TTP05-05 Energy-square equations for relativistic closed systems.

The most powerful relativistic two-body equations have only half as many components as their Dirac-Breit and Bethe-Salpeter counterparts and contain only the square of the total cms energy. In this letter, the “energy-square” theorem is extended to systems of $n>2$ Dirac particles. The case $n=3$ is discussed for baryons.