  An extension of the Skyrme model is presented in which derivative terms are
added that break chiral symmetry to isospin symmetry. The theory contains just
one new parameter and it reduces to the standard Skyrme model when this
symmetry breaking parameter vanishes. The same Faddeev-Bogomolny energy bound
applies for all parameter values, but the parameter can be tuned so that the
energy of the single Skyrmion is much closer to the bound than in the standard
Skyrme model. Applying the rational map approximation to multi-Skyrmions
suggests that, for a suitable value of the symmetry breaking parameter, binding
energies in this theory may be significantly more realistic than in the
standard Skyrme model.
