\(J\)-self-adjoint projections in Krein spaces (Q2310449)

Summary: Let \(\mathcal{H}\) be a Krein space with fundamental symmetry \(J\). Starting with a canonical block-operator matrix representation of \(J\), we study the regular subspaces of \(\mathcal{H}\). We also present block-operator matrix representations of the \(J\)-self-adjoint projections for the regular subspaces of \(\mathcal{H}\), as well as for the regular complements of the isotropic part in a pseudo-regular subspace of \(\mathcal{H}\).