Friday, 7 July 2017

The Law of the Few - Sanjeev Goyal's Oxford Mathematics Public Lecture now online

The study of networks offers a fruitful approach to understanding human behaviour. Sanjeev Goyal is one of its pioneers. In this lecture Sanjeev presents a puzzle:

In social communities, the vast majority of individuals get their information from a very small subset of the group – the influencers, connectors, and opinion leaders. But empirical research suggests that there are only minor differences between the influencers and the others. Using mathematical modelling of individual activity and networking and experiments with human subjects, Sanjeev helps explain the puzzle and the economic trade-offs it contains.

Professor Sanjeev Goyal FBA is the Chair of the Economics Faculty at the University of Cambridge and was the founding Director of the Cambridge-INET Institute.




Thursday, 6 July 2017

Alex Wilkie and Alison Etheridge win LMS Prizes

Congratulations to the Oxford Mathematicians who have just been awarded LMS prizes. Alex Wilkie receives the Pólya Prize for his profound contributions to model theory and to its connections with real analytic geometry and Alison Etheridge receives the Senior Anne Bennett Prize in recognition of her outstanding research on measure-valued stochastic processes and applications to population biology; and for her impressive leadership and service to the profession.

Thursday, 29 June 2017

Oxford Mathematics Visiting Professor Michael Duff awarded the Paul Dirac Medal and Prize

Professor Michael Duff of Imperial College London and Visiting Professor here in the Mathematical Institute in Oxford has been awarded the Dirac Medal and Prize for 2017 by the Institute of Physics for “sustained groundbreaking contributions to theoretical physics including the discovery of Weyl anomalies, for having pioneered Kaluza-Klein supergravity, and for recognising that superstrings in 10 dimensions are merely a special case of p-branes in an 11-dimensional M-theory.”

Michael Duff holds a Leverhulme Emeritus Fellowship, is a Fellow of the Royal Society, the American Physical Society and the Institute of Physics and was awarded the 2004 Meeting Gold Medal, El Colegio Nacional, Mexico. 

Wednesday, 21 June 2017

Exploding the myths of Ada Lovelace’s mathematics

Ada Lovelace (1815–1852) is celebrated as “the first programmer” for her remarkable 1843 paper which explained Charles Babbage’s designs for a mechanical computer. New research reinforces the view that she was a gifted, perceptive and knowledgeable mathematician.

Christopher Hollings and Ursula Martin of Oxford Mathematics, and Adrian Rice, of Randolph-Macon College in Virginia, are the first historians of mathematics to investigate the extensive archives of the Lovelace-Byron family, held in Oxford’s Bodleian Library. In two recent papers in the Journal of the British Society for the History of Mathematics and in Historia Mathematica they study Lovelace’s childhood education, where her passion for mathematics was complemented by an interest in machinery and wide scientific reading; and her remarkable two-year “correspondence course” on calculus with the eminent mathematician Augustus De Morgan, who introduced her to cutting edge research on the nature of algebra.

The work challenges widespread claims that Lovelace’s mathematical abilities were more “poetical” than practical, or indeed that her knowledge was so limited that Babbage himself was likely to have been the author of the paper that bears her name. The authors pinpoint Lovelace’s keen eye for detail, fascination with big questions, and flair for deep insights, which enabled her to challenge some deep assumptions in her teacher’s work. They suggest that her ambition, in time, to do significant mathematical research was entirely credible, though sadly curtailed by her ill-health and early death.

The papers, and the correspondence with De Morgan, can be read in full on the website of the Clay Mathematics Institute, who supported the work, as did the UK Engineering and Physical Sciences Research Council.

Monday, 19 June 2017

Live Podcast and Facebook. The Law of the Few - Sanjeev Goyal's Oxford Mathematics Public Lecture 28 June

The study of networks offers a fruitful approach to understanding human behaviour. Sanjeev Goyal is one of its pioneers. In this lecture Sanjeev presents a puzzle:

In social communities, the vast majority of individuals get their information from a very small subset of the group – the influencers, connectors, and opinion leaders. But empirical research suggests that there are only minor differences between the influencers and the others. Using mathematical modelling of individual activity and networking and experiments with human subjects, Sanjeev helps explain the puzzle and the economic trade-offs it contains.

Professor Sanjeev Goyal FBA is the Chair of the Economics Faculty at the University of Cambridge and was the founding Director of the Cambridge-INET Institute.

Podcast notification - 5pm on 28 June 2017

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Places still available if you wish to attend in person - Mathematical Institute, Oxford, 28 June, 5pm. Please email to register

Saturday, 17 June 2017

Oxford Mathematician Alison Etheridge awarded an OBE

Oxford Mathematician Alison Etheridge FRS has been awarded an OBE in the Queen's Birthday Honours List for Services to Science. Alison is Professor of Probability in Oxford and will take up the Presidency of the Institute of Mathematical Statistics in August 2017.

Alison's research has a particular focus on mathematical models of population genetics, where she has been involved in efforts to understand the effects of spatial structure of populations on their patterns of genetic variation. She recently gave an Oxford Mathematics Public Lecture on the mathematical modelling of genes.

Friday, 16 June 2017

Oxford Mathematicians invited to speak at ICM 2018

The International Congress of Mathematicians (ICM) is the largest conference in mathematics. It meets once every four years, hosted by the International Mathematical Union (IMU) and hands out the most important prizes in the subject, notably the Fields Medals and the Nevanlinna and Gauss Prizes. At the Congress leading mathematicians are invited to present their research and in 2018 in Rio Oxford Mathematics will be represented by Mike GilesRichard HaydonPeter KeevashJochen Koenigsmann, James Maynard and Miguel Walsh, a team whose wide-ranging interests demonstrate both the strength of the subject in Oxford, but also the scope of mathematics in the 21st Century.

Miguel and James are also Clay Research Fellows. The Clay Mathematics Institute supports the work of leading researchers at various stages of their careers and organises conferences, workshops, and summer schools. The annual Research Award recognises contemporary breakthroughs in mathematics.

If you want to know more about the ICM, Oxford Mathematician Chris Hollings explains how even mathematics cannot escape politics.

Tuesday, 13 June 2017

How fast does the Greenland Ice Sheet move?

Governments around the world are seeking to address the economic and humanitarian consequences of climate change. One of the most graphic indications of warming temperatures is the melting of the large ice caps in Greenland and Antarctica.  This is a litmus test for climate change, since ice loss may contribute more than a metre to sea-level rise over the next century, and the fresh water that is dumped into the ocean will most likely affect the ocean circulation that regulates our temperature.

Melting ice is not itself a sign of climate warming, because the ice sheet is constantly being replenished by new snow falling on its surface. The net amount of ice loss in fact results from a quite delicate imbalance between the addition of new snow and the discharge of ice to the ocean in the form of icebergs.  Understanding this imbalance requires an understanding of how fast the ice moves.   

Oxford Mathematician Ian Hewitt has been addressing this question using fluid-dynamical models. “We model glacial ice as a non-Newtonian viscous fluid. The central difficulty in computing the ice flow is the boundary condition at the base.  In conventional fluid mechanics a no-slip condition would apply, but the presence of melt water that has penetrated through cracks in the ice acts as a lubricant and effectively allows slip - often a very significant amount of slip.”   

In a recent study Ian has combined a model of the ice flow with a model for the water drainage underneath the ice to account for this varying degree of lubrication. "This new model is able to explain seasonal variations in the flow of the ice that have been observed using GPS instruments - it moves faster during spring and early summer, and slows down slightly in autumn.  Intriguingly, the net effect on the ice motion over the course of the year can be both positive and negative, depending on which of these - the acceleration or subsequent deceleration - dominates.  This depends on the amount of melt water that is produced on the surface, which has almost doubled over the last decade.”  

Ongoing work is attempting to combine the modelled behaviour with satellite observations to better constrain what might happen in the future.  Ian Hewitt talks about this research in an Oxford Sparks podcast.

Monday, 5 June 2017

The mathematics of abnormal skull growth

Mathematics is delving in to ever-wider aspects of the physical world. Here Oxford Mathematician Alain Goriely describes how mathematicians and engineers are working with medics to better understand the workings of the human brain and in particular the issue of abnormal skull growth.

"In 2013, together with Prof. Antoine Jérusalem from the Engineering Department, I opened the International Brain Mechanics and Trauma Lab (IBMTL) here in Oxford. IBMTL is a network of people interested in the many and varied problems of brain mechanics and morphogenesis. As part of our launch, in true Oxford style, we organised a workshop where I got talking to Jayaratnam Jayamohan, aka Jay Jay, MD at the John Radcliffe Hospital in Oxford and a brilliant paediatric neurosurgeon whose work has featured in BBC documentaries. Jay Jay routinely performs surgery on children to rectify abnormal skull growth (so-called “craniosynostosis”).The variety of shapes and intricacy of growth processes that he talked about immediately captured my imagination. He explained that much has been learnt about this process from a genetic and biochemical perspective and the world expert, Prof. Andrew O. M. Wilkie, also happened to be working in Oxford. I decided to pay him a visit.

Andrew Wilkie has done groundbreaking work in identifying genetic mutations behind rare craniofacial malformations and, in my discussions with him, he was particularly helpful in explaining the mechanisms underlying this fascinating process. Yet, surprisingly, I found that very little was known about the physics and bio-mechanics of the problem. And when I was told that the problem of understanding the formation of these shapes was probably too complex to be studied using mathematical modelling tools, I realised I had a challenge I couldn’t possibly resist. What’s more I had the perfect partner in Prof. Ellen Kuhl at Stanford University. Ellen is an expert in biomechanical modelling and has developed state-of-the-art computational techniques to simulate the growth of biological tissues. We had much to work on.

The growth of the skull in harmony with the brain is an extremely complex morphogenetic process. As the brain grows, the skull must grow in response to accommodate extra volume while providing a tight fit. These are very different growth processes. The extremely soft brain increases in volume while the extremely hard bone must increase in surface area. How does this process take place?

In the spirit of mathematical modelling, we started with a very simple question: how would a given shape remain invariant during such growth processes? We know that the skull grows through two different processes: first, accretion along the suture lines (transforming soft cartilage into bone) and second, remodelling of the shape to change locally the curvature. Without remodelling, the shape cannot remain invariant (since surface addition mostly happens along a line, a point with initial high curvature away from this line would remain highly curved unless a second process enabled the reduction of the curvature so that the shape remains a dilation of the original shape).

Using dimensional arguments, we concluded that the three processes (volume growth, line growth, and remodelling) are inter-dependent and must necessarily be tightly regulated. But how is this process synchronized? Since the information about the shape is global, the cues that trigger the growth process must be physical as has been suggested in the biological literature. By simple physical estimates of pressure, stresses and strains, our analysis further identified strain as the main biophysical regulator of this growth process.

At this point, a natural question to ask is what happens when this process is disrupted? We decided to extract the fundamental elements of this growth process by looking at the evolution of a semi-ellipsoid (an elongated half-sphere) divided into a number of patches representing the various bones, fontanelles (soft spots), and sutures of the cranial vault. Normal growth process is obtained by allowing the bones to grow along the suture lines. However, we decided to perturb the system by fusing some of the suture lines early as happens during craniosynostosis. To our great surprise, the various shapes obtained mirrored the ones found in craniosynostosis. We showed that idealised geometries produce good agreement between numerically predicted and clinically observed cephalic indices (defined as the cranial vault’s width by its length) as well as excellent qualitative consistency in skull shape – in other words the model worked. The particular geometric role in the relative arrangement of the early cranial vault bones and the sutures appear clearly in our models. What is truly remarkable is that, despite the extreme complexity of the underlying system, the shapes developed in these pathologies seem to be dictated mostly by geometry and mechanics.

What's next? Our models are, of course, extremely simple from a biological standpoint. However, they can be easily coupled to biochemical processes in order to analyse several open questions in morphogenesis and clinical practice such as the impact of different bone growth rates, the relative magnitude of mechanical and biochemical stimuli during normal skull growth, and the optimal dimensions of surgically re-opened sutures. Our mechanics-based model is also a tool to explore fundamental questions in developmental biology associated with the universality and optimality of cranial design in the evolution of mammalian skulls. These questions were raised exactly a century ago by d’Arcy Thompson in his seminal book “On Growth and Form” and we now have the mathematical and computational tools to answer them. We are only at the beginning."

A fuller discussion of the issues can be found in Alain and his colleagues' recently published paper. 

Monday, 5 June 2017

The mathematics of glass sheets - how to make their thickness uniform

Oxford Mathematician Doireann O'Kiely was recently awarded the IMA's biennial Lighthill-Thwaites Prize for her work on the production of thin glass sheets. Here Doireann describes her work which was conducted in collaboration with Schott AG.

"Thin glass sheets have many modern applications, including touch-screens, cameras and thumbprint sensors for smartphones. Glass sheets with thicknesses in the range 50–100µm are flexible, and may be used in bendable devices.

In the glass sheet redraw process, a prefabricated glass sheet is fed through a heater and stretched. When the glass is hot it behaves as a viscous fluid. As the glass is stretched, it gets thinner and the edges of the sheet are pulled in. This combined response means that both the thickness and the width of the sheet decrease, and the cross-section of the sheet can change shape so that the final product may not have uniform thickness.

In industrial processes, the heater is typically short compared to the sheet width to minimize width reduction and yield desirable thin, wide glass sheets. However, sheets produced in this way are typically thicker at the edge than elsewhere (see image). Asymptotic analysis of the process in this limit indicates that the behaviour in the main part of the sheet is one-dimensional – it varies only in the direction of motion – and there is a two-dimensional boundary layer near the sheet edge.

Numerical solution of the boundary-layer problem illustrates that the glass in the path of the inward-moving edge accumulates, leading to the observed thick edges. The same numerical scheme can also be used to determine the modified input shape required for the manufacture of a uniformly thin sheet. Physically, a small region at the edge of the sheet is tapered, making it thinner to compensate for the accumulation of glass during redraw."

The image above shows that the redrawn glass sheet is extremely thin, but is also relatively thick in a localised region near the sheet edge. Photo by Dominic Vella.