Strings and string breaking in 2+1 dimensional nonabelian theories

We consider properties of confining strings in 2+1 dimensional SU(2) nonabelian gauge theory with the Higgs field in adjoint representation. The analysis is carried out in the context of effective dual Lagrangian which describes the dynamics of t'Hooft's $ZN$ vorices. We point out that the same Lagrangian should be interpreted as an effective Lagrangian for the lightest glueballs. It is shown how the string tension for a fundamental string arises in this description. We discuss the properties of the adjoint string and explain how its breaking occurs when the distance between the charges exceeds a critical value. The interaction between the fundamental strings is studied. It is shown that they repel each other in the weak coupling regime. We argue that in the confining regime (pure Yang-Mills theory, or a theory with a heavy Higgs field) the strings actually attract each other and the crossover between the two regimes corresponds to the crossover between the dual superconductors of first and second kind. (author)