FAUST: Formal Abstractions of Uncountable-STate STochastic Processes
Soudjani, S Gevaerts, C Abate, A Lecture Notes in Computer Science volume 9035 272-286 (2015)
Symbolic models for stochastic switched systems: A discretization and a discretization-free approach
Zamani, M Abate, A Girard, A Automatica volume 55 183-196 (May 2015)
Thu, 28 May 2015

16:00 - 17:00
C2

Hyperbolic volume of links, via pants graph and train tracks

Antonio De Capua
(Oxford)
Abstract

A result of Jeffrey Brock states that, given a hyperbolic 3-manifold which is a mapping torus over a surface $S$, its volume can be expressed in terms of the distance induced by the monodromy map in the pants graph of $S$. This is an abstract graph whose vertices are pants decompositions of $S$, and edges correspond to some 'elementary alterations' of those.
I will show how this theorem gives an estimate for the volume of hyperbolic complements of closed braids in the solid torus, in terms of braid properties. The core piece of such estimate is a generalization of a result of Masur, Mosher and Schleimer that train track splitting sequences (which I will define in the talk) induce quasi-geodesics in the marking graph.

Thu, 21 May 2015

16:00 - 17:00
C2

Ricci flow invariant curvature conditions

Matthias Wink
(Oxford)
Abstract

In this talk we're going to discuss Hamilton's maximum principle for the Ricci flow. As an application, I would like to explain a technique due to Boehm and Wilking which provides a general tool to obtain new Ricci flow invariant curvature conditions from given ones. As we'll see, it plays a key role in Brendle and Schoen's proof of the differentiable sphere theorem.

Thu, 14 May 2015

16:00 - 17:00
C2

Zariski Geometries

Carlos Alfonso Ruiz
(Oxford)
Abstract
I will present a model theoretic point of view of algebraic geometry based on certain objects called Zariski Geometries. They were introduced by E. Hrushovski and B. Zilber and include classical objects like compact complex manifolds, algebraic varieties and rigid analytic varieties. Some connections with non commutative geometry have been found by B. Zilber too. I will concentrate on the relation between Zariski Geometries and schemes. 
Thu, 07 May 2015

16:00 - 17:00
C2

The geometry of the Ising model

Bruce Bartlett
(Oxford)
Abstract

The Ising model is a well-known statistical physics model, defined on a two-dimensional lattice. It is interesting because it exhibits a "phase transition" at a certain critical temperature. Recent mathematical research has revealed an intriguing geometry in the model, involving discrete holomorphic functions, spinors, spin structures, and the Dirac equation. I will try to outline some of these ideas.

Fri, 12 Jun 2015

12:30 - 14:00
L6

tbc

Michael Monoyios
Fri, 05 Jun 2015

12:30 - 14:00
L6

tbc

Sean Ledger
Fri, 08 May 2015

12:30 - 14:00
L5

Generalized Gauss and Expectation Inequalities via Semidefinite Programming

Paul Goulart
Abstract

This talk will describe methods for computing sharp upper bounds on the probability of a random vector falling outside of a convex set, or on the expected value of a convex loss function, for situations in which limited information is available about the probability distribution. Such bounds are of interest across many application areas in control theory, mathematical finance, machine learning and signal processing. If only the first two moments of the distribution are available, then Chebyshev-like worst-case bounds can be computed via solution of a single semidefinite program. However, the results can be very conservative since they are typically achieved by a discrete worst-case distribution. The talk will show that considerable improvement is possible if the probability distribution can be assumed unimodal, in which case less pessimistic Gauss-like bounds can be computed instead. Additionally, both the Chebyshev- and Gauss-like bounds for such problems can be derived as special cases of a bound based on a generalised definition of unmodality.

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