• Online delivery via Zoom

The Centre for Mathematical Sciences research seminars and events are listed below.

The four main seminar series are in applied mathematics, pure mathematics, statistics and theoretical physics. Visit the centre's webpages for the latest seminar updates and information.

Wednesday 17 November: Bayesian network modelling provides spatial and temporal understanding of ecosystem dynamics within shallow shelf seas

• Speaker:  Neda Trifonova (Aberdeen)

Abstract: There is about to be an abrupt step-change in the use of our coastal seas, specifically by the addition of large-scale offshore renewable energy developments to combat climate change. Many trade-offs will need to be weighed up for the future sustainable management of marine ecosystems between renewables and other uses (e.g., fisheries, marine protected areas). Therefore, we need a much greater understanding of how different marine habitats and ecosystems are likely to change with both natural and anthropogenic transformations. Ecosystems consist of complex dynamic interactions among species and the environment, the understanding of which has implications for predicting the environmental response to changes in climate and biodiversity. However, with the recent adoption of more explorative tools, like Bayesian networks, in predictive ecology, few assumptions can be made about the data and complex, spatially varying interactions can be recovered from collected field data. In this talk, Bayesian techniques will be presented to find the data-driven estimates of interactions among a set of physical and biological variables and a human pressure within the last 30 years in a well-studied shallow sea (North Sea, UK). A hidden variable is incorporated to model functional ecosystem change, where the underlying interactions dramatically change, following natural or anthropogenic disturbance. Then, the learned data-driven interactions will be used to build a dynamic Bayesian network model to examine the response of species to changes in their environment. Other examples will also be illustrated to show the applications of Bayesian network techniques in predictive ecology.

This seminar is organised by Matthew Craven and Yinghui Wei and will be delivered via Zoom. Email matthew.craven@plymouth.ac.uk or yinghui.wei@plymouth.ac.uk for information.

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PREVIOUS SEMINARS | 2021/22 ACADEMIC YEAR

Wednesday 29 September: Coherent-spin amplitudes and classical observables

• Speaker: Rafael Aoude (UC Louvain)

The quantum field-theoretic approach to classical observables due to Kosower, Maybee and O’Connell provides a rigorous pathway from on-shell scattering amplitudes to classical perturbation theory. In this talk, Rafael described how we promote this formalism to general classical spinning objects by using coherent spin states. Our approach is fully covariant with respect to the massive little group SU(2) and is therefore completely synergistic with the massive spinor-helicity formalism. We apply this approach to classical two-body scattering due gravitational interaction. Starting from the coherent-spin elastic-scattering amplitude, we derive the classical impulse and spin kick observables to first post-Minkowskian order but to all orders in the angular momenta of the massive spinning objects. Rafael described how we also extract an effective two-body Hamiltonian which can be used beyond the scattering setting.

Wednesday 6 October: New predictions for processes with >= 2 jets at the LHC

• Speaker: Jenni Smillie (Edinburgh)

The vast amount of data taken by the Large Hadron Collider (LHC) means it has become a precision experiment in very many channels. This is good news for sensitive tests of the Standard Model, but presents theory with a big challenge. Many effects which could be neglected at previous colliders now must be included to give a good description of data. One example of this is the logarithms in $\hat{s}/p_\perp$ which appear at all orders in alpha_s. The increase in centre-of-mass energy at the LHC both increases their numerical impact, and increases the phase space for the production of many jets with large transverse momentum, challenging standard fixed-order approaches. Jenni described how to perform a resummation of these logarithms in a fully flexible event generator, and illustrate the method with recent predictions for Higgs-plus-dijets, W+dijets and WW+dijets.

Wednesday 6 October: Teaching Statistics Trust Lecture | Weapons of statistical instruction

• Speaker: Rhys Jones (Surrey)

We are living in an increasingly data-centric world, where it is essential for everyone to have a statistical awareness and build upon their statistical senses. The need for statistics has never been greater. With rapidly changing times, and a world saturated with data and interesting variables, we need new ways and new ideas to help make statistics more accessible for everyone. It should come as no surprise that statistics education has also experienced seismic shifts in recent years, with respect to content and teaching methods utilised. New Zealand in particular have made significant changes in relation to their statistics curriculum and pedagogies used to deliver the subject, at the primary and secondary school level.

This talk explored interesting ideas, present useful skills, and delve into exciting contexts, to supercharge the teaching of statistics and data science. There was a focus on the visualisation of data, using free web-based software like iNZight, explaining how these displays can convey engaging data stories. Skills development in being able to read graphs and eyeball data, describe trends well and the value in using dynamic data displays, were also discussed. This then led onto the importance of context and the need to provide engaging real-world data sets that can appeal to students. The second part of the talk described how skills developed in the first part can be nurtured to enable students to craft their own interesting and engaging data stories.

Key ideas and approaches conveyed throughout the talk were supported with Rhys' experiences of working with teachers and academics in New Zealand, Australia, the US and also the UK, along with relevant evidence-based research.

Wednesday 13 October: Schwinger pair production of magnetic monopoles

• Speaker: Oliver Gould (Nottingham)

Electromagnetic duality implies that strong magnetic fields will produce magnetic monopoles by the dual Schwinger effect, if indeed magnetic monopoles exist. As a consequence, strong magnetic fields provide perhaps the best avenue to search for magnetic monopoles: the existence of any given strong magnetic field provides a lower bound on their mass. This search strategy has recently been utilised at the LHC, where the strongest known magnetic fields are produced fleetingly by heavy-ion collisions. In these fields calculations of the monopole production cross section must go beyond the locally-constant field approximation. Oliver discussed recent theoretical progress in carrying out this calculation, as well as open theoretical questions. He also commented on the relation between the probability of Schwinger pair production of magnetic monopoles and a well-known “exponentiation conjecture” for the imaginary part of the Euler-Heisenberg Lagrangian to all loop orders.

Wednesday 20 October: Resurgence and extreme field QFT

• Speaker: Gerald V Dunne (Connecticut)

Gerald proposed a new approach to multi-loop QFT computations in strong background fields, based on an application of resurgent asymptotics to the extraction of strong-field and non-perturbative information from a limited number of terms of a weak-field expansion. The proposed method is demonstrated explicitly with the one-loop and two-loop expressions for the QED Euler-Heisenberg effective action, for which a surprising amount of strong-field and non-perturbative physics may be derived from just ten terms of a weak magnetic field expansion. Gerald also discussed applications to inhomogeneous fields.

Monday 25 October: My career path to clinical trial senior statistician

• Speaker: Milensu Shanyinde (Oxford)

Milensu completed an undergraduate degree in Mathematics and Statistics at the University of Plymouth in 2009 then a masters degree in Medical Statistics at Southampton University. Following this, Milensu worked as a statistician in cancer clinical trials. Now a PhD candidate at University College London in the final stages of completing her thesis, Milensu's research examines the complication of managing HIV in relation to Hepatitis C in persons seen for routine clinical care in Italy. Milensu also works part time as a clinical trial statistician at Oxford University working on various studies related to primary care research.

This seminar focused on Milensu's journey post the bachelors degree and how she found herself working as statistician in the field of clinical trials in academia. Working as a clinical trial statistician can be extremely rewarding and one of Milensu's recent highlights was being one of the statisticians working on a nationwide study to find COVID-19 treatments.

Wednesday 27 October: Gravitational dynamics from scattering amplitudes

• Speaker: N Emil J Bjerrum-Bohr (Niels Bohr Institute)

Gravity is a fundamental force but so weak that we have limited understanding of its extreme interactions. A recent exciting development is the detection of collisions of black holes in the universe. These phenomena witnessed by the Laser Interferometer Gravitational-Wave Observatory (LIGO) have refreshed enthusiasm for exploration of gravitational interactions and stimulated critical advancement of precision analysis of merger events. This talk outlined how to derive dynamics in general relativity by application of modern on-shell amplitude techniques and discussed how such methods can complement existing technology and facilitate computational progress.

Wednesday 3 November: Integrability and chaos in super Yang-Mills theories from anomalous-dimension spectra

• Speaker: Anne Spiering (Trinity College Dublin)

The discovery of integrability in planar maximally supersymmetric Yang-Mills (SYM) theory led to considerable advances in the exact computation of its CFT data. In this talk I will review  these advances and discuss universal statistical properties of anomalous-dimension spectra in SYM theories in the planar limit and at finite rank of the gauge group. I will show how they  can give insight into the nature of the underlying model, in particular we will see integrability manifest itself in the planar integrable limit of certain SYM theories, while non-integrable spectra can be described by random matrix theory, indicating their quantum-chaotic nature.

Wednesday 10 November: The dynamics of rotating stellar systems and their black holes

• Speaker: Anna Lisa Varri (Edinburgh)

The study of self-gravitating rotating bodies is a classical fluid dynamics problem with a distinguished history, yet the equilibrium and stability of rotating spheroidal stellar systems have rarely been explored. After introducing some basic mathematical modelling tools in stellar dynamics, Anna presented a family of self-consistent equilibria describing uniformly rotating, axisymmetric quasi-relaxed stellar systems. Such equilibria define a singular perturbation Vlasov-Poisson problem with a free boundary which can be approached by means of an asymptotic expansion based on the rotation strength parameter. Anna then illustrated a generalisation to the case of stellar systems with central black holes, for which a novel treatment of the boundary conditions of the relevant Poisson equation allows for a solution with matched asymptotics. The talk conclude with a discussion on the astrophysical relevance of such results in the current era of black holes images and gravitational waves detection.

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