Related papers: Are Galaxies Cosmon Lumps?
Galaxy bias, the unknown relationship between the clustering of galaxies and the underlying dark matter density field is a major hurdle for cosmological inference from large-scale structure. While traditional analyses focus on the absolute…
We consider 2+1 gravity minimally coupled to a self-interacting scalar field. The case in which the fall-off of the fields at infinity is slower than that of a localized distribution of matter is analyzed. It is found that the asymptotic…
The stability of cosmological event and Cauchy horizons of spacetimes associated with plane symmetric domain walls are studied. It is found that both horizons are not stable against perturbations of null fluids and massless scalar fields;…
We estimate the contribution of galaxies to the cosmological density Omega_0 including also their extended dark halos. We find Omega_gal< 0.1, so implying that the matter in galaxies cannot by itself close the Universe but marginally could…
It has been shown that the presence of non-minimally coupled scalar fields giving rise to a fifth force can noticeably alter dynamics on galactic scales. Such a fifth force must be screened in the Solar System but if unscreened it can have…
In this short communication we point out to the possibility that the clouds of the negative vacuum energy around galaxies may have the same effect as dark matter. These clouds amplify the force acting on the baryonic matter around galaxies…
Stable gravitating lumps with a false vacuum core surrounded by the true vacuum in a scalar field potential exist in the presence of fermions at the core. These objects may exist in the universe at various scales.
We consider the possibility that the dark matter is coupled through its mass to a scalar field associated with the dark energy of the Universe. In order for such a field to play a role at the present cosmological distances, it must be…
The cosmological implications from a new estimate of the local X-ray galaxy cluster abundance are summarized. The results are then compared to independent observations. It is suggested that `low' values for the mean cosmic matter density…
We consider the effect of various particles on the cosmic expansion rate relative to that of the graviton. Effectively massless fermions, gauge bosons and conformally coupled scalars make only minuscule contributions due to local conformal…
Scaling relations of galaxy clusters are a powerful probe of cosmic isotropy in the late Universe. Owing to their strong cosmological dependence, galaxy cluster scaling relations can obtain tight constraints on the spatial variation of…
Loop quantum cosmology is an application of recent developments for a non-perturbative and background independent quantization of gravity to a cosmological setting. Characteristic properties of the quantization such as discreteness of…
We investigate the static and spherically symmetric solutions of Einstein's equations for a scalar field with non-canonical kinetic term, assumed to provide both the dark matter and dark energy components of the Universe. In particular, we…
We investigate the Universe at the late stage of its evolution and inside the cell of uniformity 150-370 Mpc. We consider the Universe to be filled at these scales with dust like matter, a minimally coupled Galileon field and radiation. We…
A solution for the problem of understanding observed rotation curves in galaxies without the introduction of dark matter halos is presented. This solution has been obtained upon considering the distribution of masses in the expanding…
We study the effect of the cosmological constant on the statistical properties of gravitational lenses in flat cosmologies (Omega_{0}+lambda_{0} = 1). It is shown that some of the lens observables are strongly affected by the cosmological…
Cosmological solutions of Einstein's equations for equilibrium statistical systems of particles with scalar interaction are investigated. It is shown that the scalar field can effectively change the state equation of a statistical system,…
We consider the nonunitary quantum dynamics of neutral massless scalar particles used to model photons around a massive gravitational lens. The gravitational interaction between the lensing mass and asymptotically free particles is…
Inflation and quintessence can both be described by a single scalar field. The cosmic time evolution of this cosmon field realizes a crossover from the region of an ultraviolet fixed point in the infinite past to an infrared fixed point in…
Cosmological perturbations in an expanding universe back-react on the space-time in which they propagate. Calculations to lowest non-vanishing order in perturbation theory indicate that super-Hubble-scale fluctuations act as a negative and…