Forthcoming Seminars

Mon, 18/05/2009
17:00 		Louis Nirenberg (Courant Institute) Partial Differential Equations Seminar Add to calendar Gibson 1st Floor SR
On fully nonlinear elliptic equations
Some results of R.Harvey and B.Lawson on the Dirichlet problem for a class of fully nonlinear elliptic equations will be presented. No background is required; the talk will be expository.
Tue, 19/05/2009
14:00 		Ed Segal (Imperial College London) Algebraic and Symplectic Geometry Seminar Add to calendar L1
The closed state space of affine Landau-Ginzburg B-models
I'll define the category of B-branes in a LG model, and show that for affine models the Hochschild homology of this category is equal to the physically-predicted closed state space. I'll also explain why this is a step towards proving that LG B-models define TCFTs.
Tue, 19/05/2009
14:30 		Jozef Skokan (LSE) Combinatorial Theory Seminar Add to calendar L3
Multicolour Ramsey numbers for cycles
For graphs $ L_1,\dots,L_k $, the Ramsey number $ R(L_1,\ldots,L_k) $ is the minimum integer $ N $ such that for any edge-colouring of the complete graph $ K_N $ by $ k $ colours there exists a colour $ i $ for which the corresponding colour class contains $ L_i $ as a subgraph. In this talk, we shall discuss recent developments in the case when the graphs $ L_1,\dots,L_k $ are all cycles and $ k\ge2 $.
Tue, 19/05/2009
15:45 		Kazushi Ueda (Oxford and Osaka) Algebraic and Symplectic Geometry Seminar Add to calendar L3
Homological mirror symmetry for Brieskorn-Pham singularities
A polynomial $ f $ is said to be a Brieskorn-Pham polynomial if $  f = x_1^{p_1} + ... + x_n^{p_n} $ for positive integers $ p_1,\ldots, p_n $. In the talk, I will discuss my joint work with Masahiro Futaki on the equivalence between triangulated category of matrix factorizations of $ f $ graded with a certain abelian group $ L $ and the Fukaya-Seidel category of an exact symplectic Lefschetz fibration obtained by Morsifying $ f $.
Tue, 19/05/2009
17:00 		Dave Benson (University of Aberdeen) Algebra Seminar Add to calendar L2
Localising subcategories of the stable module category for a finite group
Tue, 19/05/2009
18:00 		Andrew W. Lo (MIT) Nomura Lecture Add to calendar Said Business School
"Kill All The Quants"?: Models vs. Mania In The Current Financial Crisis
As the shockwaves of the financial crisis of 2008 propagate throughout the global economy, the "blame game" has begun in earnest, with some fingers pointing to the complexity of certain financial securities, and the mathematical models used to manage them. In this talk, I will review the evidence for and against this view, and argue that a broader perspective will show a much different picture.Blaming quantitative analysis for the financial crisis is akin to blaming F = MA for a fallen mountain climber's death. A more productive line of inquiry is to look deeper into the underlying causes of financial crisis, which ultimately leads to the conclusion that bubbles, crashes, and market dislocation are unavoidable consequences of hardwired human behavior coupled with free enterprise and modern capitalism. However, even though crises cannot be legislated away, there are many ways to reduce their disruptive effects, and I will conclude with a set of proposals for regulatory reform.
Wed, 20/05/2009
11:30 		David Craven (University of Oxford) Algebra Kinderseminar Add to calendar ChCh, Tom Gate, Room 2
The abc conjecture and related topics
We begin by proving the abc theorem for polynomial rings and looking at a couple of its consequences. We then move on to the abc conjecture and its equivalence with the generalized Szpiro conjecture, via Frey polynomials. We look at a couple of consequences of the abc conjecture, and finally consider function fields, where we introduce the abc theorem in that case.
Wed, 20/05/2009
15:00 		Y. Sengul, P. Pathmanathan (Oxford) OxMOS Workshop/Meeting/Lecture Add to calendar Gibson 1st Floor SR
OxMOS Team Meeting
Thu, 21/05/2009
09:30 		Michael Harris (Univ. Paris 7) Special Lecture Add to calendar Taught Course Center
Automorphic Forms, Galois Representations and Geometry
Thu, 21/05/2009
11:00 		Margaret Thomas (Oxford) Logic Seminar Add to calendar L3
An o-minimal structure without wild parametrization.
Thu, 21/05/2009
12:15 		Dirk Schlueter (Oxford) Junior Geometry and Topology Seminar Add to calendar SR1
Universal moduli of parabolic bundles on stable curves
A parabolic bundle on a marked curve is a vector bundle with extra structure (a flag) in each of the fibres over the marked points, together with data corresponding to a choice of stability condition Parabolic bundles are natural generalisations of vector bundles when the base comes with a marking (for example, they partially generalise the Narasimhan-Seshadri correspondence between representations of the fundamental group and semistable vector bundles), but they also play an important role in the study of pure sheaves on nodal curves (which are needed to compactify moduli of vector bundles on stable curves). Consider the following moduli problem: pairs $ (C,E) $ of smooth marked curves $ C $ and semistable parabolic bundles $ E\rightarrow C $. I will sketch a construction of projective moduli spaces which compactify the above moduli problem over the space of stable curves. I'll discuss further questions of interest, including strategies for understanding the cohomology of these moduli spaces, generalisations of the construction to higher-dimensional base schemes, and possible connections with Torelli theorems for parabolic vector bundles on marked curves.
Thu, 21/05/2009
14:00 		Dr. Christoph Ortner (Computing Laboratory, Oxford) Computational Mathematics and Applications Add to calendar Comlab
Introduction to Quasicontinuum Methods: Formulation, Classification, Analysis
Quasicontinuum methods are a prototypical class of atomistic-to-continuum coupling methods. For example, we may wish to model a lattice defect (a vacancy or a dislocation) by an atomistic model, but the elastic far field by a continuum model. If the continuum model is consistent with the atomistic model (e.g., the Cauchy–Born model) then the main question is how the interface treatment affects the method. In this talk I will introduce three of the main ideas how to treat the interface. I will explain their strengths and weaknesses by formulating the simplest possible non-trivial model problem and then simply analyzing the two classical concerns of numerical analysis: consistency and stability.
Thu, 21/05/2009
14:30 		Oeyvind Solberg (NTNU Trondheim) Representation Theory Seminar Add to calendar L3
Support varieties - an axiomatic approach
Thu, 21/05/2009
16:30 		Dominic Vella (Cambridge) Differential Equations and Applications Seminar Add to calendar DH 1st floor SR
Localized structures in elastic sheets: From a ruck in a rug to flexible electronics
An elastic sheet will buckle out of the plane when subjected to an in-plane compression. In the simplest systems the typical lengthscale of the buckled structure is that of the system itself but with additional physics (e.g. an elastic substrate) repeated buckles with a well-defined wavelength may be seen. We discuss two examples in which neither of these scenarios is realized: instead a small number of localized structures are observed with a size different to that of the system itself. The first example is a heavy sheet on a rigid floor - a ruck in a rug. We study the static properties of these rucks and also how they propagate when one end of the rug is moved quickly. The second example involves a thin film adhered to a much softer substrate. Here delamination blisters are formed with a well-defined size, which we characterize in terms of the material properties of the system. We then discuss the possible application of these model systems to real world problems ranging from the propagation of slip pulses in earthquakes to the manufacture of flexible electronic devices."
Thu, 21/05/2009
17:00 		Moshe Jarden (Tel Aviv) Logic Seminar Add to calendar L3
Diamonds in Torsion of Abelian Varieties.
A theorem of Kuyk says that every Abelian extension of a Hilbertian field is Hilbertian. We conjecture that for an Abelian variety $ A $ defined over a Hilbertian field $ K $ every extension $ L $ of $ K $ in $ K(A_\tor) $ is Hilbertian. We prove our conjecture when $ K $ is a number field. The proofs applies a result of Serre about $ l $-torsion of Abelian varieties, information about $ l $-adic analytic groups, and Haran's diamond theorem.
Fri, 22/05/2009
10:00 		Alan Cocks and Steve Roberts (Engineering Science, Oxford and Materials, Oxford (respectively)) Industrial and Interdisciplinary Workshops Add to calendar DH 1st floor SR
Failure processes in engineering materials (cavitation and crack growth) particularly at elevated temperatures (to be confirmed)
Fri, 22/05/2009
14:15 		Paolo Guasoni (Boston University) Nomura Seminar Add to calendar DH 1st floor SR
Two and Twenty: what Incentives?
Hedge fund managers receive a large fraction of their funds' gains, in addition to the small fraction of funds' assets typical of mutual funds. The additional fee is paid only when the fund exceeds its previous maximum - the high-water mark. The most common scheme is 20 percent of the fund profits + 2 percent of assets. To understand the incentives implied by these fees, we solve the portfolio choice problem of a manager with Constant Relative Risk Aversion and a Long Horizon, who maximizes the utility from future fees. With constant investment opportunities, and in the absence of fixed fees, the optimal portfolio is constant. It coincides with the portfolio of an investor with a different risk aversion, which depends on the manager's risk aversion and on the size of the fees. This portfolio is also related to that of an investor facing drawdown constraints. The combination of both fees leads to a more complex solution. The model involves a stochastic differential equation involving the running maximum of the solution, which is related to perturbed Brownian Motions. The solution of the control problem employs a verification theorem which relies on asymptotic properties of positive local martingales. Joint work with Jan Obloj.

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

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