Canonical metrics on 3-manifolds and 4-manifolds

Abstract

We prove certain weak or idealized existence results for minimizers of the natural quadratic curvature functionals on the space of metrics on 4-manifolds. Overall, we try to exhibit the relations with the picture in 3-dimensions provided by Thurston geometrization. The existence results apply in particular to the structure of the moduli spaces of such metrics, and as such generalize most of the known results for moduli of Einstein metrics.