Moser-Trudinger type inequalities for complex Monge-Amp\`ere operators and Aubin's "hypoth\`ese fondamentale"

We prove Aubin's "Hypothese fondamentale" concerning the existence of Moser-Trudinger type inequalities on any integral compact K\"ahler manifold X. In the case of the anti-canonical class on a Fano manifold the constants in the inequalities are shown to only depend on the dimension of X (but there are counterexamples to the precise value proposed by Aubin). In the different setting of pseudoconvex domains in complex space we also obtain a quasi-sharp version of the inequalities and relate it to Brezis-Merle type inequalities. The inequalities are shown to be sharp for S^{1}-invariant functions on the unit-ball. We give applications to existence and blow-up of solutions to complex Monge-Amp\`ere equations of mean field (Liouville) type.