The APS-index and the spectral flow
The APS-index and the spectral flow
We study the Atiyah-Patodi-Singer (APS) index, and its equality to the spectral flow, in an abstract, functional analytic setting.More precisely, we consider a (suitably continuous or differentiable) family of self-adjoint Fredholm operators A(t) on a Hilbert space, parametrised by t in a finite interval.We then consider two different operators, namely …