In the current paper, we have studied the effect of dark energy on for-mation where dark energy exists in the background. For this purpose, we used both WMAP9 and Planck data to study how the radius changes with redshift in these mod-els. We used different data sets to fix the cosmological parameters to obtain a solution for a spherical region under collapse. The mechanism of structure formation f...

It is demonstrated that dark energy, driven by tachyons, having non-minimal coupling with curvature and self-interacting inverse cubic potential, decays to cold dark matter in the late accelerated universe. It is found that this phenomenon yields a solution to " cosmic coincidence problem ". PACS The idea of tachyons is not new. It was proposed around 40 years back [1] and some cosmological mod...

Dark-matter halos are the scaffolding around which galaxies and clusters are built. They form when the gravitational instability of primordial density fluctuations causes regions which are denser than average to slow their cosmic expansion, recollapse, and virialize. Objects as different in size and mass as dwarf spheroidal galaxies and galaxy clusters are predicted by the CDM model to have hal...

We trace the evolution of a spherically symmetric density perturbation in the MOdified Newtonian Dynamics (MOND) model. The background cosmological model is a Λ-dominated, low-Ωb Friedmann model with no Cold Dark Matter. We include thermal processes and non-equilibrium chemical evolution of the collapsing gas. We find that the first density perturbations which collapse to form luminous objects ...

Though experience tells us we can perceive depth in dim light, it is not so obvious that one of the chief mechanisms for depth perception, stereopsis, is possible under scotopic conditions. The only studies on human stereopsis in the dark adapted state seem to be those of Nagel [(1902) Zeitschrift für Psychologie, 27, 264-266] and Mueller and Lloyd [(1948) Proceedings of the National Academy of...

A minimal renormalizable SUSY SO(10) model with B-L symmetry broken by 126 Higgs field has recently been shown to predict all neutrino mixings and the ratio ∆m⊙/∆m 2 A in agreement with observations. Unlike models where B-L is broken by 16 Higgs, this model guarantees automatic R-parity conservation and hence a stable dark matter without any additional symmetry assumptions. In this paper, we di...