Available in electronic format
Available in print format
Proceedings of the American Mathematical Society
Proceedings of the American Mathematical Society
ISSN 1088-6826 (e) ISSN 0002-9939 (p)
     

Projections from $L(E,F)$ onto $K(E,F)$

Author(s): Pierre David Saphar
Journal: Proc. Amer. Math. Soc. 127 (1999), 1127-1131.
MSC (1991): Primary 46B20; Secondary 46B28
Retrieve article in: PDF
This article is available free of charge

Abstract | References | Similar articles | Additional information

Abstract: Let $E$ and $F$ be two infinite dimensional real Banach spaces. The following question is classical and long-standing. Are the following properties equivalent?

a) There exists a projection from the space $L(E,F)$ of continuous linear operators onto the space $K(E,F)$ of compact linear operators.

b) $L(E,F)=K(E,F)$.

The answer is positive in certain cases, in particular if $E$ or $F$ has an unconditional basis. It seems that there are few results in the direction of a general solution. For example, suppose that $E$ and $F$ are reflexive and that $E$ or $F$ has the approximation property. Then, if $L(E,F)\ne K(E,F)$, there is no projection of norm 1, from $L(E,F)$ onto $K(E,F)$. In this paper, one obtains, in particular, the following result:

Theorem. Let $F$ be a real Banach space which is reflexive (resp. with a separable dual), of infinite dimension, and such that $F^*$ has the approximation property. Let $\lambda$ be a real scalar with $1<\lambda<2$. Then $F$ can be equivalently renormed such that, for any projection $P$ from $L(F)$ onto $K(F)$, one has $\|P\|\ge \lambda$. One gives also various results with two spaces $E$ and $F$.


References:

1.
P. G. Casazza and N. J. Kalton, Notes on approximation properties on separable Banach spaces, in: Geometry of Banach Spaces, London Math. Soc. Lecture Note Ser. 158, Cambridge Univ. Press (1991), 49-63. MR 92d:46022

2.
J. Dixmier, Sur un théorème de Banach, Duke Math. J. 15 (1948), 1057-1071. MR 10:306g

3.
G. Godefroy and P. D. Saphar, Duality in spaces of operators and smooth norms on Banach spaces, Illinois J. Math. 32 (1988), 673-695. MR 89j:47026

4.
G. Godefroy, N. J. Kalton and P. D. Saphar, Unconditional ideals in Banach spaces, Studia Math. 104 (1993), 13-59. MR 94k:46024

5.
K. John, On the uncomplemented subspace $K(X,Y)$, Czechoslovak Math. J. 42 (117) (1992), 167-173. MR 93b:47085

6.
J. Lindenstrauss, On nonseparable reflexive Banach spaces, Bull. Amer. Math. Soc. 72 (1966), 967-970. MR 34:4875

7.
J. Lindenstrauss and L. Tzafriri, Classical Banach spaces, vol. I, Sequence spaces, Springer-Verlag, Berlin, 1977. MR 58:17766

8.
E. Odell and H. P. Rosenthal, A double dual characterization of separable Banach spaces containing $\ell _1$, Israel J. Math. 20 (1975), 375-384. MR 51:13654

9.
H. H. Schaefer, Banach lattices and positive operators, Springer-Verlag, New York, 1974. MR 54:11023

10.
M. Zippin, Banach spaces with separable duals, Trans. Amer. Math. Soc. 310 (1988), 371-379. MR 90b:46028

11.
B. V. Godun, Unconditional bases and spanning basic sequences, Izv. Vyssh. Uchebn. Zaved. Mat. 24 (1980), 69-72. MR 82h:46017


Similar Articles:

Retrieve articles in Proceedings of the American Mathematical Society with MSC (1991): 46B20, 46B28

Retrieve articles in all Journals with MSC (1991): 46B20, 46B28


Additional Information:

Pierre David Saphar
Affiliation: Department of Mathematics, Technion--Israel Institute of Technology, Haifa, Israel
Email: saphar@techunix.technion.ac.il

DOI: 10.1090/S0002-9939-99-04645-6
PII: S 0002-9939(99)04645-6
Keywords: Space of continuous linear operators, space of compact operators, projection
Received by editor(s): October 30, 1996
Received by editor(s) in revised form: July 28, 1997
Additional Notes: This research was supported by the fund for the promotion of Research at the Technion
Communicated by: Dale E. Alspach
Copyright of article: Copyright 1999, American Mathematical Society


  AMS Website Logo Small Comments: webmaster@ams.org
© Copyright 2009, American Mathematical Society
Privacy Statement
Search the AMSPowered by Google