Equation Icon  ℰ ℰ ℰ qμ = ⃗∇ μq + ¯qμ, (257 ) ℰ ⃗ ⃗ ℰ ⃗ ℰ ℰ πμν = ∇ ⟨μ∇ ν⟩π + ∇ ⟨μ¯πν⟩ + ¯πμν. (258 )