A matrix formula for Schur complements of nonnegative selfadjoint linear relations

Maximiliano Contino, Alejandra Maestripieri, Stefania Marcantognini

If a nonnegative selfadjoint linear relation $A$ in a Hilbert space and a closed subspace $\mathcal{S}$ are assumed to satisfy that the domain of $A$ is invariant under the orthogo…