On the prescribed Q -curvature problem in Riemannian manifolds

We prove the existence of metrics with prescribed Q -curvature under natural assumptions on the sign of the prescribing function and the background metric. In the dimension four case, we also obtain existence results for curvature forms requiring only restrictions on the Euler characteristic. Moreover, we derive a prescription result for open submanifolds which allow us to conclude that any smooth function on ℝ^n can be realized as the Q -curvature of some Riemannian metric.