ANZIAM  J.  45 (2003), 207-222
The dimension of attractors of nonautonomous partial differential equations

T. Caraballo
  Dpto. Ecuaciones Diferenciales y Análisis Numérico
  Universidad de Sevilla
  Apdo. de Correos 1160
  41080-Sevilla
  Spain
    caraball@us.es
J. A. Langa
  Dpto. Ecuaciones Diferenciales y Análisis Numérico
  Universidad de Sevilla
  Apdo. de Correos 1160
  41080-Sevilla
  Spain
    langa@numer.us.es
and
J. Valero
  Universidad Cardenal Herrera CEU
  Comisario 3
  03203 Elche
  Alicante
  Spain
    valer.el@ceu.es


Abstract
The concept of nonautonomous (or cocycle) attractors has become a proper tool for the study of the asymptotic behaviour of general nonautonomous partial differential equations. This is a time-dependent family of compact sets, invariant for the associated process and attracting ``from $-\infty$''. In general, the concept is rather different to the classical global attractor for autonomous dynamical systems. We prove a general result on the finite fractal dimensionality of each compact set of this family. In this way, we generalise some previous results of Chepyzhov and Vishik. Our results are also applied to differential equations with a nonlinear term having polynomial growth at most.
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