In this paper we prove that the maximal Lp-regularity property on the
interval (0,T), T>0, for Cauchy problems associated with the square root of
Hermite, Bessel or Laguerre type operators on L2(Ω,dμ;X),
characterizes the UMD property for the Banach space X.Comment: 23 pages. To appear in Semigroup Foru