Kodaira Dimension and the Yamabe Problem

Abstract

The Yamabe invariant Y(M) of a smooth compact manifold is roughly the supremum of the scalar curvatures of unit-volume constant-scalar curvature Riemannian metrics g on M. (To be absolutely precise, one only considers constant-scalar-curvature metrics which are Yamabe minimizers, but this does not affect the sign of the answer.) If M is the underlying smooth 4-manifold of a complex algebraic surface (M,J), it is shown that the sign of Y(M) is completely determined by the Kodaira dimension Kod (M,J). More precisely, Y(M) 0 iff Kod (M,J)= -infinity.Comment: LaTeX file. With minor typographical errors correcte