We investigate a simple model for globular cluster (GC) formation. We simulate the violent relaxation of initially homogeneous isothermal stellar spheres and show that it leads to the formation of clusters with radial density profiles that match the observed profiles of GCs. The best match is achieved for dynamically unevolved clusters. In this model, all the observed correlations between globa...

The density profiles and other quantities of physical interest for spherically symmetric systems are computed by assuming that a collisionless stellar gas may relax to the non-Gaussian power law distribution suggested by the nonex-tensive kinetic theory. There are two different classes of solutions. The first class behaves like a subset of the polytropic Lane-Emden spheres, whereas the second o...

In this note, I suggest that the β−model used to fit the X-ray surface brightness profiles of extended sources, like groups and clusters of galaxies, has to be corrected when the counts are collected in a wide energy band comparable to the mean temperature of the source and a significant gradient in the gas temperature is observed. I present a revised version of the β−model for the X-ray bright...

The equation of symmetric equilibrium of an isothermal gas with an unknown boundary in the field of a body force is considered. Conditions for solvability and insolvability of the problem as well as for uniqueness and nonuniqueness of solutions are presented. Examples of finite, countable, or continual sets of solutions are constructed including equipotential ones. Static stability of solutions...

We present a detailed computer simulation and integral equation study of the phase behavior of a nematogenic system composed of hard spheres with embedded three-dimensional Maier-Saupe spins. For this well-known system, we map the gas-liquid equilibrium, which is coupled to a first-order isotropic-nematic transition. The anisotropic integral equation theory is found to yield excellent agreement...

We study the stationary half-space linearized Boltzmann equation with a force term decaying to zero at infinity. We extend to this case the results of Bardos, Caflisch and Nicolaenko for a gas of hard spheres without external force, namely we prove existence, uniqueness and asymptotic properties of the solution. Our analysis includes the case of hard potentials.

The Boltzraunn equation has been solvea by Nordsieck's Monte Carlo method for the case of translational relaxation of a gas of elastic spheres whose initial velocity distribution function has the form f(v,0) = Mexp[-n(v-ia)] + exp[-«(v+iu)] ! .

Transport properties of impurities immersed in a granular gas undergoing homogenous cooling state are studied. The results are obtained from the Boltzmann-Lorentz kinetic equation for inelastic Maxwell models in d dimensions. The kinetic equation is solved by means of the Chapman-Enskog method up to first order in the density gradient of impurities. The mass and heat fluxes associated with impu...

In this paper, the ultraspherical operational matrices of derivatives are constructed. Based on these operational matrices, two numerical algorithms are presented and analyzed for obtaining new approximate spectral solutions of a class of linear and nonlinear Lane-Emden type singular initial value problems. The basic idea behind the suggested algorithms is basically built on transforming the eq...