Mon, 11 Oct 2021

14:15 - 15:15
L4

Minimal surfaces, spectral geometry and homogenisation

Jean Lagacé
(University of Bristol)
Abstract

Free boundary minimal surfaces are a notoriously elusive object in geometric analysis. From 2011, Fraser and Schoen's research program found a relationship between free boundary minimal surfaces in unit balls and metrics which maximise the first nontrivial Steklov eigenvalue. In this talk, I will explain how we can adapt homogenisation theory, a branch of applied mathematics, to a geometric setting in order to obtain surfaces with first Steklov eigenvalue as large as possible, and how it leads to the existence of free boundary minimal surfaces which were previously thought not to exist.

Tue, 09 Nov 2021
14:00
Virtual

Classical field theory on quantum principal bundles

Branimir Cacic
(University of New Brunswick Canada)
Further Information

Please note unusual time.

Abstract

In his very first note on noncommutative differential geometry, Connes
showed that the position and momentum operators on the line could be used to
construct constant curvature connections over an irrational noncommutative

2-torus $\mathcal{A}_\theta$. When $\theta$ is a quadratic irrationality,
this yields, in particular, constant curvature connections on non-trivial
noncommutative line bundles---is there an underlying monopole on some
non-trivial noncommutative principal $U(1)$-bundle? We use this case study
to illustrate how approaches to quantum principal bundles introduced by
Brzeziński–Majid and Đurđević, respectively, can be fruitfully synthesized
to reframe classical gauge theory on quantum principal bundles in terms of
synthesis of total spaces (as noncommutative manifolds) from vertical and
horizontal geometric data.

The Mathematical Institute, Department of Computer Science and the Department of Statistics at the University of Oxford are consistently ranked amongst the very best mathematical sciences and computer science departments in the world, for both teaching and research. We are committed to attracting the world’s most talented students and working with them, to help them maximise their potential, regardless of race, gender, religion or background.

Tue, 23 Nov 2021
12:00
Virtual

Wick rotation and the axiomatisation of quantum field theory

Graeme Segal
Abstract

I shall present joint work with Maxim Kontsevich describing an interesting
domain of complex metrics on a smooth manifold. It is a complexification of
the space of ordinary Riemannian metrics, and has the Lorentzian metrics
(but not metrics of other signatures) on its boundary. Use of the domain
leads to a modified axiom system for QFT which illuminates not only the
special role of Lorentz signature, but also of features such as local
commutativity, unitarity, and global hyperbolicity.

Tue, 12 Oct 2021
12:00
Virtual

Quantized twistors and split octonions

Roger Penrose
Abstract

The non-compact exceptional simple group G_2* turns out to be the symmetry group of quantized twistor theory. Certain implications of this remarkable fact will be explored in this talk.

Thu, 14 Oct 2021

16:00 - 17:00
Virtual

Kernel-based Statistical Methods for Functional Data

George Wynne
(Imperial College London)
Further Information

ww.datasig.ac.uk/events

Abstract

Kernel-based statistical algorithms have found wide success in statistical machine learning in the past ten years as a non-parametric, easily computable engine for reasoning with probability measures. The main idea is to use a kernel to facilitate a mapping of probability measures, the objects of interest, into well-behaved spaces where calculations can be carried out. This methodology has found wide application, for example two-sample testing, independence testing, goodness-of-fit testing, parameter inference and MCMC thinning. Most theoretical investigations and practical applications have focused on Euclidean data. This talk will outline work that adapts the kernel-based methodology to data in an arbitrary Hilbert space which then opens the door to applications for functional data, where a single data sample is a discretely observed function, for example time series or random surfaces. Such data is becoming increasingly more prominent within the statistical community and in machine learning. Emphasis shall be given to the two-sample and goodness-of-fit testing problems.

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