\\
D'=4Dq \, ,
\end{array}$$ where $q$ is given by Eq. (\[acc\]). The critical points of this system are those values of $(P$, $S$, $L$, $B$, $K$, $D)$ which nullify its right-hand side. Since three equations in this system have similar form, there are three different options for the generic values of $w$, and there are also three special cases, namely, $w = -1$, $w =  1/3$ and $w = - 1/3$, which we consider separately.

### Generic situation {#generic}

$1 + 3w - 2q = 0$ and $S = L = B = K = D =
0$. Using (\[constraint1\]), we obtain $$P = \frac{1}2\, .$$

Hence, $$H^2 = \frac{\rho}{3 m^2} \, ,$$ which describes the standard Friedmann universe and is similar to case 1 of the previous subsection.

[**Case 2.**]{} $q = 0$ and $P = S = L = B = 0$.

In this case, Eq. (\[acc\]) gives the identity, and the constraint equation (\[constraint1\]) reads $$(1 + K)^2 = - D \, .$$ The universe described by this solution is dominated by the spatial curvature and/or dark radiation with negative constant $C$. In the absence of dark radiation, we have the spatially open Milne universe, similarly 