The flux-tube phase transition and bound states at high temperatures

We consider the phase transition in the dual Yang-Mills theory at finite temperature T. The phase transition is associated with a change (breaking) of symmetry. The effective mass of the dual gauge field is derived as a function of the T-dependent gauge coupling constant. We investigate the analytical criterion constraining the existence of a quark-antiquark bound state at temperatures higher than the temperature of deconfinement. The text was submitted by the author in English.