scholarly journals Cosmological constraints on entropic cosmology with matter creation

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
Hussain Gohar ◽  
Vincenzo Salzano
Keyword(s):  
Energy Exchange ◽  
Force Model ◽  
Observational Constraints ◽  
Entropic Force ◽  
Cosmological Constraints ◽  
Matter Creation ◽  
Functional Forms ◽  
Temperature Parameter ◽  
The Universe ◽  
Creation Rate

AbstractWe investigate entropic force cosmological models with the possibility of matter creation and energy exchange between the bulk and the horizon of a homogeneous and isotropic flat Universe. We consider three different kinds of entropy, Bekenstein’s, the non-extensive Tsallis–Cirto’s, and the quartic entropy, plus some phenomenological functional forms for matter creation rate to model different entropic force models and put the observational constraints on them. We show that while most of them are indistinguishable from a standard $$\Lambda $$ Λ CDM scenario, the Bekenstein entropic force model with a matter creation rate proportional to the Hubble parameter is statistically highly favored over $$\Lambda $$ Λ CDM. As a general result, we also find that both the Hawking temperature parameter $$\gamma $$ γ , which relates the energy exchange between the bulk and the boundary of the Universe, and the matter creation rate $$\Gamma (t)$$ Γ ( t ) , must be very small to reproduce observational data.

scholarly journals INTERACTION BETWEEN DARK ENERGY AND DARK MATTER: OBSERVATIONAL CONSTRAINTS FROM OHD, BAO, CMB AND SNe Ia

2013 ◽  
Vol 22 (14) ◽  
pp. 1350082 ◽  
Author(s):  
SHUO CAO ◽  
NAN LIANG
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Observational Constraints ◽  
Coincidence Problem ◽  
Cosmological Constraints ◽  
Coincidence Index ◽  
Acceleration Of The Universe ◽  
Interaction Term ◽  
Negative Coupling ◽  
The Universe

In order to test if there is energy transfer between dark energy (DE) and dark matter (DM), we investigate cosmological constraints on two forms of nontrivial interaction between the DM sector and the sector responsible for the acceleration of the universe, in light of the newly revised observations including OHD, CMB, BAO and SNe Ia. More precisely, we find the same tendencies for both phenomenological forms of the interaction term Q = 3γHρ, i.e. the parameter γ to be a small number, |γ| ≈ 10-2. However, concerning the sign of the interaction parameter, we observe that γ > 0 when the interaction between dark sectors is proportional to the energy density of dust matter, whereas the negative coupling (γ < 0) is preferred by observations when the interaction term is proportional to DE density. We further discuss two possible explanations to this incompatibility and apply a quantitative criteria to judge the severity of the coincidence problem. Results suggest that the γm IDE model with a positive coupling may alleviate the coincidence problem, since its coincidence index C is smaller than that for the γd IDE model, the interacting quintessence and phantom models by four orders of magnitude.

scholarly journals The Influence of Evolving Dark Energy on Cosmology

2005 ◽  
Vol 22 (4) ◽  
pp. 315-325 ◽  
Author(s):  
Luke Barnes ◽  
Matthew J. Francis ◽  
Geraint F. Lewis ◽  
Eric V. Linder
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Constant ◽  
Energy Exchange ◽  
Observational Evidence ◽  
Cosmological Models ◽  
Observational Constraints ◽  
Expansion Of The Universe ◽  
The Universe

AbstractObservational evidence indicating that the expansion of the universe is accelerating has surprised cosmologists in recent years. Cosmological models have sought to explain this acceleration by incorporating ‘dark energy’, of which the traditional cosmological constant is just one possible candidate. Several cosmological models involving an evolving equation of state of the dark energy have been proposed, as well as possible energy exchange to other components, such as dark matter. This paper summarizes the forms of the most prominent models and discusses their implications for cosmology and astrophysics. Finally, this paper examines the current and future observational constraints on the nature of dark energy.

BRANE WORLD DYNAMICS AND ADIABATIC MATTER CREATION

2006 ◽  
Vol 15 (03) ◽  
pp. 321-334 ◽  
Author(s):  
P. GOPAKUMAR ◽  
G. V. VIJAYAGOVINDAN
Keyword(s):  
Energy Density ◽  
Open Systems ◽  
Brane World ◽  
Creation Process ◽  
Brane Worlds ◽  
Matter Creation ◽  
Standard Scenario ◽  
Brane Models ◽  
The Universe ◽  
Creation Rate

We treat the adiabatic matter creation process in various three-brane models by applying the thermodynamics of open systems. The matter creation rate is found to affect the evolution of the scale factor and energy density of the universe. We find a modification at the early stages of cosmic dynamics. In GB and RS brane worlds, by choosing appropriate parameters we obtain the standard scenario, while the warped DGP model has different solutions. During later stages, since matter creation is negligible, the evolution reduces to FRW expansion, in the RS and GB models.

scholarly journals Natural inflation after Planck 2018

2022 ◽  
Vol 2022 (01) ◽  
pp. 022
Author(s):  
Nina K. Stein ◽  
William H. Kinney
Keyword(s):  
Symmetry Breaking ◽  
High Precision ◽  
Confidence Region ◽  
Hubble Constant ◽  
Current Data ◽  
Electroweak Symmetry Breaking ◽  
Observational Constraints ◽  
Electroweak Symmetry ◽  
History Of ◽  
The Universe

Abstract We calculate high-precision constraints on Natural Inflation relative to current observational constraints from Planck 2018 + BICEP/Keck(BK15) Polarization + BAO on r and n S, including post-inflationary history of the universe. We find that, for conventional post-inflationary dynamics, Natural Inflation with a cosine potential is disfavored at greater than 95% confidence out by current data. If we assume protracted reheating characterized by w̅>1/3, Natural Inflation can be brought into agreement with current observational constraints. However, bringing unmodified Natural Inflation into the 68% confidence region requires values of T re below the scale of electroweak symmetry breaking. The addition of a SHOES prior on the Hubble Constant H 0 only worsens the fit.

scholarly journals Observational constraints of a new unified dark fluid and the H0 tension

2019 ◽  
Vol 490 (2) ◽  
pp. 2071-2085 ◽  
Author(s):  
Weiqiang Yang ◽  
Supriya Pan ◽  
Andronikos Paliathanasis ◽  
Subir Ghosh ◽  
Yabo Wu
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Early Time ◽  
Observational Constraints ◽  
Minimal Extension ◽  
Energy Evolution ◽  
The Universe ◽  
Different Sources

ABSTRACT Unified cosmological models have received a lot of attention in astrophysics community for explaining both the dark matter and dark energy evolution. The Chaplygin cosmologies, a well-known name in this group have been investigated matched with observations from different sources. Obviously, Chaplygin cosmologies have to obey restrictions in order to be consistent with the observational data. As a consequence, alternative unified models, differing from Chaplygin model, are of special interest. In the present work, we consider a specific example of such a unified cosmological model, that is quantified by only a single parameter μ, that can be considered as a minimal extension of the Λ-cold dark matter cosmology. We investigate its observational boundaries together with an analysis of the universe at large scale. Our study shows that at early time the model behaves like a dust, and as time evolves, it mimics a dark energy fluid depicting a clear transition from the early decelerating phase to the late cosmic accelerating phase. Finally, the model approaches the cosmological constant boundary in an asymptotic manner. We remark that for the present unified model, the estimations of H0 are slightly higher than its local estimation and thus alleviating the H0 tension.

scholarly journals Photon Creation in the Universe and Primordial Nucleosynthesis

2000 ◽  
Vol 198 ◽  
pp. 113-115
Author(s):  
J.A. S. Lima ◽  
J. S. Alcaniz ◽  
J. Santos ◽  
R. Silva
Keyword(s):  
Irreversible Process ◽  
Big Bang ◽  
Radiation Temperature ◽  
Thermodynamic Approach ◽  
Phenomenological Parameter ◽  
Primordial Nucleosynthesis ◽  
Stringent Constraint ◽  
The Universe ◽  
Creation Rate

In hot big bang cosmologies, the irreversible process of continous photon creation may phenomenologically be described through a thermodynamic approach. In these models, the radiation temperature law depends on a phenomenological parameter β which is closely related to the photon creation rate. It is shown that a stringent constraint on the value of this parameter is imposed from primordial nucleosynthesis.

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