Conformally flat model of the open universe with an arbitrary function of state

The open cosmological model for a conformally flat space-time metric filled with a substance in perfect fluid approximation and a nonvanishing pressure in general case is considered. The corresponding metric is written in the Fock form as conformal to the Minkowski metric and depends only on one variable, quadrate of which represents a product of advanced and retarded times. Well-known Friedman’s solution for the open Universe, filled with an incoherent dust, is a special case for such metric. A function of state in general form is introduced into the model. With the help of the monad formalism the Einstein equations are splitted on two equations. Then this system is solved in the general case for an arbitrary function of state. In other words the Einstein equations’ solution of the model is a quadrature with an arbitrary function of state. The found solution is gauged concerning of the Friedman solution. If to restrict an equation of state only by the linear form, then we come to earlier the found results on the introduction of harmonic functions for description of the open Universe.