New Proof of Naimark's Theorem on the Existence of Nonpositive Invariant Subspaces for Commuting Families of Unitary Operators in Pontryagin Spaces.
New results for EP matrices in indefinite inner product spaces
In this paper we study -EP matrices, as a generalization of EP-matrices in indefinite inner product spaces, with respect to indefinite matrix product. We give some properties concerning EP and -EP matrices and find connection between them. Also, we present some results for reverse order law for Moore-Penrose inverse in indefinite setting. Finally, we deal with the star partial ordering and improve some results given in the “EP matrices in indefinite inner product spaces” (2012), by relaxing some...