Please note that the list below only shows forthcoming events, which may not include regular events that have not yet been entered for the forthcoming term. Please see the past events page for a list of all seminar series that the department has on offer.
14:15
A toric case of the Thomas-Yau conjecture
Abstract
We consider a class of Lagrangian sections L contained in certain Calabi-Yau Lagrangian fibrations (mirrors of toric weak Fano manifolds). We prove that a form of the Thomas-Yau conjecture holds in this case: L is isomorphic to a special Lagrangian section in this class if and only if a stability condition holds, in the sense of a slope inequality on objects in a set of exact triangles in the Fukaya-Seidel category. This agrees with general proposals by Li. On
surfaces and threefolds, under more restrictive assumptions, this result can be used to show a precise relation with Bridgeland stability, as predicted by Joyce. Based on arXiv:2505.07228 and arXiv:2508.17709.
12:30
The flow-induced compaction of visco-elastic and visco-plastic soft porous media
Abstract
The flow of viscous fluid through a soft porous medium exerts drag on the matrix and induces non-uniform deformation. This behaviour can become increasingly complicated when the medium has a complex rheology, such that deformations exhibit elastic (reversible) and plastic (irreversible) behaviour, or when the rheology has a viscous component, making the response of the medium rate dependent. This is perhaps particularly the case when compaction is repeated over many cycles, or when additional forces (e.g. gravity or an external load) act simultaneously with flow to compact the medium, as in many industrial and geophysical applications. Here, we explore the interaction of viscous effects with elastic and plastic media from a theoretical standpoint, focussing on unidirectional compaction. We initially consider how the medium responds to the reversal of flow forcing when some of its initial deformation is non-recoverable. More generally, we explore how spatial variations in stress arising from fluid flow interact with the stress history of the sample when some element of its rheology is plastic and rate-dependent, and characterise the response of the medium depending on the nature of its constitutive laws for effective stress and permeability.
15:00
Geometrically confined quantum systems
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Dr Rob Van Gorder’s research focuses on how physical phenomena can be described, predicted, and controlled using applied mathematics. He works across mathematical modelling, analytical and asymptotic methods, and numerical simulation, applying this combination to a wide range of physical systems.
His interests in fluid dynamics centre on fundamental flow structures—such as vortices, bubbles, waves, and boundary layers—and how they evolve, persist, or break apart. He also studies spatial instabilities and pattern formation, investigating how mechanisms such as Turing and Benjamin–Feir instabilities extend to heterogeneous or non-autonomous systems arising in chemistry, physics, biology, and epidemiology.
In theoretical physics, Dr Van Gorder works on quantum mechanics, quantum fluids, and nonlinear waves, including the dynamics of Bose–Einstein condensates, quantised vortices in superfluid helium, and confined quantum systems. Across these areas, he aims to understand how nonlinear and quantum systems behave under realistic constraints and external forcing.
His recent publications include work on pattern formation and diffusive instabilities in Proceedings of the Royal Society A.
Abstract
You will likely be familiar with the notion of a hydrogen atom, having seen something about its discrete energy levels and orbitals at some point or another. This is an example of a quantum system. In this talk, we explore what transpires when taking a quantum system and placing it into a three-dimensional container having some prescribed geometry. In the limit where the container is large (relative to the natural lengthscale of the quantum system), its influence over the quantum system is negligible; yet, as the container is made small (comparable to the aforementioned lengthscale), geometric information intrinsic to the container plays an important role in determining the energy and orbital structure of the system. We describe how to do (numerically-assisted) perturbation theory in this small-container limit and then match it to the large-box regime, using a combination of these asymptotics and direct simulations to tell the story of geometrically confined quantum systems. Much of our focus will be on linear Schrödinger equations governing single-particle quantum systems; however, time permitting, we will briefly discuss how to do similar things to study geometrically confined nonlinear Schrödinger equations, with geometric confinement of Bose-Einstein condensates being a primary motivation. Geometric confinement of an attractive Bose-Einstein condensate can, for instance, modify the collapse threshold and enhance stability, with the particular choice of confining geometry shifting the boundary of instability, staving off the collapse which is prevalent in three-dimensional attractive condensates.
12:45
Journal Club
Please submit papers to discuss and topic suggestions here: https://sites.google.com/view/math-phys-oxford/journal-club
The life of a Turing Pattern
Abstract
We survey the life of a Turing pattern, from initial diffusive instability through the emergence of dominant spatial modes and to an eventual spatially heterogeneous pattern. While many mathematically ideal Turing patterns are regular, repeating in structure and remaining of a fixed length scale throughout space, in the real world there is often a degree of irregularity to patterns. Viewing the life of a Turing pattern through the lens of spatial modes generated by the geometry of the bounded space domain housing the Turing system, we discuss how irregularity in a Turing pattern may arise over time due to specific features of this space domain or specific spatial dependencies of the reaction-diffusion system generating the pattern.
14:15
Metric wall-crossing
Abstract
16:00
Driven interfacial hydrodynamics, and some physics-informed machine learning
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Dr Stuart J. Thomson is an applied mathematician whose research sits at the intersection of mathematics, physics, and engineering. He works closely with table-top experiments to uncover how complex fluid and soft-matter systems give rise to novel emergent phenomena through nonlinear dynamics, many-body interactions, and geometric confinement. His interests include interfacial hydrodynamics, self-assembly, active and driven matter, interfacial robotics, transport phenomena, and fluid–structure interaction.
He is currently leading the project “The statistical physics of hydrodynamic random walkers: experiments and theory”, which combines experimental and theoretical approaches to understand how fluid-mediated interactions shape the behaviour of randomly moving microscopic walkers. Dr Thomson is based in the School of Engineering, Mathematics and Technology at the University of Bristol.
Abstract
In this talk I will present a few topics of recent interest that centre around the theme of “driven interfacial hydrodynamics”: fluid mechanical systems in which droplets and particles are self-propelled through interaction with the environment. I will also present some very recent work on using differentiable physics (a branch of physics-informed machine learning) to determine constitutive relations for highly plasticised metals.
This talk will contain elements of fluid dynamics, experimental mechanics, dynamical systems, statistical physics, and machine learning.
12:45
Journal Club
Please submit papers to discuss and topic suggestions here: https://sites.google.com/view/math-phys-oxford/journal-club
Resonances as a computational tool
Abstract
Speaker Katharina Schratz will talk about 'Resonances as a computational tool'
A large toolbox of numerical schemes for dispersive equations has been established, based on different discretization techniques such as discretizing the variation-of-constants formula (e.g., exponential integrators) or splitting the full equation into a series of simpler subproblems (e.g., splitting methods). In many situations these classical schemes allow a precise and efficient approximation. This, however, drastically changes whenever non-smooth phenomena enter the scene such as for problems at low regularity and high oscillations. Classical schemes fail to capture the oscillatory nature of the solution, and this may lead to severe instabilities and loss of convergence. In this talk I present a new class of resonance based schemes. The key idea in the construction of the new schemes is to tackle and deeply embed the underlying nonlinear structure of resonances into the numerical discretization. As in the continuous case, these terms are central to structure preservation and offer the new schemes strong geometric properties at low regularity.
Identifiability of stochastic and spatial models in mathematical biology
Abstract
Topology of smooth Gaussian fields
Abstract
Gaussian fields arise in a variety of contexts in both pure and applied mathematics. While their geometric properties are well understood, their topological features pose deeper mathematical challenges. In this talk, I will begin by highlighting some motivating examples from different domains. I will then outline the classical theory that describes the geometric behaviour of Gaussian fields, before turning to more recent developments aimed at understanding their topology using the Wiener chaos expansion.
12:30
15:30
Towards a Bogomolov-Miyaoka-Yau inequality for symplectic 4-manifolds
Abstract
The Bogomolov-Miyaoka-Yau inequality for minimal compact complex surfaces of general type was proved in 1977 independently by Miyaoka, using methods of algebraic geometry, and by Yau, as an outgrowth of his proof of the Calabi conjectures. In this talk, we outline our program to prove the conjecture that symplectic 4-manifolds with $b^+>1$ obey the Bogomolov-Miyaoka-Yau inequality. Our method uses Morse theory on the gauge theoretic moduli space of non-Abelian monopoles, where the Morse function is a Hamiltonian for a natural circle action and natural two-form. We shall describe generalizations of Donaldson’s symplectic subspace criterion (1996) from finite to infinite dimensions. These generalized symplectic subspace criteria can be used to show that the natural two-form is non-degenerate and thus an almost symplectic form on the moduli space of non-Abelian monopoles. This talk is based on joint work with Tom Leness and the monographs https://arxiv.org/abs/2010.15789 (to appear in AMS Mathematical Surveys and Monographs), https://arxiv.org/abs/2206.14710 and https://arxiv.org/abs/2410.13809.
16:00
Extreme events in atmosphere and ocean via sharp large deviations estimates
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Tobias Grafke's research focuses on developing numerical methods and mathematical tools to analyse stochastic systems. His work spans applications in fluid dynamics and turbulence, atmosphere–ocean dynamics, and biological and chemical systems. He studies the pathways and occurrence rates of rare and extreme events in complex realistic systems, develops numerical techniques for their simulation, and quantifies how random perturbations influence long-term system behaviour.
Abstract
Rare and extreme events are notoriously hard to handle in any complex stochastic system: They are simultaneously too rare to be reliably observable in experiments or numerics, but at the same time often too impactful to be ignored. Large deviation theory provides a classical way of dealing with events of extremely small probability, but generally only yields the exponential tail scaling of rare event probabilities. In this talk, I will discuss theory, and algorithms based upon it, that improve on this limitation, yielding sharp quantitative estimates of rare event probabilities from a single computation and without fitting parameters. Notably, these estimates require the computation of determinants of differential operators, which in relevant cases are not traceclass and require appropriate renormalization. We demonstrate that the Carleman--Fredholm operator determinant is the correct choice. Throughout, I will demonstrate the applicability of these methods to high-dimensional real-world systems, for example coming from atmosphere and ocean dynamics.