ArticleOriginal scientific text
Title
On having a countable cover by sets of small local diameter
Authors 1
Affiliations
- 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 has a countable cover by sets of small local norm diameter, then 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
- R. Deville, G. Godefroy and V. Zizler, Smoothness and Renormings in Banach Spaces, Longman, 1993.
- E G. E. Edgar, Measurability in a Banach space, Indiana Univ. Math. J. 28 (1979), 559-579.
- R. Engelking, General Topology, PWN, Warszawa, 1985.
- G G. Gruenhage, A note on Gul'ko compact spaces, Proc. Amer. Math. Soc. 100 (1987), 371-376.
- H R. W. Hansell, Descriptive sets and the topology of nonseparable Banach spaces, preprint (1989).
- J. E. Jayne, I. Namioka and C. A. Rogers, σ-fragmentable Banach spaces, Mathematika 39 (1992), 161-188 and 197-215.
- J. E. Jayne, I. Namioka and C. A. Rogers, Topological properties of Banach spaces, Proc. London Math. Soc. 66 (1993), 651-672.
- J. E. Jayne, I. Namioka and C. A. Rogers, Continuous functions on products of compact Hausdorff spaces, to appear.
- J. E. Jayne and C. E. Rogers, Borel selectors for upper semicontinuous set-valued maps, Acta Math. 155 (1985), 41-79.
- P. S. Kenderov and W. Moors, Fragmentability and sigma-fragmentability of Banach spaces, J. London Math. Soc. 60 (1999), 203-223.
- A. Moltó, J. Orihuela and S. Troyanski, Locally uniformly rotund renorming and fragmentability, Proc. London Math. Soc. 75 (1997), 619-640.
- A. Moltó, J. Orihuela, S. Troyanski and M. Valdivia, On weakly locally uniformly rotund Banach spaces, J. Funct. Anal. 163 (1999), 252-271.
- M W. B. Moors, manuscript, 1997.
- I. Namioka and R. Pol, Sigma-fragmentability of mappings into
, Topology Appl. 89 (1998), 249-263. - M. Raja, On topology and renorming of Banach space, C. R. Acad. Bulgare Sci. 52 (1999), 13-16.
- M. Raja, Kadec norms and Borel sets in a Banach space, Studia Math. 136 (1999), 1-16.
- N. K. Ribarska, Internal characterization of fragmentable spaces, Mathematika 34 (1987), 243-257.
- N. K. Ribarska, A Radon-Nikodym compact which is not a Gruenhage space, C. R. Acad. Bulgare Sci. 41 (1988), 9-11.
- N. K. Ribarska, A stability property for σ-fragmentability, manuscript, 1996.