The Role of Dark Matter and Dark Energy in Cosmological Models: Theoretical Overview

2009 ◽  
pp. 353-365
Author(s):  
A. F. Zakharov ◽  
S. Capozziello ◽  
F. De Paolis ◽  
G. Ingrosso ◽  
A. A. Nucita
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Models ◽  
Theoretical Overview

The Role of Dark Matter and Dark Energy in Cosmological Models: Theoretical Overview

2009 ◽  
Vol 148 (1-4) ◽  
pp. 301-313 ◽  
Author(s):  
A. F. Zakharov ◽  
S. Capozziello ◽  
F. De Paolis ◽  
G. Ingrosso ◽  
A. A. Nucita
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Models ◽  
Theoretical Overview

scholarly journals DO RECENT SUPERNOVAE Ia OBSERVATIONS TEND TO RULE OUT ALL THE COSMOLOGIES?

2007 ◽  
Vol 16 (10) ◽  
pp. 1641-1651 ◽  
Author(s):  
RAM GOPAL VISHWAKARMA
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Gravitational Lensing ◽  
Weakly Interacting Massive Particles ◽  
Cosmological Models ◽  
Accelerated Expansion ◽  
Standard Candle ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Rule Out

Dark energy and the accelerated expansion of the universe have been the direct predictions of the distant supernovae Ia observations which are also supported, indirectly, by the observations of the CMB anisotropies, gravitational lensing and the studies of galaxy clusters. Today these results are accommodated in what has become the concordance cosmology: a universe with flat spatial sections t = constant with about 70% of its energy in the form of Einstein's cosmological constant Λ and about 25% in the form of dark matter (made of perhaps weakly-interacting massive particles). Though the composition is weird, the theory has shown remarkable successes at many fronts. However, we find that as more and more supernovae Ia are observed, more accurately and towards higher redshift, the probability that the data are well-explained by the cosmological models decreases alarmingly, finally ruling out the concordance model at more than 95% confidence level. This raises doubts against the "standard candle"-hypothesis of the supernovae Ia and their use in constraining the cosmological models. We need a better understanding of the entire SN Ia phenomenon in order to extract cosmological consequences from them.

scholarly journals LITTLE RIP AND PSEUDO RIP PHENOMENA FROM COUPLED DARK ENERGY

2013 ◽  
Vol 28 (37) ◽  
pp. 1350172 ◽  
Author(s):  
I. BREVIK ◽  
A. V. TIMOSHKIN ◽  
Y. RABOCHAYA
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Equation Of State ◽  
Early Universe ◽  
Equations Of State ◽  
Cosmological Models ◽  
Ideal Fluids ◽  
Interaction Term ◽  
Gravitational Equations

We consider Little Rip (LR) and Pseudo Rip (PR) cosmological models with two interacting ideal fluids, corresponding to dark energy and dark matter. The interaction between the dark energy and the dark matter fluid components is described in terms of the parameters in the equations of state for the LR and PR universes. In contrast to a model containing only a pure dark energy, the presence of the interaction term between the fluid components in the gravitational equations leads to a modification of the equation of state parameters. The properties of the early universe in this formalism are pointed out.

scholarly journals HOLOGRAPHIC INTERACTING DARK ENERGY IN THE BRANEWORLD COSMOLOGY

2007 ◽  
Vol 22 (35) ◽  
pp. 2631-2645 ◽  
Author(s):  
KYOUNG YEE KIM ◽  
HYUNG WON LEE ◽  
YUN SOO MYUNG
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cold Dark Matter ◽  
Equations Of State ◽  
Brane Cosmology ◽  
General Decay Rate ◽  
Braneworld Cosmology ◽  
State Formula ◽  
Unified Description

We investigate a model of brane cosmology to find a unified description of the radiation-matter-dark energy universe. It is of the interacting holographic dark energy with a bulk-holographic matter χ. This is a five-dimensional cold dark matter, which plays a role of radiation on the brane. Using the effective equations of state [Formula: see text] instead of the native equations of state ωΛ, we show that this model cannot accommodate any transition from the dark energy with [Formula: see text] to the phantom regime [Formula: see text]. Furthermore, the case of interaction between four-dimensional cold dark matter and five-dimensional cold dark matter is considered for completeness. Here we find that the redshift of matter-radiation equality z eq is the same order as [Formula: see text]. Finally, we obtain a general decay rate Γ which is suitable for describing all interactions.

scholarly journals Bouncing Quantum Cosmology

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 110
Author(s):  
Nelson Pinto-Neto
Keyword(s):  
Dark Matter ◽  
Quantum Theory ◽  
Dark Energy ◽  
Quantum Cosmology ◽  
Canonical Quantization ◽  
Quantization Scheme ◽  
Physical Effects ◽  
Planck Energy ◽  
De Broglie Bohm

The goal of this contribution is to present the properties of a class of quantum bouncing models in which the quantum bounce originates from the Dirac canonical quantization of a midi-superspace model composed of a homogeneous and isotropic background, together with small inhomogeneous perturbations. The resulting Wheeler-DeWitt equation is interpreted in the framework of the de Broglie-Bohm quantum theory, enormously simplifying the calculations, conceptually and technically. It is shown that the resulting models are stable and they never get to close to the Planck energy, where another more involved quantization scheme would have to be evoked, and they are compatible with present observations. Some physical effects around the bounce are discussed, like baryogenesis and magnetogenesis, and the crucial role of dark matter and dark energy is also studied.

scholarly journals Unifying dark matter and dark energy with non-canonical scalars

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Swagat S. Mishra ◽  
Varun Sahni
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
General Condition ◽  
Cold Dark Matter ◽  
Scalar Fields ◽  
Kinetic Term ◽  
Potential Term ◽  
Small Scales ◽  
Type Potential

AbstractNon-canonical scalar fields with the Lagrangian $${{\mathcal {L}}} = X^\alpha - V(\phi )$$ L = X α - V ( ϕ ) , possess the attractive property that the speed of sound, $$c_s^{2} = (2\,\alpha - 1)^{-1}$$ c s 2 = ( 2 α - 1 ) - 1 , can be exceedingly small for large values of $$\alpha $$ α . This allows a non-canonical field to cluster and behave like warm/cold dark matter on small scales. We derive a general condition on the potential in order to facilitate the kinetic term $$X^\alpha $$ X α to play the role of dark matter, while the potential term $$V(\phi )$$ V ( ϕ ) playing the role of dark energy at late times. We demonstrate that simple potentials including $$V= V_0\coth ^2{\phi }$$ V = V 0 coth 2 ϕ and a Starobinsky-type potential can unify dark matter and dark energy. Cascading dark energy, in which the potential cascades to lower values in a series of discrete steps, can also work as a unified model.

scholarly journals Constraints on the Dark Side of the Universe and Observational Hubble Parameter Data

2010 ◽  
Vol 2010 ◽  
pp. 1-14 ◽  
Author(s):  
Tong-Jie Zhang ◽  
Cong Ma ◽  
Tian Lan
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Hubble Parameter ◽  
Future Prospect ◽  
Cosmological Models ◽  
Dark Side ◽  
Expanding Universe ◽  
Basic Principles ◽  
The Universe

This paper is a review on the observational Hubble parameter data that have gained increasing attention in recent years for their illuminating power on the dark side of the universe: the dark matter, dark energy, and the dark age. Currently, there are two major methods of independent observationalH(z)measurement, which we summarize as the “differential age method” and the “radial BAO size method.” Starting with fundamental cosmological notions such as the spacetime coordinates in an expanding universe, we present the basic principles behind the two methods. We further review the two methods in greater detail, including the source of errors. We show how the observationalH(z)data present itself as a useful tool in the study of cosmological models and parameter constraint, and we also discuss several issues associated with their applications. Finally, we point the reader to a future prospect of upcoming observation programs that will lead to some major improvements in the quality of observationalH(z)data.

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