The nature lets us observe ψˉψ,ψˉγμψ,ψˉσμνψ, it’s from Born’s rule equipped by operator’s property of eigen state and eigen value.
ψˉψ, ψˉμψ and ψˉσμνψ for Scalar, Vector and Tensor Observable
The nature lets us observe ψˉψ,ψˉγμψ,ψˉσμνψ, it’s from Born’s rule equipped by operator’s property of eigen state and eigen value.
Naixian Zhang 