We present a counterexample to the converse of results on approximate point spectra. A norm inequality in terms of a distance function is established for a quotient bounded operator on a locally convex Hausdorff space on the set of complex numbers.
Cite this article
A. K. Gaur, Spectra in Banach and locally convex algebras. Port. Math. 64 (2007), no. 1, pp. 11–19DOI 10.4171/PM/1773