Forthcoming Seminars
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Mon, 02/02/2009 17:00 |
Andrea Malchiodi (SISSA) |
Partial Differential Equations Seminar  |
Gibson 1st Floor SR |
| A classical problem in differential geometry is to deform the metric of a given manifold so that some of its curvatures become prescribed functions. Classical examples are the Uniformization problem for compact surfaces and the Yamabe problem for compact manifolds of dimension greater than two. We address a similar problem for the so-called Q-curvature, which plays an important role in conformal geometry and is a natural higher order analogue of the Gauss curvature. The problem is tackled using a variational and Morse theoretical approach. | |||
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Tue, 03/02/2009 12:00 |
Rick Blute (Ottawa, visiting Computing Lab) |
Quantum Field Theory Seminar |
L3 |
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Tue, 03/02/2009 14:30 |
Ross Kang (McGill) |
Combinatorial Theory Seminar |
L3 |
| We consider a natural generalisation of the independence and chromatic numbers and study their behaviour in Erdos-Renyi random graphs. The t-dependence number of a graph G is the size of the largest subset of the vertices of G whose induced subgraph has maximum degree at most t. The t-improper chromatic number of G is the smallest number of parts needed in a partition of the vertex set of G such that each part induces a subgraph of maximum degree at most t. Clearly, when t = 0, these parameters are, respectively, the independence and chromatic numbers of G. For dense random graphs, we determine the asymptotic ehaviour of these parameters over the range of choices for the growth of t as a function of the number of vertices. This is joint work with Nikolaos Fountoulakis and Colin McDiarmid. | |||
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Tue, 03/02/2009 15:45 |
Greg Berczi (Oxford) |
Algebraic and Symplectic Geometry Seminar |
L3 |
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Tue, 03/02/2009 16:30 |
Dr Robert B. Scott (University of Texas at Austin) |
Geophysical and Nonlinear Fluid Dynamics Seminar |
Dobson Room, AOPP |
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Tue, 03/02/2009 17:00 |
Steve Smith (University of Illinois, Chicago) |
Algebra Seminar |
L2 |
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Tue, 03/02/2009 17:00 |
Pierre Portal (Lille) |
Functional Analysis Seminar |
L3 |
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Wed, 04/02/2009 11:30 |
Teru Thomas (University of Oxford) |
Algebra Kinderseminar |
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Thu, 05/02/2009 11:00 |
Lian Duan (Mathematical Institute) |
Applied Dynamical Systems and Inverse Problems Seminar |
DH 3rd floor SR |
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Thu, 05/02/2009 12:00 |
João Lopes Costa (Oxford) |
Junior Geometry and Topology Seminar |
SR1 |
| We prove uniqueness of the Kerr black holes within the connected, non-degenerate, analytic class of regular vacuum black holes. (This is joint work with Piotr Chrusciel. arXiv:0806.0016) | |||
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Thu, 05/02/2009 12:30 |
Duvan Henao (University of Oxford) |
OxPDE Lunchtime Seminar |
Gibson 1st Floor SR |
| Motivated by the tensile experiments on titanium alloys of Petrinic et al (2006), which show the formation of cracks through the formation and coalescence of voids in ductile fracture, we consider the problem of formulating a variational model in nonlinear elasticity compatible both with cavitation and with the appearance of discontinuities across two-dimensional surfaces. As in the model for cavitation of Müller and Spector (1995) we address this problem, which is connected to the sequential weak continuity of the determinant of the deformation gradient in spaces of functions having low regularity, by means of adding an appropriate surface energy term to the elastic energy. Based upon considerations of invertibility we are led to an expression for the surface energy that admits a physical and a geometrical interpretation, and that allows for the formulation of a model with better analytical properties. We obtain, in particular, important regularity properites of the inverses of deformations, as well as the weak continuity of the determinants and the existence of minimizers. We show further that the creation of surface can be modelled by carefully analyzing the jump set of the inverses, and we point out some connections between the analysis of cavitation and fracture, the theory of SBV functions, and the theory of cartesian currents of Giaquinta, Modica and Soucek. (Joint work with Carlos Mora-Corral, Basque Center for Applied Mathematics). | |||
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Thu, 05/02/2009 13:00 |
Alex Kacelnik |
Mathematical Finance Internal Seminar |
DH 3rd floor SR |
| Virtually all decisions taken by living beings, from financial investments to life history, mate choice or anti-predator responses involve uncertainties and inter-temporal trade offs. Thus, hypothesis and formal models from these different fields often have heuristic value across disciplines. I will present theories and experiments about temporal discounting and risky choice originating in behavioural research on birds. Among other topics, I will address empirical observations showing risk aversion for gains and risk proneness for losses, exploring parallels and differences between Prospect Theory, Risk Sensitivity Theory and Scalar Utility Theory. | |||
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Thu, 05/02/2009 14:00 |
Dr Robert Nürnberg (Imperial College London) |
Computational Mathematics and Applications |
Comlab |
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Thu, 05/02/2009 14:30 |
Nathan Geer (Georgia Institute of Technology/Oxford) |
Representation Theory Seminar |
L3 |
| In this talk I will discuss how to construct generalized traces and modified dimensions in certain categories of modules. As I will explain there are several examples in representation theory where the usual trace and dimension are zero, but these generalized traces and modified dimensions are non-zero. Such examples include the representation theory of the Lie algebra sl(2) over a field of positive characteristic and of Lie superalgebras over the complex numbers. In these examples the modified dimensions can be interpreted categorically and are closely related to some basic notions involving the representation theory. This joint work with Jon Kujawa and Bertrand Patureau. | |||
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Thu, 05/02/2009 16:00 |
Damiano Testa (Oxford) |
Number Theory Seminar |
L3 |
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Thu, 05/02/2009 16:30 |
Karima Khusnutdinova (Loughborough) CANCELLED - WILL NOW BE IN TRINITY TERM 2009 |
Differential Equations and Applications Seminar |
DH 1st floor SR |
| Layered (or laminated) structures are increasingly used in modern industry (e.g., in microelectronics and aerospace engineering). Integrity of such structures is mainly determined by the quality of their interfaces: poor adhesion or delamination can lead to a catastrophic failure of the whole structure. Can nonlinear waves help us to detect such defects? We study the dynamics of a nonlinear longitudinal bulk strain wave in a split, layered elastic bar, made of nonlinearly hyperelastic Murnaghan material. We consider a symmetric two-layered bar and assume that there is perfect interface for x < 0 and splitting for x > 0, where the x-axis is directed along the bar. Using matched asymptotic multiple-scales expansions and the integrability theory of the KdV equation by the Inverse Scattering Transform, we examine scattering of solitary waves and show that the defect causes generation of more than one secondary solitary waves from a single incident soliton and, thus, can be used to detect the defect. The theory is supported by experimental results. Experiments have been performed in the Ioffe Institute in St. Petersburg (Russia), using holographic interferometry and laser induced generation of an incident compression solitary wave in two- and three-layered polymethylmethacrylate (PMMA) bars, bonded using ethyl cyanoacrylate-based (CA) adhesive. | |||
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Thu, 05/02/2009 17:00 |
Olivia Caramello (Cambridge) |
Logic Seminar |
L3 |
| We present a topos-theoretic interpretation of (a categorical generalization of) Fraïssé's construction in Model Theory, with applications to countably categorical theories. The proof of our main theorem represents an instance of exploiting the interplay of syntactic, semantic and geometric ideas in the foundations of Topos Theory. | |||
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Fri, 06/02/2009 10:00 |
Patrick Brockill (Oxford / Dept. of Physics) |
Industrial and Interdisciplinary Workshops |
DH 3rd floor SR |
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Fri, 06/02/2009 14:00 |
Dr Omer Dushek (University of British Columbia) |
Mathematical Biology Seminar |
L3 |
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Fri, 06/02/2009 14:15 |
Marek Musiela (BNP Paribas) |
Nomura Seminar |
DH 3rd floor SR |
| Since summer 2007 financial markets moved in unprecedented ways. Volatility was extremely high. Correlations across the board increased dramatically. More importantly, also much deeper fundamental changes took place. In this talk we will concentrate on the following two aspects, namely, inter-bank unsecured lending at LIBOR and 40 Before the crisis it was very realistic for the banks to consider that risk free rate of inter-bank lending, and hence also of funding, is equivalent to 3M LIBOR. This logic was extended to terms which are multiples of 3M via compounding and to arbitrary periods by interpolation and extrapolation. Driven by advances in financial mathematics arbitrage free term structure models have been developed for pricing of interest rate exotics, like LIBOR Market Model (or BGM). We explain how this methodology was challenged in the current market environment. We also point to mathematical questions that need to be addressed in order to incorporate in the pre-crisis pricing and risk management methodology the current market reality. We also discuss historically validated and universally accepted pre-crisis assumption of 40 | |||
