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25. Marek Szydłowski, Michael Heller, Zdzisław Golda Structural Stability Properties of Friedman Cosmology Gen. Rel. Grav., vol. 16, pp. 877890 (1984). [abstract] [journal]  Abstract: A dynamical system with RobertsonWalker symmetries and the equation of the state $p = \gamma\epsilon$, $0 \leq\gamma\leq 1$, considered both as a conservative and nonconservative system, is studied with respect to its structural stability properties. Different cases are shown and analyzed on the phase space ($x = R^D$, $y = \dot{x}$).  26. Z. Golda, M. Heller and M. Szydłowski Structurally Stable Approximations to Friedmann—Lemaître World Models Astrophys. Space Sci., vol. 90, pp. 313326 (1983). [abstract] [journal]  Abstract: Friedmann{}Lema\^{\i}tre cosmology is briefly reviewed in terms of dynamical systems. It is demonstrated that in certain cases bulk viscosity dissipation structurally stabilizes Friedmann{}Lema\^{\i}tre solutions. It turns out that, for $\Lambda = 0$, there are structurally stable solutions if $\zeta \sim \varepsilon^{1\slash2}$, where $\zeta$ is the bulk viscosity coefficient. For $\Lambda \neq 0$, structurally stable solutions are essentially those with $\zeta = \mbox{const}$. The role of structural stability in physics and cosmology is shortly discussed.  
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