Forthcoming Seminars
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Fri, 08/06/2012 14:00 |
Dr Guillaume Charras (University College) |
Mathematical Biology and Ecology Seminar  |
L1 |
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Fri, 08/06/2012 15:00 |
David McGady (Princeton) |
Relativity Seminar |
Gibson 1st Floor SR |
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Abstract: In this talk, I will discuss the proportionality between tree amplitudes and the ultraviolet divergences in their one-loop corrections in Yang-Mills and (N < 4) Super Yang-Mills theories in four-dimensions. From the point of view of local perturbative quantum field theory, i.e. Feynman diagrams, this proportionality is straightforward: ultraviolet divergences at loop-level are absorbed into coefficients of local operators/interaction vertices in the original tree-amplitude. Ultraviolet divergences in loop amplitudes are also calculable through on-shell methods. These methods ensure manifest gauge-invariance, even at loop-level (no ghosts), at the expense of manifest locality. From an on-shell perspective, the proportionality between the ultraviolet divergences the tree amplitudes is thus not guaranteed. I describe systematic structures which ensure proportionality, and their possible connections to other recent developments in the field. |
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Fri, 08/06/2012 16:30 |
Bruce Kleiner (NYU) |
Colloquia |
L2 |
| A map betweem metric spaces is a bilipschitz homeomorphism if it is Lipschitz and has a Lipschitz inverse; a map is a bilipschitz embedding if it is a bilipschitz homeomorphism onto its image. Given metric spaces X and Y, one may ask if there is a bilipschitz embedding X—>Y, and if so, one may try to find an embedding with minimal distortion, or at least estimate the best bilipschitz constant. Such bilipschitz embedding problems arise in various areas of mathematics, including geometric group theory, Banach space geometry, and geometric analysis; in the last 10 years they have also attracted a lot of attention in theoretical computer science. The lecture will be a survey bilipschitz embedding in Banach spaces from the viewpoint of geometric analysis. | |||
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Mon, 11/06/2012 12:00 |
David Shih (Rutgers University) |
String Theory Seminar |
L3 |
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Mon, 11/06/2012 14:15 |
KAY KIRKPATRICK (University of Illinois, Chicago) |
Stochastic Analysis Seminar |
Oxford-Man Institute |
| There are two main statistical mechanical models of ferromagnetism: the simpler and better-understood Ising model, and the more realistic and more challenging classical Heisenberg model, where the spins are in the 2-sphere instead of in {-1,+1}. In dimensions one and two, the classical Heisenberg model with nearest-neighbor interactions has no phase transition, but in three dimensions it has been intractable. To shed some light on the qualitative behavior of the 3D Heisenberg model, we use the versatile tools of mean-field theory and Stein's method in recent work with Elizabeth Meckes, studying the Heisenberg model on a complete graph with the number of vertices going to infinity. Our results include detailed descriptions of the magnetization, the empirical spin distribution, the free energy, and a second-order phase transition. | |||
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Mon, 11/06/2012 14:15 |
Reto Mueller (Imperial) |
Geometry and Analysis Seminar |
L3 |
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Mon, 11/06/2012 15:30 |
Emil Wiedemann (Leipzig) |
Partial Differential Equations Seminar |
Gibson Grd floor SR |
| An intriguing, and largely open, question in mathematical fluid dynamics is whether solutions of the Navier-Stokes equations converge in some sense to a solution of the Euler equations in the zero viscosity limit. In fact this convergence could conceivably fail due to oscillations and concentrations occuring in the sequence. In the late 1980s, R. DiPerna and A. Majda extended the classical concept of Young measure to obtain a notion of measure-valued solution of the Euler equations, which records precisely these oscillation and concentration effects. In this talk I will present a result recently obtained in joint work with L. Székelyhidi, which states that any such measure-valued solution is generated by a sequence of distributional solutions of the Euler equations. The result is interesting from two different viewpoints: On the one hand, it emphasizes the huge flexibility of the concept of weak solution for Euler; on the other hand, it provides an example of a characterization theorem for Young measures in the tradition of D. Kinderlehrer and P. Pedregal where the differential constraint on the generating sequence does not satisfy the constant rank condition. | |||
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Mon, 11/06/2012 15:45 |
FREDRIK JOHANSSON VIKLUND (Colombia University) |
Stochastic Analysis Seminar |
Oxford-Man Institute |
| The Schramm-Loewner evolution (SLE(\kappa)) is a family of random fractal curves that arise in a natural way as scaling limits of interfaces in critical models in statistical physics. The SLE curves are constructed by solving the Loewner differential equation driven by a scaled Brownian motion. We will give an overview of some of the almost sure properties of SLE curves, concentrating in particular on properties that can be derived by studying the the geometry of growing curve locally at the tip. We will discuss a multifractual spectrum of harmonic measure at the tip, regularity in the capacity parameterization, and continuity of the curves as the \kappa-parameter is varied while the driving Brownian motion sample is kept fixed. This is based on joint work with Greg Lawler, and with Steffen Rohde and Carto Wong. | |||
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Mon, 11/06/2012 15:45 |
Piotr Przytycki (Warsaw) |
Topology Seminar |
L3 |
| This is joint work with Dani Wise and builds on his earlier work. Let M be a compact oriented irreducible 3-manifold which is neither a graph manifold nor a hyperbolic manifold. We prove that the fundamental group of M is virtually special. This means that it virtually embeds in a right angled Artin group, and is in particular linear over Z. | |||
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Mon, 11/06/2012 16:00 |
Jan Vonk |
Junior Number Theory Seminar |
SR1 |
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Tue, 12/06/2012 10:30 |
Tim Adamo (Oxford) |
Geometry and Integrability |
Gibson 1st Floor SR |
| Abstract: We'll try to learn something about Nekrasov's conjecture/theorem, which relates an instanton-counting partition function to the Seiberg-Witten prepotential of N=2 SYM theory on R^4. This will entail a review of some salient aspects of N=2 SYM theories, Witten's description of Donaldson invariants in terms of correlation functions in those theories, and the physical and mathematical definition of Nekrasov's partition function. Depending on time, I might talk about computational techniques for the partition function, methods of proof for Nekrasov's conjecture, or the partition function's role in the AGT conjectures. | |||
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Tue, 12/06/2012 12:00 |
Dr Taghavi Chabert (Masaryk University) |
Relativity Seminar |
L3 |
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Tue, 12/06/2012 13:15 |
Joseph Parker |
Junior Applied Mathematics Seminar |
DH 1st floor SR |
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Nuclear fusion offers the prospect of abundant clean energy production, but the physical and engineering challenges are very great. In nuclear fusion reactors, the fuel is in the form of a plasma (charged gas) which is confined at high temperature and density using a toroidal magnetic field. This configuration is susceptible to turbulence, which transports heat out of the plasma and prevents fusion. It is believed that rotating the plasma suppresses turbulence, but experiments are expensive and even modest numerical simulation requires hundreds of thousands of CPU hours. We present a numerical technique for one of the five phase-space dimensions that both improves the accuracy of the calculation and greatly reduces the resolution required. |
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Tue, 12/06/2012 14:15 |
Prof Ted Shepherd (University of Reading) |
Geophysical and Nonlinear Fluid Dynamics Seminar |
Dobson Room, AOPP |
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Tue, 12/06/2012 15:00 |
Stephen Wolfram (Wolfram Research) |
Special Seminar |
L1 |
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Tue, 12/06/2012 17:00 |
Professor G. Clif (Alberta) |
Algebra Seminar |
L2 |
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Wed, 13/06/2012 00:00 |
Analytic Topology in Mathematics and Computer Science Workshop |
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| Organisers: Hilary Priestley, Drew Moshier and Leo Cabrer.This will be dedicated principally to extensions of duality theory beyond zero-dimensional structures and to its application in novel settings. Topics that are likely to feature include duality for bilattice-based structures and associated semantics; extensions to compact Hausdorff spaces, bitopological duality, and duality for continuous data; applications to coalgebraic logic. We shall be seeking two-way interaction between those focused on a particular application and those who are seeking to extend the theory. Keynote speakers will be Mike Mislove and Drew Moshier. Samson Abramsky will be away from Oxford fromJune 12, but we are grateful for his offer to give a talk on June 11. We are also pleased to announce that, through the good offices of Georg Gottlob (Oxford Department of Computer Science), we are able to include within W1 a tutorial lecture on the applications of bilattice semantics to computer science; this will be given by Ofer Arieli. | |||
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Wed, 13/06/2012 10:15 |
Jonathan Robbins (University of Bristol) |
OCCAM Wednesday Morning Event |
OCCAM Common Room (RI2.28) |
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We present some recent results concerning domain wall motion in one-dimensional nanowires, including the existence, velocity and stability of travelling-wave and precessing solutions. We consider the case of unixial anisotropy, characteristic of wires with symmetrical (e.g., circular) cross-section, as opposed to strongly anisotropic geometries (films and strips) that have received greater attention. This is joint work with Arseni Goussev and Valeriy Slastikov. |
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Thu, 14/06/2012 12:00 |
Dawid Kielak |
Junior Geometry and Topology Seminar |
L3 |
| This is intended as an introductory talk about one of the most important (and most geometric) aspects of Geometric Group Theory. No prior knowledge of any maths will be assumed. | |||
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Thu, 14/06/2012 12:30 |
Oliver Penrose (Heriot-Watt University) |
OxPDE Lunchtime Seminar |
Gibson 1st Floor SR |
A method of defining non-equilibrium entropy for a chaotic dynamical system is proposed which, unlike the usual method based on Boltzmann's principle  , does not involve the concept of a macroscopic state. The idea is illustrated using an example based on Arnold's `cat' map. The example also demonstrates that it is possible to have irreversible behaviour, involving a large increase of entropy, in a chaotic system with only two degrees of freedom. |
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