Thu, 11 Jun 2020
12:00
Virtual

On dynamic slip boundary condition

Erika Maringova
(Vienna University of Technology)
Abstract

In the talk, we study the Navier–Stokes-like problems for the flows of homogeneous incompressible fluids. We introduce a new type of boundary condition for the shear stress tensor, which includes an auxiliary stress function and the time derivative of the velocity. The auxiliary stress function serves to relate the normal stress to the slip velocity via rather general maximal monotone graph. In such way, we are able to capture the dynamic response of the fluid on the boundary. Also, the constitutive relation inside the domain is formulated implicitly. The main result is the existence analysis for these problems.

Thu, 28 May 2020
15:00
Virtual

Boundary regularity of area-minimizing currents: a linear model with analytic interface

Zihui Zhao
(University of Chicago)
Abstract

Given a curve , what is the surface  that has smallest area among all surfaces spanning ? This classical problem and its generalizations are called Plateau's problem. In this talk we consider area minimizers among the class of integral currents, or roughly speaking, orientable manifolds. Since the 1960s a lot of work has been done by De Giorgi, Almgren, et al to study the interior regularity of these minimizers. Much less is known about the boundary regularity, in the case of codimension greater than 1. I will speak about some recent progress in this direction.

Thu, 30 Apr 2020

16:45 - 17:30
Virtual

Extensions of C*-algebras

Christian Bonicke
(University of Glasgow)
Further Information

UK Virtual operator algebras seminar by zoom: https://sites.google.com/view/uk-operator-algebras-seminar/home

Abstract

Having its roots in classical operator theoretic questions, the theory of extensions of C*-algebras is now a powerful tool with applications in geometry and topology and of course within the theory of C*-algebras itself. In this talk I will give a gentle introduction to the topic highlighting some classical results and more recent applications and questions.

Thu, 30 Apr 2020

16:00 - 16:45
Virtual

Amenability via ultraproduct embeddings for II_1 factors

Scott Atkinson
(University of California Riverside)
Further Information

UK Virtual operator algebras seminar by zoom.  https://sites.google.com/view/uk-operator-algebras-seminar/home

Abstract

The property of amenability is a cornerstone in the study and classification of II_1 factor von Neumann algebras. Likewise, ultraproduct analysis is an essential tool in the subject. We will discuss the history, recent results, and open questions on characterizations of amenability for separable II_1 factors in terms of embeddings into ultraproducts.

Wed, 27 May 2020
10:00
Virtual

Poincare's Polyhedron Theorem and Applications to Algorithms.

Joe Scull
(University of Oxford)
Abstract

Much progress in the study of 3-manifolds has been made by considering the geometric structures they admit. This is nowhere more true than for 3-manifolds which admit a hyperbolic structure. However, in the land of algorithms a more combinatorial approach is necessary, replacing our charts and isometries with finite simplicial complexes that are defined by a finite amount of data. 

In this talk we'll have a look at how in fact one can combine the two approaches, using the geometry of hyperbolic 3-manifolds to assist in this more combinatorial approach. To do so we'll combine tools from Hyperbolic Geometry, Triangulations, and perhaps suprisingly Polynomial Algebra to find explicit bounds on the runtime of an algorithm for comparing Hyperbolic manifolds.

Wed, 13 May 2020
10:00
Virtual

A Mapping Class Group Presentation from Fatgraphs

Adele Jackson
(University of Oxford)
Abstract

The mapping class group of a surface with boundary acts freely and properly discontinuously on the fatgraph complex, which is a contractible cell complex arising from a cell decomposition of Teichmuller space. We will use this action to get a presentation of the mapping class group in terms of fat graphs, and convert this into one in terms of chord diagrams. This chord slide presentation has potential applications to computing bordered Heegaard Floer invariants for open books with disconnected binding.

Wed, 06 May 2020
10:00
Virtual

Revisiting Leighton's Theorem

Daniel Woodhouse
(University of Oxford)
Abstract

Let X_1 and X_2 be finite graphs with isomorphic universal covers.

Leighton's graph covering theorem states that X_1 and X_2 have a common finite cover.

I will discuss recent work generalizing this theorem and how myself and Sam Shepherd have been applying it to rigidity questions in geometric group theory.

Mon, 04 May 2020
12:45
Virtual

Superstrings, Calabi-Yau Manifolds and Machine-Learning -- ZOOM SEMINAR

Yang-Hui He
(City University)
Abstract

We review how historically the problem of string phenomenology lead theoretical physics first to algebraic/diffenretial geometry, and then to computational geometry, and now to data science and AI.
With the concrete playground of the Calabi-Yau landscape, accumulated by the collaboration of physicists, mathematicians and computer scientists over the last 4 decades, we show how the latest techniques in machine-learning can help explore problems of physical and mathematical interest.
 

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