Alternatively, one writes A ν ν ′ = Λ Λ ν ν ′ μ μ A μ μ . in which the primed indices denote the indices of A in the primed frame. For a general n -component object one may write X ′ α α = Π Π ( Λ Λ ) α α β β X β β , where Π is the appropriate representation of the Lorentz group, an n × n matrix for every Λ. In this case, the indices should not be thought of as spacetime indices (sometimes called Lorentz indices), and they run from 1 to n. E.g., if X is a bispinor, then the indices are called Dirac indices.