318 research outputs found
On large indecomposable Banach spaces
Hereditarily indecomposable Banach spaces may have density at most continuum
(Plichko-Yost, Argyros-Tolias). In this paper we show that this cannot be
proved for indecomposable Banach spaces. We provide the first example of an
indecomposable Banach space of density two to continuum. The space exists
consistently, is of the form C(K) and it has few operators in the sense that
any bounded linear operator T on C(K) satisfies T(f)=gf+S(f) for every f in
C(K), where g is in C(K) and S is weakly compact (strictly singular)
On Uniformly finitely extensible Banach spaces
We continue the study of Uniformly Finitely Extensible Banach spaces (in
short, UFO) initiated in Moreno-Plichko, \emph{On automorphic Banach spaces},
Israel J. Math. 169 (2009) 29--45 and Castillo-Plichko, \emph{Banach spaces in
various positions.} J. Funct. Anal. 259 (2010) 2098-2138. We show that they
have the Uniform Approximation Property of Pe\l czy\'nski and Rosenthal and are
compactly extensible. We will also consider their connection with the
automorphic space problem of Lindenstrauss and Rosenthal --do there exist
automorphic spaces other than and ?-- showing that a space
all whose subspaces are UFO must be automorphic when it is Hereditarily
Indecomposable (HI), and a Hilbert space when it is either locally minimal or
isomorphic to its square. We will finally show that most HI --among them, the
super-reflexive HI space constructed by Ferenczi-- and asymptotically
spaces in the literature cannot be automorphic.Comment: This paper is to appear in the Journal of Mathematical Analysis and
Application
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