A characterization of Gaussian law in Hilbert space.
A characterization of generalized inner product spaces (?-orthogonally additive mappings, III).
À la recherche de la preuve perdue: a simple proof of the Ficken theorem
A new proof of the Ficken criterion is given together with a comment concerning the known proofs and related results
A new type of orthogonality for normed planes
In this paper we introduce a new type of orthogonality for real normed planes which coincides with usual orthogonality in the Euclidean situation. With the help of this type of orthogonality we derive several characterizations of the Euclidean plane among all normed planes, all of them yielding also characteristic properties of inner product spaces among real normed linear spaces of dimensions .
A theorem on isotropic spaces
Let X be a normed space and the group of all linear surjective isometries of X that are finite-dimensional perturbations of the identity. We prove that if acts transitively on the unit sphere then X must be an inner product space.
Accretive metric projections.