That is, it is the (μ, ν) -component of the inverse Lorentz transformation. One defines (as a matter of notation), Λ Λ ν ν μ μ ≡ ≡ ( Λ Λ − − 1 ) μ μ ν ν , and may in this notation write A ′ ν ν = Λ Λ ν ν μ μ A μ μ .