Denseness of Operators Whose Second Adjoints Attain Their Numerical Radii
Marı́a D. Acosta, Rafael Paya · Proceedings of the American Mathematical Society · 1989
We show that for any Banach space the set of (bounded linear) operators whose second adjoints attain their numerical radii is norm-dense in the space of all operators. In particular, the numerical radius attaining operators on a reflexive space are dense.