Forthcoming Seminars

Tue, 01/12/2009
15:00 		Simon Donaldson (Imperial College London) Algebraic and Symplectic Geometry Seminar Add to calendar Imperial College
(HoRSe seminar at Imperial College) Moduli of Calabi-Yau 3-folds and instantons on $ G_2 $ manifolds
This talk will be largely speculative. First we consider the formal properties that could be expected of a "topological field theory" in 6+1 dimensions defined by $ G_2 $ instantons. We explain that this could lead to holomorphic bundles over moduli spaces of Calabi-Yau 3-folds whose ranks are the DT-invariants. We also discuss in more detail the compactness problem for $ G_2 $ instantons and associative submanifolds. The talk will be held in Room 408, Imperial College Maths Department, Huxley Building, 180 Queen’s Gate, London.
Tue, 01/12/2009
16:00 		Anne Thomas Junior Geometric Group Theory Seminar Add to calendar T14
Complexes of Groups
Tue, 01/12/2009
17:00 		Neal Bez (Glasgow) Functional Analysis Seminar Add to calendar L3
Brascamp-Lieb inequalities and some applications
I will give an overview of the classical Brascamp-Lieb inequality from its birth to recent developments. I will discuss certain nonlinear generalisations of the Brascamp-Lieb inequality and applications of such inequalities in harmonic and geometric analysis.
Wed, 02/12/2009
10:10 		Ornella Cominetti-Allende OCCAM Literature Seminar Add to calendar OCCAM Common Room (RI2.28)
A survey of kernel and spectral methods for clustering
Wed, 02/12/2009
11:30 		Matthew Clarke (University of Cambridge) Algebra Kinderseminar Add to calendar ChCh, Tom Gate, Room 2
Generalized Gelfand–Graev representations for finite groups of Lie type
This talk is about the ordinary representation theory of finite groups of Lie type. I will begin by carefully reviewing algebraic groups and finite groups of Lie type and the construction and properties of (ordinary) Gelfand–Graev characters. I will then introduce generalized Gelfand–Graev characters, which are constructed using the Lie algebra of the ambient algebraic group. Towards the end I hope to give an idea of how generalized Gelfand–Graev characters can and have been used to attack Lusztig's conjecture and the role this plays in the determination of the character tables of finite groups of Lie type.
Thu, 03/12/2009
12:00 		Martijn Kool (Oxford) Junior Geometry and Topology Seminar Add to calendar SR1
Moduli Spaces of Sheaves on Toric Varieties
Extending work of Klyachko, we give a combinatorial description of pure equivariant sheaves on a nonsingular projective toric variety X and construct moduli spaces of such sheaves. These moduli spaces are explicit and combinatorial in nature. Subsequently, we consider the moduli space M of all Gieseker stable sheaves on X and describe its fixed point locus in terms of the moduli spaces of pure equivariant sheaves on X. Using torus localisation, one can then compute topological invariants of M. We consider the case X=S is a toric surface and compute generating functions of Euler characteristics of M. In case of torsion free sheaves, one can study wall-crossing phenomena and in case of pure dimension 1 sheaves one can verify, in examples, a conjecture of Katz relating Donaldson–Thomas invariants and Gopakumar–Vafa invariants.
Thu, 03/12/2009
14:00 		Prof. Andre Weideman (University of Stellenbosch) Computational Mathematics and Applications Add to calendar 3WS SR
Rational Approximations to the Complex Error Function
We consider rational approximations to the Faddeeva or plasma dispersion function, defined as $ w(z) = e^{-z^{2}} \mbox{erfc} (-iz) $. With many important applications in physics, good software for computing the function reliably everywhere in the complex plane is required. In this talk we shall derive rational approximations to $ w(z) $ via quadrature, Möbius transformations, and best approximation. The various approximations are compared with regard to speed of convergence, numerical stability, and ease of generation of the coefficients of the formula. In addition, we give preference to methods for which a single expression yields uniformly high accuracy in the entire complex plane, as well as being able to reproduce exactly the asymptotic behaviour $ w(z) \sim i/(\sqrt{\pi} z), z \rightarrow \infty $ (in an appropriate sector). This is Joint work with: Stephan Gessner, Stéfan van der Walt
Thu, 03/12/2009
16:30 		Charlie Elliott (Warwick University) Differential Equations and Applications Seminar Add to calendar OCCAM Common Room (RI2.28)
Computational Surface Partial Differential Equations
Evolutionary PDEs on stationary and moving surfaces appear in many applications such as the diffusion of surfactants on fluid interfaces, surface pattern formation on growing domains, segmentation on curved surfaces and phase separation on biomembranes and dissolving alloy surfaces. In this talk I discuss three numerical approaches based on:- (I) Surface Finite Elements and Triangulated Surfaces, (II)Level Set Method and Implicit Surface PDEs and (III) Phase Field Approaches and Diffuse Surfaces.
Thu, 03/12/2009
17:00 		Markus Junker (Freiburg) Logic Seminar Add to calendar L3
Endomorphisms and interpretations of $ \aleph_0 $-categorical structures
Fri, 04/12/2009
11:45 		Stacy Williams (HSBC) Industrial and Interdisciplinary Workshops Add to calendar DH 3rd floor SR
Quants don't just do options - solving difficult problems in the world's largest financial market
HSBC Currency Trading has collaborated with the Oxford Maths Institute for over six years and is now working with its third DPhil student. In this workshop, we will look at the some of the academic research which has directly benefited the trading operation.
Fri, 04/12/2009
14:15 		Anis Matoussi (Le Mans) Nomura Seminar Add to calendar Eagle House
Robust utility maximization from terminal wealth and consumption considering a model with jumps : BSDE approach
We study a stochastic control problem in the context of utility maximization under model uncertainty. The problem is formulated as /max min/ problem : /max /over strategies and consumption and /min/ over the set of models (measures). For the minimization problem, we have showed in Bordigoni G., Matoussi,A., Schweizer, M. (2007) that there exists a unique optimal measure equivalent to the reference measure. Moreover, in the context of continuous filtration, we characterize the dynamic value process of our stochastic control problem as the unique solution of a generalized backward stochastic differential equation with a quadratic driver. We extend first this result in a discontinuous filtration. Moreover, we obtain a comparison theorem and a regularity properties for the associated generalized BSDE with jumps, which are the key points in our approach, in order to solve the utility maximization problem over terminal wealth and consumption. The talk is based on joint work with M. Jeanblanc and A. Ngoupeyou (2009).
Fri, 04/12/2009
16:30 		Ornella Cominetti (University of Oxford) Junior Applied Mathematics Seminar Add to calendar DH 3rd floor SR
Clustering recipes: new flavours of kernel and spectral methods
Soft (fuzzy) clustering techniques are often used in the study of high-dimensional datasets, such as microarray and other high-throughput bioinformatics data. The most widely used method is Fuzzy C-means algorithm (FCM), but it can present difficulties when dealing with nonlinear clusters. In this talk, we will overview and compare different clustering methods. We will introduce DifFUZZY, a novel spectral fuzzy clustering algorithm applicable to a larger class of clustering problems than FCM. This method is better at handling datasets that are curved, elongated or those which contain clusters of different dispersion. We will present examples of datasets (synthetic and real) for which this method outperforms other frequently used algorithms

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

Syndicate content