8 citations · 36 across the 32 of their papers we have counts for
13 papers · 1 filter
On characteristic invariants of matrix pencils and linear relations
Hannes Gernandt, Francisco Martínez Pería, Friedrich Philipp +1
The relationship between linear relations and matrix pencils is investigated. Given a linear relation, we introduce its Weyr characteristic. If the linear relation is the range (or…
Relatively bounded perturbations of J-non-negative operators
Friedrich Philipp
We improve known perturbation results for self-adjoint operators in Hilbert spaces and prove spectral enclosures for diagonally dominant -self-adjoint operator matrices. These a…
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…
Spectral Points of Type and Type of Closed Operators in Indefinite Inner Product Spaces
Friedrich Philipp, Carsten Trunk
We introduce the notion of spectral points of type and type of closed operators in a Hilbert space which is equipped with an indefinite inner product. It is shown t…
Estimates on the non-real eigenvalues of regular indefinite Sturm-Liouville problems
Jussi Behrndt, Shaozhu Chen, Friedrich Philipp +1
Regular Sturm-Liouville problems with indefinite weight functions may possess finitely many non-real eigenvalues. In this note we prove explicit bounds on the real and imaginary pa…
Local spectral theory for normal operators in Krein spaces
Friedrich Philipp, Vladimir Strauss, Carsten Trunk
Sign type spectra are an important tool in the investigation of spectral properties of selfadjoint operators in Krein spaces. It is our aim to show that also sign type spectra for…
Bounds on the non-real spectrum of differential operators with indefinite weights
Jussi Behrndt, Friedrich Philipp, Carsten Trunk
Ordinary and partial differential operators with an indefinite weight function can be viewed as bounded perturbations of non-negative operators in Krein spaces. Under the assumptio…
Variation of discrete spectra of non-negative operators in Krein spaces
Jussi Behrndt, Leslie Leben, Friedrich Philipp
We study the variation of the discrete spectrum of a bounded non-negative operator in a Krein space under a non-negative Schatten class perturbation of order . It turns out that…
Eigenvalues in gaps of selfadjoint operators in Pontryagin spaces
Friedrich Philipp
Given an open real interval Δ and two selfadjoint operators A_1, A_2 in a Π_κ-space with n-dimensional resolvent difference we show that the difference of the total multiplicities…
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…
Indefinite Sturm-Liouville operators with periodic coefficients
Friedrich Philipp
We investigate the spectral properties of the maximal operator associated with a differential expression with real-valued periodic…
Local Definitizability of and
Friedrich Philipp, André C. M. Ran, Michał Wojtylak
The spectral properties of two products and of possibly unbounded operators and in a Banach space are considered. The results are applied in the comparison of loc…