Seminormal Operators with Compact Self-Commutators
Seminormal Operators with Compact Self-Commutators
Putnam’s inequality $\pi ||{T^ \ast }T - T{T^ \ast }|| \leqq \operatorname {meas}_2({\text {sp}}(T))$ is verified for seminormal operators $T$ when ${T^ \ast }T - T{T^ \ast }$ is compact. The spectrum of the seminormal singular integral operator defined for $f \in {L^2}(0,1)$ by \[ Tf(s) = sf(s) + i\left …