English

Derivations on symmetric quasi-Banach ideals of compact operators

Operator Algebras 2012-04-23 v2

Abstract

Let I,J\mathcal{I,J} be symmetric quasi-Banach ideals of compact operators on an infinite-dimensional complex Hilbert space HH, let J:I\mathcal{J:I} be a space of multipliers from I\mathcal{I} to J\mathcal{J}. Obviously, ideals I\mathcal{I} and J\mathcal{J} are quasi-Banach algebras and it is clear that ideal J\mathcal{J} is a bimodule for I\mathcal{I}. We study the set of all derivations from I\mathcal{I} into J\mathcal{J}. We show that any such derivation is automatically continuous and there exists an operator aJ:Ia\in\mathcal{J:I} such that δ()=[a,]\delta(\cdot)=[a,\cdot], moreover aB(H)δIJ2CaJ:I\|a\|_{\mathcal{B}(H)}\leq\|\delta\|_\mathcal{I\to J}\leq 2C\|a\|_\mathcal{J:I}, where CC is the modulus of concavity of the quasi-norm J\|\cdot\|_\mathcal{J}. In the special case, when I=J=K(H)\mathcal{I=J=K}(H) is a symmetric Banach ideal of compact operators on HH our result yields the classical fact that any derivation δ\delta on K(H)\mathcal{K}(H) may be written as δ()=[a,]\delta(\cdot)=[a,\cdot], where aa is some bounded operator on HH and aB(H)δII2aB(H)\|a\|_{\mathcal{B}(H)}\leq\|\delta\|_\mathcal{I\to I}\leq 2\|a\|_{\mathcal{B}(H)}.

Keywords

Cite

@article{arxiv.1204.4297,
  title  = {Derivations on symmetric quasi-Banach ideals of compact operators},
  author = {A. F. Ber and V. I. Chilin and G. B. Levitina and F. A. Sukochev},
  journal= {arXiv preprint arXiv:1204.4297},
  year   = {2012}
}

Comments

21 pages