Tensors, 2-inner products and projections. (English) Zbl 0627.46022

The paper deals for a given linear space L of dimension \(>1\) with two special types of covariant tensors on L of rank 4, with 2-inner products on L and with normal families of projections of L onto its 2-dimensional linear subspaces and shows that between these notions there exist interesting close relations.


46C99 Inner product spaces and their generalizations, Hilbert spaces