# Seminars this semester

Jan 16 | Wed |
Atsushi Takahashi (Osaka) | Algebra / Algebraic Geometry seminar |

16:00 |
J11 | On a full exceptional collection in the category of maximally graded matrix factorizations of an invertible polynomial of chain type | |

Abstract:In ’77 Orlik-Randell asked about the existence of a certain distinguished basis of vanishing cycles in the Milnor fiber associated to an invertible polynomial of chain type. With my student, Daisuke Aramaki we transport their conjecture to the category of matrix factorizations by the (conjectural) homological mirror symmetry equivalence and then prove the resulting statement. |
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Jan 17 | Thu |
Ricardo Gaferia (Instituto de Astrofísica de Andalucía - CSIC ) | SP2RC seminar |

10:00 |
LT 10 |
Machine learning assisted parallel inversions | |

Abstract:With the increase of data volume and the need of more complex inversion codes to interpret and analyze solar observations, it is necessary to develop new tools to boost inversions and reduce computation times and costs. In this presentation, I discuss the possibilities and limitations of using machine learning as a tool to estimate optimum initial physical atmospheric models necessary for initializing spectral line inversions. Tests have been carried out for the SIR and DeSIRer inversion codes. This approach allows firstly to reduce the number of cycles in the inversion and increase the number of nodes and secondly to automatically cluster pixels which is an important step to invert maps where completely different regimes are present. Finally, I also present a warp for SIR and DeSIRer inversion codes that allows the user to easily set up parallel inversions. |
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Jan 18 | Fri | Norbert Gyenge (Sheffield) | SP2RC seminar |

13:00 | LT 10 |
The Nonaxisymmetric Behaviour Of Solar Eruptive Events | |

Abstract:This thesis investigates new approaches for predicting the occurrence of solar eruptive events based on coronal mass ejection (CME), solar flare and sunspot group observations. The scope of the present work is to study the spatio-temporal properties of the above-mentioned solar features. The analysis may also provide a deeper understanding of the subject of solar magnetic field reorganisation. Furthermore, the applied approaches may open opportunities for connecting these local phenomena with the global physical processes that generate the magnetic field of the Sun, called the solar dynamo. The investigation utilises large solar flare statistical populations and advanced computational tools, such as clustering techniques, wavelet analysis, autoregressive moving average (ARIMA) forecast, kernel density estimations (KDEs) and so on. This work does not attempt to make actual predictions because it is out of the scope of the recent investigation. However, the thesis introduces new possible approaches in the subject of flare and CME forecasting. The future aim is to construct a real-time database with the ability to forecast eruptive events based on the findings of this thesis. This potential forecasting model may be crucial for protecting a wide range of satellite systems around the Earth or predicting space weather based on the obtained results may also assist to plan safe space exploration in the future. |
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Jan 23 | Wed | Richard Webb (Cambridge) | Pure Maths Colloquium |

14:00 | J11 | An interplay between topology, geometry, and the algebra of the mapping class group | |

Abstract:The braid groups were defined by Artin in 1925, and are usually defined in terms of strings in 3-dimensional space. However there is a fruitful 2-dimensional perspective of the braid groups as homeomorphisms (up to some natural equivalence) of a disc with holes, in other words, the braid groups are special cases of mapping class groups of surfaces. Mapping class groups can be viewed in a number of ways, and are of interest in several different fields, such as dynamics, algebraic geometry, surface bundles, hyperbolic geometry, to name a few. A key theorem that demonstrates this intradisciplinary feature is the Nielsen--Thurston classification. I will explain what the Nielsen--Thurston classification is, describe some basic examples and analogies, and highlight its importance. I will then explain how to view this from the geometric group theory perspective, and discuss my work with Mark Bell that uses this point of view to solve the conjugacy problem for mapping class groups in polynomial time. At the end of the talk I will discuss some new ideas that may lead to applications in knot theory via the braid groups. |
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Jan 25 | Fri | Kalevi Mursula (University of Oulu) | SP2RC seminar |

10:30 |
LT E |
Centennial evolution and terrestrial effects of the global solar magnetic field | |

Jan 31 | Thu | Prof. Valery Nakariakov (Centre for Fusion, Space and Astrophysics, University of Warwick) | Plasma Dynamics Group |

15:00 | Lecture theatre 1 (Hicks Building) |
The effect of thermal misbalance on compressive oscillations in solar coronal loops | |

Abstract:Fast and slow magnetoacoustic waves are a promising tool for the seismological diagnostics of physical parameters of various plasma structures in the corona of the Sun. In particular, compressive waves can provide us with information about the thermodynamic equilibrium in the coronal plasma, and hence the heating function. Compressive perturbations of the thermodynamic equilibrium by magnetoacoustic waves can cause the misbalance of the radiative cooling and unspecified heating. The effect of the misbalance is determined by the derivatives of the combined heating/cooling function with respect to the plasma density and temperature, and can lead to either enhanced damping of the compressive oscillations or their magnification. Moreover, in the regime of strong misbalance, compressive MHD waves are subject to wave dispersion that can slow down the formation of shocks and can cause the formation of quasi-periodic wave trains. |
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Feb 6 | Wed | Viveka Erlandsson (Bristol) | Pure Maths Colloquium |

14:00 | J11 | Determining the shape of a billiard table from its bounces | |

Abstract:Consider a billiard table shaped as a Euclidean polygon with labeled sides. A ball moving around on the table determines a bi-infinite “bounce sequence” by recording the labels of the sides it bounces off. We call the set of all possible bounce sequences the “bounce spectrum” of the table. In this talk I will explain why the bounce spectrum essentially determines the shape of the table: with the exception of a very small family (right-angled tables), if two tables have the same bounce spectrum, then they have to be related by a Euclidean similarity. The main ingredient in proving this fact is a technical result about non-singular geodesics on surfaces equipped with flat cone metrics. This is joint work with Moon Duchin, Chris Leininger, and Chandrika Sadanand. |
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Feb 7 | Thu | Jeremy Colman (Sheffield) | Statistics Seminar |

14:00 | LT E |
Accounting for Uncertainty in Estimates of Extremes | |

Abstract:Devastating consequences can flow from the failure of certain structures, such as coastal flood defences, nuclear installations, and oil rigs. Their design needs to be robust under rare (p < 0.0001) extreme conditions, but how can the designers use data typically from only a few decades to predict the size of an event that might occur once in 10,000 years? Extreme Value Theory claims to provide a sound basis for such far-out-of-sample prediction, and using Bayesian methods a full posterior distribution can be obtained. If the past data are supplemented by priors that take into account expert opinion, seemingly tight estimates result. Are such claims justified? Has all uncertainty been taken into account? My research is addressing these questions. |
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Feb 7 | Thu |
Masahiro Nakahara (Manchester) | Number Theory seminar |

14:00 | J11 | Index of Fibrations and Brauer classes that never obstruct the Hasse principle | |

Abstract:Let X be a smooth projective variety over a number field with a fibration into varieties that satisfy a certain condition. We study the classes in the Brauer group of X that never obstruct the Hasse principle for X. We prove that if the generic fiber has a zero-cycle of degree d over the generic point, then the Brauer classes whose orders are prime to d do not play a role in the Brauer-Manin obstruction. As a result we show that the odd torsion Brauer classes never obstruct the Hasse principle for del Pezzo surfaces of degree 2, certain K3 surfaces, and Kummer varieties. |
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Feb 13 | Wed | Ana Caraiani (Imperial) | Pure Maths Colloquium |

14:00 | J11 | On the Ramanujan conjecture and its generalisations | |

Abstract:In 1916, Ramanujan made a conjecture that can be stated in completely elementary terms: he predicted an upper bound on the coefficients of a power series obtained by expanding a certain infinite product. In this talk, I will discuss a more sophisticated interpretation of this conjecture, via the Fourier coefficients of a highly symmetric function known as a modular form. I will give a hint of the idea in Deligne’s proof of the conjecture in the 1970’s, who related it to the arithmetic geometry of smooth projective varieties over finite fields. Finally, I will discuss generalisations of this conjecture and some recent progress on these using the machinery of the Langlands program. The last part is based on joint work with Allen, Calegari, Gee, Helm, Le Hung, Newton, Scholze, Taylor, and Thorne. |
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Feb 14 | Thu | Carolina Robustini (Stockholm University) | |

10:00 | Chromospheric observations and magnetic configuration of a supergranular structure | ||

Abstract:We present high spatial resolution narrow-band images in three different chromospheric spectral lines, including Ca II K with the new CHROMospheric Imaging Spectrometer installed at the Swedish 1-m Solar Telescope. These observations feature a unipolar region enclosed in a supergranular cell, and located 68º off the disk-centre. The observed cell exhibits a radial arrangement of the fibrils which recalls of a chromospheric rosette. However, in this case, the convergence point of the fibrils is located at the very centre of the supergranular cell. Our study aims to show how the chromosphere appears in this peculiar region and retrieve its magnetic field and velocity distribution. In the centre of the cell, we measured a significant blue-shift in the Ca II K nominal line core associated to an intensity enhancement. We interpreted it as the product of a strong velocity gradient along the line of sight. In this talk, we will discuss the techniques employed to obtain magnetic field maps so close to the limb and suggest a possible configuration that takes into account also the measured velocity within the unipolar region. |
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Feb 14 | Thu | Eleanor Stillman (Sheffield) | |

12:00 | Hicks LT5 | An overview of the HEA direct application process. | |

Abstract:This talk will outline the process of directly applying to become a (associate-principal) fellow of the HEA. The talk will help Ph.D. students to Professors understand what is required in the application and how to be successful. We may also discuss the value and implications of receiving professional recognition from the HEA. |
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Feb 14 | Thu | Andrey Lazarev (Lancaster) | Topology seminar |

16:00 | J11 | Homotopy theory of monoids | |

Abstract:I will explain how the category of discrete monoids models the homotopy category of connected spaces. This correspondence is based on derived localization of associative algebras and could be viewed as an algebraization result, somewhat similar to rational homotopy theory (although not as structured). Closely related to this circle of ideas is a generalization of Adams’s cobar construction to general nonsimply connected spaces due to recent works of Rivera-Zeinalian and Hess-Tonks. (joint with J. Chuang and J. Holstein) |
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Feb 14 | Thu | Will Hulme / Nick Monk / Rhoda Hawkins (Manchester / Sheffield / Sheffield) | RSS Seminar Series |

16:30 |
Hicks Room F38 |
Experiences of AIMS | |

Abstract:AIMS is an academic network that enables Africa’s talented students to become innovators who propel scientific, educational and economic self-sufficiency. The RSS Local Group are delighted to welcome Will Hulme (University of Manchester, taught at AIMS Cameroon), Prof Nick Monk (University of Sheffield, SOMAS, taught at AIMS Ghana) and Dr Rhoda Hawkins (University of Sheffield, Department of Physics and Astronomy, taught at AIMS South Africa, Senegal and Ghana) to present on their experiences on the AIMS project. Tutor/lecturer opportunities that may be of interest will be highlighted. |
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Feb 15 | Fri | Dan Graves | THH reading group |

14:00 | J11 | Hochschild Homology and Cyclic Homology of rings | |

Feb 20 | Wed | Farrell Brumley (Paris 13) | Northern Number Theory Seminar |

11:00 |
J11 | Concentration properties of theta lifts | |

Abstract:I will present some results on the concentration properties of automorphic forms obtained through the theta correspondence. Among other things, the method relies on a distinction principle for these lifts, which detect their functorial origin via the non vanishing of orthogonal periods. The examples we treat are in higher rank, and shed light on a purity conjecture of Sarnak. This is joint work with Simon Marshall. |
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Feb 20 | Wed | Heather Harrington (Oxford) | Applied Mathematics Colloquium |

14:00 | Hicks, LT 9 | Comparing models and biological data using computational algebra and topology | |

Abstract:Many biological problems, such as tumor-induced angiogenesis (the growth of blood vessels to provide nutrients to a tumor), or signaling pathways involved in the dysfunction of cancer (sets of molecules that interact that turn genes on/off and ultimately determine whether a cell lives or dies), can be modeled using differential equations. There are many challenges with analyzing these types of mathematical models, for example, rate constants, often referred to as parameter values, are difficult to measure or estimate from available data. I will present mathematical methods we have developed to enable us to compare mathematical models with experimental data. Depending on the type of data available, and the type of model constructed, we have combined techniques from computational algebraic geometry and topology, with statistics, networks and optimization to compare and classify models without necessarily estimating parameters. Specifically, I will introduce our methods that use computational algebraic geometry (e.g., Gröbner bases) and computational algebraic topology (e.g., persistent homology). I will present applications of our methodology on datasets involving cancer. Time permitting, I will conclude with our current work for analyzing spatio-temporal datasets with multiple parameters using computational algebraic topology. Mathematically, this is studying a module over a multivariate polynomial ring, and finding discriminating and computable invariants. |
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Feb 20 | Wed | Andreea Mocanu (University of Nottingham) | Northern Number Theory Seminar |

14:00 |
J11 | Newform theory for Jacobi forms of lattice index | |

Abstract:I will give a brief introduction to Jacobi forms, including some examples and their relation to other types of modular forms. After that, I will discuss some of the ingredients that go into developing a theory of newforms for Jacobi forms of lattice index, namely Hecke operators, level raising operators and orthogonal groups of discriminant modules. |
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Feb 20 | Wed |
Clark Barwick (Edinburgh) | Topology seminar |

16:00 | LT11 |
Primes, knots, and exodromy | |

Abstract:Half a century ago, Barry Mazur and David Mumford suggested a remarkable dictionary between prime numbers and knots. I will explain how the story of exodromy permits one to make this dictionary precise, and I will describe some applications. |
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Feb 21 | Thu |
Farrell Brumley (Paris 13) | Pure Maths Colloquium |

14:00 | J11 | Automorphic forms and rational points | |

Abstract:In what sense can automorphic forms or Galois representations be viewed as rational points on an algebraic variety? One way to explore this question is by counting arguments. The first result in this direction dates back to an early theorem of Drinfeld, which computes the number of 2-dimensional Galois representations of a function field in positive characteristic; the resulting expression is reminiscent of a Lefschetz fixed point theorem on a smooth algebraic variety over a finite field. More recently it was observed that in the number field setting there are formal similarities between the asymptotic counting problems for rational points on Fano varieties and for automorphic representations on reductive algebraic groups. Very little is known in the latter context. I’ll discuss joint work on this topic with Djordje Milicevic, in which we (mostly) solve the automorphic counting problem on the general linear group. Our results can be viewed as being analogous to the well-known result of Schanuel on the number of rational points of bounded height on projective spaces. If time permits, I may also present a short argument, using sphere packings in large dimensions, to give upper bounds on such automorphic counts. |
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Feb 21 | Thu | Sophia Wright (Warwick) | Statistics Seminar |

14:00 | LT E |
Bayesian Networks, Total Variation and Robustness | |

Abstract:This talk explores the robustness of large Bayesian Networks when applied in decision support systems which have a pre-specified subset of target variables. We develop new methodology, underpinned by the total variation distance, to determine whether simplifications which are currently employed in the practical implementation of such graphical systems are theoretically valid. This same process can identify areas of the system which should be prioritised if elicitation is required. This versatile framework enables us to study the effects of misspecification within a Bayesian network (BN), and also extend the methodology to quantify temporal effects within Dynamic BNs. Unlike current robustness analyses, our new technology can be applied throughout the construction of the BN model; enabling us to create tailored, bespoke models. For illustrative purposes we shall explore the field of Food Security within the UK. |
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Feb 22 | Fri | James Cranch | THH reading group |

14:00 | J11 | Topological Hochschild Homology | |

Feb 27 | Wed | Raven Waller (Nottingham) | ShEAF: postgraduate pure maths seminar |

16:00 | J11 Hicks | Level structures - a crossroads between topology, representation theory, and number theory | |

Abstract:The arithmetic, algebraic, and topological properties of local fields are intimately related. For higher dimensional local objects these relationships begin to break down, and this may cause considerable difficulty when studying them. The notion of a level structure allows us to work around some of these issues. We will discuss various applications of level structures, including the explicit study of representations of reductive groups over higher dimensional local fields, which is also related to the geometric Langlands program. |
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Feb 28 | Thu | Wil Ward (Sheffield) | Statistics Seminar |

14:00 | LT E |
A Variational Approach to Approximating State Space Gaussian Processes | |

Abstract:The state space representation of a Gaussian process (GP) models the dynamics of an unknown (non-linear) function as a white-noise driven Itô differential equation. Representation in this form allows for the construction of joint models that mix known dynamics (e.g. population) with latent unknown input. Where these interactions are non-linear, or observed through non-Gaussian likelihoods, there is no exact solution and approximation techniques are required. This talk introduces an approach using black box variational inference to model surrogate samples and estimate the underlying parameters. The approximations are compared with full batch solutions and demonstrated to be indistinguishable in two-sample tests. Software and implementation challenges will also be addressed. |
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Feb 28 | Thu | Scott Balchin (Warwick) | Topology seminar |

16:00 | J11 | Adelic reconstruction in prismatic chromatic homotopy theory | |

Abstract:Prismatic homotopy theory is the study of stable monoidal homotopy theories through their Balmer spectrum. In this talk, I will discuss how one can use localised p-complete data at each Balmer prime in an adelic fashion to reconstruct the homotopy theory in question. There are two such models, one is done by moving to categories of modules, which, for example, recovers the algebraic models for G-equivariant cohomology theories. The other, newer model, works purely at the categorical level and requires the theory of weighted homotopy limits. This is joint work with J.P.C Greenlees. |
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Feb 28 | Thu | Mark Wrigley (Chair IOP Yorkshire) | Plasma Dynamics Group |

16:00 |
Room K14 (Hicks Building) | 1201 Alarm Project | |

Abstract:The 1201 Alarm Project is the restoration, exhibition and sharing of materials recorded in 1969 of the Apollo moon landings from a domestic television. The talk will review the Apollo flight plan, the recording technologies of the day and the impact that it had on the speaker. The materials will form the basis for an exhibition celebrating the 50th anniversary of moon landings to be held at the National Science and Media Museum in Bradford, Yorkshire. |
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Mar 1 | Fri | Callum Reader | THH reading group |

14:00 | J11 | Computations of THH | |

Mar 6 | Wed |
Matt Aldridge / Sarah Penington / Helena Stage / Henning Sulzbach (Leeds / Bath / Manchester / Birmingham) | Probability in the North East |

12:30 |
LT C |
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Mar 6 | Wed | Gwyneth Stallard (Open University) | Pure Maths Colloquium |

14:00 | J11 | Complex dynamics: the intriguing case of wandering domains | |

Abstract:Complex dynamics concerns the iteration of analytic functions of the complex plane. For each function, the plane is split into two sets: the Fatou set (where the behaviour of the iterates is stable under local variation) and the Julia set (where the behaviour is chaotic). The dynamical behaviour of the iterates inside the periodic components of the Fatou set was classified into four different types by the founders of the subject and this classification has played a key role in the development of the subject. One of the most dramatic breakthroughs was given by Sullivan in the 1980s when he proved that, for rational functions, all components of the Fatou set are eventually periodic and there are no so-called wandering domains. For transcendental functions, however, wandering domains can exist and the rich variety of possible behaviours that can occur is only just becoming apparent. |
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Mar 6 | Wed | Rachael Hardman (SoMaS) | Applied Mathematics Colloquium |

14:00 | Hicks, K14 |
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Mar 6 | Wed | Paolo Dolce (Nottingham) | ShEAF: postgraduate pure maths seminar |

16:00 | J11 Hicks | ||

Mar 7 | Thu | Christian Fonseca Mora (Costa Rica) | Statistics Seminar |

14:00 | LT E |
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Mar 7 | Thu |
Jean-Stefan Koskivirta (Tokyo) | Number Theory seminar |

14:00 | J11 | TBA | |

Mar 7 | Thu | David Robinson (Capital One) | RSS Seminar Series |

16:30 |
F38 |
Data Science & Machine Learning | |

Abstract:David will start his talk with a brief history of Statistics and Data Science at Capital One: how we got here, what's changed, and what the current expectations and challenges are in the era of "Big Data" and "Machine Learning". The main technical focus will then be on the use of "Gradient Boosting Machines", which over the last few years have emerged as the modelling method of choice for most classification problems within Financial Services. David will cover what they are, why they have become popular and how many of the practical considerations and pitfalls of traditional statistical techniques still very much apply. Example uses will focus on credit risk and affordability, looking at how we can ensure we make fair lending decisions when faced with unfair and biased data. |
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Mar 8 | Fri | Nicola Bellumat | THH reading group |

14:00 | J11 | Periodic Theories | |

Mar 8 | Fri |
Hope Thackary, Jake Percival, Bryony Moody (Sheffield) | Postgraduate seminars |

16:00 |
J11 | PGR Student Seminar | |

Abstract:Abstracts to follow. |
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Mar 13 | Wed | Fatemeh Mohammadi (Bristol) | Pure Maths Colloquium |

14:00 | J11 | Chip-firing game and Riemann-Roch theory for graphs | |

Abstract:Theory of divisors on graphs is analogous to the classical theory for algebraic curves. The combinatorial language in this setting is "chip-firing game” which has been independently introduced in other fields. A divisor on a graph is simply a configuration of dollars (integer numbers) on its vertices. In each step of the chip-firing game we are allowed to select a vertex and then lend one dollar to each of its neighbors, or borrow one dollar from each of its neighbors. The goal of the chip-firing game is to get all the vertices out of debt. In this setting, there is a combinatorial analogue of the classical Riemann-Roch theorem. I will explain the mathematical structure arising from this process and how it sits in a more general framework of (graphical) hyperplane arrangements. |
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Mar 13 | Wed | Tobias Grafke (Warwick) | Applied Mathematics Colloquium |

14:00 | Hicks, LT 9 | Hydrodynamic instantons and the universal route to rogue waves | |

Abstract:In stochastic systems, extreme events are known to be described by "instantons", saddle point configurations of the action of the associated stochastic field theory. In this talk, I will present experimental evidence of a hydrodynamic instanton in a real world fluid system: A 270m wave channel experiment in Norway. The experiment attempts to model conditions on the ocean in order to observe so-called rogue waves, realisations of extreme ocean surface elevation out of relatively calm surroundings. These rogue waves are also observed in the ocean, where they are rare and hard to predict but pose significant danger to naval vessels. We show that the instanton approach, which is rigorously grounded in large deviation theory, offers a unified description of rogue waves in the water tank, covering the entire range of parameters for deep water waves in the ocean. In particular, this approach allows for a unified description of both the predominantly linear and the highly nonlinear regimes, and is able to explain the experimental data in the tank regardless of the strength of the nonlinearity. |
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Mar 13 | Wed | Karoline Van Gemst (Birmingham) | ShEAF: postgraduate pure maths seminar |

16:00 | J11 Hicks | ||

Mar 15 | Fri | Jordan Williamson | THH reading group |

14:00 | J11 | Tate Diagonal | |

Mar 20 | Wed | Sven Meinhardt (Sheffield) | Pure Maths Colloquium |

14:00 | J11 | ||

Mar 20 | Wed | Gianmarco Brocchi (Birmingham) | ShEAF: postgraduate pure maths seminar |

16:00 | J11 Hicks | ||

Mar 21 | Thu | Theo Kypraios (Nottingham) | Statistics Seminar |

14:00 | LT E |
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Mar 21 | Thu |
Tom Fisher (Cambridge) | Number Theory seminar |

14:00 | J11 | TBA | |

Mar 22 | Fri | Luca Pol | THH reading group |

14:00 | J11 | Topological Cyclic Homology | |

Mar 27 | Wed | Daniele Avitabile (Nottingham) | Applied Mathematics Colloquium |

14:00 | Hicks, LT 9 | ||

Mar 27 | Wed | Andreea Mocanu (Nottingham) | ShEAF: postgraduate pure maths seminar |

16:00 | J11 Hicks | ||

Mar 28 | Thu | Hannuun Yaacob (Sheffield) | Statistics Seminar |

14:00 | LT E |
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Mar 29 | Fri | James Brotherston | THH reading group |

14:00 | J11 | Loop Spaces | |

Apr 3 | Wed | Mahesh Kakde (King's College London) | Pure Maths Colloquium |

14:00 | J11 | ||

Apr 3 | Wed | Matt Turner (Surrey) | Applied Mathematics Colloquium |

14:00 | Hicks, LT 9 | ||

Apr 4 | Thu | Fabrizio Leisen (Kent) | Statistics Seminar |

14:00 | LT E |
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Apr 4 | Thu |
Chris Birkbeck (UCL) | Number Theory seminar |

14:00 | J11 | TBA | |

May 1 | Wed | Sam Falle (Leeds) | Applied Mathematics Colloquium |

14:00 | Hicks, LT 9 | Shock structures described by hyperbolic balance laws | |

Abstract:In this talk I will consider shock structures that arise in systems of hyperbolic balance laws, i.e. hyperbolic systems of conservation laws with source terms. I show how the Whitham criterion for the existence of such shock structures can be extended to systems with more than one relaxation variable. In addition, I descibe a method based on the Hermite-Biehler theorem that is useful for determining the stability of the equilibrium states of such systems. The utility of this method is illustrated by a number of examples: ideal gas with two internal degrees of freedom, two fluid magnetohydrodynamics and magnetohydrodynamics with tensor resistivity. |
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May 2 | Thu | Daniel Williamson (Exeter) | Statistics Seminar |

14:00 | LT E |
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May 8 | Wed | Aditi Kar (Royal Holloway) | Pure Maths Colloquium |

14:00 | J11 | ||

May 8 | Wed | Kasia Rejzner (York) | Applied Mathematics Colloquium |

14:00 | Hicks, LT 9 | ||

May 9 | Thu | Rebecca Killick (Lancaster) | Statistics Seminar |

14:00 | LT E |
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May 14 | Tue |
Anna Krystalli / Alison Parton / Lyn Taylor (Sheffield / Sheffield / Phastar) | RSS Seminar Series |

16:00 |
LT 5 |
Putting the R in Reproducible Research / Cloud Computing with R / R Validation Hub Project | |

Abstract:R and its ecosystem of packages offers a wide variety of statistical and graphical techniques and is increasing in popularity as the tool of choice for data analysis in academia. In addition to its powerful analytical features, the R ecosystem provides a large number of tools and conventions to help support more open, robust and reproducible research. This includes tools for managing research projects, building robust analysis workflows, documenting data and code, testing code and disseminating and sharing analyses. In this talk we’ll take a whistle-stop tour of the breadth of available tools, demonstrating the ways R and the Rstudio integrated development environment can be used to underpin more open reproducible research and facilitate best practice. R has cemented itself as the language of choice for many a statistician and data scientist, but is often heckled as a sluggish competitor to the likes of python. This talk will discuss one avenue for maintaining the comfort and power of R (see Anna’s talk!) without having to wait days for your desktop analysis to complete. The foreach package is a set of functions that allow virtually anything that can be expressed as a for-loop as a set of parallel tasks. By registering a parallel backend through the doParallel package, you can speed up the run-time of your work by utilising the full capacity of your machine. I’ll introduce how to rewrite workflows to utilise the foreach approach and show how you can implement a parallel workflow on your own machine with doParallel. For a low-range machine, this will reduce your run-time by 4-fold and for those lucky few with high-range budgets you’ll receive something around 16-fold. So how about going one step further, and increasing to hundreds-fold? We can achieve this by using cloud computing services, taking the load away from your own machine. Cloud computing services have been seen to have a steep learning curve and this has led to many shying away from using such a useful resource. I’ll introduce you to the doAzureParallel package for R, create by Microsoft to bypass this learning curve and allow you to implement the foreach package in parallel in the cloud with only minor amendments to the R code that has been blighting you for months. To date, the use of R Software in the pharmaceutical industry has been relatively limited to exploratory work and not routinely used in regulatory submissions where SAS® Software is still favored. One of the difficulties in using R for submissions is being able to provide the regulators with appropriate documentation of testing and validation for the packages used. In June 2018 the R consortium granted funding for a PSI AIMS SIG initiative to create an online ‘R package validation repository’. With representatives from Abbvie, Amgen, Biogen, Eli Lilly, FDA, GSK, J&J, Merck, Merck KGaA, Novartis, PPD, PRA, Pfizer, Roche / Genentech, Syne qua non and the Transcelerate project, the ‘R Validation Hub’ team launched a free to access web site to host validation documentation and metrics for R packages (https://www.pharmar.org/). Although, the project is still in its early stages, we are looking to expand on the website content and encourage contribution of R metrics and tests for packages from all R-users. The talk will discuss what is meant by validation, how R differs to SAS, justify our approach to the validation issue and present the future capabilities of the website and how all R-users are set to benefit from the work. |
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May 15 | Wed | Martina Balagovic (Newcastle) | Pure Maths Colloquium |

14:00 | J11 | ||

May 15 | Wed | Didier Leibovici (Sheffield) | Applied Mathematics Colloquium |

14:00 | Hicks, LT 9 | ||

May 16 | Thu | Christopher Fallaize (Nottingham) | Statistics Seminar |

14:00 | LT E |
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