Fri, 04 Mar 2016

15:30 - 16:30
L2

Hurricanes and Climate Change

Professor Kerry Emanuel
(MIT)
Abstract

In his talk, Kerry will explore the pressing practical problem of how hurricane activity will respond to global warming, and how hurricanes could in turn be influencing the atmosphere and ocean

Wed, 02 Mar 2016

16:00 - 17:00
C3

Group Cohomology and Quasi-Isometries

Alex Margolis
(Oxford)
Abstract

I will present a basic overview of finiteness conditions, group cohomology, and related quasi-isometry invariance results. In particular, I will show that if a group satisfies certain finiteness conditions, group cohomology with group ring coefficients encodes some structure of the `homology at infinity' of a group. This is seen for hyperbolic groups in the work of Bestvina-Mess, which relates the group cohomology to the Čech cohomology of the boundary.

Tue, 03 May 2016
14:30
L3

Optimal preconditioners for systems defined by functions of Toeplitz matrices

Sean Hon
(University of Oxford)
Abstract

We propose several optimal preconditioners for systems defined by some functions $g$ of Toeplitz matrices $T_n$. In this paper we are interested in solving $g(T_n)x=b$ by the preconditioned conjugate method or the preconditioned minimal residual method, namely in the cases when $g(T_n)$ are the analytic functions $e^{T_n}$, $\sin{T_n}$ and $\cos{T_n}$. Numerical results are given to show the effectiveness of the proposed preconditioners.

Wed, 24 Feb 2016

16:00 - 17:00
C3

CAT(0) Boundaries

Robert Kropholler
(Oxford University)
Abstract

I will talk about the boundaries of CAT(0) groups giving definitions, some examples and will state some theorems. I may even prove something if there is time. 

Tue, 01 Mar 2016
14:30
L3

Kerdock matrices and the efficient quantization of subsampled measurements

Andrew Thompson
(University of Oxford)
Abstract

Kerdock matrices are an attractive choice as deterministic measurement matrices for compressive sensing. I'll explain how Kerdock matrices are constructed, and then show how they can be adapted to one particular  strategy for quantizing measurements, in which measurements exceeding the desired dynamic range are rejected.

Wed, 17 Feb 2016

11:00 - 11:30
N3.12

The Riemann zeta function, quantum chaos and random matrices

Simon Myerson
(Oxford)
Abstract
The Riemann zeta function is linked to quantum chaology by some totally neat results and utterly wacky conjectures concerning random matrices. Join me to see the horrifying extent of these unexpected connections!
Wed, 24 Feb 2016

11:00 - 12:30
N3.12

Outer Automorphisms of Hyperbolic Groups

Alex Margolis
(Oxford)
Abstract

I will talk about a remarkable theorem by Paulin, which says
that if a one-ended hyperbolic group has infinite outer automorphism
group, then it splits over a two-ended subgroup. In particular, this
gives a condition which ensures a hyperbolic group doesn't have property
(T).

 

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