It follows that P,.(k,l) = •(k,l)Pt for k,l ::
2002
In the following the system Zt+t = ~AtZt for.., E a+ = (0, oo) will play an important role and one can easily see that •-y(k,l) := (~)i-l•(k,l) is its evolution operator. If Zt+t = ~AtZt admits an ED then its invariant projector Pis also invariant for Zt+t = A,z,, i.e. (2) holds. The dichotomy estimates are equivalent to We follow Aulbach [1] and introduce a handy notion describing exponential growth of functions.