Abstract
In this paper we obtain some results concerning the set \(\mathcal{M} = \cup \left\{ {\overline {R(\delta _A )} \cap \{ A\} ':A \in \mathcal{L}(\mathcal{H})} \right\}\), where \(\overline {R(\delta _A )} \) is the closure in the norm topology of the range of the inner derivation δ A defined by δ A (X) = AX − XA. Here \(\mathcal{H}\) stands for a Hilbert space and we prove that every compact operator in \(\overline {R(\delta _A )} ^{\omega } \cap \{ A^* \} '\) is quasinilpotent if A is dominant, where \(\overline {R(\delta _A )} ^{\omega } \) is the closure of the range of δ A in the weak topology.
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Mecheri, S. Commutants and derivation ranges. Czechoslovak Mathematical Journal 49, 843–847 (1999). https://doi.org/10.1023/A:1022465420571
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DOI: https://doi.org/10.1023/A:1022465420571