A parametric operator Ω {\displaystyle \Omega } with parameter α {\displaystyle \alpha } in the parametric set A {\displaystyle {\mathcal {A}}} is an indexed family of operators ( Ω α ) A = { Ω α : α ∈ A } {\displaystyle (\Omega _{\alpha })_{\mathcal {A}}=\{\Omega _{\alpha }:\alpha \in {\mathcal {A}}\}} with index α {\displaystyle \alpha } in the index set A {\displaystyle {\mathcal {A}}} .
