An approach to the theory of gravity with an arbitrary reference level of energy density

Five-vectors theory of gravity is proposed, which admits an arbitrary choice of the energy density reference level. This theory is formulated as the constraint theory, where the Lagrange multipliers turn out to be restricted to some class of vector fields unlike the General Relativity (GR), where they are arbitrary. A possible cosmological implication of the proposed model is that the residual vacuum fluctuations dominate during the whole evolution of the universe. That resembles the universe having a nearly linear dependence of a scale factor on cosmic time.

Cosmological Implication of Electroweak Monopole

We estimate the remnant electroweak monopole density of the standard model in the present universe. We show that, although the electroweak phase transition is of the first order, the monopole production comes from the thermal fluctuations of the Higgs field after the phase transition, not the vacuum bubble collisions during the phase transition. Moreover, most of the monopoles produced initially are annihilated as soon as created, and this annihilation continues very long time, longer than the muon pair annihilation time. As the result the remnant monopole density at present universe becomes very small, of 10-11 of the critical density, too small to be the dark matter. We discuss the physical implications of our results on the ongoing monopole detection experiments.

The role of anisotropy in holographic modified gravity

In this paper, we study a cosmological implication of holographic dark energy in modified gravity. We employ the holographic model of dark energy to obtain the equation of state for the holographic energy density in a nonisotropic universe. The purpose of this work is to develop a reconstruction scheme for the modified gravity with f(R) action using the holographic energy density. Hence one can generate a phantom-like equation of state from a holographic dark energy model in a nonisotropic universe in the modified gravity cosmology framework.

QUASAR CLUSTERING AND ITS COSMOLOGICAL IMPLICATION

The clusterings of quasars and absorption line clouds have been analyzed from the viewpoint of the structure formation of the universe. It was found that the features of quasar clustering are quite different from those of galaxies. These results have already given several meaningful constraints on the structure formation, as follows: (a) quasar clustering is much weaker than in galaxies; (b) large scale structures, such as superclusters, should probably be formed after the epoch z~2; (c) the amplitude of the total density inhomogeneity seems to be less than that of galaxy distribution by at least a factor of 3–5 (in a Ω=1 universe); (d) Ly-α absorption clouds may be formed by different processes of clustering from that of glaxies.

Cosmological implication of the emission line redshift distribution of quasars

The peaks and dips in the quasar redshift distribution seem to be incompatible with the cosmological principle. This lays the cosmological redshift hypothesis under suspicion and censure, and has been considered by some investigators as a manifestation of the intrinsic nature of quasar's redshift. So it is worthwhile studying whether the redshift distribution of quasars could be explained in the framework of cosmological redshift. As we know, this distribution is affected not only by the possible physical origin of redshift but also by the selection effects in the observations (Zhou, Deng, Zhou 1983). From this we have the redshift distribution function f(z) = P(z)R(z), where P(z) is the real distribution function which depends on the evolutionary properties of quasars and the space-time structure of the Universe, and R(z) is the factor caused by the selection effect in the line identification.