Minimal submanifolds in differential geometry

Speaker: 

Richard Schoen, Bass Professor of Humanities and Sciences

Institution: 

Stanford University

Time: 

Tuesday, March 12, 2013 - 2:00pm to 3:00pm

Location: 

RH 306

The theory of minimal surfaces arose historically from work of J. L. Lagrange and physical observations of J. Plateau almost 200 years ago. Rigorous mathematical theory was developed in the 20th century. In more recent times the theory has found important applications to diverse areas of geometry and relativity. In this talk, which is aimed at a general mathematical audience, we will introduce the subject and describe a few recent applications of the theory.

A Brief History of Interval Exchange Transformations

Speaker: 

Scott Northrup

Institution: 

UC Irvine

Time: 

Tuesday, March 12, 2013 - 1:00am to 2:00am

Location: 

RH 440R

Consider a permutation $\tau$ of the set $\{1,2,\dots,n,\}$.  If we divide the unit interval $[0,1)$ into $n$ half-open subintervals, we can consider the map $f$ which rearranges the subinterval according to the permutation $\tau$.  Such maps are called interval exchange transformations (IETs) and are the order preserving piecewise isometries of intervals, and preserve the Lebesgue measure.  IETs were first studied by Sinai in 1973, and then Keane in 1977, who showed that each minimal IET had a finite number of ergodic measures and conjectured that the Lebesgue measure was in fact the only ergodic invariant measure for such maps.  Much of the following research on IETs was based around proofs of this conjecture and will be discussed in the talk.

Using Mathematics to Design Cancer Vaccines

Abstract:  "How much?", "How often?", "Where?" The answers to these three
questions are crucial in the design of cancer vaccines: treatments designed
to trigger an improved immune response to an existing tumor.   Mathematical
models that describe tumor growth in tissue, the immune response, and the
administration of different therapies can suggest treatment strategies that
optimize treatment efficacy and minimize negative side-effects.  However,

Complete Kahler manifolds with nonnegative curvature: examples and related results

Speaker: 

Bo Yang

Institution: 

UC San Diego

Time: 

Tuesday, April 9, 2013 - 4:00pm

Location: 

RH 306

The uniformization conjecture states that any complete noncompact Kahler manifold with positive bisectional curvature is biholomorphic to C^n.  Perhaps one of reasons that the problem is difficult is lack of examples. Recently assuming U(n) symmetry Wu and Zheng gave a systematic construction on examples of such metrics,  we will talk about some related results.

A brief account of my life in academia

Speaker: 

Jiaping Wang

Institution: 

University of Minnesota

Time: 

Tuesday, April 23, 2013 - 12:00pm to 1:00pm

Location: 

NatSci2 1201

After quickly explaining my mathematical research, I will mention my current involvement in the Institute for Mathematics and its Applications and reminisce on my graduate study experience at UCI.

Hamiltonian Monte Carlo and Its Variations

Speaker: 

Babak Shababa

Institution: 

UCI

Time: 

Monday, March 11, 2013 - 3:00pm

Location: 

RH 306

Improving the efficiency of Markov Chain Monte Carlo algorithms is an active area of re-

search in statistics. I will start this talk by providing a brief overview of Hamiltonian Monte

Carlo (HMC), which improves the computational eciency of the Metropolis algorithm by

reducing its random walk behavior. This of course requires numerical simulation of Hamilto-

nian dynamics and costly evaluation of the gradient of the log density function. Next, I will

present our recent work on improving HMC by ``splitting" the Hamiltonian in a way that

allows much of the movement around the parameter space to be done at low computational

cost. I will then discuss Riemannian Manifold HMC (RMHMC), which further improves

HMC's performance by exploiting the geometric properties of the parameter space. The ge-

ometric integrator used for RMHMC however involves implicit equations that require costly

numerical analysis (e.g., fixed-point iteration). I will finish my talk by presenting our recent

work on developing an explicit geometric integrator that replaces the momentum variable in

RMHMC by velocity.

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