Skyrmions and bags in the 2D-O(3) model

摘要

Localized static solutions of the 2D-O(3) model are investigated in a representation with the 3-vector field Phi split into the unit vector <(Phi)over cap>, and the modulus Phi. As in the nonlinear version of the model the requirement of continuity in the angular variables then allows for the definition of a topological winding number B and separation of the complete configuration space into distinct B-sectors. For small values of the Phi(4)-coupling strength the stable energy minima in these sectors are characterized by bag formation in the modulus field which in the standard cartesian representation of the linear O(3) model would be unstable towards decay into the trivial B = 0 vacuum. Stabilized by B-conservation they exhibit a surprising variety of very appealing features for multiply charged systems. With the total charge bound into one common deep bag opposite ways of distributing the topological charge density inside the bag can be realized: Point-like structures which retain the individuality of single constituents (or doubly charged pairs), or a deconfined charge density spread uniformly throughout the interior of the bag. It is suggested that the corresponding extension to the 3D-O(4) model may supply a crucial link to overcome the unsatisfactory existing mismatch between multiskyrmion configurations and nuclear structure. (C) 2000 Elsevier Science B.V. All rights reserved. [References: 25]