Current algebra and the cloudy-bag model

Two versions of the cloudy-bag model (surface and volume coupling) satisfy the commutation relations of current algebra. Perturbation-theory evaluations of various observables are compared for the two treatments. The electromagnetic properties are essentially the same in both versions. The volume-coupling model contains, in lowest order, a pion-quark contact interaction that contributes to the axial-vector current. Including the effect of this term leads to a computed value of gA of about 1.25, if the radius of the nucleon bag is around 1.0 fm.M. A. Morgan, G. A. Miller, and A. W. Thoma