Limits on decaying dark energy density models from the CMB temperature–redshift relation

Making use of the generalized form of the Ghost dark energy density, which has the functional form [Formula: see text] where [Formula: see text] represents the Hubble expanding rate, the present accelerated enlargement behavior of the cosmos is investigated from the Rastall theory perspective. After finding a relation for the Hubble cosmic expansion rate, we consider recent cosmology-independent measurements calculated for the expansion history of the cosmos to fit the model via the [Formula: see text]-analysis. Moreover, we discuss the cosmographic properties of the model with the help of some cosmological quantities. We show that our model is stable and consistent with the recent astrophysical data. Also, for our model, we investigate cosmological interpretations of thermodynamics.

Download Full-text

Cosmological Constant from the Entropy Balance Condition

Advances in High Energy Physics ◽

10.1155/2018/3702498 ◽

2018 ◽

Vol 2018 ◽

pp. 1-5

Author(s):

Merab Gogberashvili

Keyword(s):

Dark Energy ◽

Energy Density ◽

Apparent Horizon ◽

Critical Density ◽

Zero Energy ◽

Dark Energy Density ◽

Event Horizons ◽

Balance Condition ◽

Quantum Particles ◽

Hubble Horizon

In the action formalism variations of metric tensors usually are limited by the Hubble horizon. On the contrary, variations of quantum fields should be extended up to the event horizon, which is the real boundary of the spacetime. As a result the entanglement energy of quantum particles across the apparent horizon is missed in the cosmological equations written for the Hubble volume. We identify this missing boundary term with the dark energy density and express it (using the zero energy assumption for the finite universe) as the critical density multiplied by the ratio of the Hubble and event horizons radii.

Download Full-text

FRW viscous modified cosmic Chaplygin gas cosmology in the presence of cosmological constant

International Journal of Geometric Methods in Modern Physics ◽

10.1142/s021988781950141x ◽

2019 ◽

Vol 16 (09) ◽

pp. 1950141 ◽

Cited By ~ 1

Author(s):

G. S. Khadekar ◽

Aina Gupta ◽

Kalpana Pande

Keyword(s):

Dark Energy ◽

Energy Density ◽

Cosmological Constant ◽

Chaplygin Gas ◽

Frw Universe ◽

Dark Energy Density ◽

Linear Combinations ◽

Linear Differential ◽

The Stability ◽

Cardassian Universe

In this paper, we study viscous Modified Cosmic Chaplygin Gas (MCCG) in the presence of cosmological constant in flat FRW universe. We assume that bulk viscosity [Formula: see text] and cosmological constant [Formula: see text] are the linear combinations of two terms, one is constant and other is a function of dark energy density [Formula: see text]. In this framework, we solve the non-linear differential equation analytically and numerically and obtain time dependent dark energy density. We also consider two separate cases of early and late universe and discussed the evolution of dark energy density. We investigate the effect of viscosity and cosmological constant to the evolution of universe and discuss the stability of the model by square of speed of sound. Finally, we compare our model with Cardassian universe.

Download Full-text

Holographic dark energy in a vector field cosmology

International Journal of Geometric Methods in Modern Physics ◽

10.1142/s0219887815501194 ◽

2015 ◽

Vol 12 (10) ◽

pp. 1550119 ◽

Cited By ~ 3

Author(s):

S. Davood Sadatian

Keyword(s):

Dark Energy ◽

Vector Field ◽

Equation Of State ◽

Energy Density ◽

Holographic Dark Energy ◽

Lorentz Invariance ◽

Holographic Model ◽

Dark Energy Density ◽

Invariance Violation ◽

Lorentz Invariance Violation

We obtain interacting holographic dark energy density in the framework of vector field cosmology (LIV). We consider possible modification of equation of state for the holographic energy density in lorentz invariance violation cosmology. In this case we select Jeans length as the IR cut-off in the holographic model. Then we consider the interaction between holographic energy densities ρΛ and ρm in this framework.

Download Full-text

Measuring Time Dependence of Dark Energy Density from Type Ia Supernova Data

The Astrophysical Journal ◽

10.1086/320552 ◽

2001 ◽

Vol 552 (2) ◽

pp. 445-451 ◽

Cited By ~ 79

Author(s):

Yun Wang ◽

Peter M. Garnavich

Keyword(s):

Dark Energy ◽

Energy Density ◽

Time Dependence ◽

Measuring Time ◽

Dark Energy Density ◽

Type Ia Supernova ◽

Type Ia

Download Full-text

SUPERNOVA Ia AND GALAXY CLUSTER GAS MASS FRACTION CONSTRAINTS ON DARK ENERGY

Modern Physics Letters A ◽

10.1142/s0217732306021530 ◽

2006 ◽

Vol 21 (29) ◽

pp. 2197-2204 ◽

Cited By ~ 40

Author(s):

KYLE M. WILSON ◽

GANG CHEN ◽

BHARAT RATRA

Keyword(s):

Dark Energy ◽

Energy Density ◽

Cosmological Constant ◽

Mass Fraction ◽

Galaxy Cluster ◽

Apparent Magnitude ◽

Model Parameters ◽

Dark Energy Density ◽

Energy Models ◽

Fraction Versus

We use the Riess et al. (2004)1 supernova Ia apparent magnitude versus redshift data and the Allen et al. (2004)2 galaxy cluster gas mass fraction versus redshift data to constrain dark energy models. These data provide complementary constraints that when combined together significantly restrict model parameters and favor slowly-evolving dark energy density models, close to the Einstein cosmological constant limit of dark energy.

Download Full-text