Principal part of resolvent and factorization of an increasing nonanalytic operator-function

Alexander Markus, Vladimir Matsaev

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Let a selfadjoint operator-valued function L(λ) be given on the interval [a,b] such that L(a)≪0, L(b)≫0, L′(λ)≫0 (a≤λ≤b), and L″(λ) has a certain smoothness (for instance, it satisfies Hölder's condition). It turns out that the spectral theory of the operator-valued function L(λ) can be reduced to the spectral theory of one operator Z, the spectrum of which lies on (a, b) and which is similar to a selfadjoint operator. In particular, the factorization takes place:L(λ)=M(λ)(λI-Z), where the operator-valued function M(λ) is invertible on [a, b]. Earlier similar results were known only for analytic operator-valued functions. The authors had to use new methods for the proof of the described theorem. The key moment is the decomposition of L-1(λ) into the sume of its principal and regular parts.

Original languageEnglish
Pages (from-to)716-746
Number of pages31
JournalIntegral Equations and Operator Theory
Issue number5
StatePublished - 1 Sep 1991

ASJC Scopus subject areas

  • Analysis
  • Algebra and Number Theory


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