Functional calculus for -groups using (co)type
arXiv:1508.02036 · doi:10.1093/qmath/hay032
Abstract
We study the functional calculus properties of generators of -groups under type and cotype assumptions on the underlying Banach space. In particular, we show the following. Let generate a -group on a Banach space with type and cotype . Then has a bounded -calculus from to , i.e. is bounded for each bounded holomorphic function on a sufficiently large strip. As a corollary of our main theorem, for sectorial operators we quantify the gap between bounded imaginary powers and a bounded -calculus in terms of the type and cotype of the underlying Banach space. For cosine functions we obtain similar results as for -groups. We extend our results to -bounded operator-valued calculi, and we give an application to the theory of rational approximation of -groups.
Minor modifications, 27 pages. Published online in Quarterly Journal of Mathematics