Forthcoming Seminars

Tue, 10/03/2009
15:45 		Ian Grojnowksi (Cambridge) Algebraic and Symplectic Geometry Seminar Add to calendar L3
Almost local difference operators
Tue, 10/03/2009
17:00 		Gunter Malle (University of Kaiserslautern) Algebra Seminar Add to calendar L2
On the number of conjugacy classes of a finite group
We classify certain linear representations of finite groups with a large orbit. This is motivated by a question on the number of conjugacy classes of a finite group.
Wed, 11/03/2009
11:30 		George Raptis (University of Oxford) Algebra Kinderseminar Add to calendar
A Categorical Galois Theorem (Held in ChCh Tom Gate, Room 2)
Wed, 11/03/2009
13:00 		François Genoud (OxPDE, University of Oxford) OxPDE Lunchtime Seminar Add to calendar Gibson 1st Floor SR
Bifurcation and orbital stability of standing waves for some nonlinear Schrödinger equations
The aim of my talk is to present the work of my PhD Thesis and my current research. It is concerned with local/global bifurcation of standing wave solutions to some nonlinear Schrödinger equations in $ \mathbb{R}^N \ (N\geq1) $ and with stability properties of these solutions. The equations considered have a nonlinearity of the form $ V(x)|\psi|^{p-1}\psi $, where $ V:\mathbb{R}^N\to\mathbb{R} $ decays at infinity and is subject to various assumptions. In particular, $ V $ could be singular at the origin. Local/global smooth branches of solutions are obtained for the stationary equation by combining variational techniques and the implicit function theorem. The orbital stability of the corresponding standing waves is studied by means of the abstract theory of Grillakis, Shatah and Strauss.
Wed, 11/03/2009
14:15 		Paul Glasserman (Columbia) Nomura Seminar Add to calendar Oxford-Man Institute
Risk Horizon and Rebalancing Horizon
We analyze the impact of portfolio rebalancing frequency on the measurement of risk over a moderately long horizon. This problem arises from an incremental capital charge recently proposed by the Basel Committee on Banking Supervision. The new risk measure calculates VaR over a one-year horizon at a high confidence level and assigns different rebalancing frequencies to different types of assets to capture potential illiquidity. We analyze the difference between discretely and continuously rebalanced portfolios in a simple model of asset dynamics by examining the limit as the rebalancing frequency increases. This leads to alternative approximations at moderate and extreme loss levels. We also show how to incorporate multiple scales of rebalancing frequency in the analysis
Thu, 12/03/2009
09:00 		Benson Muite and Yichao Zhu (Oxford) OxMOS Workshop/Meeting/Lecture Add to calendar Gibson 1st Floor SR
OxMOS Team Meeting
Thu, 12/03/2009
11:00 		Prof. Chris Farmer (OCIAM & Schlumberger Abingdon Technology Centre, Oxford) Applied Dynamical Systems and Inverse Problems Seminar Add to calendar DH 3rd floor SR
Optimal control and data assimilation: principles and approximations
Thu, 12/03/2009
12:00 		Ben Davison (Oxford) Junior Geometry and Topology Seminar Add to calendar SR1
Counting invariants and wall crossing
This talk concerns the relationships between Donaldson-Thomas, Pandharipande-Thomas, and Szendroi invariants established via analysis of the geometry of wall crossing phenomena of suitably general moduli spaces. I aim to give a reasonably detailed account of the simplest example, the conifold, where in fact all of the major ideas can be easily seen.
Thu, 12/03/2009
12:30 		Habib Ammari (CNRS) OxPDE Lunchtime Seminar Add to calendar Gibson 1st Floor SR
Multi-scale elastic imaging
Thu, 12/03/2009
14:00 		Prof Ke Chen (The University of Liverpool) Computational Mathematics and Applications Add to calendar Rutherford Appleton Laboratory, nr Didcot
On fast multilevel algorithms for nonlinear variational imaging models

In recent years, the interdisciplinary field of imaging science has been experiencing an explosive growth in research activities including more models being developed, more publications generated, and above all wider applications attempted.
In this talk I shall first give an overview of the various imaging work carried out in our Liverpool group, some with collaborations with UCLA (T F Chan), CUHK (R H Chan) and Bergen (X C Tai) and several colleagues from other departments in Liverpool. Then I shall focus on two pieces of recent work, denoising and segmentation respectively:
(i) Image denoising has been a research topic deeply investigated within the last two decades. Even algorithmically the well-known ROF model (1992) can be solved efficiently. However less work has been done on models using high order regularization. I shall describe our first and successful attempt to develop a working multilevel algorithm for a 4th order nonlinear denoising model, and our work on solving the combined denoising and deblurring problem, different from the reformulation approach by M N Ng and W T Yin (2008) et al.
(ii) the image active contour model by Chan-Vese (2001) can be solved efficiently both by a geometric multigrid method and by an optimization based multilevel method. Surprisingly the new multilevel methods can find a solution closer to the global minimize than the existing unilevel methods. Also discussed are some recent work (jointly with N Badshah) on selective segmentation that has useful medical applications.
Thu, 12/03/2009
14:30 		Gus Lehrer (Sydney/Oxford) Representation Theory Seminar Add to calendar L3
Non-commutative Invariant Theory
Thu, 12/03/2009
16:00 		Ian Kiming (Copenhagen) Number Theory Seminar Add to calendar L3
On modular mod p^m Galois representations.
Thu, 12/03/2009
16:30 		Mark Kelmanson (University of Leeds) Differential Equations and Applications Seminar Add to calendar DH 1st floor SR
On the Moffatt-Pukhnachov problem
The classic coating-flow problem first studied experimentally by Moffat and asymptotically by Pukhnachov in 1977 is reconsidered in the framework of multiple-timescale asymptotics. Two-timescale approximations of the height of the thin film coating a rotating horizontal circular cylinder are obtained from an asymptotic analysis, in terms of small gravitational and capillary parameters, of Pukhnachov's nonlinear evolution for the film thickness. The transition, as capillary effects are reduced, from smooth to shock-like solutions is examined, and interesting large-time dynamics in this case are determined via a multiple-timescale analysis of a Kuramoto-Sivashinsky equation. A pseudo-three-timescale method is proposed and demonstrated to improve the accuracy of the smooth solutions, and an asymptotic analysis of a modified Pukhnachov's equation, one augmented by inertial terms, leads to an expression for the critical Reynolds number above which the steady states first analysed by Moffatt and Pukhnachov cannot be realised. As part of this analysis, some interesting implications of the effects of different scalings on inertial terms is discussed. All theoretical results are validated by either spectral or extrapolated numerics.
Fri, 13/03/2009
10:00 		Mark Wakefield (Schlumberger) Industrial and Interdisciplinary Workshops Add to calendar DH 1st floor SR
Thermal Effects in Porous Medium Flow
Fri, 13/03/2009
14:30 		Dr Kieran Neylon, (Schlumberger Oil Field Research Services) Mathematical Geoscience Seminar Add to calendar DH 3rd floor SR
Oil reservoir simulation - a well posed problem or just plain boring?
Fri, 13/03/2009
16:30 		James MacLaurin (University of Oxford) Junior Applied Mathematics Seminar Add to calendar DH 3rd floor SR
The Buckling of Capillaries within Tumours

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

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