DEPARTMENT OF MATHEMATICS
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The Aziz Lectures
Numerical Solution of Differential Equations

The Aziz Lectures are sponsored by Prof. A. Kadir Aziz. The purpose of the series is to bring distinguished mathematicians to the University of Maryland, College Park to give survey lectures on the numerical solution of differential equations.

Prof. Aziz received his Ph.D. from the University of Maryland, College Park in 1957. He was on the faculty of Georgetown University from 1956 to 1967, and has been on the faculty at the University of Maryland, Baltimore County since 1967. He is presently Professor Emeritus of Mathematics and Statistics at UMBC. Throughout his career Prof. Aziz has been an active member of the Numerical Analysis group at College Park.

The Aziz lecture is given at 3pm in the Math Colloquium Room (MTH 3206).

Usually the speaker gives a related talk in the Applied Math Colloquium on the previous day (Thursday at 3:30pm).

Aziz Lectures 2007

Nov. 16, 2007

Adaptive Approximation by Greedy Algorithms

Prof. Albert Cohen
Laboratoire Jacques-Louis Lions, Université Pierre et Marie Curie,
Paris, France

This talk will discuss computational algorithms that deal with the following general task: given a function f and a dictionary of functions D in a Hilbert space, extract a linear combination of N functions of D which approximates f at best. We shall review the convergence properties of existing algorithms. This work is motivated by applications as various as data compression, adaptive numerical simulation of PDE's, statistical learning theory.

May 4, 2007

Compressive Sampling

Prof. Emmanuel J. Candes
California Institute of Technology

One of the central tenets of signal processing is the Shannon/Nyquist sampling theory: the number of samples needed to reconstruct a signal without error is dictated by its bandwidth-the length of the shortest interval which contains the support of the spectrum of the signal under study. Very recently, an alternative sampling or sensing theory has emerged which goes against this conventional wisdom. This theory allows the faithful recovery of signals and images from what appear to be highly incomplete sets of data, i.e. from far fewer data bits than traditional methods use. Underlying this metholdology is a concrete protocol for sensing and compressing data simultaneously.

This talk will present the key mathematical ideas underlying this new sampling or sensing theory, and will survey some of the most important results. We will argue that this is a robust mathematical theory; not only is it possible to recover signals accurately from just an incomplete set of measurements, but it is also possible to do so when the measurements are unreliable and corrupted by noise. We will see that the reconstruction algorithms are very concrete, stable (in the sense that they degrade smoothly as the noise level increases) and practical; in fact, they only involve solving very simple convex optimization programs.

An interesting aspect of this theory is that it has bearings on some fields in the applied sciences and engineering such as statistics, information theory, coding theory, theoretical computer science, and others as well. If time allows, we will try to explain these connections via a few selected examples.

Aziz Lectures 2006

December 1, 2006

Imaging in random media

Prof. George C. Papanicolaou
Mathematics Department
Stanford University

I will present an overview of some recently developed methods for imaging with array and distributed sensors when the environment between the objects to be imaged and the sensors is complex and only partially known to the imager. This brings in modeling and analysis in random media, and the need for statistical algorithms that increase the computational complexity of imaging, which is done by backpropagating local correlations rather than traces (interferometry). I will illustrate the theory with applications from non-destructive testing and from other areas.

April 21, 2006

String integration of some MHD equations

Prof. Yann Brenier
Laboratoire Alexandre Dieudonné
Université de Nice-Sophia-Antipolis, France

We first review the link between strings and some Magnetohydrodynamics equations. Typical examples are the Born-Infeld system, the Chaplygin gas equations and the shallow water MHD model. They arise in Physics at very different (from subatomic to cosmologic) scales. These models can be exactly integrated in one space dimension by solving the 1D wave equation and using the d'Alembert formula. We show how an elementary "string integrator" can be used to solve these MHD equations through dimensional splitting. A good control of the energy conservation is needed due to the repeated use of Lagrangian to Eulerian grid projections. Numerical simulations in 1 and 2 dimensions will be shown.

February 3, 2006

Multiscale Analysis in Micromagnetics

Prof. Felix Otto
Institute for Applied Mathematics
University of Bonn, Germany

From the point of view of mathematics, micromagnetics is an ideal playground for a pattern forming system in m aterials science: There are abundant experiments on a wealth of visually attractive phenomena and there is a well-accepted continuum model.

In this talk, I will focus on two specific experimental pattern for thin film ferromagnetic elements. One pattern is a ground state, the other pattern is a metastable state. Starting point for our analysis is the micromagnetic model which has three length scales and thus many parameter regimes. For both pattern, we identify the appropriate paramater regime and rigorously derive a reduced model via Γ-convergence. We numerically simulate the reduced model and compare to experimental data.

This is joint work with A. DeSimone, R. V. Kohn, and S. Müller for the first part and with R. Cantero-Alvarez and J. Steiner for the second part.

Aziz Lectures 2005

December 9, 2005

Multiscale Modeling in Biosciences:
Ion Transport through Membranes

Prof. Willi Jäger
Institute for Applied Mathematics
University of Heidelberg, Germany

Aziz Lectures 2004

November 19, 2004

Electromagnetic imaging for small inhomogeneities

Prof. Michael Vogelius
Department of Mathematics, Rutgers University

May 7, 2004

Mathematical models for cell motion

Prof. Benoît Perthame
École Normale Supérieure, Paris

Aziz Lectures 2003

November 14, 2003

Multiscale Modeling and Computation of Flow in Heterogeneous Media

Prof. Tom Hou
Caltech

March 7, 2003

Mathematical and Numerical Modeling of the Cardiovascular System

Prof. Alfio Quarteroni
Politecnico di Milano, Milan, Italy, and
EPFL, Lausanne, Switzerland

Aziz Lectures 2002

Dec. 6, 2002

The regularity of minimizers in elasticity

Prof. John Ball
Department of Mathematics, Oxford

May 3, 2002

Multigrid: From Fourier to Gauss

Prof. Randolph E. Bank
Department of Mathematics, University of California at San Diego

Aziz Lectures 2001

Nov. 16, 2001

Mathematical Problems in Meteorology and Oceanography

Prof. Roger Temam
Institute for Scientific Computing and Applied Mathematics, Indiana University

April 23, 2001

Recent Approaches in the Treatment of Subgrid Scales

Prof. Franco Brezzi
Istituto di Analisi Numerica del CNR and Dipartimento di Matematica, Universita di Pavia, Italy

Aziz Lectures 2000

March 15, 2000

Time Stepping in Parabolic Problems - Approximation of Analytic Semigroups

Prof. Vidar Thomée
Dept. of Mathematics, Chalmers University of Technology and Göteborg University

Aziz Lectures 1999

December 10, 1999

Colliding Black Holes and Gravity Waves: A New Computational Challenge

Prof. Douglas N. Arnold
Dept. of Mathematics, Pennsylvania State University

September 24, 1999

A Priori and A Posteriori Error Estimates in Finite Element Approximation

Prof. Lars B. Wahlbin
Dept. of Mathematics, Cornell University

February 19, 1999

Mathematical Problems Related to the Reliability of Finite Element Analysis in Practice: When Can We Trust the Computational Results for Engineering Decisions

Prof. Ivo Babuska
University of Texas, Austin, Emeritus Professor at University of Maryland

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