Signatures for $J$-hermitians and $J$-unitaries on Krein spaces with Real structures

Hermann Schulz-Baldes, Carlos Villegas-Blas

For $J$-hermitian operators on a Krein space $(\mathcal{K},J)$ satisfying an adequate Fredholm property, a global Krein signature is shown to be a homotopy invariant. It is argued…