An interesting example for spectral invariants

作者:Benameur Moulay Tahar*; Heitsch James L; Wahl Charlotte
来源:Journal of K-Theory, 2014, 13(2): 305-311.
DOI:10.1017/is014002020jkt255

摘要

In [HL99], the heat operator of a Bismut superconnection for a family of generalized Dirac operators is defined along the leaves of a foliation with Hausdorff groupoid. The Novikov-Shubin invariants of the Dirac operators were assumed greater than three times the codimension of the foliation. It was then shown that the associated heat operator converges to the Chern character of the index bundle of the operator. In [BH08], this result was improved by reducing the requirement on the Novikov-Shubin invariants to one half of the codimension. In this paper, we construct examples which show that this is the best possible result.