ArticleOriginal scientific text

Title

On having a countable cover by sets of small local diameter

Authors 1

Affiliations

  1. Department of Mathematics and Informatics, University of Sofia, J. Bourchier boul. 5a, 1164 Sofia, Bulgaria

Abstract

A characterization of topological spaces admitting a countable cover by sets of small local diameter close in spirit to known characterizations of fragmentability is obtained. It is proved that if X and Y are Hausdorff compacta such that C(X) has an equivalent p-Kadec norm and Cp(Y) has a countable cover by sets of small local norm diameter, then Cp(X×Y) has a countable cover by sets of small local norm diameter as well.

Keywords

countable cover by sets of small local diameter, fragmentability, Kadec renorming

Bibliography

  1. R. Deville, G. Godefroy and V. Zizler, Smoothness and Renormings in Banach Spaces, Longman, 1993.
  2. E G. E. Edgar, Measurability in a Banach space, Indiana Univ. Math. J. 28 (1979), 559-579.
  3. R. Engelking, General Topology, PWN, Warszawa, 1985.
  4. G G. Gruenhage, A note on Gul'ko compact spaces, Proc. Amer. Math. Soc. 100 (1987), 371-376.
  5. H R. W. Hansell, Descriptive sets and the topology of nonseparable Banach spaces, preprint (1989).
  6. J. E. Jayne, I. Namioka and C. A. Rogers, σ-fragmentable Banach spaces, Mathematika 39 (1992), 161-188 and 197-215.
  7. J. E. Jayne, I. Namioka and C. A. Rogers, Topological properties of Banach spaces, Proc. London Math. Soc. 66 (1993), 651-672.
  8. J. E. Jayne, I. Namioka and C. A. Rogers, Continuous functions on products of compact Hausdorff spaces, to appear.
  9. J. E. Jayne and C. E. Rogers, Borel selectors for upper semicontinuous set-valued maps, Acta Math. 155 (1985), 41-79.
  10. P. S. Kenderov and W. Moors, Fragmentability and sigma-fragmentability of Banach spaces, J. London Math. Soc. 60 (1999), 203-223.
  11. A. Moltó, J. Orihuela and S. Troyanski, Locally uniformly rotund renorming and fragmentability, Proc. London Math. Soc. 75 (1997), 619-640.
  12. A. Moltó, J. Orihuela, S. Troyanski and M. Valdivia, On weakly locally uniformly rotund Banach spaces, J. Funct. Anal. 163 (1999), 252-271.
  13. M W. B. Moors, manuscript, 1997.
  14. I. Namioka and R. Pol, Sigma-fragmentability of mappings into Cp(K), Topology Appl. 89 (1998), 249-263.
  15. M. Raja, On topology and renorming of Banach space, C. R. Acad. Bulgare Sci. 52 (1999), 13-16.
  16. M. Raja, Kadec norms and Borel sets in a Banach space, Studia Math. 136 (1999), 1-16.
  17. N. K. Ribarska, Internal characterization of fragmentable spaces, Mathematika 34 (1987), 243-257.
  18. N. K. Ribarska, A Radon-Nikodym compact which is not a Gruenhage space, C. R. Acad. Bulgare Sci. 41 (1988), 9-11.
  19. N. K. Ribarska, A stability property for σ-fragmentability, manuscript, 1996.
Pages:
99-116
Main language of publication
English
Received
1998-12-22
Accepted
2000-01-13
Published
2000
Exact and natural sciences