable group $G$ is called sofic if it admits a sofic approximation: a sequence of asymptotically free almost actions on finite sets. Given a sofic group $G$, it is a natural problem to try to classify all its sofic approximations and, more...

Nov
03
2020

SL2 Seminar

Decomposition numbers in defining characteristic
4:00pm|Remote Access

The decomposition of the reduction of a Deligne--Lusztig character as a sum of Weyl modules is given by Jantzen's formula. In the case of $SL_2(F_q)$ the formula can be proved by a direct computation, and as a result we will see that the entries in...