Thu, 13 Oct 2022
14:00
L6

1-form symmetry versus large N QCD

Theodore Jacobson
(University of Minnesota)

Note: we would recommend to join the meeting using the Zoom client for best user experience.

Further Information

It is possible to join online via Zoom.

Abstract

It has long been appreciated that in QCD-like theories without fundamental matter, confinement can be given a sharp characterization in terms of symmetry. More recently, such symmetries have been identified as 1-form symmetries, which fit into the broader category of generalized global symmetries.  In this talk I will discuss obstructions to the existence of a 1-form symmetry in large N QCD, where confinement is a sharp notion. I give general arguments for this disconnect between 1-form symmetries and confinement, and use 2d scalar QCD on the lattice as an explicit example.  

Thu, 06 Oct 2022
14:00
N3.12

Gravitational Regge bounds

Kelian Haring
(Cern)

Note: we would recommend to join the meeting using the Zoom client for best user experience.

Further Information

It is possible to join online via Zoom.

Abstract

I will review the basic assumptions and spell out the arguments that lead to the bound on the Regge growth of gravitational scattering amplitudes. I will discuss the Regge bounds both at fixed transfer momentum and smeared over it. Our basic conclusion is that gravitational scattering amplitudes admit dispersion relations with two subtractions. For a sub-class of smeared amplitudes, black hole formation reduces the number of subtractions to one. Finally, I will discuss bounds on local growth derived using dispersion relations. This talk is based on https://arxiv.org/abs/2202.08280.

Wed, 05 Oct 2022
17:00
Lecture Theatre 1, Mathematical Institute, Radcliffe Observatory Quarter, Woodstock Road, OX2 6GG

The million-dollar shuffle: symmetry and complexity - Colva Roney-Dougal

Colva Roney-Dougal
(University of St Andrews)
Further Information

In 1936, Alan Turing proved the startling result that not all mathematical problems can be solved algorithmically. For those which can be, we still do not always know when there's a clever technique which could give us the answer quickly. In particular, the famous "P = NP" question asks whether, for problems where the correct solution has a proof which can easily be checked, in fact there's a quick way to find the answer.

Many difficult problems become easier if they have symmetries: finding the shortest route to deliver many parcels would be easy if all the houses were neatly arranged in a circle. This lecture will explore the interactions between symmetry and complexity.

Colva Roney-Dougal is Professor of Pure Mathematics at the University of St Andrews and Director of the Centre for Interdisciplinary Research in Computational Algebra.

Please email @email to register.

The lecture will be available on our Oxford Mathematics YouTube Channel on 12 October at 5 pm.

The Oxford Mathematics Public Lectures are generously supported by XTX Markets.

Tue, 22 Nov 2022
14:00
L6

Character sheaves and Khovanov-Rozansky homology

Kostiantyn Tolmachov
(Edinburgh University)
Abstract

Khovanov-Rozansky homology is a link invariant that categorifies the HOMFLY-PT polynomial. I will describe a geometric model for this invariant, living in the monodromic Hecke category. I will also explain how it allows to identify objects representing graded pieces of Khovanov-Rozansky homology, using a remarkable family of character sheaves. Based on joint works with Roman Bezrukavnikov.

Moving beyond landscape resistance: considerations for the future of connectivity modelling and conservation science
Unnithan Kumar, S Turnbull, J Hartman Davies, O Hodgetts, T Cushman, S Landscape Ecology volume 37 2465-2480 (13 Aug 2022)
Polynomial bounds for chromatic number. I. Excluding a biclique and an induced tree
Scott, A Seymour, P Spirkl, S Journal of Graph Theory volume 102 issue 3 458-471 (01 Mar 2023)
Fri, 25 Nov 2022

12:00 - 13:00
N3.12

Knutson's Conjecture on the Representation Ring

Diego Martin Duro
(University of Warwick)
Abstract

Donald Knutson proposed the conjecture, later disproven and refined by Savitskii, that for every irreducible character of a finite group, there existed a virtual character such their tensor product was the regular character. In this talk, we disprove both this conjecture and its refinement. We then introduce the Knutson Index as a measure of the failure of Knutson's Conjecture and discuss its algebraic properties.

Thu, 03 Nov 2022

16:00 - 17:00
L3

Decentralised Finance and Automated Market Making: Optimal Execution and Liquidity Provision

Fayçal Drissi
Abstract

Automated Market Makers (AMMs) are a new prototype of 
trading venues which are revolutionising the way market participants 
interact. At present, the majority of AMMs are Constant Function 
Market Makers (CFMMs) where a deterministic trading function 
determines how markets are cleared. A distinctive characteristic of 
CFMMs is that execution costs for liquidity takers, and revenue for 
liquidity providers, are given by closed-form functions of price, 
liquidity, and transaction size. This gives rise to a new class of 
trading problems. We focus on Constant Product Market Makers with 
Concentrated Liquidity and show how to optimally take and make 
liquidity. We use Uniswap v3 data to study price and liquidity 
dynamics and to motivate the models.

For liquidity taking, we describe how to optimally trade a large 
position in an asset and how to execute statistical arbitrages based 
on market signals. For liquidity provision, we show how the wealth 
decomposes into a fee and an asset component. Finally, we perform 
consecutive runs of in-sample estimation of model parameters and 
out-of-sample trading to showcase the performance of the strategies.

Thu, 24 Nov 2022

12:00 - 13:00
L1

Hypergraphs for multiscale cycles in structured data (Yoon) Minmax Connectivity and Persistent Homology (Yim)

Ambrose Yim & Iris Yoon (OCIAM)
(Mathematical Institute)
Abstract

Hypergraphs for multiscale cycles in structured data

Iris Yoon

Understanding the spatial structure of data from complex systems is a challenge of rapidly increasing importance. Even when data is restricted to curves in three-dimensional space, the spatial structure of data provides valuable insight into many scientific disciplines, including finance, neuroscience, ecology, biophysics, and biology. Motivated by concrete examples arising in nature, I will introduce hyperTDA, a topological pipeline for analyzing the structure of spatial curves that combines persistent homology, hypergraph theory, and network science. I will show that the method highlights important segments and structural units of the data. I will demonstrate hyperTDA on both simulated and experimental data. This is joint work with Agnese Barbensi, Christian Degnbol Madsen, Deborah O. Ajayi, Michael Stumpf, and Heather Harrington.

 

Minmax Connectivity and Persistent Homology 

Ambrose Yim

We give a pipeline for extracting features measuring the connectivity between two points in a porous material. For a material represented by a density field f, we derive persistent homology related features by exploiting the relationship between dimension zero persistent homology of the density field and the min-max connectivity between two points. We measure how the min-max connectivity varies when spurious topological features of the porous material are removed under persistent homology guided topological simplification. Furthermore, we show how dimension one persistent homology encodes a relaxed notion of min-max connectivity, and demonstrate how we can summarise the multiplicity of connections between a pair of points by associating to the pair a sub-diagram of the dimension one persistence diagram.

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