Jeans instability is derived for the case of a low density self-gravitating fully ionized gas in the presence of a constant magnetic field. A new Jeans wave number, substantially enhanced by the magnetic field, is established under a suitable symmetry assumption. Nevertheless, from our present knowledge regarding the existence of primeval magnetic fields in the Universe, it appears that they ar...

An analysis of the gravitational instability in presence of dissipative effects is addressed. In particular, the standard Jeans Mechanism and the generalization in treating the Universe expansion are both analyzed when bulk viscosity affects the first-order Newtonian dynamics. As results, the perturbation evolution is founded to be damped by dissipative processes and the top-down mechanism of s...

The Jeans equations give the second moments or stresses required to support a stellar population against the gravity field. A general solution of the Jeans equations for arbitrary axisymmetric scale-free densities in flattened scale-free potentials is given. A two-parameter subset of the solution for the second moments for the self-consistent density of the power-law models, which have exactly ...

The effect of the magnetic field on the Jeans instability of self-gravitating strongly coupled dusty plasma is investigated. The medium consists of extremely massive, negatively charged strongly correlated dust grains and weakly correlated Boltzmann distributed electrons and ions. The basic equations of the problem are constructed using generalized hydrodynamic model. In deriving dispersion rel...

This paper presents the theoretical backgr ound of a large-scale lexicological research project on lexical variation that was carried out at the university of Leuven in the last three years. The project is situated in the framework of Cognitive Semantics in the sense of Lakoff (1987), Langacker (1990), Geeraerts (1989b), and Taylor (1989); it links up with the explorations of the relevance of p...