Forthcoming Seminars
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Fri, 04/06/2010 10:00 |
Andy Stove (Thales) |
Industrial and Interdisciplinary Workshops  |
DH 1st floor SR |
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'Compressive sampling' is a topic of current interest. It relies on data being sparse in some domain, which allows what is apparently 'sub Nyquist' sampling so that the quantities of data which must be handled become more closely related to the information rate. This principal would appear to have (at least) three applications for radar and electronic warfare: The most modest application is to reduce the amount of data which we must handle: radar and electronic warfare receivers generate vast amounts of data (up to 1Gbit/second or even 10Gbit.sec). It is desirable to be able to store this data for future analysis and it is also becoming increasingly important to be able to share it between different sensors, which, prima facie, requires vast communication bandwidths and it would be valuable to be able to find ways to handle this more efficiently. The second advantage is that if suitable data domains can be identified, it may also be possible to pre-process the data before the analogue to digital converters in the receivers, to reduce the demands on these critical components. The most ambitious use of compressive sensing would be to find ways of modifying the radar waveforms, and the electronic warfare receiver sampling strategies, to change the domain in which the information is represented to reduce the data rates at the receiver 'front ends', i.e. make the data at the front end better match the information we really want to acquire. The aim of the presentation will be to describe the issues with which we are faced, and to discuss how compressive sampling might be able to help. A particular issue which will be raised is how we might find domains in which the data is sparse. |
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Fri, 04/06/2010 11:30 |
Ron Reid-Edwards (Oxford) |
Twistor Workshop |
Gibson 1st Floor SR |
| This will discuss the paper of Ricci, Tseytlin & Wolf from 2007. | |||
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Fri, 04/06/2010 14:15 |
Gordan Zitkovic (UT Austin) |
Nomura Seminar |
DH 1st floor SR |
| In addition to existence, the excess-demand approach allows us to establish uniqueness and provide efficient computational algorithms for various complete- and incomplete-market stochastic financial equilibria. A particular attention will be paid to the case when the agents exhibit constant absolute risk aversion. An overview of recent results (including those jointly obtained with M. Anthropelos and with Y. Zhao) will be given. | |||
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Fri, 04/06/2010 14:30 |
Dr Roiy Sayag (DAMTP) |
Mathematical Geoscience Seminar |
DH 3rd floor SR |
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Fri, 04/06/2010 17:00 |
Tristan Denley (Austin Peay) |
Combinatorial Theory Seminar |
L3 |
| Whether as the sudoku puzzles of popular culture or as restricted coloring problems on graphs or hypergraphs, completing partial Latin squares and cubes present a framework for a variety of intriguing problems. In this talk we will present several recent results on completing partial Latin squares and cubes. | |||
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Mon, 07/06/2010 12:00 |
Dario Martelli (Kings College London) |
String Theory Seminar |
L3 |
| We study a gravity solution corresponding to fivebranes wrapped on the S^2 of the resolved conifold. By changing a parameter the solution continuously interpolates between the deformed conifold with flux and the resolved conifold with branes. Therefore, it displays a geometric transition, purely in the supergravity context. The solution is a simple example of torsional geometry and may be thought of as a non-Kahler analog of the conifold. By U-duality transformations we can add D3 brane charge and recover the solution in the form originally derived by Butti et al. This describes the baryonic branch of the Klebanov-Strassler theory. Far along the baryonic branch the field theory gives rise to a fuzzy two-sphere. This corresponds to the D5 branes wrapping the two-sphere of the resolved conifold in the gravity solution. | |||
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Mon, 07/06/2010 14:15 |
Pierre-Henri Chaudouard (Orsay) |
Geometry and Analysis Seminar |
L3 |
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Mon, 07/06/2010 14:15 |
James Norris (Cambridge) |
Stochastic Analysis Seminar |
Eagle House |
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Mon, 07/06/2010 15:45 |
Christopher Douglas (Berkeley) |
Topology Seminar |
L3 |
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Mon, 07/06/2010 15:45 |
Sergei Zuyev (Chalmers University of Technology) |
Stochastic Analysis Seminar |
Eagle House |
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Mon, 07/06/2010 17:00 |
Mikhail Feldman (University of Wisconsin at Madison) |
Partial Differential Equations Seminar |
Gibson 1st Floor SR |
| In this talk we describe some recent work on shock reflection problems for the potential flow equation. We will start with discussion of shock reflection phenomena. Then we will describe the results on existence, structure and regularity of global solutions to regular shock reflection. The approach is to reduce the shock reflection problem to a free boundary problem for a nonlinear elliptic equation, with ellipticity degenerate near a part of the boundary (the sonic arc). We will discuss techniques to handle such free boundary problems and degenerate elliptic equations. This talk is based on joint works with Gui-Qiang Chen, and with Myoungjean Ba | |||
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Tue, 08/06/2010 11:00 |
Pierre-Henri Chaudouard (Orsay) |
Special Lecture |
SR1 |
| We shall explain what is the weighted fundamental lemma and how it is related to the truncated Hitchin fibration. | |||
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Tue, 08/06/2010 12:00 |
Dr Dunajski (DAMTP) |
Relativity Seminar |
L3 |
| Consider the space M of parabolas y=ax^2+bx+c, with (a, b, c) as coordinates on M. Two parabolas generically intersect at two (possibly complex) points, and we can define a conformal structure on M by declaring two points to be null separated iff the corresponding parabolas are tangent. A simple calculation of discriminant shows that this conformal structure is flat. In this talk (based on joint works with Godlinski and Sokolov) I shall show how replacing parabolas by rational plane curves of higher degree allows constructing curved conformal structures in any odd dimension. In dimension seven one can use this "twistor" construction to find G_2 structures in a conformal class. | |||
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Tue, 08/06/2010 14:30 |
Bill Jackson (QMUL) |
Combinatorial Theory Seminar |
L3 |
Consider a configuration of points in  -dimensional Euclidean space
together with a set of constraints
which fix the direction or the distance between some pairs of points.
Basic questions are whether the constraints imply that the configuration
is unique or locally unique up to congruence, and whether it is bounded. I
will describe some solutions
and partial solutions to these questions. |
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Tue, 08/06/2010 15:45 |
David Stern (Maseno University) |
Algebraic and Symplectic Geometry Seminar |
L3 |
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Tue, 08/06/2010 16:00 |
Richard Wade (Oxford) |
Junior Geometric Group Theory Seminar |
DH 3rd floor SR |
| Starting from a definition of the cohomology of a group, we will define the bounded cohomology of a group. We will then show how quasi-homomorphisms lead to cocycles in the second bounded cohomology group, and use this to look at the second bounded cohomology of some of our favourite groups. If time permits we will end with some applications. | |||
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Tue, 08/06/2010 17:00 |
Christopher S Hoskin (Oxford) |
Functional Analysis Seminar |
L3 |
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Tue, 08/06/2010 17:00 |
Yiftach Barnea (Royal Holloway) |
Algebra Seminar |
L2 |
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Wed, 09/06/2010 09:00 |
Chris Douglas |
K-Theory Day |
L3 |
| Ordinary homology is a geometrically defined invariant of spaces: the 0-th homology group counts the number of components; the n-th homology group counts n-cycles, which correspond to an intuitive notion of 'n-dimensional holes' in a space. K-theory, or more specifically the 0-th K-theory group, is defined in terms of vector bundles, and so also has an immediate relationship to geometry. By contrast, the n-th K-theory group is typically defined homotopy-theoretically using the black box of Bott periodicity. I will describe a more geometric perspective on K-theory, using Z/2-graded vector bundles and bundles of modules for Clifford algebras. Along the way I will explain Clifford algebras, 2-categories, and Morita equivalence, explicitly check the purely algebraic 8-fold periodicity of the Clifford algebras, and discuss how and why this periodicity implies Bott periodicity. The talk will not presume any prior knowledge of K-theory, Clifford algebras, Bott periodicity, or the like. Based on joint work with Arthur Bartels and Andre Henriques | |||
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Wed, 09/06/2010 11:00 |
Pierre-Henri Chaudouard (Orsay) |
Special Lecture |
SR1 |
| We shall explain what is the weighted fundamental lemma and how it is related to the truncated Hitchin fibration. | |||
