Monopole Chains in the Compact Abelian Higgs Model with doubly-charged   Matter Field
  We study the properties of topological defects in the lattice compact Abelian Higgs Model with charge Q=2 matter field. We find that monopoles and antimonopoles form chain-like structures which are dense in the confinement/symmetric phase. In this phase the mentioned structures explain both the confinement of single-charged and the breaking of strings spanned between doubly-charged test particles. This observation helps to understand how the non-diagonal gluons, once taken into consideration in the Abelian projection of gluodynamics, could reproduce in this framework the string breaking for adjoint charges. 
M. N. Chernodub, R. Feldmann, E.-M. Ilgenfritz, A. Schiller