On varieties whose universal cover is a product of curves

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 $C={\text{PP}}^{1}or\text{HH}$: 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., ${\eta }^2\cong {\text{hol}}_X$). 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.