Thu, 30 Nov 2023
15:00
L4

A gentle introduction to Ricci flow

John Hughes
(University of Oxford)
Abstract

Richard Hamilton introduced the Ricci flow as a way to study the Poincaré conjecture, which says that every simply connected, compact three-manifold is homeomorphic to the three-sphere. In this talk, we will introduce the Ricci flow in a way that is accessible to anyone with basic knowledge of Riemannian geometry. We will give some examples, discuss finite time singularities, and give an application to a theorem of Hamilton which says that every compact Riemannian 3-manifold with positive Ricci curvature admits a metric of constant positive sectional curvature.

Thu, 16 Nov 2023
15:00
L4

Compactness problems in new gauge theories

Alfred Holmes
(University of Oxford)
Abstract

Two areas of current research in Mathematical Gauge Theory are the study of higher dimensional instantons on manifolds with special holonomy (for example, Calabi-Yau three folds, Gand Spin(7) manifolds), and low dimensional gauge theories (for example the Kapustin-Witten, Haydys-Witten and ADHM Seiberg-Witten equations). A common feature of these two sets of theories is that the moduli spaces of solutions are in general not compact. In both cases, compactness issues arise because of solutions to a certain non-linear equation called the Fueter equation. In this talk, I'll explain how this non compactness gives a relationship between these high and low dimensional gauge theories.

Thu, 02 Nov 2023
15:00
L4

Generalising fat bundles and positive curvature

Alberto Rodriguez Vazquez
(KU Leuven)
Abstract

Alan Weinstein, introduced the concept of "fat bundle" as a tool to understand when the total space of a fiber bundle with totally geodesic fibers allows a metric with positive sectional curvature. 

In recent times, certain weaker notions than the condition of having a metric with positive sectional curvature have been studied due to the apparent scarcity of spaces that meet this condition. Positive kth-intermediate Ricci curvature (Rick > 0) on a Riemannian manifold Mn is a condition that bridges the gap between positive sectional curvature and positive Ricci curvature. Indeed, when k = 1, this condition corresponds to positive sectional curvature, and when k = n−1, it corresponds to positive Ricci curvature. 

In this talk, I will discuss an ongoing project with Miguel Domínguez Vázquez, David González-Álvaro, and Jason DeVito, which aims to create new examples of compact Riemannian manifolds with Ric2 > 0. We achieve this by employing a certain generalisation of the "fat bundle" concept.

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One-Dimensional Sectors From the Squashed Three-Sphere
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Isoperimetric stability in lattices
Barber, B Erde, J Keevash, P Roberts, A Proceedings of the American Mathematical Society volume 151 issue 12 5021-5029 (26 Sep 2023)
On Sárközy’s theorem for shifted primes
Green, B Journal of the American Mathematical Society volume 37 issue 4 1121-1201 (28 Sep 2023)
Spherical Branes
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Supersymmetric Yang-Mills, Spherical Branes, and Precision Holography
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Wrapped branes and punctured horizons
Bobev, N Bomans, P Gautason, F (10 Dec 2019)
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