Wed, 28 Mar 2007
15:00
L3

Blurred exponentiation and the geometry of exponential fields

Jonathan Kirby
(UIC, Chicago)
Abstract
  I will discuss the proof that the exponential algebraic closure operator on the complex exponential field is isomorphic to the pregeometry which controls the "pseudoexponential" field.  
Wed, 28 Mar 2007
11:00
L3

From Polynomial Interpolation to the Complexity of Ideals

David Eisenbud, MSRI
(Berkeley)
Abstract

 

 

One natural question in interpolation theory is: given a finite set of points

in R^n, what is the least degree of polynomials on R^n needed to induce every

function from the points to R? It turns out that this "interpolation degree" is

closely related to a fundamental measure of complexity in algebraic geometry

called Castelnuovo-Mumford regularity. I'll explain these ideas a new

application to projections of varieties.

 

Mon, 26 Mar 2007
15:45
DH 3rd floor SR

From Ising 2D towards Mumford-Shah (joint work with Reda Messikh)

Professor Raphael Cerf
(Universite de Paris XI)
Abstract
  The talk will be self-contained and does not require specific knowledge on the Ising model. I will present the basic results concerning the Wulff crystal of the Ising model and I will study its behaviour near the critical point. Finally I will show how to apply these results to the problem of image segmentation.  
Thu, 15 Mar 2007

14:00 - 15:00
Rutherford Appleton Laboratory, nr Didcot

New developments in LAPACKJ and ScaLAPACK

Sven Hammarling
(Numerical Algorithms Group & University of Manchester)
Abstract

In this talk we shall be looking at recent and forthcoming developments in the widely used LAPACK and ScaLAPACK numerical linear algebra libraries.

Improvements include the following: Faster algorithms, better numerical methods, memory hierarchy optimizations, parallelism, and automatic performance tuning to accommodate new architectures; more accurate algorithms, and the use of extra precision; expanded functionality, including updating and downdating and new eigenproblems; putting more of LAPACK into ScaLAPACK; and improved ease of use with friendlier interfaces in multiple languages. To accomplish these goals we are also relying on better software engineering techniques and contributions from collaborators at many institutions.

After an overview, this talk will highlight new more accurate algorithms; faster algorithms, including those for pivoted Cholesky and updating of factorizations; and hybrid data formats.

This is joint work with Jim Demmel, Jack Dongarra and the LAPACK/ScaLAPACK team.

Fri, 09 Mar 2007
14:15
Dennis Sciama LT

TBA

Beatriz de Carlos
(Southampton)
Thu, 08 Mar 2007
16:30
DH Common Room

Analysis for the Nonlinear Electrolyte Wedge Problem

Joseph Fehribach
(Worcester Polytechnic Institute, USA)
Abstract

This talk will discuss recent work on 3-phase junctions (electrolyte wedges)

in porous electrodes, including nonlinear reaction kinetics. Recent work on

reaction route representations (Kirchoff graphs) will also be discussed.

Thu, 08 Mar 2007
16:15
Fisher Room of NAPL

TBA

John March-Russell
(Oxford)
Wed, 07 Mar 2007
12:00
Comlab

Team Meeting

Guest speaker Antonio Orlando
(Swansea)
Abstract

The modelling of the elastoplastic behaviour of single

crystals with infinite latent hardening leads to a nonconvex energy

density, whose minimization produces fine structures. The computation

of the quasiconvex envelope of the energy density involves the solution

of a global nonconvex optimization problem. Previous work based on a

brute-force global optimization algorithm faced huge numerical

difficulties due to the presence of clusters of local minima around the

global one. We present a different approach which exploits the structure

of the problem both to achieve a fundamental understanding on the

optimal microstructure and, in parallel, to design an efficient

numerical relaxation scheme.

This work has been carried out jointly with Carsten Carstensen

(Humboldt-Universitaet zu Berlin) and Sergio Conti (Universitaet

Duisburg-Essen)

Mon, 05 Mar 2007
14:15
DH 3rd floor SR

Pinning of a polymer in a random medium and interacting particle system.

Dr Vincent Beffara
(ENS Lyon)
Abstract
  We present a link between polymer pinning by a columnar defect in a random medium and a particular model of interacting particles on the line, related to polynuclear growth. While the question of whether an arbitrarily small intensity for the defect always results in pinning is still open, in a 'randomized' version of the model, which is closely related to the zero-temperature Glauber dynamics of the Ising model, we are able to obtain explicit results and a complete understanding of the process. This is joint work with Vladas Sidoravicius and Maria Eulalia Vares.  
Fri, 02 Mar 2007
16:30
L2

How model theory looks at Lie groups and Lie Algebra

Prof. Angus MacIntyre
(Queen Mary University, London)
Abstract
  Model theory typically looks at classical mathematical structures in novel ways. The guiding principle is to understand what relations are definable, and there are usually related questions of effectivity. In the case of Lie theory, there are two current lines of research, both of which I will describe, but with more emphasis on the first. The most advanced work concerns exponentials and logarithms, in both real and complex situations. To understand the definable relations, and to show various natural problems are decidable, one uses a mixture of analytic geometry with number-theoretic conjectures related to Schanuel's Conjecture. More recent work, not yet closely connected to the preceding, concerns the limit behaviour (model-theoretically), of finite -dimensional modules over semisimple Lie algebras, and here again, for decidability, one seems obliged to consider number-theoretic decision problems, around Siegel's Theorem.