Central European Journal of Mathematics

, Volume 5, Issue 2, pp 335–344

Limit points of eigenvalues of truncated unbounded tridiagonal operators


  • E.K. Ifantis
    • Department of MathematicsUniversity of Patras
  • C.G. Kokologiannaki
    • Department of MathematicsUniversity of Patras
  • E. Petropoulou
    • Department of MathematicsUniversity of Patras
Research Article

DOI: 10.2478/s11533-007-0009-1

Cite this article as:
Ifantis, E., Kokologiannaki, C. & Petropoulou, E. centr.eur.j.math. (2007) 5: 335. doi:10.2478/s11533-007-0009-1


Let T be a self-adjoint tridiagonal operator in a Hilbert space H with the orthonormal basis {en}n=1, σ(T) be the spectrum of T and Λ(T) be the set of all the limit points of eigenvalues of the truncated operator TN. We give sufficient conditions such that the spectrum of T is discrete and σ(T) = Λ(T) and we connect this problem with an old problem in analysis.


Tridiagonal operatorsspectrumlimit points of eigenvaluesorthogonal polynomialscontinued fractions

MSC (2000)


Copyright information

© Versita Warsaw and Springer-Verlag Berlin Heidelberg 2007