Departmental Colloquia Autumn 2011

Colloquium talks will take place some Tuesdays at 4.00 pm in Room D103 in 25 Gordon Street. See how to find us for further details. There will be tea afterwards in room 606.

If you require any more information on these talks, please contact either Prof Alex Sobolev (e-mail: a.sobolev AT ucl.ac.uk or tel: 020-7679-2863) or Professor Yaroslav Kurylev (e-mail: y.kurylev AT ucl.ac.uk or tel: 020-7679-7896).

22 November 2011 

Nick Trefethen - Oxford University

Robust Rational Approximation


Rational approximations are at the heart of powerful algorithms, but they are notoriously fragile. In different contexts they may fail to exist, fail to be unique, or depend discontinuously on the data. Some approximations show forests of seemingly meaningless pole-zero pairs or "Froissart doublets", and when these artifacts should not be there in theory, they still often appear in practice because of rounding errors on the computer. Here, in joint work with Pedro Gonnet and Ricardo Pachon, we present a method for getting around many of these problems using the singular value decomposition.