The space-time wavefunction is now ψ ψ ( r , t ) and the expectation value of the position operator r ^ ^ at the state ψ ψ is ⟨ r ^ ^ ⟩ ψ ψ = ∫ ∫ r | ψ ψ | 2 d 3 r where the integral is taken over all space. The position operator is r ^ ^ ψ ψ = r ψ ψ .