Noether-Lefschetz Theory and Geometric Methods in Commutative Algebra

Speaker: 

John Brevik

Institution: 

CalState - Long Beach

Time: 

Thursday, November 17, 2011 - 2:00pm

Location: 

RH 440R

The classical Noether-Lefschets Theorem states that for a sufficiently general surface S in P^3 the only algebraic curves lying on S are the complete intersections. In 2010 we proved an extension of this result to surfaces (and higher dimensional hypersurfaces in P^n) containing a fixed base locus. I will discuss this result and the describe how it can be applied together with tools from complex geometry and formal power series, to the study of class groups of local rings, in particular how they vary within an analytic isomorphism class. Among other things, we prove that any hypersurface singularity is analytically isomorphic to one whose local ring is a UFD and give a complete classification of the possible class groups for rational double point surface singularities.

Global Springer theory

Speaker: 

Michael Skirvin

Institution: 

Northwestern University

Time: 

Thursday, November 10, 2011 - 2:00pm

Location: 

RH 440R

Springer theory is a branch of geometric representation theory revolving around objects such as the nilpotent cone, flag variety, and Weyl group, and which received significant study in the 70's and 80's. We will give a brief review of Springer theory, while emphasizing parallels between the adjoint quotient map of Lie theory and the Hitchin fibration. We will then explain a "global" version of Springer theory in the context of the Hitchin fibration and global nilpotent cone, and discuss a recent construction of a resolution of singularities of the global nilpotent cone in the case of SL_2. Whatever time remains will be spent discussing conjectures on how to move forward from here.

Fish and Dipoles

Speaker: 

Eva Kanso

Institution: 

USC

Time: 

Monday, January 23, 2012 - 4:00pm

Location: 

RH 306

I will present low-order models for fluid-structure interactions in fish locomotion and comment on both active (controlled) and passive (open-loop) dynamics and stability. I will also discuss a finite dipole model. The motivation for the latter is to develop scalable models for fish schooling that account for the role of hydrodynamic coupling among the fish in a school. The finite dipole model exhibits interesting dynamics. I conclude by commenting on the advantages and limitations of such low-order modeling approach.

A universality in the regular-to-chaos transition in rough quantum billiards.

Speaker: 

Maxim Olshanii

Institution: 

UMass Boston

Time: 

Thursday, October 27, 2011 - 2:00pm

Location: 

RH 440R

We demonstarte that in rough quantum billiards, the memory of the initial conditions is governed by a single universal energy-dependent parameter---one of the inverse participation ratios---that governs all functions of the to-be-destroyed integrals of motion as observables and all eigenstates of the to-be-perturbed integrable system as the initial states

Disorder chaos in the Sherrington-Kirkpatrick model with external field.

Speaker: 

Wei-Kuo Chen

Institution: 

UCI

Time: 

Thursday, November 3, 2011 - 2:00pm

Location: 

RH 306

In physics, the main objective in spin glasses is to understand
the strange magnetic properties of alloys.
Yet the models invented to explain the observed phenomena are of a rather
fundamental nature in mathematics. In this talk, we will focus on one of the most important mean field
models,
called the Sherrington-Kirkpatrick model,
and discuss its disorder chaos problem. Using Guerra's replica
symmetric-breaking bound, we present a mathematically rigorous proof for this problem.

The Shoenfield tree.

Speaker: 

Geoff Galgon and Garrett Ervin

Institution: 

UCI

Time: 

Monday, October 31, 2011 - 4:00pm

Location: 

RH 440R

Given a lightface $\Sigma^1_2$ set of reals A we present the construction of a tree on $\omega\times\omega_1$ such that A is the projection of T. Moreover, the tree T is an element of any transitive model of ZF-PowerSetAxiom that has $\omega_1$ as element.

Local well-posedness for a fluid-structure interaction model

Speaker: 

Igor Kukavica

Institution: 

University of Southern California

Time: 

Thursday, January 26, 2012 - 3:00pm

Location: 

RH 306

In the talk we address a system of PDEs describing an
interaction between an incompressible fluid and an elastic
body. The fluid motion is modeled by the Navier-Stokes
equations while an elastic body evolves according to an
linear elasticity equation. On the common boundary, the
velocities and stresses are matched. We discuss available
results on local well-posedness and prove new existence and
uniqueness results with the velocity and the displacement
belonging to low regularity spaces.

The results are joint with A. Tuffaha.

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