Metastability of solitons in a generalized Skyrme model

We consider soliton solutions in the generalized chirally symmetric Skyrme model which includes, in addition to the usual commutator term, a symmetric term of fourth order in the field derivatives. With respect to the parameter characterizing the relative contribution of these two terms, the classical energy of static hedgehog field configurations lies on two disconnected branches. On one of these branches, next to the Skyrme combination, we find a region where numerical solutions either are metastable (due to the energy being unbounded from below) or do not exist at all. We also study the exact quantization of the isorotational collective coordinates. Our conclusion is that, demanding consistency with meson phenomenology for the signs of the parameters, the model discussed in this paper can lead to reliable physical results only for small deviations from Skyrme's original stabilizing term. (orig.)