This is an announcement for the paper "Stampacchia's property, self-duality and orthogonality relations" by Nikos Yannakakis.

Abstract: We show that if the conclusion of the well known Stampacchia Theorem, on variational inequalities, holds on a Banach space X, then X is isomorphic to a Hilbert space. Motivated by this we obtain a relevant result concerning self-dual Banach spaces and investigate some connections between existing notions of orthogonality and self-duality. Moreover, we revisit the notion of the cosine of a linear operator and show that it can be used to characterize Hilbert space structure. Finally, we present some consequences of our results to quadratic forms and to evolution triples.

Archive classification: math.FA

Submitted from: nyian@math.ntua.gr

The paper may be downloaded from the archive by web browser from URL

http://front.math.ucdavis.edu/1008.4958

or

http://arXiv.org/abs/1008.4958