Banach spaces widely complemented in each other

• Autorzy: Elói Medina Galego
• Języki publikacji: EN

Abstrakty

EN

Suppose that X and Y are Banach spaces that embed complementably into each other. Are X and Y necessarily isomorphic? In this generality, the answer is no, as proved by W. T. Gowers in 1996. However, if X contains a complemented copy of its square X², then X is isomorphic to Y whenever there exists p ∈ ℕ such that $X^{p}$ can be decomposed into a direct sum of $X^{p-1}$ and Y. Motivated by this fact, we introduce the concept of (p,q,r) widely complemented subspaces in Banach spaces, where p,q and r ∈ ℕ. Then, we completely determine when X is isomorphic to Y whenever X is (p,q,r) widely complemented in Y and Y is (t,u,v) widely complemented in X. This new notion of complementability leads naturally to an extension of the Square-cube Problem for Banach spaces, the p-q-r Problem.

Kategorie tematyczne

• 46B03: Isomorphic theory (including renorming) of Banach spaces
• 46B25: Classical Banach spaces in the general theory

• Wydawca: Institute of Mathematics Polish Academy of Sciences
• Czasopismo: Colloquium Mathematicum
• Rocznik: 2013
• Tom: 133
• Numer: 2
• Strony: 283-291

Daty

wydano

2013

Twórcy

autor

Elói Medina Galego

• Department of Mathematics, University of São Paulo, São Paulo, Brazil 05508-090

Identyfikatory

DOI

10.4064/cm133-2-14