Extremal Kaehler metrics and Ray-Singer analytic torsion

Abstract

Let (X,[ω]) be a compact Kaehler manifold with a fixed Kaehler class [ω]. Let K_ωbe the set of all Kaehler metrics on X whose Kaehler class equals [ω]. In this paper we investigate the critical points of the functional Q(g)= |v|_g T_0(X,g)^{1/2} for g \in K_ω, where v is a fixed nonzero vector of the determinant line λ(X) associated to H^*(X) and T_0(X,g) is the Ray-Singer analytic torsion. For a polarized algebraic manifold (X,L) we consider a twisted version Q_L(g) of this functional and assume that c_1(L)=[ω]. Then the critical points of Q_L are exactly the metrics g\in K_ωof constant scalar curvature. In particular, if c_1(X)=0 or if c_1(X)<0 and 1/(2π)[ω] = -c_1(X), then K_ωcontains a unique Kaehler-Einstein metric g_{KE} and Q_L attains its absolut maximum at g_{KE}.