Dynamical Model of theΣ

In the spirit of the bootstrap hypothesis, a dynamical model is developed for the $\Sigma$ hyperon, taking into account the $\pi \Lambda$ and $\pi \Sigma$ channels. Born amplitudes for the exchange of $\Lambda$, $\Sigma$, ${Y_1}^{*} \left(1385\mathrm{} \mathrm{MeV}\right)$, ${Y_0}^{*} \left(1405\mathrm{} \mathrm{MeV}\right)$, and $\rho$ form the inputs to dynamical calculations that are based on the matrix $N{D}^{-1\mathrm{}}$ method and are intended partly as a practical study of this technique. It is shown that the $N{D}^{-1\mathrm{}}$ formalism can be trivially extended to handle the situation where an input force cut overlaps the unitarity cut below physical threshold.