scholarly journals Dark Energy and Inflation from Gravitational Waves

2017 ◽  
Author(s):  
Leonid Marochnik
Keyword(s):  
Dark Energy ◽  
Gravitational Waves ◽  
De Sitter ◽  
Wick Rotation ◽  
Physical Explanation ◽  
Evolution Of The Universe ◽  
The Universe ◽  
Universe Evolution ◽  
Matter Fields ◽  
Metric Fluctuations

In this three-part paper, we show that gravitational waves (classical and quantum) produce the accelerated de Sitter expansion at the start and by the end of the cosmological evolution of the Universe. In these periods of time, the Universe contains no matter fields but contains classical and quantum metric fluctuations, i.e. it is filled with classical gravitational waves and gravitons. In such gravitational wave and graviton dominated eras of evolution of the Universe, the de Sitter state is the exact solution to the self-consistent equations for gravitational waves and gravitons and background geometry for the empty (with no matter fields) space-time with FLRW metric. In both classical and quantum cases, this solution is of the instanton origin since it is obtained by Wick rotation with the subsequent analytic continuation to real time. The cosmological acceleration from gravitational waves and gravitons provides a transparent physical explanation to the coincidence and threshold paradoxes of dark energy avoiding recourse to the anthropic principle. The cosmological acceleration from gravitons/gravitational waves at the start of the Universe evolution produces inflation which is consistent with the observational data on CMB anisotropy.

scholarly journals Dark Energy and Inflation from Gravitational Waves

2017 ◽  
Author(s):  
Leonid Marochnik
Keyword(s):  
Dark Energy ◽  
Gravitational Waves ◽  
De Sitter ◽  
Wick Rotation ◽  
Physical Explanation ◽  
Evolution Of The Universe ◽  
The Universe ◽  
Universe Evolution ◽  
Matter Fields ◽  
Metric Fluctuations

In this three-part paper, we show that gravitational waves (classical and quantum) produce the accelerated de Sitter expansion at the start and by the end of the cosmological evolution of the Universe. In these periods of time, the Universe contains no matter fields but contains classical and quantum metric fluctuations, i.e. it is filled with classical gravitational waves and gravitons. In such gravitational wave and graviton dominated eras of evolution of the Universe, the de Sitter state is the exact solution to the self-consistent equations for gravitational waves and gravitons and background geometry for the empty (with no matter fields) space-time with FLRW metric. In both classical and quantum cases, this solution is of the instanton origin since it is obtained by Wick rotation with the subsequent analytic continuation to real time. The cosmological acceleration from gravitational waves and gravitons provides a transparent physical explanation to the coincidence and threshold paradoxes of dark energy avoiding recourse to the anthropic principle. The cosmological acceleration from gravitons/gravitational waves at the start of the Universe evolution produces inflation which is consistent with the observational data on CMB anisotropy.

scholarly journals A Study on Ricci Dark Energy in Bulk-Brane Interaction

2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Surajit Chattopadhyay
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Energy Density ◽  
Power Law ◽  
Ricci Dark Energy ◽  
Dark Energy Density ◽  
Evolution Of The Universe ◽  
The Impact ◽  
The Universe ◽  
Matter Fields

We have investigated the effects of the interaction between a brane universe and the bulk in which it is embedded. Considering the effects of the interaction between a brane universe and the bulk, we have obtained the equation of state for the interacting holographic Ricci dark energy density ρΛ=3c2(H˙+2H2) in the flat universe. We have investigated the impact of c2 on the equation of state ωΛ. Also, considering the power law for of the scale factor, we have observed that nontrivial contributions of dark energy which differ from the standard matter fields confined to the brane are increasing with the evolution of the universe.

scholarly journals From Quantum Unstable Systems to the Decaying Dark Energy: Cosmological Implications

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Aleksander Stachowski ◽  
Marek Szydłowski ◽  
Krzysztof Urbanowski
Keyword(s):  
Dark Energy ◽  
Time Reversal ◽  
Hubble Parameter ◽  
Decay Process ◽  
Time Dependent ◽  
Time Reversal Symmetry ◽  
Exponential Form ◽  
Cosmological Time ◽  
Evolution Of The Universe ◽  
The Universe

We consider a cosmology with decaying metastable dark energy and assume that a decay process of this metastable dark energy is a quantum decay process. Such an assumption implies among others that the evolution of the Universe is irreversible and violates the time reversal symmetry. We show that if we replace the cosmological time t appearing in the equation describing the evolution of the Universe by the Hubble cosmological scale time, then we obtain time dependent Λ(t) in the form of the series of even powers of the Hubble parameter H: Λ(t)=Λ(H). Our special attention is focused on radioactive-like exponential form of the decay process of the dark energy and on the consequences of this type decay.

scholarly journals De Sitter and power-law solutions in non-local Gauss–Bonnet gravity

2018 ◽  
Vol 15 (11) ◽  
pp. 1850188 ◽  
Author(s):  
E. Elizalde ◽  
S. D. Odintsov ◽  
E. O. Pozdeeva ◽  
S. Yu. Vernov
Keyword(s):  
Power Law ◽  
Sufficient Conditions ◽  
Model Parameters ◽  
Local Form ◽  
De Sitter ◽  
Dynamical Equations ◽  
Non Local ◽  
Necessary And Sufficient ◽  
The Universe ◽  
Universe Evolution

The cosmological dynamics of a non-locally corrected gravity theory, involving a power of the inverse d’Alembertian, is investigated. Casting the dynamical equations into local form, the fixed points of the models are derived, as well as corresponding de Sitter and power-law solutions. Necessary and sufficient conditions on the model parameters for the existence of de Sitter solutions are obtained. The possible existence of power-law solutions is investigated, and it is proven that models with de Sitter solutions have no power-law solutions. A model is found, which allows to describe the matter-dominated phase of the Universe evolution.

scholarly journals Generalized emergent dark energy: observational Hubble data constraints and stability analysis

2020 ◽  
Vol 497 (2) ◽  
pp. 1590-1602
Author(s):  
A Hernández-Almada ◽  
Genly Leon ◽  
Juan Magaña ◽  
Miguel A García-Aspeitia ◽  
V Motta
Keyword(s):  
Dark Energy ◽  
Stability Analysis ◽  
Degree Of Freedom ◽  
Dark Energy Density ◽  
Homogeneous Sample ◽  
The Standard Model ◽  
Yield Values ◽  
Data Constraints ◽  
The Universe ◽  
Universe Evolution

ABSTRACT Recently, a phenomenologically emergent dark energy (PEDE) model was presented with a dark energy density evolving as $\widetilde{\Omega }_{\rm {DE}}(z) = \Omega _{\rm {DE,0}}[ 1 - {\rm {tanh}}({\log }_{10}(1+z))]$, i.e. with no degree of freedom. Later on, a generalized model was proposed by adding one degree of freedom to the PEDE model, encoded in the parameter Δ. Motivated by these proposals, we constrain the parameter space ($h,\Omega _m^{(0)}$) and ($h,\Omega _m^{(0)}, \Delta$) for PEDE and generalized emergent dark energy (GEDE), respectively, by employing the most recent observational (non-)homogeneous and differential age Hubble data. Additionally, we reconstruct the deceleration and jerk parameters and estimate yield values at z = 0 of $q_0 = -0.784^{+0.028}_{-0.027}$ and $j_0 = 1.241^{+0.164}_{-0.149}$ for PEDE and $q_0 = -0.730^{+0.059}_{-0.067}$ and $j_0 = 1.293^{+0.194}_{-0.187}$ for GEDE using the homogeneous sample. We report values on the deceleration–acceleration transition redshift with those reported in the literature within 2σ CL. Furthermore, we perform a stability analysis of the PEDE and GEDE models to study the global evolution of the Universe around their critical points. Although the PEDE and GEDE dynamics are similar to the standard model, our stability analysis indicates that in both models there is an accelerated phase at early epochs of the Universe evolution.

scholarly journals The investigation of detectability of the relic gravitational waves based on the WMAP-9 and Planck

2017 ◽  
Vol 26 (02) ◽  
pp. 1750003 ◽  
Author(s):  
Basem Ghayour
Keyword(s):  
Scalar Field ◽  
Gravitational Waves ◽  
Crucial Role ◽  
Planck Data ◽  
Evolution Of The Universe ◽  
Cosmological Observations ◽  
Relic Gravitational Waves ◽  
The Waves ◽  
The Universe ◽  
General Range

The generated relic gravitational waves underwent several stages of evolution of the universe such as inflation and reheating. These stages were affected on the shape of spectrum of the waves. As well known, at the end of inflation, the scalar field [Formula: see text] oscillates quickly around some point where potential [Formula: see text] has a minimum. The end of inflation stage played a crucial role on the further evolution stages of the universe because particles were created and collisions of the created particles were responsible for reheating the universe. There is a general range for the frequency of the spectrum [Formula: see text])[Formula: see text]Hz. It is shown that the reheating temperature can affect on the frequency of the spectrum as well. There is constraint on the temperature from cosmological observations based on WMAP-9 and Planck. Therefore, it is interesting to estimate allowed value of frequencies of the spectrum based on general range of reheating temperature like few MeV [Formula: see text] GeV, WMAP-9 and Planck data then compare the spectrum with sensitivity of future detectors such as LISA, BBO and ultimate-DECIGIO. The obtained results of this comparison give us some more chance for detection of the relic gravitational waves.

scholarly journals Cosmology from multimeasure multifield model

2019 ◽  
Vol 34 (19) ◽  
pp. 1950099 ◽  
Author(s):  
Denitsa Staicova ◽  
Michail Stoilov
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Model Potential ◽  
Higgs Mechanism ◽  
Evolution Of The Universe ◽  
Slow Roll ◽  
Cosmological Application ◽  
Proposed Model ◽  
Model Setup ◽  
The Universe

We consider the cosmological application of a (variant of) relatively newly proposed model1 unifying inflation, dark energy, dark matter, and the Higgs mechanism. The model was originally defined using additional non-Riemannian measures, but it can be reformulated into effective quintessential model unifying inflation, dark energy and dark matter. Here, we demonstrate numerically that it is capable of describing the entire evolution of the Universe in a seamless way, but this requires some revision of the model setup. The main reason is that there is a strong effective friction in the model, a feature which has been neglected in the pioneer work. This improves the model potential for proper description of the evolution of the Universe, because the friction ensures a finite time inflation with dynamically maintained low-value slow-roll parameters in the realistic scenarios. In addition, the model predicts the existence of a constant scalar field in late Universe.

scholarly journals ATTRACTOR SOLUTION IN COUPLED YANG–MILLS FIELD DARK ENERGY MODELS

2009 ◽  
Vol 18 (09) ◽  
pp. 1331-1342 ◽  
Author(s):  
WEN ZHAO
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
De Sitter ◽  
Yang Mills ◽  
Constraint Equations ◽  
Energy Models ◽  
Big Rip ◽  
Attractor Solution ◽  
The Universe ◽  
Mills Field

We investigate the attractor solution in the coupled Yang–Mills field dark energy models with the general interaction term, and obtain the constraint equations for the interaction if the attractor solution exists. The research also shows that, if the attractor solution exists, the equation of state of dark energy must evolve from wy > 0 to wy ≤ -1, which is slightly suggested by the observation. At the same time, the total equation of state in the attractor solution is w tot = -1, the universe is a de Sitter expansion, and the cosmic big rip is naturally avoided. These features are all independent of the interacting forms.

scholarly journals LITTLE RIP COSMOLOGICAL MODELS WITH TIME-DEPENDENT EQUATION OF STATE

2012 ◽  
Vol 27 (36) ◽  
pp. 1250210 ◽  
Author(s):  
I. BREVIK ◽  
V. V. OBUKHOV ◽  
K. E. OSETRIN ◽  
A. V. TIMOSHKIN
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Models ◽  
Time Dependent ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Energy Models ◽  
Sitter Spacetime ◽  
The Universe ◽  
Far Future

Specific dark energy models, leading to the Little Rip (LR) cosmology in the far future, are investigated. Conditions for the occurrence of LR in terms of the parameters present in the proposed equation of state for the dark energy cosmic fluid are studied. Estimates about the time needed before the occurrence of the small singularity in the standard LR model in which the universe approaches the de Sitter spacetime asymptotically, are given.

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