##### Department of Mathematics,

University of California San Diego

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### Math 209 - Number Theory

## Jesse Wolfson

#### UC Irvine

## The Theory of Resolvent Degree - After Hamilton, Hilbert, Segre, and Brauer

##### Abstract:

Resolvent degree is an invariant of a branched cover which quantifies how ``hard'' is it to specify a point in the cover given a point under it in the base. Historically, this was applied to the branched cover $\mathbb{P}^n/S_{n-1}\to \mathbb{P}^n/S_n$, from the moduli of degree n polynomials with a specified root to the moduli of degree n polynomials. Classical enumerative problems and congruence subgroups provide two additional sources of branched covers to which this invariant applies. In ongoing joint work with Benson Farb, we develop the theory of resolvent degree as an extension of Buhler and Reichstein's theory of essential dimension. We apply this theory to systematize an array of classical results and to relate the complexity of seemingly different problems such as finding roots of polynomials, lines on cubic surfaces, and level structures on intermediate Jacobians.

Host: Kiran Kedlaya

### November 30, 2017

### 1:00 PM

### AP&M 7321

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