Mathematics seminars
Explore the seminars we run, from research to undergraduate level.
Undergraduate and for all
Dynamical Systems and Partial Differential Equations seminars
Time: Tuesdays from 2pm - 3pm or Friday's from 2pm - 3pm.
For further information, please contact the organisers Jon Bevan and Sergey Zelik.
Upcoming seminars
There are currently no upcoming seminars. Please check back at a later date.
Past seminars
On the unique ergodicity, regularity, and mixing for the weakly-damped stochastic KdV equation
Speaker: Vincent Martinez
Date: Friday 16 September
Abstract: We discuss the existence, uniqueness, and regularity of invariant measures for the damped-driven stochastically forced Korteweg-de Vries equation, where the noise is additive and sufficiently non-degenerate. It is shown that a simple, but versatile control strategy, typically employed to establish exponential mixing for strongly dissipative systems such as the 2D Navier-Stokes equations, can nevertheless be applied in this weakly dissipative setting to establish elementary proofs of both unique ergodicity, albeit without mixing rates, as well as regularity of the support of the invariant measure.
Under the assumption of large damping, however, a one-force, one-solution principle is established, from which we are able to deduce the existence of a spectral gap with respect to a Wasserstein distance-like function. Our treatment is paradigmatic and should be applicable to many other weakly dissipative systems that are stochastically forced in this way.
On the unique ergodicity, regularity, and mixing for the weakly-damped stochastic KdV equation
Speaker: Vincent Martinez, City University of New York
Date: Friday 16 September 2022
Abstract: We discuss the existence, uniqueness, and regularity of invariant measures for the damped-driven stochastically forced Korteweg-de Vries equation, where the noise is additive and sufficiently non-degenerate. It is shown that a simple, but versatile control strategy, typically employed to establish exponential mixing for strongly dissipative systems such as the 2D Navier-Stokes equations, can nevertheless be applied in this weakly dissipative setting to establish elementary proofs of both unique ergodicity, albeit without mixing rates, as well as regularity of the support of the invariant measure. Under the assumption of large damping, however, a one-force, one-solution principle is established, from which we are able to deduce the existence of a spectral gap with respect to a Wasserstein distance-like function. Our treatment is paradigmatic and should be applicable to many other weakly dissipative systems that are stochastically forced in this way.
Inverse optical tomography through PDE constrained optimisation in L-infinity
Speaker: Nikos Katsourakis (Department of Mathematics, University of Reading)
Date: Tuesday 26 November 2019
Abstract: Fluorescent Optical Tomography (FOT) is a new bio-medical imaging method with wider industrial applications. It is currently intensely researched since it is very precise and with no side effects for humans, as it uses non-ionising red and infrared light. Mathematically, FOT can be modelled as an inverse parameter identification problem, associated with a coupled elliptic system with Robin boundary conditions. Herein we utilise novel methods of Calculus of Variations in L∞ to lay the mathematical foundations of FOT which we pose as a PDE-constrained minimisation problem in Lp and L∞.
Injective nonlinear elasticity via penalty terms: analysis and numerics
Speaker: Stefan Krömer (UTIA, Czech Academy of Sciences, Prague)
Date: Friday 22 November 2019
Abstract: I will present some new ideas for nonlinear elasticity with a global injectivity constraint preventing self-interpenetration of the elastic body. Our main focus are penalization terms replacing this injectivity constraint, the Ciarlet-Ne\v{c}as condition. Among other things, the penalization can be chosen in such a way that self-interpenetration is prevented even at finite value of the penalization parameter, and not just in the limit. Our penalty method provides a working numerical scheme with provable convergence along a subsequence, for models of non-simple materials (i.e. including a term with higher order derivatives).
Curvature-stabilized skyrmions with angular momentum
Speaker: Zisis Sakellaris (Department of Mathematics, University of Surrey).
Date: Tuesday 5 November 2019
Abstract: I will present recent results on the Landau-Lifshitz equation in a geometric context. In particular, we will be concerned with the existence of skyrmionic field configurations on a spherical ferromagnet, under large anisotropy assumptions, modelled on the 2-sphere S2. These fields correspond to a family of solutions of the Landau–Lifshitz equation, that are topologically distinct from the ground state and not equivariant. Our analysis involves the solution of constrained variational problems in a geometric context, giving rigorous footing to recent results in the Physics literature.
This is based on joint work with Christof Melcher from RWTH Aachen, recently published.
Dynamics of dissipative PDEs workshop
Dedicated to mathematician Igor Dmitrievich
Date: Monday 10 - Friday 14 September 2018
Abstract: Find out more.
Mathematics Colloquia seminars
Time: Wednesdays or Fridays.
For further information, please contact the organiser Dr Bin Cheng.
Upcoming seminars
There are currently no upcoming seminars. Please check back at a later date.
Past seminars
$\Gamma$-convergence of Onsager--Machlup functionals and MAP estimation in non-parametric Bayesian inverse problems
Speaker: Tim Sullivan (Warwick and Alan Turing Institute)
Date: Wednesday 25 May 2022
Abstract: The Bayesian solution to a statistical inverse problem can be summarised by a mode of the posterior distribution, i.e.\ a MAP estimator. The MAP estimator essentially coincides with the (regularised) variational solution to the inverse problem, seen as minimisation of the Onsager--Machlup functional of the posterior measure. An open problem in the stability analysis of inverse problems is to establish a relationship between the convergence properties of solutions obtained by the variational approach and by the Bayesian approach. To address this problem, we propose a general convergence theory for modes that is based on the $\Gamma$-convergence of Onsager--Machlup functionals, and apply this theory to Bayesian inverse problems with Gaussian and edge-preserving Besov priors. Joint work with Birzhan Ayanbayev, Ilja Klebanov, and Han Cheng Lie.
Slow travelling wave solutions of the nonlocal Fisher-KPP equation
Speaker: John Billingham (Nottingham)
Date: Wednesday 6 April 2022
Abstract: In this talk I will discuss travelling wave solutions, u = U(x-ct), of the nonlocal Fisher-KPP equation in one spatial dimension,
u_t = D u_xx + u(1-phi*u)
with D << 1 and c << 1, where phi*u is the spatial convolution of the population density, u(x,t), with a continuous, symmetric, strictly positive kernel, phi(x), which is decreasing for x>0 and has a finite derivative as x -> 0+.
The formal method of matched asymptotic expansions and numerical methods can be used to solve the travelling wave equation for various kernels, phi(x), when c << 1. The most interesting feature of the leading order solution behind the wavefront is a sequence of tall, narrow spikes with O(1) weight, separated by regions where U is exponentially small. The regularity of phi(x) at x=0 is a key factor in determining the number and spacing of the spikes, and the spatial extent of the region where spikes exist.
Studying dynamics using computational polynomial optimization
Speaker: David Goluskin (University of Victoria, Canada)
Date: Wednesday 2 February 2022
Abstract: For nonlinear ODEs and PDEs that cannot be solved exactly, various properties can be inferred by constructing functions that satisfy suitable inequalities. Although the most familiar example is proving stability of an equilibrium by constructing Lyapunov functions, similar approaches can produce many other types of mathematical statements, including for systems with chaotic behavior. Such statements include bounds on attractor properties or on transient behavior, estimates of basins of attraction, and design of nonlinear controls. Analytical results of these types often trade precision for tractability. Much greater precision can be achieved by using computational methods of polynomial optimization to construct functions that satisfy the desired inequalities. This talk will provide an overview of the different ways in which polynomial optimization can be used to study dynamics. I will show various examples in which polynomial optimization produces arbitrarily sharp results while other methods do not. I will focus on the ODE case, where theory and computational methods are more complete. Extensions to PDEs may be discussed briefly.
Deep learning of conjugate mappings
Speaker: Jason Bramburger (George Mason University, Virginia)
Date: Wednesday 27 October 2021
Abstract: Despite many of the most common chaotic dynamical systems being continuous in time, it is through discrete time mappings that much of the understanding of chaos is formed. Henri Poincaré first made this connection by tracking consecutive iterations of the continuous flow with a lower-dimensional, transverse subspace. The mapping that iterates the dynamics through consecutive intersections of the flow with the subspace is now referred to as a Poincaré map, and it is the primary method available for interpreting and classifying chaotic dynamics. Unfortunately, in all but the simplest systems, an explicit form for such a mapping remains outstanding. In this talk I present a method of discovering explicit Poincaré mappings using deep learning to construct an invertible coordinate transformation into a conjugate representation where the dynamics are governed by a relatively simple chaotic mapping. The invertible change of variable is based on an autoencoder, which allows for dimensionality reduction, and has the advantage of classifying chaotic systems using the equivalence relation of topological conjugacies. We illustrate with low-dimensional systems such as the Rössler and Lorenz systems, while also demonstrating the utility of the method on the infinite-dimensional Kuramoto--Sivashinsky equation.
Ant trail formation, Bose-Einstein condensation, and quantum gravity
Speaker: Masanori Hanada
Date: Wednesday 5 May
Abstract: In string theory, a black hole can be described as a bound state of D-branes (something like particles) connected by strings. By identifying D-brane, open string and black hole with ants, pheromone and ant trail, we can see a striking resemblance between string theory and collective behaviour of ants. This analogy enables us to understand an important property of a black hole discovered by Hawking --- bigger black hole is colder --- in an intuitive manner.
Playing pool with |ψ⟩
Speaker: Adam R. Brown
Affiliation: Google and Stanford
Date: Wednesday 10 February
Abstract: In "Playing Pool with π", Galperin invented an extraordinary method to learn the digits of π by counting the collisions of billiard balls. Here I demonstrate a surprising connection between Galperin's bouncing billiards and Grover's algorithm for quantum search. Based on Playing Pool with |ψ⟩: from Bouncing Billiards to Quantum Search, see also How Pi Connects Colliding Blocks to a Quantum Search Algorithm.
Minimal Lagrangians and where to find them
Speaker: Jason Lota (Oxford)
Date: Wednesday 27 May 2020
Abstract: A classical problem going back to ancient Greece is to find the shortest curve in the plane enclosing a given area: the isoperimetric problem. A similar question is whether given a curve on a surface it can be deformed to a shortest one. Whilst the solutions to these classical problems are well-known, natural generalisations in higher dimensions are mostly unsolved. I will explain how this leads us to the study of minimal Lagrangians and the question of how to find them, which will take us to the interface between symplectic topology, Riemannian geometry and analysis of nonlinear PDEs, with links to theoretical physics.
How directed is a directed network?
Speaker: R.S.MacKay (University of Warwick)
Date: Wednesday 29 April 2020
Abstract: Many systems can be represented by directed graphs, e.g. food webs, supply networks, social networks, metabolic networks, language networks, financial networks. The nodes represent the objects and a directed edge indicates a flow from one node to another or influence of one node on another.
In some networks, the edges line up in an overall direction; in others, they do not. The old notion of “trophic level” from ecology, and its more recent analogue “upstreamness” in economics, provide one way to quantify this, but they require basal or top nodes and have various other shortcomings.
In joint work with Samuel Johnson and Bazil Sansom, we present an improved notion of trophic level and a resulting notion of trophic coherence. We illustrate their application to a wide variety of real-world networks and we derive some nice mathematical relationships of trophic coherence with other significant network properties like non-normality, stability of contagion processes, and cyclicality.
The work was supported by the Economic and Social Research Council via the Instability hub of the Rebuilding Macroeconomics programme of the National Institute for Economic and Social Research.
Is dispersion a stabilising or destabilising mechanism? Landau-damping induced by fast background flows
Speaker: Edriss Titi (Cambridge, Texas A&M Univ, Weizmann Institute of Science)
Date: Wednesday 4 March 2020
Abstract: In this talk Edriss Titi will present a unified approach for the effect of fast rotation and dispersion as an averaging mechanism for, on the one hand, regularising and stabilising certain evolution equations, such as the Navier-Stokes and Burgers equations. On the other hand, Edriss will present some results in which large dispersion acts as a destabilising mechanism for the long-time dynamics of certain dissipative evolution equations, such as the Kuramoto-Sivashinsky equation. In addition, they will present some new results concerning two- and three-dimensional turbulent flows with high Reynolds numbers in periodic domains, which exhibit ``Landau-damping" mechanism due to large spatial average in the initial data.
Weighing the Fog of War: A physicist's adventures in operations research and history
Speaker: Niall MacKay (York)
Date: Wednesday 11 December 2019
Abstract: A tour through ten years' work with operations researchers and historians on combat modelling, military history and their interaction. I'll begin with some elementary ideas from Lanchester theory and present some neat results for multilateral models. Then I shall describe some of our historical work, including on the First World War at sea and the Second World War in the air.
Global stability properties of the climate: Melancholia states, invariant measures, and phase transitions
Speaker: Valerio Lucarini (Reading)
Date: Tuesday 3 December 2019
Abstract: For a wide range of values of the incoming solar radiation, the Earth features at least two attracting states, which correspond to competing climates. The warm climate is analogous to the present one; the snowball climate features global glaciation and conditions that can hardly support life forms. Paleoclimatic evidences suggest that in past our planet flipped between these two states. The main physical mechanism responsible for such instability is the ice-albedo feedback. Following an idea developed by Eckhardt and co. for the investigation of multistable turbulent flows, we study the global instability giving rise to the snowball/warm multistability in the climate system by identifying the climatic edge state, a saddle embedded in the boundary between the two basins of attraction of the stable climates. We refer to these states as Melancholia States. We then introduce random perturbations as modulations to the intensity of the incoming solar radiation. We observe noise-induced transitions between the competing basins of attractions. In the weak noise limit, large deviation laws define the invariant measure and the statistics of escape times. By empirically constructing the instantons, we show that the Melancholia states are the gateways for the noise-induced transitions. In the region of multistability, in the zero-noise limit, the measure is supported only on one of the competing attractors. For low (high) values of the solar irradiance, the limit measure is the snowball (warm) climate. The changeover between the two regimes corresponds to a first order phase transition in the system. The framework we propose seems of general relevance for the study of complex multistable systems. Finally, we propose a new method for constructing Melancholia states from direct numerical simulations, thus bypassing the need to use the edge-tracking algorithm.
Refs.
On extreme and record events in dynamical systems
Speaker: Mark Holland (Exeter)
Date: Wednesday 6 November 2019
Abstract: Understanding extreme events, such as severe weather, climatic or financial events is a major challenge. In this talk I will explain some of the mathematical approaches used in understanding extreme events, such as finding their probability distribution. We will assume that the underlying time series process is modelled by a deterministic dynamical system, such as a discrete time map or differential equation. These latter processes have some dependency, and so any results known about extremes for independent, identically distributed (i.i.d) random processes cannot immediately be transferred to dynamical systems. As part of the talk, I will review relevant extreme value theory associated to the i.i.d case. I will then discuss this theory for dynamical systems, illustrating with examples from low dimensional chaotic maps.
Amazing Maths undergraduate seminars
Time: 5-6pm on Fridays. Please contact the organiser Dr Andrea Prinsloo for further details.
These seminars are organised in collaboration with the Maths Society at the University of Surrey.
Upcoming seminars
There are currently no upcoming seminars. Please check back at a later date.
Past seminars
Constructing an experimental design by colouring vertices
Speaker: Janet Godolphin (Mathematics at the Interface Group, University of Surrey)
Date: Friday 23 February 2024
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Mathematics of sleep: why do we sleep so late?
Speaker: Anne Skeldon (Mathematics at the Interface Group, University of Surrey)
Date: Friday 17 November 2023
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New physics in the days of Oppenheimer
Speaker: Alessandro Torrielli (Mathematics of Gravity and Quantum Field Theory Group, University of Surrey)
Date: Friday 6 October 2023
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Invisible in the Storm: the role of mathematics in understanding weather
Speaker: Ian Roulstone (Nonlinear Waves and Geometric Fluid Dynamics Group, University of Surrey)
Date: Friday 18 November 2022
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The weird world of black holes
Speaker: Jan Gutowski (Fields, Strings and Geometry Group, University of Surrey)
Date: Friday 7 October 2022
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Mathematics, Machine Learning and Medicine
Speaker: Philip Aston (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Wednesday 11 May 2022
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Quantum Mechanics’ strangest puzzle
Speaker: Alessandro Torrielli (Fields, Strings and Geometry Group, University of Surrey)
Date: Wednesday 16 February 2022
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How does a machine learn?
Speaker: Stefan Klus (Data Science and Dynamics Group, University of Surrey)
Date: Wednesday 1 December 2021
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Spheres, hyperspheres, and the human shoulder
Speaker: Tom Bridges (Nonlinear Waves and Geometric Fluid Dynamics Group, University of Surrey)
Date: Wednesday 6 October 2021
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To sleep, perchance to dream... of Maths
Speaker: Anne Skeldon (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Wednesday 28 April 2021
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Solving the unsolvable
Speaker: David Fisher (Department of Mathematics, University of Surrey)
Date: Wednesday 24 February 2021
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Classical and quantum many-body chaos
Speaker: Masanori Hanada (Fields, Strings and Geometry Group, University of Surrey)
Date: Wednesday 25 November 2020
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Constructing an experimental design by colouring vertices
Speaker: Janet Godolphin (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Wednesday 21 October 2020
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Materials with memory: modelling and applications
Speaker: Jonathan Bevan (Dynamical Systems and PDEs Group, University of Surrey)
Date: Wednesday 7 October 2020
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Applied Statistics undergraduate seminars
Time: The Applied Statistics seminars are held from 5-6pm on Fridays. Please contact the organiser Dr Janet Godolphin for further details.
These seminars are organised in collaboration with the Maths Society at the University of Surrey.
Upcoming seminars
There are currently no upcoming seminars. Please check back at a later date.
Past seminars
From data entry and giraffes to creating dataviz and a PhD – a 10-year journey
Speaker: Clareece Nevill (Biostatistics Research Group, Department of Health Sciences, University of Leicester)
Date: Friday 30 September 2022
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How much analytics can there be in advertising?
Speaker: Emily Weldon (Senior Data Scientist)
Company: Medialab
Date: Wednesday 9 February 2022
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Statistical Work on Placement
Speakers: Dan Hulkes, Hayden Spicer and Samiah Haroon (University of Surrey)
Date: Wednesday 27 October 2021
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How can we use statistical methods to determine whether a new treatment is effective, and which patients might benefit most?
Speaker: Peter J Godolphin (Institute of Clinical Trials and Methodology, University College London)
Date: Wednesday 29 September 2021
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Where fortune tellers go wrong and meteorologists succeed: How to predict the future
Speaker: Rebecca Atkinson (University of Surrey and the Met Office)
Date: Wednesday 21 April 2021
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Statistics and Anglo-Saxon archaeology
Speaker: Wilfrid Kendall (University of Warwick)
Date: Wednesday 3 March 2021
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Genetics, medicine and game shows – a statistician reviews his life choices
Speaker: Dr Jonathan Cairns (Senior Biostatistician)
Company: AstraZeneca
Date: Wednesday 18 November 2020
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A career in Data Science: where to even begin!
Speaker: Will Davis (Chief Planning Officer), Emily Weldon (Senior Data Scientist) and Tim Nguyen (Senior Data Engineer)
Company: Medialab
Date: Wednesday 30 September 2020
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Industrial undergraduate seminars
The Industrial seminars aim to give undergraduate mathematics and mathematics with statistics students a broader knowledge of real-world applications of mathematics and statistics in industry.
Time: The Industrial seminars are held from 5-6pm on Fridays. Please contact the organiser Dr James Roberts for further details.
These seminars are organised in collaboration with the Maths Society at the University of Surrey.
Upcoming seminars
There are currently no upcoming seminars. Please check back at a later date.
Past seminars
Data Science in Healthcare at NPL: quantitative measurements and methods for healthcare problems
Speaker: Nadia Smith
Company: National Physics Laboratory
Date: Friday 28 October 2022
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TBA
Speaker: TBA
Company: TBA
Date: Friday 25 November 2022
Data visualization and analytics
Speaker: Anna van der Vliet
Company: Sandoz
Date: Wednesday 4 May 2022
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Potential impacts of climate change on peak river flows in Great Britain, and modelling crops
Speaker: Ali Rudd (Hydrological Modeller) and Matt Brown (Research Assistant)
Company: UK Centre for Ecology & Hydrology
Date: Wednesday 23 February 2022
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Quantitative Trading
Speaker: Saul Harris
Company: Winterflood Securities
Date: Wednesday 13 October 2021
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Maths and marketing
Speaker: Matt Richards (Head of Digital Marketing)
Company: BrewDog
Date: Wednesday 10 March 2021
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Mathematics and quantitative development
Speaker: Hasan Hasanov (Associate Director)
Company: Royal Bank of Canada
Date: Wednesday 10 February 2021
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Taste of Research undergraduate seminars
The Taste of Research undergraduate seminars by PhD students are designed to introduce undergraduate mathematics students to a taste of mathematics doctoral research.
Time: the seminars are held from 5-6pm on Fridays. Please contact the organiser Mr Steve Falconer for further details.
These seminars are organised in collaboration with the Maths Society at the University of Surrey.
Upcoming seminars
There are currently no upcoming seminars. Please check back at a later date.
Past seminars
Stuck in a Well: Badgers Moving on an Energy Surface
Speaker: Jessica Furber (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Friday 21 October 2022
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Modelling dynamical systems directly from data
Speaker: Steve Falconer (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Wednesday 6 April 2022
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Effect of compliance on the stability of jets and wakes
Speaker: Ryan Poole (Nonlinear Waves and Geometric Fluid Dynamics Group, University of Surrey)
Date: Wednesday 2 March 2022
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Mechanobiology: A tense situation
Speaker: Kieran Boniface (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Wednesday 17 November 2021
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Dynamical systems and crime
Speaker: Laura Jones (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Wednesday 20 October 2021
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Dynamic mode decomposition: finding patterns in space and time
Speaker: Steve Falconer (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Wednesday 5 May 2021
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The importance of being Integrable: on the methods and usefulness of Integrability
Speaker: Leander Wyss (Fields, Strings and Geometry Group, University of Surrey)
Date: Wednesday 17 February 2021
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Something from nothing: Investigating the emergence of localised patterns
Speaker: Dan Hill (Nonlinear Waves and Geometric Fluid Dynamics Group, University of Surrey)
Date: Wednesday 2 December 2020
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Symmetric Projection Attractor Reconstruction: Multi-dimensional Embedding of Physiological Signals
Speaker: Jane Lyle (Mathematics of Life and Social Sciences Group, University of Surrey)
Date: Wednesday 14 October 2020
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