NTSGrad Spring 2022/Abstracts: Difference between revisions

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| bgcolor="#F0A0A0" align="center" style="font-size:125%" | ''' '''
| bgcolor="#F0A0A0" align="center" style="font-size:125%" | '''Jerry Yu Fu'''
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
| bgcolor="#BCD2EE"  align="center" | ''Canonical lifting and isogeny classes of Abelian varieties over finite field''
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| bgcolor="#BCD2EE"  | In his [https://people.math.wisc.edu/~ellenber/gradstudents.html notes for students], Jordan has a list of general topics and references in number theory/algebraic geometry/arithmetic geometry that students in arithmetic geometry should be comfortable with after a certain point of time. I will introduce some language used in these general topics for beginners.
| bgcolor="#BCD2EE"  | I will give a brief introduction from Serre-Tate's canonical lifting, the Grothendieck-Messing theory and their applications to class group and estimation of size of isogeny classes of certain type of abelian varieties over finite fields.
I will present some recently proved results by me and some with my collaborator.  
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
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| bgcolor="#BCD2EE"  | In this talk, I will go over the history of rational/integral points on curves. In particular, I will introduce a recent proof of the S-unit equation using p-adic period maps, given by Lawrence-Venkatesh.
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| bgcolor="#F0A0A0" align="center" style="font-size:125%" | ''' '''
| bgcolor="#F0A0A0" align="center" style="font-size:125%" | '''Di Chen'''
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
| bgcolor="#BCD2EE"  align="center" | ''A non-trivial bound on 5-torsion in class groups.''
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| bgcolor="#BCD2EE"  | I will discuss A. Shankar and J. Tsimerman’s recent work on a non-trivial bound on 5-torsion in class groups of imaginary quadratic fields. I focus on ideas of proofs and assume several black boxes without proofs. This is a good application of elliptic curves and Galois cohomology.
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| bgcolor="#F0A0A0" align="center" style="font-size:125%" | ''' '''
| bgcolor="#F0A0A0" align="center" style="font-size:125%" | '''John Yin'''
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
| bgcolor="#BCD2EE"  align="center" | ''Bertini Theorems over Finite Fields/Poonen Sieve''
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| bgcolor="#BCD2EE"  | Geometry over char p is fascinating or frustrating, depending on who you are. However varieties over char 0 could be enjoyed by geometers of all kinds. We will dicuss one way of lifting a smooth projective variety from char p to char 0. After applying our technique to curves we briefly mention the situation in higher dimensions. And if time permits, we discuss a non-liftable example by Serre.  
| bgcolor="#BCD2EE"  | Consider the question: What's the probability that a projective plane curve of degree d over F_q is smooth as d approaches infinity? Assuming some sort of independence, this should be something like the product over closed points in P^2 of the proportion of plane curves which are smooth at the closed point. A version of this turns out to be true, and it is proven through the Poonen Sieve.
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
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| bgcolor="#BCD2EE"  | I will introduce Euler's classical result over Q, Klingen-Siegel theorem over totally real number fields, and Zagier's theorems and conjectures over general number fields. I will give many examples and discuss their proofs. If time permits, I will discuss its relation with K-theory.
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
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| bgcolor="#BCD2EE"  | Diophantine approximation is a crucial tool in studying integral points and Schlickewei's theorem is a very useful theorem in proving finiteness theorems on integral points. In the first part of my talk I will show some elegant proof as applications of the subspace theorem such as Vojta's theorem, the S-unit equation, and then I will introduce main conjectures: Vojta, Mordell, Bombieri and Lang, and their relations to each other.
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| bgcolor="#F0A0A0" align="center" style="font-size:125%" | ''' '''
| bgcolor="#F0A0A0" align="center" style="font-size:125%" | '''Tejasi Bhatnagar'''
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
| bgcolor="#BCD2EE"  align="center" | ''The theorem of Honda and Tate''
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In this talk, we aim to understand the classification of abelian varieties over finite fields, up to isogeny. To every abelian variety, we can associate a certain algebraic number. This is called a Weil-q number. The Theorem of Honda and Tate tells us that, up to isogeny this association is a bijection. We won’t necessarily prove the entire theorem, but we will see bits and pieces to understand whatever we can and mostly try and get an understanding of the important objects that we’ll come across.
 
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| bgcolor="#F0A0A0" align="center" style="font-size:125%" | ''' '''
| bgcolor="#F0A0A0" align="center" style="font-size:125%" | '''Hyun Jong Kim'''
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
| bgcolor="#BCD2EE"  align="center" | ''Cohen-Lenstra for imaginary quadratic function fields''
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I will talk about local reciprocity, a correspondence of the Galois group of the maximal abelian extension and the multiplicative group. In particular, I will talk about Lubin-Tate theory which constructs this map.
A Cohen-Lenstra type statement is one which claims or states that certain objects are distributed inversely proportional to the size of their automorphism groups. Originally stated for class groups of quadratic number fields, Ellenberg, Venkatesh, and Westerland showed that an analogue for imaginary quadratic function fields over finite fields hold. I will introduce the Cohen-Lenstra heuristics for number fields and outline the proof to Ellenberg, Venkatesh, and Westerland's theorem.
 
 


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| bgcolor="#F0A0A0" align="center" style="font-size:125%" | ''' '''
| bgcolor="#F0A0A0" align="center" style="font-size:125%" | '''Qiao He'''
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
| bgcolor="#BCD2EE"  align="center" | ''Does rigid analytic varieties has Hodge symmetry?''
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| bgcolor="#BCD2EE"  | In this talk, we will walk through a simple example of counting quadratic extensions using the discriminant. Although, this has been done using classical methods, we will highlight the techniques used by Bhargava through our example, that were essentially used to count the higher degree cases.
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I will survey a paper by our last week’s speaker Alexander Petrov. It is well known that there is a symmetry between the Hodge numbers of a Kahler Manifold (in particular, projective variety). In the p-adic world, we have similar analytic space: rigid analytic variety. Then it is a natural question to ask whether the Hodge number of rigid analytic variety still has a symmetry. It turns out that the answer is no! I will try to explain how to construct a counterexample in the talk.




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| bgcolor="#BCD2EE"  align="center" | ''TBA''
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| bgcolor="#BCD2EE"  | Given a positive definite quadratic form X_1^2+...+X_n^2, a natural question to ask is can we find a formula for $r_n(m)=\#\{X\in Z^n| Q(X)=m\}$. Although no explicit formula for $r_n(m)$ is known in general, there do exist an average formula, which is a prototype of the so called Siegel-Weil formula. In this talk, I will introduce Siegel-Weil formula, and show how Deuring's mass formula for supersingular elliptic curve and Hurwitz class number formula follows from Siegel-Weil formula.
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| bgcolor="#BCD2EE"  align="center" | ''TBA''
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| bgcolor="#BCD2EE"  | I will motivate and introduce the definition of a height. Then, I will talk a bit about Arakelov height. This will then lead into a recent paper by Ellenberg, Satriano, and Zureick-Brown, which introduces a notion of height on stacks.
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Latest revision as of 18:21, 11 April 2022

This page contains the titles and abstracts for talks scheduled in the Spring 2022 semester. To go back to the main GNTS page, click here.


Jan 25

Jerry Yu Fu
Canonical lifting and isogeny classes of Abelian varieties over finite field
I will give a brief introduction from Serre-Tate's canonical lifting, the Grothendieck-Messing theory and their applications to class group and estimation of size of isogeny classes of certain type of abelian varieties over finite fields.

I will present some recently proved results by me and some with my collaborator.


Feb 1

TBA


Feb 8

Di Chen
A non-trivial bound on 5-torsion in class groups.
I will discuss A. Shankar and J. Tsimerman’s recent work on a non-trivial bound on 5-torsion in class groups of imaginary quadratic fields. I focus on ideas of proofs and assume several black boxes without proofs. This is a good application of elliptic curves and Galois cohomology.



Feb 15

John Yin
Bertini Theorems over Finite Fields/Poonen Sieve
Consider the question: What's the probability that a projective plane curve of degree d over F_q is smooth as d approaches infinity? Assuming some sort of independence, this should be something like the product over closed points in P^2 of the proportion of plane curves which are smooth at the closed point. A version of this turns out to be true, and it is proven through the Poonen Sieve.


Feb 25

TBA


Mar 1

TBA


Mar 8

TBA


Mar 15

TBA


Mar 22

TBA


Mar 29

Tejasi Bhatnagar
The theorem of Honda and Tate

In this talk, we aim to understand the classification of abelian varieties over finite fields, up to isogeny. To every abelian variety, we can associate a certain algebraic number. This is called a Weil-q number. The Theorem of Honda and Tate tells us that, up to isogeny this association is a bijection. We won’t necessarily prove the entire theorem, but we will see bits and pieces to understand whatever we can and mostly try and get an understanding of the important objects that we’ll come across.


Apr 5

Hyun Jong Kim
Cohen-Lenstra for imaginary quadratic function fields

A Cohen-Lenstra type statement is one which claims or states that certain objects are distributed inversely proportional to the size of their automorphism groups. Originally stated for class groups of quadratic number fields, Ellenberg, Venkatesh, and Westerland showed that an analogue for imaginary quadratic function fields over finite fields hold. I will introduce the Cohen-Lenstra heuristics for number fields and outline the proof to Ellenberg, Venkatesh, and Westerland's theorem.


Apr 12

Qiao He
Does rigid analytic varieties has Hodge symmetry?

I will survey a paper by our last week’s speaker Alexander Petrov. It is well known that there is a symmetry between the Hodge numbers of a Kahler Manifold (in particular, projective variety). In the p-adic world, we have similar analytic space: rigid analytic variety. Then it is a natural question to ask whether the Hodge number of rigid analytic variety still has a symmetry. It turns out that the answer is no! I will try to explain how to construct a counterexample in the talk.



Apr 19

TBA



Apr 26

TBA




May 3

Jerry Yu Fu
Canonical lifting and size of isogeny classes
I will give a brief review from Serre-Tate's canonical lifting theorem, the Grothendieck-Messing theory and their applications to class group and isogeny classes of certain type of abelian varieties over finite fields.

I will present some recently proved results by me and some with my collaborator.