Evolution of the energy density in the static universe

The Einstein static model of the universe as a whole is considered. The Hubble law is explained by the Doppler effect due to the downward inertial acceleration along a certain radius experienced by an observer in the center of the universe, with the total acceleration over all radii being equal zero. Evolution of the universe is introduced through the wave function of the universe dependent on time. This yields the energy density of the universe hence the temperature of the universe dependent on time. On the contrary, the energy, forth and intensity of radiation are fixed with time that allows to develop the Newtonian physics in the whole universe. The time-temperature relation of the universe in the model considered is the same as in the radiation dominated universe in the Friedmann model that allows to explain primordial nucleosynthesis as it is in the standard scenario. The modern parameters of the universe in the model considered are consistent with the observations.     

Cosmic microwave background radiation of black hole universe

Modifying slightly the big bang theory, the author has recently developed a new cosmological model called black hole universe. This new cosmological model is consistent with the Mach principle, Einsteinian general theory of relativity, and observations of the universe. The origin, structure, evolution, and expansion of the black hole universe have been presented in the recent sequence of American Astronomical Society (AAS) meetings and published recently in a scientific journal: Progress in Physics. This paper explains the observed 2.725 K cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present universe with hundred billion-trillions of solar masses. According to the black hole universe model, the observed cosmic microwave background radiation can be explained as the black body radiation of the black hole universe, which can be considered as an ideal black body. When a hot and dense star-like black hole accretes its ambient materials and merges with other black holes, it expands and cools down. A governing equation that expresses the possible thermal history of the black hole universe is derived from the Planck law of black body radiation and radiation energy conservation. The result obtained by solving the governing equation indicates that the radiation temperature of the present universe can be ∼2.725 K if the universe originated from a hot star-like black hole, and is therefore consistent with the observation of the cosmic microwave background radiation. A smaller or younger black hole universe usually cools down faster. The characteristics of the original star-like or supermassive black hole are not critical to the physical properties of the black hole universe at present, because matter and radiation are mainly from the outside space, i.e., the mother universe.     

The wave function of the universe in the superstring theory

Wave function of the universe in the superstring theory is discussed and using Vilenkin's boundary condition, the probability density of the scale factor a at a given value of the dilaton field, is obtained. It is shown that when the universe spontaneously nucleates, the minimum value of the scale factor of the classical universe is of the order of the Planck length, that is, quantum effects can prevent the universe from collapsing to a single point.     

Nonconservation of baryons in cosmology—revisited

The concept of the steady-state universe discussed by Hoyle & Narlikar two decades ago is revived in the light of the present discussions of the phase transition in the early big-bang universe. It is shown that with suitable scaling the bubble universe solution bears a striking similarity to the inflationary scenarios being discussed today. The currently discussed idea of cosmic baldness was also anticipated in the C-field cosmology of the steady-state universe. An erratum to this article is available at .     

The Einstein static model of the universe as a whole

The Einstein static model of the universe as a whole is considered in Euclidean space and absolute time of a privileged reference frame. The universe as a whole is stable that specifies observers at rest relative to the global space of the universe. An observer in the centre of the universe is assumed to experience downward inertial acceleration along a certain radius due to the kinetic energy of the universe, with the total acceleration over all radii being equal zero. This yields the Doppler effect for the photon coming from the distant source that may explain the Hubble law in the static universe. The predictions of the model are qualitatively in agreement with the observations in the cosmological tests of a standard candle and a standard rod. Explanation of stretching of the light curve of SN Ia is proposed within the model considered.     

Light propagation in a universe with spatial inhomogeneities

A light propagation in a universe which is homogeneous only in average systematically differs from a light propagation in a strictly homogeneous Universe. We demonstrate a link between this effect and the general theory of transport phenomenon in random media. The effective spatial curvature of a universe which is homogeneous only in average is introduced. This curvature is governing a light propagation in such universe. We show that the effective spatial curvature is lower than the average curvature. It implies that a universe with critical mean density looks like a space with negative curvature.     

Thermodynamic study of non-linear electrodynamics in loop quantum cosmology

In this work, we have discussed the Maxwell’s electrodynamics in non-linear forms in FRW universe. The energy density and pressure for non-linear electrodynamics have been written in the electro-magnetic universe. The Einstein’s field equations for flat FRW model in loop quantum cosmology have been considered if the universe is filled with the matter and electro-magnetic field. We separately assumed the magnetic universe and electric universe. The interaction between matter and magnetic field have been considered in one section and for some particular form of interaction term, we have found the solutions of magnetic field and the energy density of matter. We have also considered the interaction between the matter and electric field and another form of interaction term has been chosen to solve the field equations. The validity of generalized second law of thermodynamics has been investigated on apparent and event horizons using Gibb’s law and the first law of thermodynamics for magnetic and electric universe separately.     

Evolution of the universe in inverse and lnf(R) gravity

Evolution of the universe is discussed in the framework of f(R) theory of gravity. The deceleration parameter is used to interpret various phases of the universe. We investigate the future evolution of the flat FRW universe by using observationally viable f(R) models. A numerical technique is applied to solve the evolution equation in terms of Hubble parameter which is used to explore late time acceleration of the universe. Some novel and interesting results based on the choice of coupling parameters in gravitational action are obtained. We can conclude that the considered f(R) models imply unification of matter dominated epoch with present accelerating phase of the universe.     

Interacting new agegraphic dark energy in a cyclic universe

The main goal of this work is investigation of NADE in the cyclic universe scenario. Since, cyclic universe is explained by a phantom phase (ω<−1), it is shown when there is no interaction between matter and dark energy, ADE and NADE do not produce a phantom phase, then can not describe cyclic universe. Therefore, we study interacting models of ADE and NADE in the modified Friedmann equation. We find out that, in the high energy regime, which it is a necessary part of cyclic universe evolution, only NADE can describe this phantom phase era for cyclic universe. Considering deceleration parameter tells us that the universe has a deceleration phase after an acceleration phase, and NADE is able to produce a cyclic universe. Also it is found valuable to study generalized second law of thermodynamics. Since the loop quantum correction is taken account in high energy regime, it may not be suitable to use standard treatment of thermodynamics, so we turn our attention to the result of Li et al. (Adv. High Energy Phys. 2009: 905705, 2009), which the authors have studied thermodynamics in loop quantum gravity, and we show that which condition can satisfy generalized second law of thermodynamics.     

Scalar-tensor theory of gravity and generalized second law of?thermodynamics on?the?event horizon

Here we consider our universe as homogeneous spherically symmetric FRW model and analyze the thermodynamics of this model of the universe in scalar-tensor theory. Assuming the first law of thermodynamics validity of the generalized second law of thermodynamics (GSLT) at the event horizon is examined in both the cases when the universe is filled with perfect fluid and the holographic dark energy.     

具有旋量场的量子宇宙学

本文利用Hartle和Hawking的方法,讨论了具有旋量场的量子宇宙学,得到了相应的Wheeler-De Witt方程。求出了具有旋量场的宇宙波函数。从波函数可以看出,当标度因子α很小时,旋量场的影响很强,具体的形式与初始条件有关,而当标度因子α很大时,旋量场的行为和标量场一样。     

A model of the late universe with viscous Zel’ldovich fluid and decaying vacuum

Many have speculated about the presence of a stiff fluid in very early stage of the universe. Such a stiff fluid was first introduced by Zel’dovich. Recently the late acceleration of the universe was studied by taking bulk viscous stiff fluid as the dominant cosmic component, but the age predicted by such a model is less than the observed value. We consider a flat universe with viscous stiff fluid and decaying vacuum energy as the cosmic components and found that the model predicts a reasonable background evolution of the universe with de Sitter epoch as end phase of expansion. More over, the model also predicts a reasonable value for the age of the present universe. We also performed a dynamical system analysis of the model and found that the end de Sitter phase predicted by the model is stable.     

Concerning the instantaneous mass and the extent of an expanding universe

In this article we want to answer the cosmologically relevant question what, with some good semantic and physical reason, could be called the massM _u of an infinitely extended, homogeneously matter‐filled and expanding universe. To answer this question we produce a space‐like sum of instantaneous cosmic energy depositions surrounding equally each spacepoint in the homogeneous universe. We calculate the added‐up instantaneous cosmic energy per volume around an arbitrary space point in the expanding universe. To carry out this sum we use as basic metrics an analogy to the inner Schwarzschild metric applied to stars, but this time applied to the spacepoint‐related universe. It is then shown that this leads to the added‐up proper energy within a sphere of a finite outer critical radius defining the point‐related infinity. As a surprise this radius turns out to be reciprocal to the square root of the prevailing average cosmic energy density. The equivalent mass of the universe can then also be calculated and, by the expression which is obtained here, shows a scaling with this critical radius of this universe, a virtue of the universe which was already often called for in earlier works by E. Mach, H. Thirring and F. Hoyle and others. This radius on the other hand can be shown to be nearly equal to the Schwarzschild radius of the so‐defined mass M _u of the universe. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bianchi type-V Lyttleton-Bondi universe

The exterior field of the Bianchi type-V metric in the Lyttleton-Bondi universe is considered. It is shown that the Bianchi type-V Lyttleton-Bondi universe, under certain conditions, does not exist.     

The Universe Evolution as Possible Mechanism of Formation of Galaxies and Their Clusters

The Kepler problem is studied in a space with the Friedmann-Lemaitre-Robertson-Walker metrics of the expanding universe. Cosmic evolution leads to decreasing energy of particles, causing free particles to be captured in bound states, so that the evolution of the universe can be treated as a possible mechanism of the formation of galaxies and clusters of galaxies. The cosmological model is considered where the evolution of the universe plays the role usually inscribed to cold dark matter.     

Statefinder description of a cosmological model based on a mixture of five fluids

In this paper, we have considered a model of our universe containing five components as its constituents. Then, we have done here the statefinder diagnostics for this model. This model can successfully explain the accelerated expansion of the universe given that it satisfies a certain condition. Here we have considered the modified Chaplygin gas as the dynamically changing part of the dark energy component of our universe. Chaplygin gas provides early deceleration and late time acceleration of the universe. The graphical representation of statefinder parameters shows that the total evolution of the universe starts from radiation era to phantom model.     

Cosmological evolution for dark energy models in f(T) gravity

In this paper, we investigate the behavior of equation of state parameter and energy density for dark energy in the framework of f(T) gravity. For this purpose, we use anisotropic LRS Bianchi type I universe model. The behavior of accelerating universe is discussed for some well-known f(T) models. It is found that the universe takes a transition between phantom and non-phantom phases for f(T) models except exponential and logarithmic models. We conclude that our results are relativity analogous to the results of FRW universe.     

The effect of cosmological background dynamics on the spherical collapse in MOND

The effect of background dynamics of the universe on formation of large scale structures in the framework of Modified Newtonian Dynamics (MOND) is investigated. A spherical collapse model is used for modeling the formation of the structures. This study is done in two extreme cases: (i) assuming a universe with a low-density baryonic matter without any cold dark matter and dark energy; (ii) a dark energy dominated universe with baryonic matter, without cold dark matter. We show that for the case (ii) the structures virialize at lower redshifts with larger radii compared to the low-density background universe. The dark energy slow downs the collapse of the structures. We show that our results are compatible with recent simulations of the structure formation in MOND.     

An FLRW interacting dark energy model of the Universe

In this paper, we have presented an FLRW universe containing two-fluids (baryonic and dark energy), by assuming the deceleration parameter as a linear function of the Hubble function. This results in a time-dependent deceleration parameter (DP) having a transition from past decelerating to the present accelerating universe. In this model, dark energy (DE) interacts with dust to produce a new law for the density. As per our model, our universe is at present in a phantom phase after passing through a quintessence phase in the past. The physical importance of the two-fluid scenario is described in various aspects. The model is shown to satisfy current observational constraints such as recent Planck results. Various cosmological parameters relating to the history of the universe have been investigated.     

A possible symmetry and role for Euclidean space-time in cosmology

In this paper, we consider conservation equation in cosmology and propose four possible forms of space-times for universe resulting from dual symmetry between scale factor and energy density in the universe with constant equation of state. We start to describe these four possible types of space-times for universe and it’s possible consequences. Due to the uniformity of the metric signature in Euclidean space-time, for the first  time, we introduce a new symmetry for Euclidean space-time and consider it as a transition unstable state between the visible 4D universe and the invisible world with an extra dimension. Finally, we schematically represent these four possible space-times in a unique scenario for the universe.