Perturbation expansion in phase-ordering kinetics: I. Scalar order parameter

A consistent perturbation theory expansion is presented for phase-ordering kinetics in the case of a nonconserved scalar order parameter. At zeroth order in this expansion, one obtains the theory due to Ohta, Jasnow, and Kawasaki (OJK). At the next nontrivial order in the expansion, worked out in d dimensions, one has small corrections to the OJK result for the nonequilibrium exponent lambda and the introduction of a new exponent nu governing the algebraic component of the decay of the order parameter scaling function at large scaled distances.