Tue, 11 Oct 2022

14:30 - 15:00
L3

Fooled by optimality

Nick Trefethen
(University of Oxford)
Abstract

An occupational hazard of mathematicians is the investigation of objects that are "optimal" in a mathematically precise sense, yet may be far from optimal in practice. This talk will discuss an extreme example of this effect: Gauss-Hermite quadrature on the real line. For large numbers of quadrature points, Gauss-Hermite quadrature is a very poor method of integration, much less efficient than simply truncating the interval and applying Gauss-Legendre quadrature or the periodic trapezoidal rule. We will present a theorem quantifying this difference and explain where the standard notion of optimality has failed.

Forgive a cliché, but musician. political exile and government minister Gilberto Gil's life certainly throws some light on Brazilian culture and politics from the 1960s. Musically he is a mix of Samba and wider African and Caribbean beats as well as Rock Music (he likes punk as well). Andar com fé (walk with faith) is one of his most popular songs.

Dance away the heartache.

Thu, 20 Oct 2022

14:00 - 15:00
L3

Twenty examples of AAA approximation

Nick Trefethen
(University of Oxford)
Abstract

For the first time, a method has become available for fast computation of near-best rational approximations on arbitrary sets in the real line or complex plane: the AAA algorithm (Nakatsukasa-Sète-T. 2018).  After a brief presentation of the algorithm this talk will focus on twenty demonstrations of the kinds of things we can do, all across applied mathematics, with a black-box rational approximation tool.
 

AAA interpolation of equispaced data
Huybrechs, D Trefethen, L (24 Jul 2022)
Gaussian fields and percolation
Beliaev, D (27 Jul 2022)
Entropy-based random models for hypergraphs
Saracco, F Petri, G Lambiotte, R Squartini, T (21 Jul 2022)
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