“…Finally, let us sketch the entirely analogous development for helicity ±2, that is, linearized Einstein gravity. Here the starting point is the covariant representation U 0,+, (1,1) of P , realized on the space of symmetric tensor fields h µν (x) on Minkowski space, which satisfy the wave equation h µν = 0, with Fourier coefficients in L 2 (R 3 , d ′ p)⊗C 10 . The gauge group G now consists of those non-constant weak solutions ξ µ (x) of the wave equation for which the quantity (δξ…”