Can the $\Sigma^- nn$ System be Bound?
  Motivated by the $\Sigma$-hypernuclear states reported in ($K^-,\pi^{\pm}$) experiments, we have explored the possibility that there exists a particle-stable $\Sigma^- nn$ bound state. For the J\"ulich \~A hyperon-nucleon, realistic-force model, our calculations yield little reason to expect a positive-parity bound state in either the $J = \frac{1}{2}$ or the $J = \frac{3}{2}$ channels. 
A. Stadler and B. F. Gibson