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A polynomial iteration for the spectral family of an operator

Published online by Cambridge University Press:  18 May 2009

F. F. Bonsall
Affiliation:
King's CollegeDurham UniversityNewcastle upon Tyne
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Let T be a bounded symmetric operator in a Hilbert space H. According to the spectral theorem, T can be expressed as an integral in terms of its spectral family {Eλ}, each Eλ being a certain projection which is known to be the strong limit of some sequence of polynomials in T. It is a natural question to ask for an explicit sequence of polynomials in T that converges strongly to Eλ. So far as the author knows, no complete solution of this problem has been given even when H has finite dimension, i.e. when T is a finite symmetric matrix. Since a knowledge of the spectral family {Eλ} of a finite symmetric matrix carries with it a knowledge of the eigenvalues and eigenvectors, a solution of the problem may have some practical value.

Type
Research Article
Copyright
Copyright © Glasgow Mathematical Journal Trust 1963

References

REFERENCES

1.Bonsall, F. F., A formula for the spectral family of an operator, J. London Math. Soc. 35 (1960), 321333.CrossRefGoogle Scholar
2.Riesz, F. and Sz.-Nagy, B., Leçons d'Analyse Fonctionelle (Budapest, 1952).Google Scholar