On Positive Vectors in Indefinite Inner Product Spaces

Fabio Bagarello, Sergiusz Kuzel

Let $\mathcal{H}$ be a linear space equipped with an indefinite inner product $[\cdot ,\cdot ]$. Denote by ${\mathcal{F}}_{++}=\{f\in \mathcal{H}:[f,f]>0\}$ the nonlinear set of…