Counting points on reductions of CM abelian surfaces

Speaker: 

Nick Alexander

Institution: 

UCI

Time: 

Tuesday, May 18, 2010 - 2:00pm

Location: 

RH 306

We construct explicit genus 2 hyperelliptic curves whose Jacobian varieties have complex multiplication and are defined over an explicit algebraic number field. For these Jacobians, we give a formula for the number of points on their reductions modulo primes of good reduction. The construction and results can be viewed as a dimension 2 generalization of results of H. Stark. These formulas have application to cryptography and the CM method in dimension 2.

On Endoscopy Structures of Automorphic Forms

Speaker: 

Professor Dihua Jiang

Institution: 

University of Minnesota

Time: 

Tuesday, April 13, 2010 - 2:00pm

Location: 

RH 306

Endoscopy structures of automorphic forms was one of the
basic structures discovered through the Arthur-Selberg trace formula method to establish the Langlands functoriality for classical groups.

In this talk, we will discuss my recent work on characterization of the endoscopy structure in terms of the order of pole at s=1 of certain L-functions, and in terms of a family of periods of automorphic forms, which was discovered jointly with David Ginzburg. At the end, I may discuss how to contruct the
endoscopy transfer by integral operators, which is
a joint work with Ginzburg and Soudry.

Variables Separated Equations and Finite Simple Groups

Speaker: 

Professor Mike Fried

Institution: 

Montana State U-Billings, Emeritus UCI

Time: 

Tuesday, April 6, 2010 - 2:00pm

Location: 

RH 306

Variables Separated Equations and Finite Simple Groups: Davenport's
problem is to figure out the nature of two polynomials over a number
field having the same ranges on almost all residue class fields of the
number field. Solving this problem initiated the monodromy method.
That included two new tools: the B(ranch)C(ycle)L(emma) and the
Hurwitz monodromy group. By walking through Davenport's problem with
hindsight, variables separated equations let us simplify lessons on
using these tools. We attend to these general questions:
1. What allows us to produce branch cycles, and what was their effect
on the Genus 0 Problem (of Guralnick/Thompson)?
2. What is in the kernel of the Chow motive map, and how much is it
captured by using (algebraic) covers?
3. What groups arise in 'nature' (a 'la a paper by R. Solomon)?
Each phrase addresses formulating problems based on equations. We seem
to need explicit algebraic equations. Yet why, and how much do we lose/
gain in using more easily manipulated surrogates for them? To make
this clear we consider the difference in the result for Davenport's
Problem and that for its formulation over finite fields, using a
technique of R. Abhyankar.

On distribution of well-rounded lattices in the plane

Speaker: 

Professor Lenny Fukshansky

Institution: 

Claremont College

Time: 

Tuesday, March 2, 2010 - 2:00pm

Location: 

RH 306

A lattice of rank N is called well-rounded (abbreviated WR) if its minimal vectors span R^N. WR lattices are extremely important for discrete optimization problems. In this
talk, I will discuss the distribution of WR lattices in R^2, specifically concentrating
on WR sublattices of Z^2. Studying the structure of the set C of similarity classes of
these lattices, I will show that elements of C are in bijective correspondence with
certain ideals in Gaussian integers, and will construct an explicit parametrization of
lattices in each such similarity class by elements in the corresponding ideal. I will
then use this parameterization to investigate some basic analytic properties of zeta
function of WR sublattices of Z^2.

Some elliptic curves with large rank over $\bar{F_q}(t)$

Speaker: 

Tommy Occhipinti

Institution: 

University of Arizona

Time: 

Tuesday, February 2, 2010 - 2:00pm

Location: 

RH 306

It is a fascinating result of Ulmer that the elliptic curve y^2=x^4+x^3+t^d attains arbitrarily large rank over $\bar{F_q}(t)$ as d varies over the positive integers. In this talk we will provide some new examples of this phenomenon and provide an overview of previous work in this area, particularly that of Ulmer and Berger.

A Small Survey of Rigid Analytic Geometry and Further Directions

Speaker: 

Mr. Damek Davis

Institution: 

UCI

Time: 

Tuesday, January 26, 2010 - 2:00pm

Location: 

RH 306

We will discuss some of the local theory of rigid-analytic spaces including Tate's algebra, affinoid algebras, Washnitzer's algebra and dagger algebras. After we provide enough motivation we will discuss the results of research completed by myself and Professor Daqing Wan. The results of this research form a basis for generalizing Washnitzer's algebra.

De Rham Cohomology of Algebraic Varieties

Speaker: 

Chris Davis

Institution: 

Max Planck Institute

Time: 

Tuesday, January 5, 2010 - 2:00pm

Location: 

RH 306

To an algebraic variety over the complex numbers, we can associate a complex analytic space. When the result is a smooth complex manifold, we can compute its de Rham cohomology. I would like to discuss some ways to compute this cohomology directly from our algebraic variety, and how these methods can be adapted to more general varieties. None of the material I will present is original. The results are due to many people, especially Grothendieck.

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