Forthcoming Seminars

Thu, 20/01/2011
16:00
Jonathan Pila (Oxford) Number Theory Seminar Add to calendar
Thu, 20/01/2011
16:00
Stephen Roberts (Oxford) Differential Equations and Applications Seminar Add to calendar DH 1st floor SR
This talk will focus on a family of Bayesian inference algorithms built around Gaussian processes. We firstly introduce an iterative Gaussian process for multi-sensor inference problems. Extensions to our algorithm allow us to tackle some of the decision problems faced in sensor networks, including observation scheduling. Along these lines, we also propose a general method of global optimisation, Gaussian process global optimisation (GPGO). This paradigm is extended to the Bayesian decision problem of sequential multi-scale observation selection. We show how the hyperparameters of our system can be marginalised by use of Bayesian quadrature and frame the selection of the positions of the hyperparameter samples required by Bayesian quadrature as a sequential decision problem, with the aim of minimising the uncertainty we possess about the values of the integrals we are approximating.
Thu, 20/01/2011
17:00
Tobias Kaiser (Passau) Logic Seminar Add to calendar L3
Thu, 20/01/2011
17:00
Professor Tobias Kaiser Logic Seminar Add to calendar L3

We are interested in measure theory and integration theory that ¯ts into the
o-minimal context. Therefore we introduce the following de¯nition:
Given an o-minimal structure M on the ¯eld of reals and a measure ¹ de¯ned on the
Borel sets of some Rn, we call ¹ M-tame if there is an o-minimal expansion of M such
that for every parameter family of functions on Rn that is de¯nable in M the family of
integrals with respect to ¹ is de¯nable in this o-minimal expansion.
In the ¯rst part of the talk we give the de¯nitions and motivate them by existing and
many new examples. In the second one we discuss the Lebesgue measure in this context.
In the ¯nal part we obtain de¯nable versions of important theorems like the theorem of
Radon-Nikodym and the Riesz representation theorem. These results allow us to describe
tame measures explicitly.
1

Fri, 21/01/2011
09:45
OCIAM Meeting Industrial and Interdisciplinary Workshops Add to calendar DH 3rd floor SR
Fri, 21/01/2011
14:00
Prof Mark Sansom (University of Oxford) Mathematical Biology and Ecology Seminar Add to calendar L1
Fri, 21/01/2011
14:15
Prof Josef Teichmann (ETH Zurich) Nomura Seminar Add to calendar DH 1st floor SR
We present theory and numerics of affine processes and several of their applications in finance. The theory is appealing due to methods from probability theory, analysis and geometry. Applications are diverse since affine processes combine analytical tractability with a high flexibility to model stylized facts like heavy tails or stochastic volatility.
Mon, 24/01/2011
12:00
Mathew Bullimore (Oxford) String Theory Seminar Add to calendar L3
Recently, there has been exciting progress in scattering amplitudes in supersymmetric gauge theories, one aspect of which is the remarkable duality between amplitudes and Wilson loops. I will explain how the complete planar S-matrix of N=4 super Yang-Mills theory is encoded in the complex analogue of a Wilson loop in holomorphic Chern-Simons theory on twistor space. The dynamics of the theory are encoded in loop equations, which describe deformations of the Wilson Loop and provide new insight into the nature of the amplitude-Wilson loop duality. The loop equations themselves yield powerful recursive methods for scattering amplitudes which are revealed as holomorphic skein relations by interpreting the Wilson loop as the complex analogue of a knot invariant. The talk will be based on the preprint arXiv:1101.1329.
Mon, 24/01/2011
14:15
Hendrik Weber Stochastic Analysis Seminar Add to calendar Eagle House
Abstract: We construct solutions to Burgers type equations perturbed by a multiplicative space-time white noise in one space dimension. Due to the roughness of the driving noise, solutions are not regular enough to be amenable to classical methods. We use the theory of controlled rough paths to give a meaning to the spatial integrals involved in the definition of a weak solution. Subject to the choice of the correct reference rough path, we prove unique solvability for the equation. We show that our solutions are stable under smooth approximations of the driving noise. A more general class of approximations will also be discussed. This is joint work with Martin Hairer and Jan Maas.
Mon, 24/01/2011
14:15
Lothar Goettsche (ICTP) Geometry and Analysis Seminar Add to calendar L3
Mon, 24/01/2011
15:45
Andre Henriques (Universiteit Utrecht) Topology Seminar Add to calendar L3
Roughly speaking, a quantum field theory is a gadget that assigns algebraic data to manifolds. The kind of algebraic data depends on the dimension of the manifold.Conformal nets are an example of this kind of structure. Given a conformal net, one can assigns a von Neumann algebra to any 1-dimensional manifold, and (at least conjecturally) a Hilbert space to any 2-dimensional Riemann surfaces.I will start by explaining what conformal nets are. I will then give some examples of conformal net: the ones associated to loop groups of compact Lie groups. Finally, I will present a new proof of a celebrated result of Kawahigashi, Longo, andMueger:The representation category of a conformal net (subject to appropriate finiteness conditions) is a modular tensor category.All this is related to my ongoing research projects with Chris Douglas and Arthur Bartels, in which we investigate conformal nets from a categorytheoretical perspective.
Mon, 24/01/2011
15:45
Ni Hao Stochastic Analysis Seminar Add to calendar Eagle House
The signature of the path is an essential object in rough path theory which takes value in tensor algebra and it is anticipated that the expected signature of Brownian motion might characterize the rough path measure of Brownian path itself. In this presentation we study the expected signature of a Brownian path in a Bananch space E stopped at the first exit time of an arbitrary regular domain, although we will focus on the case E=R^{2}. We prove that such expected signature of Brownian motion should satisfy one particular PDE and using the PDE for the expected signature and the boundary condition we can derive each term of expected signature recursively. We expect our method to be generalized to higher dimensional case in R^{d}, where d is an integer and d >= 2.
Mon, 24/01/2011
17:00
Jean-Yves Chemin (Universite Pierre et Marie Curie) Partial Differential Equations Seminar Add to calendar Gibson 1st Floor SR
The purpose of this talk is to provide a large class of examples of large initial data which gives rise to a global smooth solution. We shall explain what we mean by large initial data. Then we shall explain the concept of slowly varying function and give some flavor of the proofs of global existence.
Tue, 25/01/2011
13:15
Hermes Gadelha (CMB) Junior Applied Mathematics Seminar Add to calendar DH 1st floor SR

Abstract: Flagella and cilia are ubiquitous in biology as a means of motility and critical for male gametes migration in reproduction, to mucociliary clearance in the lung, to the virulence of devastating parasitic pathogens such as the Trypanosomatids, to the filter feeding of the choanoflagellates, which are constitute a critical link in the global food chain. Despite this ubiquity and importance, the details of how the ciliary or flagellar waveform emerges from the underlying mechanics and how the cell, or the environs, may control the beating pattern by regulating the axoneme is far from fully understood. We demonstrate in this talk that mechanics and modelling can be utilised to interpret observations of axonemal dynamics, swimming trajectories and beat patterns for flagellated motility impacts on the science underlying numerous areas of reproductive health, disease and marine ecology. It also highlights that this is a fertile and challenging area of inter-disciplinary research for applied mathematicians and demonstrates the importance of future observational and theoretical studies in understanding the underlying mechanics of these motile cell appendages.

		
Tue, 25/01/2011
14:00
Jun Li (Stanford) Algebraic and Symplectic Geometry Seminar Add to calendar SR1
We first present the localized virtual cycles by cosections of obstruction sheaves constructed by Kiem and Li. This construction has two kinds of applications: one is define invariants for non-proper moduli spaces; the other is to reduce the obstruction classes. We will present two recent applications of this construction: one is the Gromov-Witten invariants of stable maps with fields (joint work with Chang); the other is studying Donaldson-Thomas invariants of Calabi-Yau threefolds (joint work with Kiem).
Tue, 25/01/2011
14:15
Prof. David Dritschel (Mathematical Institute (University of St Andrews)) Geophysical and Nonlinear Fluid Dynamics Seminar Add to calendar Dobson Room, AOPP
Tue, 25/01/2011
15:45
Jun Li (Stanford) Algebraic and Symplectic Geometry Seminar Add to calendar L3
We first present the localized virtual cycles by cosections of obstruction sheaves constructed by Kiem and Li. This construction has two kinds of applications: one is define invariants for non-proper moduli spaces; the other is to reduce the obstruction classes. We will present two recent applications of this construction: one is the Gromov-Witten invariants of stable maps with fields (joint work with Chang); the other is studying Donaldson-Thomas invariants of Calabi-Yau threefolds (joint work with Kiem).
Tue, 25/01/2011
17:00
Les Bunce (Reading) Functional Analysis Seminar Add to calendar L3
Tue, 25/01/2011
17:00
Prof. D. Segal (Oxford) Algebra Seminar Add to calendar L2
Wed, 26/01/2011
11:30
David Hume (University of Oxford) Algebra Kinderseminar Add to calendar ChCh, Tom Gate, Room 2
Many problems in computer science can be modelled as metric spaces, whereas for mathematicians they are more likely to appear as the opening question of a second year examination. However, recent interesting results on the geometry of finite metric spaces have led to a rethink of this position. I will describe some of the work done and some (hopefully) interesting and difficult open questions in the area.
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