On the geometry of numerical ranges

Mehdi Radjabalipour and Heydar Radjavi

Vol. 61 (1975), No. 2, 507–511

DOI: 10.2140/pjm.1975.61.507

Abstract

A bounded convex set G in the plane is the numerical range of an operator on a separable Hilbert space if G∖G⁰ is a countable union of arcs of conic sections and singletons. This result answers, in particular, a question raised by Joel Anderson.

Mathematical Subject Classification 2000

Primary: 47A10

Milestones

Received: 5 May 1975

Published: 1 December 1975