Compact Complex Manifolds

Abstract

In this chapter we shall apply the differential equations and differential geometry of the previous two chapters to the study of compact complex manifolds. In Sec. 1 we shall present a discussion of the exterior algebra on a Hermitian vector space, introducing the fundamental 2-form and the Hodge *-operator associated with the Hermitian metric. In Sec. 2 we shall discuss and prove the principal results concerning harmonic forms on compact manifolds (real or complex), in particular, Hodge’s harmonic representation for the de Rham groups, and special cases of Poincaré and Serre duality. In Sec. 3 we present the finite-dimensional representation theory for the Lie algebra 31(2, C), from which we derive the Lefschetz decomposition theorem for a Hermitian exterior algebra. In Sec. 4 we shall introduce the concept of a Kahler metric and give various examples of Kahler manifolds (manifolds equipped with a Kahler metric). In terms of a Hermitian metric we define the Laplacian operators associated with the operators d, d, and d and show that when the metric is Kahler that the Laplacians are related in a simple way. We shall use this relationship in Sec. 5 to prove the Hodge decomposition theorem expressing the de Rham group as a direct sum of the Dolbeault groups (of the same total degree). In Sec. 6 we shall state and prove Hodge’s generalization of the Riemann period relations for integrals of harmonic forms on a Kahler manifold. We shall then use the period relations and the Hodge decomposition to formulate the period mapping of Griffiths. In particular, we shall prove the Kodaira-Spencer upper semicontinuity theorem for the Hodge numbers on complex-analytic families of compact manifolds.KeywordsFundamental FormDifferential FormComplex ManifoldHodge StructureExterior AlgebraThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.