In a front-form relativistic quantum theory the three interacting generators of the Poincaré group are P − − := H − − P → → ⋅ ⋅ n ^ ^ , the generator of translations normal to the light front, and J → → ⊥ ⊥ := J → → − − n ^ ^ ( n ^ ^ ⋅ ⋅ J → → ) , the generators of rotations transverse to the light-front. P − − is called the "light-front" Hamiltonian.