31. Marek Szydłowski, Michael Heller, Zdzisław Golda
Structural Stability Properties of Friedman Cosmology
Gen. Rel. Grav., vol. 16, pp. 877-890 (1984).
[abstract] [journal]

Abstract:
A dynamical system with Robertson-Walker 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 ($x = R^D$, $y = \dot{x}$).

32. Z. Golda, M. Heller and M. Szydłowski
Structurally Stable Approximations to Friedmann—Lemaître World Models
Astrophys. Space Sci., vol. 90, pp. 313-326 (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.

33. J. Gruszczak, M. Heller, M. Szydlowski
The Universe as a Stochastic Process
Physics Letters A, vol. 100, pp. 82-84 (1982).
[abstract]

Abstract:
Abstract