Thu, 26 Jan 2017

14:00 - 15:00
L5

New challenges in the numerical solution of large-scale inverse problems

Dr Silvia Gazzola
(University of Bath)
Abstract

Inverse problems are ubiquitous in many areas of Science and Engineering and, once discretised, they lead to ill-conditioned linear systems, often of huge dimensions: regularisation consists in replacing the original system by a nearby problem with better numerical properties, in order to find meaningful approximations of its solution. In this talk we will explore the regularisation properties of many iterative methods based on Krylov subspaces. After surveying some basic methods such as CGLS and GMRES, innovative approaches based on flexible variants of CGLS and GMRES will be presented, in order to efficiently enforce nonnegativity and sparsity into the solution.

Mon, 07 Nov 2016

16:00 - 17:00
L4

Equilibrium measure for a nonlocal dislocation energy

Lucia Scardia
(University of Bath)
Abstract

In this talk I will present a recent result on the characterisation of the equilibrium measure for a nonlocal and non-radial energy arising as the Gamma-limit of discrete interacting dislocations.

Fri, 29 Apr 2016

16:00 - 17:00
L1

InFoMM CDT Annual Lecture

Professor Chris Budd
(University of Bath)
Abstract

Some models for climate change, the good the bad and the ugly

Modelling climate presents huge challenges for mathematicians and scientists, and has a large effect on policy makers.  Climate models themselves vary from simple to complex with a huge range in between.  But how good and/or reliable are they?

In this talk I will describe some of the various mathematical models of climate that are both used to understand past climate and also to predict future climate.  I will also try to show that an understanding of non-smooth effects in dynamical systems can give us useful insights into the behaviour and analysis of these models.

Thu, 19 May 2016

14:00 - 15:00
L5

Computing defective eigenpairs in parameter-dependent eigenproblems

Dr. Melina Freitag
(University of Bath)
Abstract

The requirement to compute Jordan blocks for multiple eigenvalues arises in a number of physical problems, for example panel flutter problems in aerodynamical stability, the stability of electrical power systems, and in quantum mechanics. We introduce a general method for computing a 2-dimensional Jordan block in a parameter-dependent matrix eigenvalue problem based on the so called Implicit Determinant Method. This is joint work with Alastair Spence (Bath).

Mon, 08 Feb 2016

16:00 - 17:00
L4

Pseudo-differential operators on Lie groups

Veronique Fischer
(University of Bath)
Abstract
In this talk, I will present some recent developments in the theory of pseudo-differential operators on Lie groups. First I will discuss why `reasonable' Lie groups are the interesting manifolds where one can develop global symbolic pseudo-differential calculi. I will also give a brief overview of the analysis in the context of Lie groups. I will conclude with some recent works developing pseudo-differential calculi on certain classes of Lie groups.
Thu, 05 Feb 2015

17:30 - 18:30
L6

Triangulation of definable monotone families of compact sets

Nicolai Vorobjov
(University of Bath)
Abstract

Let $K\subset {\mathbb R}$ be a compact definable set in an o-minimal structure over $\mathbb R$, e.g. a semi-algebraic or a real analytic set. A definable family $\{S_\delta\ |  0<\delta\in{\mathbb R}\}$ of compact subsets of $K$, is called a monotone family if $S_\delta\subset S_\eta$ for all sufficiently small $\delta>\eta>0$. The main result in the talk is that when $\dim K=2$ or $\dim K=n=3$ there exists a definable triangulation of $K$ such that for each (open) simplex $\Lambda$ of the triangulation and each small enough $\delta>0$, the intersections $S_\delta\cap\Lambda$ is equivalent to one of five (respectively, nine) standard families in the standard simplex (the equivalence relation and a standard family will be formally defined). As a consequence, we prove the two-dimensional case of the topological conjecture on approximation of definable sets by compact families.

This is joint work with Andrei Gabrielov (Purdue).

Thu, 04 Dec 2014

14:00 - 15:00
L5

Is the Helmholtz equation really sign-indefinite?

Dr Euan Spence
(University of Bath)
Abstract

The usual variational formulations of the Helmholtz equation are sign-indefinite (i.e. not coercive). In this talk, I will argue that this indefiniteness is not an inherent feature of the Helmholtz equation itself, only of its standard formulations. I will do this by presenting new sign-definite formulations of several Helmholtz boundary value problems.

This is joint work with Andrea Moiola (Reading).
 

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