Quadratic and quasi-quadratic functionals

Peter Šemrl
1993 Proceedings of the American Mathematical Society  
In this note we show how Jordan *-derivations arise as a "measure" of the representability of quasi-quadratic functionals by sesquilinear ones. Our main result can be considered as an extension of the Jordan-von Neumann characterization of pre-Hilbert space.
doi:10.1090/s0002-9939-1993-1158008-3 fatcat:3muy3fr2lrbgxcdoxsrjg2virq