2 ALTERNATIVE DESCRIPTIONS OF 2ND-ORDER PHASE-TRANSITIONS - LANDAU THEORY AND THE SELF-CONSISTENT APPROACH

Two alternative descriptions of second order phase transitions are con sidered, Landau theory and the self-consistent approach. The temperatu re dependence of the heat capacity in these two descriptions is consid ered. The Landau theory gives only a jump in the heat capacity. It is not defined by the Gibbs-Boltzmann entropy, which is equal to zero in the Landau approach, but by the thermal thermodynamical force, The sel f-consistent approach gives not only this jump, but also the peak in t he temperature dependence of the heat capacity near the lambda-point. The latter is defined by the Gibbs-Boltzmann entropy. On the basis of the S-theorem the relative degree of order of the states above and bel ow the lambda-point is defined. It is shown that the state below the l ambda-point is more ordered. Thus, the transition from the more symmet rical state to the less symmetrical one corresponds to self-organizati on. The possibility of a kinetic description of second order phase tra nsitions is considered.