4 papers
Spectral enclosures for a class of block operator matrices
Juan Giribet, Matthias Langer, Francisco Martínez Pería +2
We prove new spectral enclosures for the non-real spectrum of a class of block operator matrices with self-adjoint operators and on the diagonal and operators $B…
The numerical range of non-negative operators in Krein spaces
Friedrich Philipp, Carsten Trunk
We define and characterize the Krein space numerical range and the Krein space co-numerical range of a non-negative operator in a Krein space. It is show…
Locally definite normal operators in Krein spaces
Friedrich Philipp
We introduce the spectral points of two-sided positive type of bounded normal operators in Krein spaces. It is shown that a normal operator has a local spectral function on sets wh…
Spectral functions of products of selfadjoint operators
Tomas Ya. Azizov, Mikhail Denisov, Friedrich Philipp
Given two possibly unbounded selfadjoint operators A and G such that the resolvent sets of AG and GA are non-empty, it is shown that the operator AG has a spectral function on IR w…