Forthcoming Seminars
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Mon, 17/01/2011 12:00 |
David Berman (Queen Mary University of London) |
String Theory Seminar  |
L3 |
| Abstract: We reformulate M-theory in terms of a generalised metric that combines the usual metric and the three form potential. The U-duality group is then a manifest symmetry. | |||
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Mon, 17/01/2011 14:15 |
Ying Hu |
Stochastic Analysis Seminar |
Eagle House |
| Abstract: In this talk, we first introduce the notion of ergodic BSDE which arises naturally in the study of ergodic control. The ergodic BSDE is a class of infinite-horizon BSDEs:Y_{t}^{x}=Y_{T}^{x}+∫_{t}^{T}[ψ(X^{x}_{σ},Z^{x}_{σ})-λ]dσ-∫_{t}^{T}Z_{σ}^{x}dB_{σ}, P-<K1.1/>, ∀0≤t≤T<∞,<K1.1 ilk="TEXTOBJECT" > <screen-nom>hbox</screen-nom> <LaTeX>\hbox{a.s.}</LaTeX></K1.1> where X^{x} is a diffusion process. We underline that the unknowns in the above equation is the triple (Y,Z,λ), where Y,Z are adapted processes and λ is a real number. We review the existence and uniqueness result for ergodic BSDE under strict dissipative assumptions.Then we study ergodic BSDEs under weak dissipative assumptions. On the one hand, we show the existence of solution to the ergodic BSDE by use of coupling estimates for perturbed forward stochastic differential equations. On the other hand, we show the uniqueness of solution to the associated Hamilton-Jacobi-Bellman equation by use of the recurrence for perturbed forward stochastic differential equations.Finally, applications are given to the optimal ergodic control of stochastic differential equations to illustrate our results. We give also the connections with ergodic PDEs. | |||
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Mon, 17/01/2011 14:15 |
Roger Bielawski (Leeds) |
Geometry and Analysis Seminar |
L3 |
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Mon, 17/01/2011 15:45 |
John MacKay (University of Illinois at Urbana-Champaign) |
Topology Seminar |
L3 |
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What is a random group? What does it look like? In Gromov's few relator |
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Mon, 17/01/2011 15:45 |
Ana Bela Cruziero |
Stochastic Analysis Seminar |
Eagle House |
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We analyse stability properties of stochastic Lagrangian Navier stokes flows on compact Riemannian manifolds. |
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Mon, 17/01/2011 16:00 |
Lillian Pierce (Oxford) |
Junior Number Theory Seminar |
SR1 |
| An old conjecture of Hardy and Littlewood posits that on average, the number of representations of a positive integer N as a sum of k, k-th powers is "very small." Recently, it has been observed that this conjecture is closely related to properties of a discrete fractional integral operator in harmonic analysis. This talk will give a basic introduction to the two key problems, describe the correspondence between them, and show how number theoretic methods, in particular the circle method and mean values of Weyl sums, can be used to say something new in abstract harmonic analysis. | |||
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Mon, 17/01/2011 17:00 |
Jonathan Ben-Artzi (Brown University) |
Partial Differential Equations Seminar |
Gibson 1st Floor SR |
| We consider the Relativistic Vlasov-Maxwell system of equations which describes the evolution of a collisionless plasma. We show that under rather general conditions, one can test for linear instability by checking the spectral properties of Schrodinger-type operators that act only on the spatial variable, not the full phase space. This extends previous results that show linear and nonlinear stability and instability in more restrictive settings. | |||
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Tue, 18/01/2011 12:00 |
Prakash Panangaden (McGill, visiting Comlab) |
Quantum Field Theory Seminar |
L3 |
| Communication between observers in a relativistic scenario has proved to be a setting for a fruitful dialogue between quantum field theory and quantum information theory. A state that an inertial observer in Minkowski space perceives to be the vacuum will appear to an accelerating observer to be a thermal bath of radiation. We study the impact of this Davies-Fulling-Unruh noise on communication, particularly quantum communication from an inertial sender to an accelerating observer and private communication between two inertial observers in the presence of an accelerating eavesdropper. In both cases, we establish compact, tractable formulas for the associated communication capacities assuming encodings that allow a single excitation in one of a fixed number of modes per use of the communications channel. | |||
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Tue, 18/01/2011 14:15 |
Dr Robin Hankin (Department of Land Economy ( University of Cambridge)) |
Geophysical and Nonlinear Fluid Dynamics Seminar |
Dobson Room, AOPP |
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Tue, 18/01/2011 14:30 |
Christopher Dowden |
Combinatorial Theory Seminar |
L3 |
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Tue, 18/01/2011 15:45 |
Artan Sheshmani (University of Illinois at Urbana Champaign) |
Algebraic and Symplectic Geometry Seminar |
L3 |
We introduce a higher rank analog of Pandharipande-Thomas theory of stable pairs. Given a Calabi-Yau threefold  , we define the higherrank stable pairs (which we call frozen triples) given by the data  where  is a pure coherent sheaf with one dimensional support over and  is a map. We compute the Donaldson-Thomas type invariants associated to the frozen triples using the wall-crossing formula of Joyce-Song and Kontsevich-Soibelman. This work is a sequel to arXiv:1011.6342, where we gave a deformation theoretic construction of a higher rank enumerative theory of stable pairs over a Calabi-Yau threefold, and we computed similar invariants using Graber-Pandharipande virtual localization technique. |
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Tue, 18/01/2011 17:00 |
Prof. J. S. Wilson (Oxford) |
Algebra Seminar |
L2 |
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Wed, 19/01/2011 10:00 |
OCCAM Wednesday Morning Event |
OCCAM Common Room (RI2.28) | |
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As many of you are no doubt aware, a Study Group of particular significance will take place in Thuwal, Saudi Arabia, from 23rd January - 26th January 2011. The problem statements, in their preliminary form can be found at: |
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Wed, 19/01/2011 11:30 |
Algebra Kinderseminar |
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Wed, 19/01/2011 16:00 |
Andrew Sale (Oxford University) |
Junior Geometric Group Theory Seminar |
SR2 |
| A brief survey of the above. | |||
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Thu, 20/01/2011 12:30 |
Thierry Goudon (Lille 1 University) |
OxPDE Lunchtime Seminar |
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| Considering kinetic equations (Boltzmann, BGK, say...) in the small mean free path regime lead to conservation laws (the Euler system, typically) When the problem is set in a domain, boundary layers might occur due to the fact that incoming fluxes could be far from equilibrium states. We consider the problem from a numerical perspective and we propose a definition of numerical fluxes for the Euler system which is intended to account for the formation of these boundary layers. | |||
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Thu, 20/01/2011 13:00 |
Terry Lyons |
Mathematical Finance Internal Seminar |
DH 1st floor SR |
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Thu, 20/01/2011 13:00 |
Tom Sutherland (University of Oxford) |
Junior Geometry and Topology Seminar |
SR1 |
| This talk will be an introduction to the space of Bridgeland stability conditions on a triangulated category, focussing on the case of the derived category of coherent sheaves on a curve. These spaces of stability conditions have their roots in physics, and have a mirror theoretic interpretation as moduli of complex structures on the mirror variety. For curves of genus g > 0, we will see that any stability condition comes from the classical notion of slope stability for torsion-free sheaves. On the projective line we can study the more complicated behaviour via a derived equivalence to the derived category of modules over the Kronecker quiver. | |||
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Thu, 20/01/2011 14:00 |
Dr Sebastien Loisel (Heriot-Watt University) |
Computational Mathematics and Applications |
Gibson Grd floor SR |
| In various fields of application, one must solve very large scale boundary value problems using parallel solvers and supercomputers. The domain decomposition approach partitions the large computational domain into smaller computational subdomains. In order to speed up the convergence, we have several “optimized” algorithm that use Robin transmission conditions across the artificial interfaces (FETI-2LM). It is known that this approach alone is not sufficient: as the number of subdomains increases, the number of iterations required for convergence also increases and hence the parallel speedup is lost. A known solution for classical Schwarz methods as well as FETI algorithms is to incorporate a “coarse grid correction”, which is able to transmit low-frequency information more quickly across the whole domain. Such algorithms are known to “scale weakly” to large supercomputers. A coarse grid correction is also necessary for FETI-2LM methods. In this talk, we will introduce and analyze coarse grid correction algorithms for FETI-2LM domain decomposition methods. | |||
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Thu, 20/01/2011 14:30 |
M.J. Collins (Oxford) |
Representation Theory Seminar |
L3 |
