  Denote by g the Gauss measure on R^n and by L the Ornstein-Uhlenbeck
operator. In this paper we introduce a local Hardy space h^1(g) of Goldberg
type and we compare it with the Hardy space H^1(g) introduced in a previous
paper by Mauceri and Meda. We show that for each each positive r the imaginary
powers of the operator rI+L are unbounded from h^1(g) to L^1(g). This result is
in sharp contrast both with the fact that the imaginary powers are bounded from
$H^1(g}$ to L^1(g), and with the fact that for the Euclidean laplacian \Delta
and the Lebesgue measure \lambda) the imaginary powers of rI-\Delta are bounded
from the Goldberg space h^1(\lambda) to L^1(\lambda). We consider also the case
of Riemannian manifolds M with Riemannian measure m. We prove that, under
certain geometric assumptions on M, an operator T, bounded on L^2(m), and with
a kernel satisfying certain analytic assumptions, is bounded from H^1(m) to
L^1(m) if and only if it is bounded from h^1(m) to L^1(m). Here H^1(m) denotes
the Hardy space on locally doubling metric measure spaces introduced by the
authors in arXiv:0808.0146, and h^1(m) is a Goldberg type Hardy space on M,
equivalent to a space recently introduced by M. Taylor. The case of translation
invariant operators on homogeneous trees is also considered.
