Department of

# Mathematics

Seminar Calendar
for events the day of Tuesday, February 25, 2020.

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events for the
events containing

Questions regarding events or the calendar should be directed to Tori Corkery.
     January 2020          February 2020            March 2020
Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa   Su Mo Tu We Th Fr Sa
1  2  3  4                      1    1  2  3  4  5  6  7
5  6  7  8  9 10 11    2  3  4  5  6  7  8    8  9 10 11 12 13 14
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Tuesday, February 25, 2020

11:00 am in 243 Altgeld Hall,Tuesday, February 25, 2020

#### \'Etale K-theory

###### Akhil Mathew (U Chicago)

Abstract: I will explain some general structural results about algebraic K-theory and its \'etale sheafification, in particular its approximation by Selmer K-theory. This is based on some recent advances in topological cyclic homology. Joint work with Dustin Clausen.

1:00 pm in 243 Altgeld Hall,Tuesday, February 25, 2020

#### Geometry of the Minimal Solutions of Linear Diophantine Equations

###### Papa A. Sissokho (Illinois State Univeristy)

Abstract: Let ${\bf a}=(a_1,\ldots,a_n)$ and ${\bf b}=(b_1,\ldots,b_m)$ be vectors with positive integer entries, and let $\mathcal{S}({\bf a},{\bf b})$ denote the set of all nonnegative solutions $({\bf x},{\bf y})$, where ${\bf x}=(x_1,\ldots,x_n)$ and ${\bf y}=(y_1,\ldots,y_m)$, of the linear Diophantine equation $x_1a_1+...+ x_na_n=y_1b_1+...+y_mb_m$. A solution is called minimal if it cannot be written as the sum of two nonzero solutions in $\mathcal{S}({\bf a},{\bf b})$. The set of all minimal solutions, denoted by $\mathcal{H}({\bf a},{\bf b})$, is called the Hilbert basis of $\mathcal{S}({\bf a},{\bf b})$. The solution ${\bf g}_{i,j}=(b_j{\bf e}_i,a_i{\bf e}_{n+j})$ of the above Diophantine equation, where ${\bf e}_k$ is the $k$th standard unit vector of $\mathbb{R}^{n+m}$, is called a generator. In this talk, we discuss a recent result which shows that every minimal solution in $\mathcal{H}({\bf a},{\bf b})$ is a convex combination of the generators and the zero-solution.

2:00 pm in 345 Altgeld Hall,Tuesday, February 25, 2020

#### Multiple SLE from a loop measure perspective

###### Vivian Healey (U Chicago Math)

Abstract: I will discuss the role of Brownian loop measure in the study of Schramm-Loewner evolution. This powerful perspective allows us to apply intuition from discrete models (in particular, the λ-SAW model) to the study of SLE while simultaneously reducing many SLE computations to problems of stochastic calculus. I will discuss recent work on multiple radial SLE that employs this method, including the construction of global multiple radial SLE and its links to locally independent SLE and Dyson Brownian motion. (Joint work with Gregory F. Lawler.)

4:00 pm in 245 Altgeld Hall,Tuesday, February 25, 2020

#### Counting

###### Frank Calegari (University of Chicago)

Abstract: What can one say about a system of polynomial equations with integer coefficients simply by counting the number of solutions to these equations modulo primes? We begin with the case of polynomials in one variable and relate this to how the polynomial factors and to Galois theory. We then discuss what happens in higher dimensions, and are led to a conjectural notion of the "Galois group" of an algebraic variety. This will be a colloquium style talk and will be independent of the first talk.