Speaker:Prof. Michael Proctor, FRS (DAMTP)
Venue: Old Combination Room, Trinity College
Time: 20/11/2006 20:30, drinks from 20:15

We are accustomed to thinking of the stability of a configuration of a physical system in black and white terms: either small disturbances grow or they decay. But there are many important situations where the system is ultimately stable, but which can act as a powerful amplifier for a long period of time. The situation is particularly important when the system has a long spatial extent, so that these non-instabilities (convective instabilities) can produce large amplitude structures which can be sustained by small amounts of noise. In contrast, when the system is absolutely unstable no noise is needed to sustain the structures. This dichotomy is related to the behaviour of linear dynamical systems with non-normal matrices.