Editing Nucleon (section)

===Skyrmion models===
The [[skyrmion]] models the nucleon as a [[topological soliton]] in a nonlinear [[SU(2)]] [[pion]] field. The topological stability of the skyrmion is interpreted as the conservation of [[baryon number]], that is, the non-decay of the nucleon. The local [[topological winding number]] density is identified with the local [[baryon number]] density of the nucleon. With the pion isospin vector field oriented in the shape of a [[hedgehog space]], the model is readily solvable, and is thus sometimes called the ''hedgehog model''. The hedgehog model is able to predict low-energy parameters, such as the nucleon mass, radius and [[axial coupling constant]], to approximately 30% of experimental values.