Tue, 22 Oct 2019
14:15
L4

Representations associated to gradations of colour Lie algebras

Philippe Meyer
(Oxford University)
Abstract

The notion of colour Lie algebra, introduced by Ree (1960), generalises notions of Lie algebra and Lie superalgebra. From an orthogonal representation V of a quadratic colour Lie algebra g, we give various ways of constructing a colour Lie algebra g’ whose bracket extends the bracket of g and the action of g on V. A first possibility is to consider g’=g⊕V and requires the cancellation of an invariant studied by Kostant (1999). Another construction is possible when the representation is ``special’’ and in this case the extension is of the form g’=g⊕sl(2,k)⊕V⊗k^2. Covariants are associated to special representations and satisfy to particular identities generalising properties studied by Mathews (1911) on binary cubics. The 7-dimensional fundamental representation of a Lie algebra of type G_2 and the 8-dimensional spinor representation of a Lie algebra of type so(7) are examples of special representations.

Reversible signal transmission in an active mechanical metamaterial
Browning, A Woodhouse, F Simpson, M Proceedings of the Royal Society A volume 475 issue 2227 20190146 (24 Jul 2019)
Fri, 25 Oct 2019

17:30 - 18:30
L1

Jon Chapman - Waves and resonance: from musical instruments to vacuum cleaners, via metamaterials and invisibility cloaks

Jon Chapman
(University of Oxford)
Further Information

Oxford Mathematics Public Lectures 

Jon Chapman - Waves and resonance: from musical instruments to vacuum cleaners, via metamaterials and invisibility cloaks.

Friday 25 October 2019

5.30pm-6.30pm, Mathematical Institute, Oxford

Please email @email to register.

Watch live:
https://facebook.com/OxfordMathematics
https://livestream.com/oxuni/chapman

Jon Chapman is Professor of Mathematics and its Applications in Oxford.

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

Fri, 15 Nov 2019

10:00 - 11:00
L3

Single molecule tracking, Metropolis-Hastings sampling and graphs

Michael Hirsch
(STFC)
Abstract

Optical super-resolution microscopy enables the observations of individual bio-molecules. The arrangement and dynamic behaviour of such molecules is studied to get insights into cellular processes which in turn lead to various application such as treatments for cancer diseases. STFC's Central Laser Facility provides (among other) public access to super-resolution microscope techniques via research grants. The access includes sample preparation, imaging facilities and data analysis support. Data analysis includes single molecule tracking algorithms that produce molecule traces or tracks from time series of molecule observations. While current algorithms are gradually getting away from "connecting the dots" and using probabilistic methods, they often fail to quantify the uncertainties in the results. We have developed a method that samples a probability distribution of tracking solutions using the Metropolis-Hastings algorithm. Such a method can produce likely alternative solutions together with uncertainties in the results. While the method works well for smaller data sets, it is still inefficient for the amount of data that is commonly collected with microscopes. Given the observations of the molecules, tracking solutions are discrete, which gives the proposal distribution of the sampler a peculiar form. In order for the sampler to work efficiently, the proposal density needs to be well designed. We will discuss the properties of tracking solutions and the problems of the proposal function design from the point of view of discrete mathematics, specifically in terms of graphs. Can mathematical theory help to design a efficient proposal function?

Tue, 24 Sep 2019
14:15
L4

Contravariant forms on Whittaker modules

Adam Brown
(IST Austria)
Abstract

In 1985, McDowell introduced a family of parabolically induced Whittaker modules over a complex semisimple Lie algebra, which includes both Verma modules and the nondegenerate Whittaker modules studied by Kostant. Many classical results for Verma modules and the Bernstein--Gelfand--Gelfand category O have been generalized to the category of Whittaker modules introduced by Milicic--Soergel, including the classification of irreducible objects and the Kazhdan--Lusztig conjectures. Contravariant forms on Verma modules are unique up to scaling and play a key role in the definition of the Jantzen filtration. In this talk I will discuss a classification of contravariant forms on parabolically induced Whittaker modules. In a recent result, joint with Anna Romanov, we show that the dimension of the space of contravariant forms on a parabolically induced Whittaker module is given by the cardinality of a Weyl group. This result illustrates a divergence from classical results for Verma modules, and gives insight to two significant open problems in the theory of Whittaker modules: the Jantzen conjecture and the absence of an algebraic definition of duality.

Search for PeV Gamma-Ray Emission from the Southern Hemisphere with 5
Years of Data from the IceCube Observatory
Bagherpour, H Argüelles, C Auffenberg, J Anderson, T Ansseau, I Backes, P Anton, G Axani, S Bai, X Bernardini, E Besson, D Blaufuss, E Bindig, D BenZvi, S Berley, D Tjus, J Binder, G Blot, S Brostean-Kaiser, J Busse, R Chirkin, D Burgman, A Buscher, J Carver, T Cheung, E The Astrophysical Journal: an international review of astronomy and astronomical physics (27 Feb 2020)
Tue, 03 Dec 2019

11:00 - 12:00
L6

Babbage's mechanical notation

Adrian Johnstone
(Royal Holloway University of London)
Abstract

Charles Babbage (1791–1871) was Lucasian Professor of mathematics in Cambridge from 1828–1839. He displayed a fertile curiosity that led him to study many contemporary processes and problems in a way which emphasised an analytic, data driven view of life.

In popular culture Babbage has been celebrated as an anachronistic Victorian engineer. In reality, Babbage is best understood as a figure rooted in the enlightenment, who had substantially completed his core investigations into 'mechanisation of thought' by the mid 1830s: he is thus an anachronistic Georgian: the construction of his first difference engine design is contemporary with the earliest public railways in Britain.

A fundamental question that must strike anybody who examines Babbage's precocious designs is: how could one individual working alone have synthesised a workable computer design, designing an object whose complexity of behaviour so far exceeded that of contemporary machines that it would not be matched for over a hundred years?

We shall explore the extent to which the answer lies in the techniques Babbage developed to reason about complex systems. His Notation which shows the geometry, timing, causal chains and the abstract components of his machines, has a direct parallel in the Hardware Description Languages developed since 1975 to aid the design of large scale electronics. In this presentation, we shall provide a basic tutorial on Babbage's notation showing how his concepts of 'pieces' and 'working points' effectively build a graph in which both parts and their interactions are represented by nodes, with edges between part-nodes and interaction-nodes denoting ownership, and edges between interaction-nodes denoting the transmission of forces between individual assemblies within a machine. We shall give examples from Babbage's Difference Engine 2 for which a complete set of notations was drawn in 1849, and compare them to a design of similar complexity specified in 1987 using the Inmos HDL.

Mon, 23 Sep 2019 11:00 -
Wed, 25 Sep 2019 16:00
L3

EUROMECH: Fluid and solid mechanics for tissue engineering

Various Speakers
Further Information

In vitro tissue engineering (TE) aims to create functional tissue and organ samples external to the body to replace damaged or diseased tissues and organs. By using cells (e.g. autologous or allogenic) in combination with natural or synthetic biomaterial scaffolds and biochemical factors, tissueengineered products have many advantages over traditional approaches such as donor tissue and organ transplantation that can elicit an adverse immune response. The development of the growing tissue construct, the combination of scaffold, cells, extracellular matrix (ECM) and biochemical factors, often occurs within a bioreactor that enables precise control of the bio-mechanochemical environment experienced by the cells within the growing construct.


This is particularly important in the development of mechanosensitive tissues, such as bone. Successfully engineering tissues in vitro has required the development of new smart biomaterials, new tissue growth strategies involving defined biological cues, and novel and bespoke bioreactor environments for growing tissue under physiological mechanical conditions. To date, only simple avascular tissues have been successfully generated to a standard where they can be used in a clinical setting, and research into methods for improving tissue viability is essential.


In TE systems, fluid and solid mechanics are used to provide mechanical load (e.g. via fluid shear, elastic deformation) to mechanosensitive tissues such as bone and vasculature, and a key challenge is to recreate the mechanical environment within the bioreactor system that is unique to the tissue under consideration. The fluid flows and solid deformations are intricate, requiring an understanding of novel fluid-structure interactions between the fluid flows, the cells and their ECM, and the (often deformable) biomaterial.  Furthermore, successful tissue growth in bioreactor systems relies on appropriate solute delivery to and waste-product removal from the cells in the tissue construct. To promote transport (without recourse to agitation methods that can be damaging to cells in a tissue-engineering setting), fluid flows are exploited to enhance transport by advection. 

In this colloquium, we will present state-of-the-art theoretical and experimental fluid and solid mechanics for TE, and explore the transformative potential of combined quantitative theoretical and experimental approaches to inform in vitro TE protocols. The theoretical models will be validated via detailed comparison of the theoretical model predictions with quantitative data obtained from state-of-the art biomechanics experiments. The hybrid approach of combining the resulting insights from the validated theoretical models with in vitro TE experiments can then be used to inform bioreactor and smart biomaterial design for TE strategies, with the aim of improving tissue viability.

Delegates are drawn from the theoretical and experimental fluid and solid mechanics communities. To ensure the focus remains applicable to the TE challenges, we have invited leading figures from the TE community, which will also facilitate new opportunities for interdisciplinary collaboration.

Abstract

Here is the scientific program.

 

Keynote speakers:

Roger Kamm, Cecil and Ida Green Distinguished Professor of Biological and Mechanical Engineering, MIT

Alicia El Haj,  Interdisciplinary Chair of Cell Engineering, Healthcare Technology Institute, University of Birmingham

 

Invited speakers (confirmed to date):

Davide Ambrosi, Politecnico di Torino, Italy

Anthony Callanan, University of Edinburgh, UK

Ruth Cameron, University of Cambridge, UK

Sonia Contera, University of Oxford, UK

Linda Cummings, New Jersey Institute of Technology, USA

Mohit Dalwadi, University of Oxford, UK

John Dunlop, University of Salzburg, Austria

John King, Nottingham, UK

Nati Korin, Technion, Israel

Catriona Lally, Trinity College Dublin, Ireland

Sandra Loerakker, TU Eindhoven, Netherlands

Ivan Martin, University of Basel, Switzerland

Scott McCue, Queensland University of Technology, Australia

Pierre-Alexis Mouthuy, University of Oxford, UK

Tom Mullin,  University of Oxford, UK

Ramin Nasehi, Politecnico di Milano, Italy

Reuben O'Dea, University of Nottingham, UK

James Oliver, University of Oxford, UK

Ioannis Papantoniou, KU Leuven, Belgium

Ansgar Petersen, Julius Wolf Institute Berlin, Germany

Luigi Preziosi, Politecnico di Torino, Italy

Rebecca Shipley, University College London, UK

Barbara Wagner, Weierstrass Institute for Applied Analysis and Stochastics, Berlin

Cathy Ye, Oxford University, UK

Feihu Zhao, TU Eindhoven, Netherlands

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