Multi-time scale integration.

 > In the literature on multi-time scale integration, a lot of importance is
 > placed on time reversibility.  Why this is so important is something
 > that I have never been able to figure out.  If an integration
 > algorithm is efficient and produces a small global error then why is
 > this not sufficient.  If anybody can enlighten me on this subject I
 > would appreciate it.
 > --
 > Don Steiger
 > dons #*at*#
 Newton's equations are time-reversible, and Hamiltonian dynamics
 preserves phase space volume. Non-reversible integration schemes do not
 preserve volume in phase space and usually show also long-term energy
 drifts. The reasons for wanting time-reversibility are therefore
 eminently physical and not mathematical. A good reference is the book by
 Daan Frenkel and Berends Smit, "Understanding Molecular Simulation",
 Academic Press 1996.
 Dr. Guido Germano
 Research Assistant in Theoretical Physics, University of Bristol, England
 Tel. +44-117-928 9000 ext. 8755,