Narrow Results

In this paper, $F(\nu )$ cosmology is proposed for the accelerating universe with asymptotic de Sitter expansion in terms of Hankel function index $\nu$. To some extent, both the initial expansion during early inflation and the current accelerated expansion can be studied with a vacuum cosmic fluid, i.e. $\mathrm{\Lambda }$ in the pure de Sitter phase. Observational data further support the notion of a quasi-vacuum fluid, rather than a pure vacuum, contributing to the quasi-de Sitter acceleration in both the early and late universe. By examining the asymptotic expansion of the Henkel function as an approximate solution of the Mukhanov–Sasaki equation, we seek a more detailed study of quasi-de Sitter solutions in cosmology containing vacuum-like fluid.

In this paper, we considered four observationally constrained, one-parameter dark energy models to see their plausible impacts on the tidal ellipticity and related statistics of cosmic voids. Our main question is to see if different models of dark energy could be distinguished through ellipticity of cosmic voids. In this way, we employed an analytic method on the base of local tidal tensor. In this method, the center of a void is located at local minimum of the linear density field. At first, we obtained the effect of the one-parameter DE models on the distribution function of the cosmic voids and simultaneously compared the results with the standard cosmology ($\mathrm{\Lambda }$CDM). We found that the distribution function of these models is different with respect to that of $\mathrm{\Lambda }$CDM. In addition, we obtained the mean ellipticity of cosmic voids, $〈\epsilon 〉$, against redshift and found that in all models the $〈\epsilon 〉$ as well as ${\epsilon }_{max}$ has a decaying trend. Besides, we considered the mean ellipticity evolution versus the smoothing scale of voids ($R_L$). We found that the differences between dark energy models are significantly discernible via the ellipticity evolution versus the void scale ($R_L$). We saw that the studied models result in different ellipticity evolutions (versus $R_L$) up to $5\%$ smaller with respect to that of the $\mathrm{\Lambda }$CDM.

Cosmic voids, the emptiest regions of the universe are a promising tool to constrain cosmological models. In this paper I introduce the use of voids for cosmology and focus on one of the main systematic effects undermining the optimal extraction of cosmological information from the under-dense regions: peculiar velocities. I present guidelines reduce the impact of peculiar velocities by performing optimal cuts on void catalogues. Additionally I discuss the considerable increase in void statistics to be expected from future surveys and present an estimate of the number of voids to be obtained from two upcoming surveys: the ESA-lead Euclid survey and the NASA-lead WFIRST mission.

Gravitational hydrodynamics acknowledges that hydrodynamics is essentially nonlinear and viscous. In the plasma, at z = 5100, the viscous length enters the horizon and causes fragmentation into plasma clumps surrounded by voids. The latter have expanded to 38 Mpc now, explaining the cosmic void scale 30/h = 42 Mpc. After the decoupling the Jeans mechanism fragments all matter in clumps of ca 40,000 solar masses. Each of them fragments due to viscosity in millibrown dwarfs of earth weight, so each Jeans cluster contains billions of them. The Jeans clusters act as ideal gas particles in the isothermal model, explaining the flattening of rotation curves. The first stars in old globular clusters are formed by aggregation of milli brown dwarfs, without dark period. Star formation also happens when Jean clusters come close to each other and agitate and heat up the cooled milli brown dwarfs, which then expand and coalesce to form new stars. This explains the Tully-Fischer and Jackson-Faber relations, and the formation of young globular clusters in galaxy mergers. Thousand of milli brown dwarfs have been observed in quasar microlensing and some 40,000 in the Helix planetary nebula.

While the milli brown dwarfs, i.e., dark baryons, constitute the galactic dark matter, cluster dark matter consists probably of 1.5 eV neutrinos, free streaming at the decoupling. These two types of dark matter explain a wealth of observations.