ON THE NONRELATIVISTIC LIMIT OF THE φ4 THEORY IN 2+1 DIMENSIONS
We study the nonrelativistic limit of the quantum theory of a real scalar field with quartic self-interaction. The two-body scattering amplitude is written in such way as to separate the contributions of high and low energy intermediary states. From this result and the two-loop computation of the self-energy correction, we determine an effective nonrelativistic action.