“…When M=T, (50) gives rise to a solution of the model with a doubly-periodic lattice structure. Such a situation corresponds to the so-called vortex condensation phenomenon [1,2,3,10,25,30,33]. When M=R 2 , (50) gives rise to a highly localized vortex-like soliton solution which is often interpreted as representing a multiple particle system at equilibrium [8,20,7,26,28,35].…”