Related papers: Effect of multiplicity of stellar encounters and t…
For the first time we calculate quantitatively the influence of inhomogeneities on the global expansion factor by averaging the Friedmann equation. In the framework of the relativistic second-order Zel'dovich-approximation scheme for…
We investigate through a Generalized Langevin formalism the phenomenon of anomalous diffusion for asymptotic times, and we generalized the concept of the diffusion exponent. A method is proposed to obtain the diffusion coefficient…
Nowadays, the calculation of the Galactic Cosmic Rays diffusion coefficient with direct microscopic numerical simulations is a widespread approach. In this work, we investigated the numerical limits for such calculations and demonstrated…
Collective diffusion coefficient in a one dimensional lattice gas adsorbate is calculated using variational approach. Particles interact via either a long-range, or a long range electron-gas-mediated (for a metallic substrate), or a…
Dynamical friction leads to an orbital decay of massive objects like young compact star clusters or Massive Black Holes in central regions of galaxies. The dynamical friction force can be well approximated by Chandrasekhar's standard…
(context) Different cosmological data are consistent with an accelerated expansion produced by an exotic matter-energy component, dubbed "dark-energy''. A cosmological constant is a possibility since it satisfies most of the observational…
We consider extended slow-fast systems of N interacting diffusions. The typical behavior of the empirical density is described by a nonlinear McKean-Vlasov equation depending on , the scaling parameter separating the time scale of the slow…
The concept of diffusion in collisionless space plasmas like those near the magnetopause and in the geomagnetic tail is reexamined from a fundamental statistical point of view making use of the division of particle orbits into waiting…
Models of the very early universe, including inflationary models, are argued to produce varying universe domains with different values of fundamental constants and cosmic parameters. Using the cosmological hydrodynamical simulation code…
In homogeneous cosmological models the wavelength $\lambda$ of a photon exchanged between two fundamental observers changes in proportion to expansion of the space $D$ between them, so $\Delta\log(\lambda / D) = 0$. This is exactly the same…
We propose a time-varying cosmological constant with a fixed equation of state, which evolves mainly through its interaction with the background during most of the long history of the universe. However, such interaction does not exist in…
The optical properties of plasmas with high densities and medium temperatures are analyzed by the use of a free electron model with Fermi-Dirac statistics. For the present collisional plasma the frequency of electron-ion collision is very…
We investigate the effect of the accelerated expansion of the Universe due to a cosmological constant, $\Lambda$, on the cosmic star formation rate. We utilise hydrodynamical simulations from the EAGLE suite, comparing a $\Lambda$CDM…
Since microscopic velocity diffusion can be incorporated into general relativity in a consistent way, we study cosmological background solutions when the diffusion phenomena takes place in an expanding universe. Our focus here relies on the…
We investigate the effect of a density gradient on Chandrasekhar's dynamical friction formula based on the method of 2-body encounters in the local approximation. We apply these generalizations to the orbit evolution of satellite galaxies…
We study the effects of the cluster environment on galactic morphology by defining a dimensionless angular momentum parameter $\lambda_{d}$, to obtain a quantitative and objective measure of galaxy type. The use of this physical parameter…
Clumping in stellar winds of hot stars is a possible consequence of radiative-acoustic instability appearing in solutions of radiative-hydrodynamical equations. However, clumping is usually included to stellar atmosphere modeling and…
There are two popular ways to speed up simulations of planet formation via increasing the collision probability: ({\it i}) confine motion to 2D, ({\it ii}) artificially enhance the physical radii of the bodies by an expansion factor. In…
The secular evolution of a collisional star cluster of $N$-'point' stars have been conventionally discussed based on cumulative two-body relaxation process. The relaxation process requires a cut-off on the range of two-body encounter…
The adiabatic index of a relativistic star (modeled by a perfect fluid) is shown to act as a dissipation constant due to considerations of mesoscopic scale stochastic effects. This dissipative effect arises without taking heat flux in the…