  We investigate a necessary condition for a compact complex manifold X of
dimension n in order that its universal cover be the Cartesian product $C^n$ of
a curve $C = \PP^1 or \HH$: the existence of a semispecial tensor $\omega$. A
semispecial tensor is a non zero section $ 0 \neq \omega \in H^0(X,
S^n\Omega^1_X (-K_X) \otimes \eta) $), where $\eta$ is an invertible sheaf of
2-torsion (i.e., $\eta^2\cong \hol_X$). We show that this condition works out
nicely, as a sufficient condition, when coupled with some other simple
hypothesis, in the case of dimension $n= 2$ or $ n= 3$; but it is not
sufficient alone, even in dimension 2. In the case of K\"ahler surfaces we use
the above results in order to give a characterization of the surfaces whose
universal cover is a product of two curves, distinguishing the 6 possible
cases.

Algebraic Geometry;Complex Variables