Comment Triton Binding Energy and Minimal Relativity

For relativistic three-body calculations, essentially two different approaches are in use: field theory and relativistic direct interactions. However, while results based upon relativistic field theory show an increase of the triton binding energy by about 0.3 MeV due to relativistic effects, calculations that claim to apply relativistic direct interactions obtain 0.3 MeV repulsion. In this paper, we discuss the origin of such a discrepancy. We show that the use of an invariant two-body amplitude increases the triton binding energy by about 0.3 MeV, consistent with the results from relativistic field theory. Furthermore, we point out that in calculations relying on the direct-interactions approach, indeed expansions are used, which may be a bad approximation and the reason for the discrepancy. Received November 4, 1996; revised January 15, 1998; accepted for publication January 19, 1998