MATHEMATISCHE NACHRICHTEN, cilt.280, sa.8, ss.924-931, 2007 (SCI-Expanded)
Let T = {T (t)}(t is an element of R) be a Co-group on a Banach space X with generator A. Under what conditions the assumption sigma (A) = {0} implies that A = 0 ? This is called "A = 0" problem. In this paper we present some results related to this problem. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.