Inspired by the One World Probability Project and supported by the Bernoulli Society, the One World Extremes Seminar is an initiative to keep researchers with an interest in Extreme Value Theory (EVT) virtually connected in novel ways. It features both theoretical advances and important applications of EVT.
Abstract: The talk will describe a novel approach to mixture modelling for asymptotically dependent sample extremes, based on a tilting transformation suggested by Coles and Tawn, the value of which seems to have been under-appreciated. The approach is Bayesian and allows the soft clustering of extreme events, fitted by a reversible jump Markov chain algorithm. The method is applied to sectorial data from the S&P 500 index.
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Graphical models for infinite measures with applications to extremes
Abstract: Statistical modelling of complex dependencies in extreme events requires meaningful sparsity structures in multivariate extremes. In this context two perspectives on conditional independence and graphical models have recently emerged: One that focuses on threshold exceedances and multivariate pareto distributions, and another that focuses on max-linear models and directed acyclic graphs. What connects these notions is the exponent measure that lies at the heart of each approach. In this work we develop a notion of conditional independence defined directly on the exponent measure (and even more generally on measures that explode at the origin) that builds a bridge between these approaches. We characterize this conditional independence in various ways through kernels and factorization of a modified density, including a Hammersley-Clifford type theorem for undirected graphical models. As opposed to the classical conditional independence, our notion is intimately connected to the support of the measure. Structural max-linear models turn out to form a Bayesian network with respect to our new form of conditional independence. Our general theory unifies and extends recent approaches to graphical modeling in the fields of extreme value analysis and Lévy processes. Our results for the corresponding undirected and directed graphical models lay the foundation for new statistical methodology in these areas.
This is joint work with Sebastian Engelke and Jevgenijs Ivanovs.
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Dan Cooley (Colorado State University)
Anna Kiriliouk (Université catholique de Louvain)
Jordan Richards (University of Edinburgh)
Tiandong Wang (Fudan University)
Kirstin Strokorb (Bath University) - past organiser, now technical advice
Gilles Stupfler (ENSAI) - newsletter editor
2023 - 2025
Thomas Opitz (INRAE, Avignon)
Kate Saunders (Monash University)
Emma Simpson (University College London)
Stilian Stoev (University of Michigan)
2020 - 2023
Raphaël Huser (KAUST)
Natalia Nolde (UBC Vancouver)
Marco Oesting (University of Stuttgart)
Kirstin Strokorb (Cardiff University)
Gilles Stupfler (ENSAI)
Yizao Wang (University of Cincinnati)