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The conditions for the appearance of the Little Rip, Pseudo Rip and Quasi Rip universes in the terms of the parameters in the equation of state of some dark fluid are investigated. Several examples of the Rip cosmologies are investigated.

The appearance of new cosmological models is connected with the discovery of the accelerated expansion of the universe. Cosmic acceleration can be introduced via dark energy [

In this review article we study the influence of the time-dependent thermodynamic parameter

We suppose that our universe is filled with an ideal fluid (dark energy) obeying an inhomogeneous EoS [

The Friedmann equation for a spatially flat universe is:
^{2} = 8π

Let us write down the energy conservation law:

We now consider examples of the dark energy models corresponding to the LR, QR and PR universes. For simplicity it will be assumed that the universe consists of the dark energy only.

Let us a Hubble parameter has the following form [_{0} > 0, _{0} is the present-time Hubble parameter.

We assume that the parameter _{0}.

Taking into account Equations (1)–(4) and solve the Equation (3) with respect to Λ(

Thus, if we assume an ideal fluid obeying the EoS Equations (1) and (5), then we obtain the LR scenario.

Let us consider another LR model [_{0},

Now writing the parameter

Let us choose the cosmological model with more complicated behavior of _{0}, _{1}, …, _{n}

Here we have defined _{n}

We consider also the example of the brane LR cosmology [

Let us choose the parameter

As result, we have obtained a brane dark energy universe from the standpoint of 4d FRW cosmology without introducing the brane conception.

Let us investigate a PR model with the parameter Hubble [_{0}, _{1} and λ are the positive constants. We assume that _{0} > _{1} when

If _{0} and the universe asymptotically approaches the de Sitter space. It may correspond to a PR model.

We will consider this cosmological model in analogy with the LR model.

Let us take the parameter

In the next example we have investigated the appearance of the asymptotic de Sitter regime on the brane from 4d cosmology [_{0} is the present time and λ is a negative tension (λ < 0). If

Now writing the parameter

In this case we have modeled the QR universe induced by the dark fluid EoS. Let us take the energy density as a function of the scale factor _{0} is the energy density at a present time _{0}. Now we write the EoS parameters

Choosing the parameter

In this section we will consider the examples of the viscous LR cosmology in an isotropic cosmic fluid in the later stage of the evolution of the universe.

Let us write the expression for the time-dependent energy density for the viscous LR cosmology [

If the parameter

The validity of the Equations (24) and (25) means an equivalent description the viscous LR (23).

In the later stages of the evolution of the universe near the future singularity it is necessary to take into account a transition into the turbulence motion. Let us consider the cosmic fluid as a two-component fluid and introduce the effective energy density in the view [_{turb}_{turb}_{turb}_{turb}

Let us consider the case _{turb}

The viscous LR model for a perfect fluid can be realized via the choice in the EoS the parameter

Note, that there is another method of the solving this problem, which is connected with the transition of a one-component cosmic fluid from the viscous era into the turbulent era [

Several dark energy models have been analyzed in the present review article. We showed that these cosmological models can be caused via the corresponding choice of the cosmological constant or the thermodynamic parameter in the dark fluid inhomogeneous EoS within the framework of 4d FRW cosmology.

This work has been supported by project 2.1839.2011 of Ministry of Education and Science (Russia) and LRSS project 224.2012.2 (Russia). We are very grateful to Professor Sergei Odintsov for helpful discussions.

The authors declare no conflict of interest.