NTSGrad Spring 2021/Abstracts

This page contains the titles and abstracts for talks scheduled in the Spring 2021 semester. To go back to the main GNTS page, click here.

Jan 26

Eiki Norizuki

$p$-adic groups and their representations

This will be a prep talk for Thursday's NTS talk. We will talk about subgroups and decompositions of $p$-adic groups as well as the Bruhat-Tits tree of $\text{SL}_2$. We try to understand the right class of representations for $p$-adic groups which turn out to be smooth admissible representations.

Feb 2

Qiao He

Supersingular locus of Unitary Shimura variety

I will give a summary of supersingular locus of Unitary Shimura variety. This description is really the first and an important step to understand the structure of Unitary Shimura variety. Turns out that the description of such locus will boil down to certain linear algebra. The final result will be the supersingular locus have a stratification, and the incidence relation will be closely related with the Bruhat-Tits building of unitary group. Also, each strata is closely related with affine Deligne Lustig variety. The Dieudonne module theory will be summarized. Take it for granted, all the remaining material can follow easily!

Feb 9

Ivan Aidun

Simple Sieving

The idea of sieving out primes is among the oldest in mathematics. However, it has proven incredibly fruitful, and now sieve techniques lie behind some of the most striking results in modern number theory, such as the results of Zhang, Maynard, and the Polymath project on bounded gaps between primes. In this talk, I will develop some of the basic sieve constructions, from Eratosthenes and Legendre to Brun, and hint at some of the developments that lie beyond. This talk will be accessible to a general mathematical audience.

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Feb 16

Asvin G

F_un with F_1

You have probably heard of a field with one element in various places and might have been, very understandably, confused. How can there be a field with one element and even if there is, how could it possible be interesting? I will try and explain the philosophy behind why this is a reasonable thing to wish for and various mathematical facts that *should* be interpreted through this lens. The talk will just be a bunch of examples of the various manifestations of the field with one element throughout mathematics!

Feb 23

Yu Fu

CM liftings of Abelian Varieties

This will be a introductory talk to introduce the CM liftings of Abelian Varieties. Honda-Tate theory tells us every abelian variety over a finite field can be lifted to an abelian variety with smCM in characteristic 0. There are various lifting problems if you drop/change some of the conditions, i.e. Is it an isogeny or residue class field extension necessary? Can we lift any abelian variety over a finite field to a normal domain up to isogeny? Etc.etc. Let's explore with some fun examples!

Mar 2

Will Hardt

Linear Relations Among Galois Conjugates

In 1986, Smyth asked, and conjectured an answer to, the question of what can be the coefficients of a linear relation among Galois conjugates over Q. That is, for which (a_1,...,a_n) in Z^n do there exist Galois conjugates \gamma_1, ..., \gamma_n such that \sum_{i=1}^n a_i \gamma_i = 0? I will talk about joint work with John Yin in which we answer the analogous question over the function field F_q(t). We also formulate what we think is the right generalization of Smyth's Conjecture over a general number field.

Mar 9

Di Chen

Negative Pell Equations

I will review negative Pell equations and introduce Stevenhagen’s conjecture briefly. Then I discuss its relation with 2^k-rank of class groups and introduce basic tools like genus theory, Artin pairing, Redei matrices and Redei reciprocity.

Mar 16

Hyun Jong Kim

Comparison of A1-degrees

I recently talked about the Grothendieck-Witt ring and some A1-enriched enumerations, such as degrees, during my specialty exam. I will go into some more detail on when and how some of A1-enumerations, such as Morel's A1 Brouwer degree, the local A^1 Brouwer degree, the enriched Euler number and the A1-degree of maps of more general maps of schemes, are defined.

Mar 23

Asvin Gothandaraman

Computational number theory

I will talk about computational number theory. It will all be pretty elementary and I will cover topics like how to factor integers quickly using number fields or elliptic curves and some related topics.

Mar 30

Ruofan Jiang

Galois theory over k(x)

When k=C, this is the very classical theory of Riemann surface; for other k, especially when k is char p, the Galois theory of k(x) becomes much wilder. One way to study it is via rigid geometry, which enable us to talk about “analytical patching” in a much general context....

Apr 6

Ruofan Jiang

Hecke algebras for p-adic groups

Given a smooth representation of some p-adic group, we can associate it with modules over Hecke algebras. We will introduce the Satake transform which identifies the spherical Hecke algebra of a reductive group w.r.t a special maximal compact subgroup with a commutative ring of Weyl group invariants. The Satake isomorphism can help us understand spherical representations.