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Theory and Observation

Abstract

The physical nature of the presently dominating enigmatic dark energy in the expanding universe is demonstrated to be explainable as an excess of the kinetic energy with respect to its potential energy. According to traditional Friedman cosmology, any non-zero value of the total energy integral is ascribed to the space curvature. However, as we show, in the flat universe the total energy also can be different from zero. Initially, a very small excess of kinetic energy originates from the early universe. The present observational data show that our universe has probably a flat space with an excess of kinetic energy. The evolutionary scenario shows that the universe presently is in the transitional stage where its radial coordinate expansion approaches the velocity of light. A possibility of the closed Bubble universe with the local Big Bang and everlasting expansion is demonstrated. Dark matter can be essentially contributed by the non-relativistic massive neutrinos, which have cooled to very low temperatures and velocities thus favoring the formation of the observed broad equipotential wells in galaxies.

1 Introduction Observational studies [ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ] have established accelerated expansion of the current universe, and it is believed that this acceleration is due to some missing component characterised by negative pressure. This missing component is dubbed as “dark energy” (DE), and several DE models have been proposed till date. Such models are reviewed in [ 6 ], [ 7 ], [ 8 ], [ 9 ], [ 10 ], [ 11 ], [ 12 ], [ 13 ], [ 14 ], [ 15 ], [ 16 ], [ 17 ], [ 18 ]. The negative pressure ( p DE ) leads to negative equation of state (EoS) parameter w

1 Introduction In recent years, it has been confirmed through cosmic microwave background radiation anisotropies and Sloan digital sky survey (with help of other cosmological observations) [ 1 ], [ 2 ], [ 3 ], [ 4 ] that apart from the early inflationary expansion, the universe has another accelerated phase; that is, the late time acceleration through which the universe is passing through. This epoch is also called the dark energy (DE) epoch. The cosmological constant Λ is the simplest candidate for the DE, and is supported by observations. However, it cannot

Abstract

We investigate the generalized Quantum Chromodynamics (QCD) ghost model of dark energy in the framework of Einstein gravity. First, we study the non-interacting generalized ghost dark energy in a flat Friedmann-Robertson-Walker (FRW) background. We obtain the equation of state parameter, w D = p/ρ, the deceleration parameter, and the evolution equation of the generalized ghost dark energy. We find that, in this case, w D cannot cross the phantom line (w D > −1) and eventually the universe approaches a de-Sitter phase of expansion (w D → −1). Then, we extend the study to the interacting ghost dark energy in both a flat and non-flat FRW universe. We find that the equation of state parameter of the interacting generalized ghost dark energy can cross the phantom line (w D < −1) provided the parameters of the model are chosen suitably. Finally, we constrain the model parameters by using the Markov Chain Monte Carlo (MCMC) method and a combined dataset of SNIa, CMB, BAO and X-ray gas mass fraction.

Abstract

The exact solutions of the Einstein field equations for dark energy in Kantowski-Sachs metric under the assumption on the anisotropy of the fluid are obtained for exponential and power-law volumetric expansions. The isotropy of the fluid, space and expansion are examined.

the range of attractive gravitation. ) see Part I] is introduced, and its consequences regarding the group structure of particle physics will be considered. Of prime importance is the prediction of additional gravitational bosons that would allow the generation of extreme gravity fields outside GR, as will be outlined further in detail in Section 5 . With regard to cosmology, a tentative explanation of the origin of dark energy (DE) is given, where the picture of a hot Big Bang is questioned by the idea of a Quantised Bang (Section 6 ). In Section 4 , we start

Arthur Gibson Intuition, Counter-Intuition & the Absence of Ontology for Dark Energy Abstract: The chapter evaluates the terminology used to address the assumption of a ‘dark energy’ in astrophysics. In a brief retrospection, the author contrasts the scientific principles underlying physics and philosophy. In this context the view that all truths derive from logical and scientific investigation and that this is self-evident is put in question. First, the author presents an analyses of intuition and second, counter-intuition is studied in the context of ‘dark

Abstract

In this paper, we examine the interacting dark energy model in f(T) cosmology. We assume dark energy as a perfect fluid and choose a specific cosmologically viable form f(T) = β√T. We show that there is one attractor solution to the dynamical equation of f(T) Friedmann equations. Further we investigate the stability in phase space for a general f(T) model with two interacting fluids. By studying the local stability near the critical points, we show that the critical points lie on the sheet u* = (c − 1)v* in the phase space, spanned by coordinates (u, v, Ω, T). From this critical sheet, we conclude that the coupling between the dark energy and matter c ∈ (−2, 0).

Chapter 9 Dark energy discovered In the 1950s, Friedmann’s universe with its origin a long time ago and the steady state cosmos, without beginning (Bondi and Gold 1948, Hoyle 1948), were com- peting alternative cosmological models. This was before the discovery of the cosmic microwave background radiation in 1965 which quickly made the Big Bang idea the ruling paradigm. The accurate thermal spectrum of the background radiation was naturally explained as the cooled down relict of the hot big bang. This pre- dicted cooling as a function of redshift (TðzÞ ¼ T0ð1þ