DMCA
K-theory for operator algebras (1998)
| Venue: | Mathematical Sciences Research Institute Publications |
| Citations: | 556 - 0 self |
BibTeX
@ARTICLE{Blackadar98k-theoryfor,
author = {Bruce Blackadar},
title = {K-theory for operator algebras},
journal = {Mathematical Sciences Research Institute Publications},
year = {1998}
}
Share
 |
 |
 |
 |
||
OpenURL
Abstract
p. XII line-5: since p. 1-2: I blew this simple formula: should be α = −〈ξ, η〉/〈η, η〉. p. 2 I.1.1.4: The Riesz-Fischer Theorem is often stated this way today, but neither Riesz nor Fischer (who worked independently) phrased it in terms of completeness of the orthogonal system {e int}. If [a, b] is a bounded interval in R, in modern language the original statement of the theorem was that L 2 ([a, b]) is complete and abstractly isomorphic to l 2. According to [Jah03, p. 385], the name “Hilbert space ” was first used in 1908 by A. Schönflies, apparently to refer to what we today call l 2. Von Neumann used the same name for Hilbert spaces in the modern sense (complete inner product spaces), which he defined in 1928. p. 3 line-6: At the end of the line, 2ɛ should be 4ɛ. p. 3 I.1.2.3: The statement that a dense subspace of a Hilbert space H contains an orthonormal basis for H can be false if H is nonseparable. In fact, I. Farah (private communication) has shown that a Hilbert space of dimension 2ℵ0 has a dense subspace which does not contain any uncountable orthonormal set. A similar example was obtained by Dixmier [Dix53]. p. 8-9 I.2.4.3(i): Some of the statements on p. 9 can be false if the measure space is not σ-finite. p. 13: add after I.2.6.16: I.2.6.17. If X is a compact subset of C not containing 0, and k ∈ N, there is in general no bound on the norm of T −1 as T ranges over all operators with ‖T ‖ ≤ k and σ(T) ⊆ X. For example, let Sn ∈ L(l 2) be the truncated shift: Sn(α1, α2,...) = (0, α1, α2,..., αn, 0, 0,...) and let Tn = I − Sn. ‖Sn ‖ = 1, so ‖Tn ‖ ≤ 2 for all n. Since Sn is nilpotent, σ(Sn) = {0}, so σ(Tn) = {1} for all n. Tn is invertible, with T −1 n = I + Sn + ξ1 ‖ = √ n + 1, so ‖T −1
Keyphrases
operator algebra hilbert space dense subspace riesz-fischer theorem original statement similar example measure space complete inner product space truncated shift private communication uncountable orthonormal set simple formula name hilbert space sch nflies orthonormal basis compact subset modern language orthogonal system int dixmier dix53 xii line-5 way today von neumann bounded interval modern sense
