We note that, in the limit where the and scattering lengths, and , go to infinity, the leading terms in the effective field theory for strong interactions are invariant under Wigner's SU(4) spin-isospin symmetry. This explains why the leading effects of radiation pions on the -wave scattering amplitudes vanish as and go to infinity. The implications of Wigner symmetry for axion and are also considered.
- Received 22 February 1999
©1999 American Physical Society