Forthcoming Seminars

Fri, 12/11/2010
09:45 		David Nowell (Department of Engineering Science, University of Oxford) Industrial and Interdisciplinary Workshops Add to calendar DH 1st floor SR
Challenges in Frictional Contact
Please note the earlier than usual start-time!
Fri, 12/11/2010
11:15 		Various OCCAM Special Seminar Add to calendar OCCAM Common Room (RI2.28)
OCCAM Group Meeting
  • Ian Griffiths - "Taylor Dispersion in Colloidal Systems".
  • James Lottes - "Algebraic multigrid for nonsymmetric problems".
  • Derek Moulton - "Surface growth kinematics"
  • Rob Style - "Ice lens formation in freezing soils"
Fri, 12/11/2010
14:00 		Prof Kevin Burrage (Computing Laboratory)) Mathematical Biology and Ecology Seminar Add to calendar L1
Coping with heterogeneity: from cells to tissue
Fri, 12/11/2010
14:15 		Yuri Kabanov (Universite de Franche-Compte) Nomura Seminar Add to calendar DH 1st floor SR
No-arbitrage criteria under small transaction costs
The talk will be devoted to criteria of absence of arbitrage opportunities under small transaction costs for a family of multi-asset models of financial market.
Fri, 12/11/2010
16:30 		Professor Luis Caffarelli Colloquia Add to calendar L2
Non linear problems involving anomalous diffusion
Anomalous ( non local) diffusion processes appear in many subjects: phase transition, fracture dynamics, game theory I will describe some of the issues involved, and in particular, existence and regularity for some non local versions of the p Laplacian, of non variational nature, that appear in non local tug of war.
Mon, 15/11/2010
12:00 		Alan Barr (Oxford) String Theory Seminar Add to calendar L3
The Large Hadron Collider – the story so far
String theory has a vested interest in a particular S1xS1 object found just outside Geneva. The machine in question has been colliding protons at high energy since March this year, and by now the ATLAS and CMS experiments have clocked up more than 10^12 high-energy events. In this seminar I present the status of the accelerator and detectors, highlight the major physics results obtained so far, and discuss the extent to which information from the LHC can inform us about TeV-scale theory.
Mon, 15/11/2010
14:15 		Dimitris Cheliotis Stochastic Analysis Seminar Add to calendar Eagle House
The critical curve for pinning of random polymers. A large deviations approach
We consider a directed random polymer interacting with an interface that carries random charges some of which attract while others repel the polymer. Such a polymer can be in a localized or delocalized phase, i.e., it stays near the interface or wanders away respectively.  The phase it chooses depends on the temperature and the average bias of the disorder. At a given temperature, there is a critical bias separating the two phases. A question of particular interest, and which has been studied extensively in the Physics and Mathematics literature, is whether the quenched critical bias differs from the annealed critical bias. When it does, we say that the disorder is relevant. Using a large deviations result proved recently by Birkner, Greven, and den Hollander, we derive a variational formula for the quenchedcritical bias. This leads to a necessary and sufficient condition for disorder relevance that implies easily some known results as well as new ones. The talk is based on joint work with Frank den  Hollander.
Mon, 15/11/2010
15:45 		Hubert Lacoin Stochastic Analysis Seminar Add to calendar Eagle House
Crossing a repulsive interface: slowing of the dynamic and metastability phenomenon
We study a simple heat-bath type dynamic for a simple model of polymer interacting with an interface. The polymer is a nearest neighbor path in Z, and the interaction is modelised by energy penalties/bonuses given when the path touches 0. This dynamic has been studied by D. Wilson for the case without interaction, then by Caputo et al. for the more general case. When the interface is repulsive, the dynamic slows down due to the appearance of a bottleneck in the state space, moreover, the systems exhibits a metastable behavior, and, after time rescaling, behaves like a two-state Markov chain.
Mon, 15/11/2010
15:45 		Pierre Pansu (Orsay) Topology Seminar Add to calendar L3
$ L^p $ cohomology and pinching
We prove that no Riemannian manifold quasiisometric to complex hyperbolic plane can have a better curvature pinching. The proof uses cup-products in $ L^p $-cohomology.
Mon, 15/11/2010
16:00 		Hung Bui (Oxford) Junior Number Theory Seminar Add to calendar SR1
Central values of L-functions
Mon, 15/11/2010
17:00 		Lisa Beck (Scuola Normale Superiore di Pisa) Partial Differential Equations Seminar Add to calendar Gibson 1st Floor SR
The role of small space dimensions in the regularity theory of elliptic problems
Let $ u \in W^{1,p}(\Omega,\R^N) $, $ \Omega $ a bounded domain in $ \R^n $, be a minimizer of a convex variational integral or a weak solution to an elliptic system in divergence form. In the vectorial case, various counterexamples to full regularity have been constructed in dimensions $ n \geq 3 $, and it is well known that only a partial regularity result can be expected, in the sense that the solution (or its gradient) is locally continuous outside of a negligible set. In this talk, we shall investigate the role of the space dimension $ n $ on regularity: In arbitrary dimensions, the best known result is partial regularity of the gradient $ Du $ (and hence for $ u $) outside of a set of Lebesgue measure zero. Restricting ourselves to the partial regularity of $ u $ and to dimensions $ n \leq p+2 $, we explain why the Hausdorff dimension of the singular set cannot exceed $ n-p $. Finally, we address the possible existence of singularities in two dimensions.
Tue, 16/11/2010
10:00 		Dr R Reid-Edwards (Oxford) Twistor Workshop Add to calendar Gibson 1st Floor SR
More on 6-dimensional spinor-helicity and amplitudes
Tue, 16/11/2010
12:00 		Prof F Burstall (University of Bath) Relativity Seminar Add to calendar L3
Twistors, 4-symmetric spaces and integrable systems
Tue, 16/11/2010
13:15 		Chris Lustri (OCIAM) Junior Applied Mathematics Seminar Add to calendar DH 1st floor SR
"Exponential Asymptotics and Free-Surface Fluid Flow"
We investigate the behaviour of free-surface waves on time-varying potential flow in the limit as the Froude number becomes small. These waves are exponentially small in the Froude number, and are therefore inaccessible to ordinary asymptotic methods. As such, we demonstrate how exponential asymptotic techniques may be applied to the complexified free surface in order to extract information about the wave behaviour on the free surface, using a Lagrangian form of the potential flow equations. We consider the specific case of time-varying flow over a step, and demonstrate that the results are consistent with the steady state case.
Tue, 16/11/2010
14:00 		Kai Behrend (Vancouver) Algebraic and Symplectic Geometry Seminar Add to calendar SR1
(HoRSe seminar) On the calculus underlying Donaldson-Thomas theory I
On a manifold there is the graded algebra of polyvector fields with its Lie-Schouten bracket, and the module of de Rham differentials with exteriour differentiation. This package is called a "calculus". The moduli space of sheaves (or derived category objects) on a Calabi-Yau threefold has a kind of "virtual calculus" on it, at least conjecturally. In particular, this moduli space has virtual de Rham cohomology groups, which categorify Donaldson-Thomas invariants, at least conjecturally. We describe some attempts at constructing such a virtual calculus. This is work in progress.
Tue, 16/11/2010
14:15 		Dr Dan Cornford (Computer Science and NCRG) Geophysical and Nonlinear Fluid Dynamics Seminar Add to calendar Dobson Room, AOPP
Bayesian 4DVAR: An extension to weak constraint 4DVAR data assimilation
Tue, 16/11/2010
14:30 		John Talbot (UCL) Combinatorial Theory Seminar Add to calendar L3
Triangles in tripartite graphs
How many triangles must a graph of density d contain? This old question due to Erdos was recently answered by Razborov, after many decades of progress by numerous authors. We will consider the analogous question for tripartite graphs. Given a tripartite graph with prescribed edges densities between each pair of classes how many triangles must it contain?
Tue, 16/11/2010
15:45 		Kai Behrend (Vancouver) Algebraic and Symplectic Geometry Seminar Add to calendar L3
(HoRSe seminar) On the calculus underlying Donaldson-Thomas theory II
On a manifold there is the graded algebra of polyvector fields with its Lie-Schouten bracket, and the module of de Rham differentials with exterior differentiation. This package is called a "calculus". The moduli space of sheaves (or derived category objects) on a Calabi-Yau threefold has a kind of "virtual calculus" on it, at least conjecturally. In particular, this moduli space has virtual de Rham cohomology groups, which categorify Donaldson-Thomas invariants, at least conjecturally. We describe some attempts at constructing such a virtual calculus. This is work in progress.
Tue, 16/11/2010
16:00 		Martin Palmer (Oxford University) Junior Geometric Group Theory Seminar Add to calendar DH 3rd floor SR
Introduction to homology-stability
Tue, 16/11/2010
17:00 		Raphaël Rouquier (Oxford) Algebra Seminar Add to calendar L2
Finite generation of group cohomology

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

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