Positive elementary operators compressing spectrum (Q1370173)

By giving an affirmative answer to the problem raised in \textit{M. Gao's} paper [Chin. Ann. Math., Ser. A 14, No. 3, 295-301 (1993; Zbl 0806.47031)], the authors obtain a characterization of spectrum-preserving positive elementary operators. They also show that the spectrum properties of preserving the compressing spectrum and preserving invertibility are equivalent for positive elementary operators.