The current 3-form J is J = − − ρ ρ d x ∧ ∧ d y ∧ ∧ d z + j x d t ∧ ∧ d y ∧ ∧ d z + j y d t ∧ ∧ d z ∧ ∧ d x + j z d t ∧ ∧ d x ∧ ∧ d y and the corresponding dual 1-form is ⋆ ⋆ J = − − ρ ρ d t + j x d x + j y d y + j z d z .