Abstract
In a given dynamical system there are essentially two different
types of information which could be of practical interest: on the
one hand there is the need to describe the behavior of single
trajectories in detail. This information is helpful for the analysis
of transient behavior and also in the investigation of geometric
properties of dynamical systems. On the other hand, if the
underlying invariant set is generated by complicated dynamics then
the computation of single trajectories may give misleading results.
In this case there still exists important set related information
covering both topological and statistical aspects of the underlying
dynamical behavior. Within the DFG-Schwerpunkt we have focussed on
the development of set oriented methods for the numerical
approximation of
- invariant sets, with particular attention to invariant
manifolds;
- (natural) invariant measures;
- almost invariant sets.
The basic concept is a subdivision algorithm which is similar in
spirit to the well known cell mapping techniques but with the crucial
difference that the numerical effort mainly depends on the complexity
of the dynamics rather than on the dimension of the underlying state
space. First, the invariant set is covered by boxes and then the
dynamical behavior on the set is approximated by a Markov chain based
on transition probabilities between elements of this covering. The
algorithms have been implemented in the software package GAIO
Global Analysis of Invariant Objects), and in
this article we describe both the related numerical techniques
together with their theoretical foundations and how to use them within
GAIO. We will also discuss details concerning the implementation
such as adaptive versions of the methods.