Forthcoming Seminars
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Tue, 17/11/2009 17:00 |
Vincent Franjou (Nantes) |
Algebra Seminar  |
L2 |
| A classic problem in invariant theory, often referred to as Hilbert's 14th problem, asks, when a group acts on a finitely generated commutative algebra by algebra automorphisms, whether the ring of invariants is still finitely generated. I shall present joint work with W. van der Kallen treating the problem for a Chevalley group over an arbitrary base. Progress on the corresponding problem of finite generation for rational cohomology will be discussed. | |||
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Wed, 18/11/2009 10:10 |
Hayder Salman |
OCCAM Literature Seminar |
OCCAM Common Room (RI2.28) |
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Wed, 18/11/2009 11:30 |
David Craven (University of Oxford) |
Algebra Kinderseminar |
ChCh, Tom Gate, Room 2 |
| The representation theory of groups is surrounded by deep and difficult conjectures. In this talk we will take a tour of (some of) these problems, including Alperin's weight conjecture, Broué's conjecture, and Puig's finiteness conjecture. | |||
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Thu, 19/11/2009 11:00 |
Lian Duan (OCCAM (Oxford)) |
Applied Dynamical Systems and Inverse Problems Seminar |
DH 3rd floor SR |
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Thu, 19/11/2009 12:00 |
Richard Wade (Oxford) |
Junior Geometry and Topology Seminar |
SR1 |
| We describe John Stalling's method of studying finitely generated free groups via graphs and moves on graphs called folds. We will then discuss how the theory can be extended to study the automorphism group of a finitely generated free group. | |||
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Thu, 19/11/2009 12:30 |
Luc Nguyen (University of Oxford) |
OxPDE Lunchtime Seminar |
Gibson 1st Floor SR |
| According to the Ernst-Geroch reduction, in an axially symmetric stationary electrovac spacetime, the Einstein-Maxwell equations reduce to a harmonic map problem with singular boundary data. I will discuss the “regularity” of the reduced harmonic maps near the boundary and its implication on the regularity of the corresponding spacetimes. | |||
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Thu, 19/11/2009 14:00 |
Dr. Pedro Gonnet (ETH Zurich and Oxford University) |
Computational Mathematics and Applications |
3WS SR |
| Molecular Dynamics Simulations are a tool to study the behaviour of atomic-scale systems. The simulations themselves solve the equations of motion for hundreds to millions of particles over thousands to billions of time steps. Due to the size of the problems studied, such simulations are usually carried out on large clusters or special-purpose hardware. At a first glance, there is nothing much of interest for a Numerical Analyst: the equations of motion are simple, the integrators are of low order and the computational aspects seem to focus on hardware or ever larger and faster computer clusters. The field, however, having been ploughed mainly by domain scientists (e.g. Chemists, Biologists, Material Scientists) and a few Computer Scientists, is a goldmine for interesting computational problems which have been solved either badly or not at all. These problems, although domain specific, require sufficient mathematical and computational skill to make finding a good solution potentially interesting for Numerical Analysts. The proper solution of such problems can result in speed-ups beyond what can be achieved by pushing the envelope on Moore's Law. In this talk I will present three examples where problems interesting to Numerical Analysts arise. For the first two problems, Constraint Resolution Algorithms and Interpolated Potential Functions, I will present some of my own results. For the third problem, using interpolations to efficiently compute long-range potentials, I will only present some observations and ideas, as this will be the main focus of my research in Oxford and therefore no results are available yet. | |||
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Thu, 19/11/2009 14:30 |
Juergen Mueller (Aachen) |
Representation Theory Seminar |
L3 |
| Let G be a finite group, let A be a prime block of G having an abelian defect group D, let N be the normaliser in G of D, and let B be the Brauer correspondent of A. Then the abelian defect group conjecture says that the bounded derived categories of the module categories of A and B equivalent as triangulated categories. Although this conjecture is in the focus of intensive studies since almost two decades now, it has only been verified for certain cases and a general proof seems to be out of sight. In this talk, we briefly introduce the notions to state the abelian defect group conjecture, report on the current state of knowledge, and on the strategies to prove it for explicit examples. Then we show how these strategies are pursued and combined with techniques from computational representation theory to prove the abelian defect group conjecture for the sporadic simple Harada-Norton group; this is joint work with Shigeo Koshitani. | |||
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Thu, 19/11/2009 16:00 |
Dorian Goldfeld (Columbia) |
Number Theory Seminar |
L3 |
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Thu, 19/11/2009 16:30 |
Stephen Creagh (Nottingham) |
Differential Equations and Applications Seminar |
DH 1st floor SR |
| Whispering gallery modes in optical resonators have received a lot of attention as a mechanism for constructing small, directional lasers. They are also potentially important as passive optical components in schemes for coupling and filtering signals in optical fibres, in sensing devices and in other applications. In this talk it is argued that the evanescent field outside resonators that are very slightly deformed from circular or spherical is surprising in a couple of respects. First, even very small deformations seem to be capable of leading to highly directional emission patterns. Second, even though the undelying ray families are very regular and hardly differ from the integrable circular or spherical limit inside the resonator, a calculation of the evanescent field outside it is not straightforward. This is because even very slight nonintegrability has a profound effect on the complexified ray families which guide the external wave to asymptopia. An approach to describing the emitted wave is described which is based on canonical perturbation theory applied to the ray families and extended to comeplx phase space. | |||
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Thu, 19/11/2009 17:00 |
Florian Pop (Philadelphia) |
Logic Seminar |
L3 |
| After a short introduction to the section conjecture, I plan to present a "minimalistic" form of the birational p-adic section conjecture. The result is related to both: Koenigsmann's proof of the birational p-adic section conjecture, and a "minimalistic" Galois characterisation of formally p-adic valuations. | |||
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Fri, 20/11/2009 00:00 |
Mathematical Biology and Ecology Seminar |
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Fri, 20/11/2009 09:00 |
Various |
Industrial and Interdisciplinary Workshops |
DH 1st floor SR |
| Collaborators from Industry will speak to us about their proposed projects for the MSc in Math Modelling and Scientific Computation. Potential supervisors should attend. All others welcome too. | |||
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Fri, 20/11/2009 11:30 |
Apala Majumdar, Stephen Peppin and Lian Duan (OCCAM, Oxford) |
Industrial and Interdisciplinary Workshops |
OCCAM Common Room (RI2.28) |
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Fri, 20/11/2009 14:15 |
Jan Kallsen (Kiel) |
Nomura Seminar |
DH 1st floor SR |
| We reconsider Merton's problem under proportional transaction costs. Beginning with Davis and Norman (1990) such utility maximization problems are usually solved using stochastic control theory. Martingale methods, on the other hand, have so far only been used to derive general structural results. These apply the duality theory for frictionless markets typically to a fictitious shadow price process lying within the bid-ask bounds of the real price process. In this study we show that this dual approach can actually be used for both deriving a candidate solution and verification. In particular, the shadow price process is determined explicitly. | |||
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Fri, 20/11/2009 14:30 |
Dr. Ed King (Cambridge) |
Mathematical Geoscience Seminar |
DH 3rd floor SR |
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Fri, 20/11/2009 16:30 |
Jason Zhong (University of Oxford) |
Junior Applied Mathematics Seminar |
DH 1st floor SR |
| Hairsine-Rose (HR) model is the only multi sediment size soil erosion model. The HR model is modifed by considering the effects of sediment bedload and bed elevation. A two step composite Liska-Wendroff scheme (LwLf4) which designed for solving the Shallow Water Equations is employed for solving the modifed Hairsine-Rose model. The numerical approximations of LwLf4 are compared with an independent MOL solution to test its validation. They are also compared against a steady state analytical solution and experiment data. Buffer strip is an effective way to reduce sediment transportation for certain region. Modifed HR model is employed for solving a particular buffer strip problem. The numerical approximations of buffer strip are compared with some experiment data which shows good matches. | |||
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Mon, 23/11/2009 12:00 |
Max Banados (Pontificia Universidad Católica de Chile and Oxford) |
String Theory Seminar |
L3 |
| We give a review of several aspects of three dimensional gravity which were discovered long ago but remain active and present in the literature up to today. | |||
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Mon, 23/11/2009 13:00 |
Tatyana Shaposhnikova (Linköping University, Sweden) |
OxPDE Lunchtime Seminar |
Gibson 1st Floor SR |
| Given a bounded Lipschitz domain, we consider the Dirichlet problem with boundary data in Besov spaces for divergence form strongly elliptic systems of arbitrary order with bounded complex-valued coefficients. The main result gives a sharp condition on the local mean oscillation of the coefficients of the differential operator and the unit normal to the boundary (automatically satisfied if these functions belong to the space VMO) which guarantee that the solution operator associated with this problem is an isomorphism. | |||
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Mon, 23/11/2009 14:15 |
Eulalia Nualart (Universite Paris 13) |
Stochastic Analysis Seminar |
Eagle House |
