P.COLLET
AMPLITUDE EQUATION FOR LATTICE MAPS,
A RENORMALIZATION GROUP APPROACH
(106K, Postscript gzipped uuencoded)

ABSTRACT.  We consider the development of instabilities of  homogeneous
stationary solutions of discrete time lattice maps. Under some generic
hypothesis we derive an amplitude equation which is the space-time
continuous Ginzburg-Landau equation. Using dynamical renormalization
group methods we control the accuracy of this approximation in a large 
ball of its basin of attraction.