Condensation of the singularities in the theory of operator ideals

Authors

  • Cristina Antonescu University of Hannover, Germany
  • Wolfgang W. Breckner “Babes-Bolyai” University, Cluj-Napoca, Romania

DOI:

https://doi.org/10.33993/jnaat332-769

Keywords:

singularities of a family of real-valued functions, residual sets, operator ideals
Abstract views: 168

Abstract

In the present paper there are given some applications of the principle of condensation of the singularities of families of nonnegative functions established by W. W. Breckner in 1984. They reveal Baire category information on certain subsets of a normed linear space \(X\) of the second category that are defined by means of an inequality of the type \(f(x)<\infty\), where \(f\) is a given function from \(X\) to \([0,\infty]\). Sets of this type occur frequently in the theory of operator ideals. They are constructed individually by using entropy or approximation numbers of operators. By specializing the general results given in the paper it follows that such operator sets are of the first category, while their complements are residual \(G_\delta\)-sets, of the second category, uncountable and dense.

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References

Breckner, W. W., Condensation and double condensation of the singularities of families of numerical functions. In: I. Maruşciac and W. W. Breckner (Editors), Proceedings of the Colloquium on Approximation and Optimization, Cluj-Napoca, October 25-27, 1984, University of Cluj-Napoca, Cluj-Napoca, pp. 201-212, 1985.

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Published

2004-08-01

How to Cite

Antonescu, C., & Breckner, W. W. (2004). Condensation of the singularities in the theory of operator ideals. Rev. Anal. Numér. Théor. Approx., 33(2), 149–156. https://doi.org/10.33993/jnaat332-769

Issue

Vol. 33 No. 2 (2004)

Section

Articles

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Copyright (c) 2015 Journal of Numerical Analysis and Approximation Theory

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