Using h to denote the gravitational potential, the Lagrangian for the graviton has terms proportional to h, h cubed, and h times this operation applied to h. In classical field theory, applying this operation to some function of the wavenumber, k, is equivalent to multiplying the function by negative k squared. In the Lorenz gauge, applying this operation (-5[1])to the vector potential (-5[1])gives negative mu-nought times the current (-5[1])density. This (*) Lorentz-invariant operation is applied to a function to give zero in the most (10[1])compact representation of the wave equation. It is defined (10[1])as one over (10[1])c squared times the second time derivative, minus the square of the gradient. Either a box or “box squared” (10[1])symbolizes, for 10 points, what operation named for a French physicist, the analogue of the Laplacian in Minkowski space? (0[1])■END■