Dynamics of cosmological models with nonlinear classical phantom scalar fields. II. Qualitative analysis and numerical modeling

A detailed qualitative analysis and numerical modeling of the evolution of cosmological models based on nonlinear classical and phantom scalar fields with self-action are performed. Complete phase portraits of the corresponding dynamical systems and their projections onto the Poincar\'e sphere are constructed. It is shown that the phase trajectories of the corresponding dynamical systems can, depending on the parameters of the model of the scalar field, split into bifurcation trajectories along 2, 4, or 6 different dynamical flows. In the phase space of such systems, regions can appear which are inaccessible for motion. Here phase trajectories of the phantom scalar field wind around one of the symmetric foci (centers) while the phase trajectories of the classical scalar field can have a limit cycle determined by the zero effective energy corresponding to a Euclidean Universe.Comment: 10 pages, 16 figure

Kinetic equations for ultrarelativistic particles in a Robertson-Walker Universe and isotropization of relict radiation by gravitational interactions

Kinetic equations for ultrarelativistic particles with due account of gravitational interactions with massive particles in the Robertson-Walker universe are obtained. On the basis of an exact solution of the kinetic equations thus obtained, a conclusion is made as to the high degree of the uniformity of the relict radiation on scales with are less than $10'$.Comment: 19 pages, 2 figures, 13 reference

Parametric excitation of plasma waves by gravitational radiation

We consider the parametric excitation of a Langmuir wave and an electromagnetic wave by gravitational radiation, in a thin plasma on a Minkowski background. We calculate the coupling coefficients starting from a kinetic description, and the growth rate of the instability is found. The Manley-Rowe relations are fulfilled only in the limit of a cold plasma. As a consequence, it is generally difficult to view the process quantum mechanically, i.e. as the decay of a graviton into a photon and a plasmon. Finally we discuss the relevance of our investigation to realistic physical situations.Comment: 5 pages, REVTe

Spherically symmetric perturbation of an ultrarelativistic fluid in a homogeneous and isotropic universe

A solution of the linearized Einstein equations for a spherically symmetric perturbation of the ultrarelativistic fluid in the homogeneous and isotropic universe is obtained. Conditions on the boundary of the perturbation are discussed. Examples of particle-like and wave-like solutions are given