Adiabatic Decomposition of the Ζ-determinant of the Dirac Laplacian I. the Case of an Invertible Tangential Operator

Abstract. We discuss the decomposition of the ζ-determinant of the square of the Dirac operator into the contributions coming from the different parts of the manifold. The result was announced in [16] . The proof sketched in [16] was based on results of Brüning and Lesch (see [4]). In the meantime we have found another proof, more direct and elementary, and closer to the spirit of the original papers which initiated the study of the adiabatic decomposition of the spectral invariants (see [7] and [21]). We discuss this proof in detail. We study the general case (non-invertible tangential operator) in forthcoming work (see [17] and [18]). In the Appendix we present the computation of the cylinder contribution to the ζ-function of the Dirac Laplacian on a manifold with boundary, which we need in the main body of the paper. This computation is also used to show the vanishing result for the ζ-function on a manifold with boundary.