Two-component perfect fluid in FRW universe
  We consider the cosmological model which allows to describe on equal footing
the evolution of matter in the universe on the time interval from the inflation
till the domination of dark energy. The matter is considered as a two-component
perfect fluid imitated by homogeneous scalar fields between which there is
energy exchange. Dark energy is represented by the cosmological constant, which
is supposed invariable during the whole evolution of the universe. The matter
changes its equation of state with time, so that the era of radiation
domination in the early universe smoothly passes into the era of a pressureless
gas, which then passes into the late-time epoch, when the matter is represented
by a gas of low-velocity cosmic strings. The inflationary phase is described as
an analytic continuation of the energy density in the very early universe into
the region of small negative values of the parameter which characterizes
typical time of energy transfer from one matter component to another. The
Hubble expansion rate, energy density of the matter, energy density parameter,
and deceleration parameter as functions of time are found.
