Forthcoming Seminars

Tue, 24/02/2009
12:00 		Jose Maciel Natario (Lisboa) Relativity Seminar Add to calendar L3
Asymptotic Quasinormal Frequencies for d-Dimensional Black Holes
I will explain what quasinormal modes are and how to obtain asymptotic formulae for the quasinormal frequencies of static, spherically symmetric black hole spacetimes in d dimensions in the limit of very large imaginary part.
Tue, 24/02/2009
14:30 		Peter Cameron (QMUL) Combinatorial Theory Seminar Add to calendar L3
Synchronization and homomorphisms
A graph homomorphism is a mapping of vertices which takes edges to edges. The endomorphisms of a graph (homomorphisms to itself) form a submonoid of he full transformation monoid on the vertex set. In the other direction, there is a construction of a graph from a transformation monoid, which will be described in the talk. Composing these maps gives closure operators on graphs and on monoids which have some interesting properties. There are also connections with finite automata and permutation groups.
Tue, 24/02/2009
17:00 		Gus Lehrer (University of Sydney) Algebra Seminar Add to calendar L2
Endomorphisms of tensor space and cellular algebras
I shall show how cellularity may be used to obtain presentations of the endomorphism algebras in question, both in the classical and quantum cases.
Thu, 26/02/2009
11:00 		Dr Geoff Nicholls (Statistics Department) Applied Dynamical Systems and Inverse Problems Seminar Add to calendar DH 3rd floor SR
What is the use of Markov Chain Monte Carlo?
Thu, 26/02/2009
12:00 		Dusa McDuff (Columbia) Geometry and Analysis Seminar Add to calendar L3
Some 6-dimensional Hamiltonian S^1-manifolds
Thu, 26/02/2009
12:30 		Frédéric de Gournay (Université Versailles-Saint-Quentin) OxPDE Lunchtime Seminar Add to calendar Gibson 1st Floor SR
Robust shape optimization via the level-set method
We are interested in optimizing the compliance of an elastic structure when the applied forces are partially unknown or submitted to perturbations, the so-called "robust compliance". For linear elasticity,the compliance is a solution to a minimizing problem of the energy. The robust compliance is then a min-max, the minimum beeing taken amongst the possible displacements and the maximum amongst the perturbations. We show that this problem is well-posed and easy to compute. We then show that the problem is relatively easy to differentiate with respect to the domain and to compute the steepest direction of descent. The levelset algorithm is then applied and many examples will explain the different mathematical and technical difficulties one faces when one tries to tackle this problem.
Thu, 26/02/2009
14:00 		Dr Richard Katz (Department of Earth Sciences, University of Oxford) Computational Mathematics and Applications Add to calendar Comlab
Golden syrup, lubrication theory, and PETSc – a recipe for models of ice-sheet dynamics
Thu, 26/02/2009
14:30 		Rolf Farnsteiner (Universität Kiel) Representation Theory Seminar Add to calendar L3
Jordan Types of Indecomposable Modules
Thu, 26/02/2009
16:30 		Oliver Jensen (Nottingham) Differential Equations and Applications Seminar Add to calendar DH 1st floor SR
Instabilities of flows through deformable tubes and channels
I will provide an overview of theoretical models aimed at understanding how self-excited oscillations arise when flow is driven through a finite-length flexible tube or channel. This problem is approached using a hierarchy of models, from one to three spatial dimensions, combining both computational and asymptotic techniques. I will explain how recent work is starting to shed light on the relationship between local and global instabilities, energy balances and the role of intrinsic hydrodynamic instabilities. This is collaborative work with Peter Stewart, Robert Whittaker, Jonathan Boyle, Matthias Heil and Sarah Waters.
Fri, 27/02/2009
10:00 		Ken Peach (John Adams Institute for Accelerator Science) Industrial and Interdisciplinary Workshops Add to calendar DH 1st floor SR
Curing Cancer with accelerators
About a third of us will have a cancer during our lives, and we all know someone with the disease. Despite enormous progress in recent years, so that being diagnosed with cancer is not the death sentence that it once was, treatment can be aggressive, leading to short and long term reductions in quality of life. Cancer and its treatment is still feared, and rightly so - it is a major health concern. Destroying cancer non-invasively using protons or charged light ions such as carbon (Particle Therapy Cancer Research or PTCR) offers advantages over conventional radiotherapy using x-rays, since far lower radiation dose is delivered to healthy normal tissues. PT is also an alternative to radical cancer surgery. Most radiotherapy uses a small electron linear accelerator to accelerate an electron beams to a few million volts and then to generate hard x-rays, whereas CPT uses cyclotrons or synchrotrons to accelerate protons to a few hundred million volts, which themselves sterilise the tumour. More recently, a new concept in accelerators – the “non-scaling Fixed Field Alternating Gradient” accelerator – has been advanced, which offers the prospect of developing relatively compact, high acceleration rate accelerators for a variety of purposes, from neutrino factories and muon acceleration to cancer therapy. However, there are formidable technical challenges to be overcome, including resonance crossing. We have recently been awarded funding in the UK to construct a demonstrator non-scaling FFAG at the Daresbury laboratory (EMMA, the Electron Model with Many Applications), and to design a prototype machine for proton and carbon ion cancer therapy (PAMELA, the Particle Accelerator for MEdicaL Applications). I will describe some of the motivations for developing this new type of accelerator. Finally, although the physics of CPT says that it should be qualitatively and quantitatively better than conventional radiotherapy, the robust clinical analyses (for example, randomised control trials) have not been done, and the meta-analyses seem to suffer from large sample biases. The Particle Therapy Cancer Research Institute (part of the James Martin 21st Century School in Oxford) will study the clinical effectiveness of charged particle therapy to treat cancer, promoting its use in the UK and elsewhere on the basis of robust clinical evidence and analysis.
Fri, 27/02/2009
14:15 		Mark Owen (Heriot-Watt University, Edinburgh) Nomura Seminar Add to calendar DH 1st floor SR
Multivariate utility maximization with proportional transaction costs
My talk will be about optimal investment in Kabanov's model of currency exchange with transaction costs. The model is general enough to allow a random, discontinuous bid-offer spread. The investor wishes to maximize their "direct" utility of consumption, which is measured in terms of consumption assets linked to some (but not necessarily all) of the traded currencies. The analysis will centre on two conditions under which the existence of a dual minimiser leads to the existence of an optimal terminal wealth. The first condition is a well known, but rather unintuitive, condition on the utility function. The second weaker, and more natural condition is that of "asymptotic satiability" of the value function. We show that the portfolio optimization problem can be reformulated in terms of maximization of a terminal liquidation utility function, and that both problems have a common optimizer. This is joint work with Luciano Campi.
Fri, 27/02/2009
14:30 		Prof. Neil Crout (University of Nottingham.) Mathematical Geoscience Seminar Add to calendar DH 3rd floor SR
Testing the formulation of biological and environmental models.
Fri, 27/02/2009
15:15 		Alexandru Aleman (NBFAS Meeting) (Lund) Functional Analysis Seminar Add to calendar L3
Nearly Invariant Spaces of Analytic Functions
We consider Hilbert spaces $ H $ which consist of analytic functions in a domain $ \Omega\subset\mathbb{C} $ and have the property that any zero of an element of $ H $ which is not a common zero of the whole space, can be divided out without leaving $ H $. This property is called near invariance and is related to a number of interesting problems that connect complex analysis and operator theory. The concept probably appeared first in L. de Branges' work on Hilbert spaces of entire functions and played later a decisive role in the description of invariant subspaces of the shift operator on Hardy spaces over multiply connected domains. There are a number of structure theorems for nearly invariant spaces obtained by de Branges, Hitt and Sarason, and more recently by Feldman, Ross and myself, but the emphasis of my talk will be on some applications; the study of differentiation invariant subspaces of $ C^\infty(\mathbb{R}) $, or invariant subspaces of Volterra operators on spaces of power series on the unit disc. Finally, we discuss near invariance in the vector-valued case and show how it can be related to kernels of products of Toeplitz operators. More precisely, I will present in more detail the solution of the following problem: If a finite product of Toeplitz operators is the zero operator then one of the factors is zero.
Fri, 27/02/2009
16:30 		Lennart Hilbert (University of Oxford) Junior Applied Mathematics Seminar Add to calendar DH 3rd floor SR
Numerical treatment of Brownian Molecular Motors or "I beat you till you talk!"
Brownian Molecular Motors are crucial for cell motility, muscle contraction or any other mechanical task carried out by proteins. After a short introduction to protein motors, I will talk about a numerical appraoch I worked on during the last months, which should enable us to deduct properties for a broad range of protein motors. A special focus should lie on the calculation of the eigenvalue spectrum, which gives insight to motors' stability.
Fri, 27/02/2009
16:45 		Alexandru Aleman (NBFAS Meeting) Functional Analysis Seminar Add to calendar L3
Nearly Invariant Spaces of Analytic Functions (cont)
Sat, 28/02/2009
10:00 		Ralph Chill (NBFAS Meeting) (Metz) Functional Analysis Seminar Add to calendar L3
Regularity of functions, and the norm-continuity problem for semigroups
It is a fundamental problem in harmonic analysis to deduce regularity or asymptotic properties of a bounded, vector-valued function, defined on a half-line, from properties of its Laplace transform. In the first part of this talk, we will study how the analytic extendability of the Laplace transform to certain large domains, and the boundedness therein, (almost) characterizes regularity properties like analyticity and differentiability of the original function. We will also see that it is not clear how to characterize continuity in this way; naive counterparts/generalizations of the results which hold for analyticity and differentiability admit easy counterexamples. Characterizing continuity becomes not easier, if one considers bounded, strongly continuous semigroups: it was a longstanding open problem whether the decay to zero of the resolvent of the generator along vertical lines characterizes immediate norm-continuity of the semigroup with respect to the operator-norm. After several affirmative results in Hilbert space and for positive semigroups on $ L^p $ spaces, a negative answer to this question was recently given by Tamas Matrai. In the second part of this talk, we will give some counterexamples which are conceptually different to the one given by Matrai. In fact, we will present a new method of constructing semigroups, by considering operators and algebra homomorphisms on $ L^1 $ with specific properties. Our examples rule out the possibility of characterizing norm-continuity of semigroups on arbitrary Banach spaces in terms of resolvent-norm decay on vertical lines.

For any corrections/updates to these listings, please contact seminars [-at-] maths [dot] ox [dot] ac [dot] uk.

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