Equation Icon  ′ 1- ( − 1 ′ ′ −1 ′T) 𝒞 (ξ, ξ) := 2 Tr M (ξ ) ⋅ Q (ξ,ξ ) ⋅ M (ξ ) ⋅ Q(ξ,ξ ) . (105 )