  We propose new canonical form of the fluctuational Hamiltonian which takes
into account the fact that in the vicinity of the critical point there are two
fluctuating fields. They are the field of the number density and the entropy.
The proposed canonical form is based on the $D_5$ catastrophe. In contrast to
the standard approach of Landau-Ginzburg Hamiltonian which is based on $A_3$
catastrophe the canonical form proposed for the fluctuational Hamiltonian
naturally includes the asymmetric coupling between the fields.
