scholarly journals Forecasts of redshift drift constraints on cosmological parameters

2019 ◽  
Vol 488 (3) ◽  
pp. 3607-3624 ◽  
Author(s):  
C S Alves ◽  
A C O Leite ◽  
C J A P Martins ◽  
J G B Matos ◽  
T A Silva
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Intensity Mapping ◽  
Cosmological Observations ◽  
Universe Expand ◽  
Redshift Drift ◽  
Expansion Of The Universe ◽  
Model Independent ◽  
Weak Constraints ◽  
The Universe

ABSTRACT Cosmological observations usually map our present-day past light cone. However, it is also possible to compare different past light cones. This is the concept behind the redshift drift, a model-independent probe of fundamental cosmology. In simple physical terms, this effectively allows us to watch the Universe expand in real time. While current facilities only allow sensitivities several orders of magnitude worse than the expected signal, it should be possible to detect it with forthcoming ones. Here, we discuss the potential impact of measurements by three such facilities: the Extremely Large Telescope (the subject of most existing redshift drift forecasts), but also the Square Kilometre Array and intensity mapping experiments. For each of these we assume the measurement sensitivities estimated respectively in Liske et al. (2008), Klockner et al. (2015), and Yu, Zhang & Pen (2014). We focus on the role of these measurements in constraining dark energy scenarios, highlighting the fact that although on their own they yield comparatively weak constraints, they do probe regions of parameter space that are typically different from those probed by other experiments, as well as being redshift dependent. Specifically, we quantify how combinations of several redshift drift measurements at different redshifts, or combinations of redshift drift measurements with those from other canonical cosmological probes, can constrain some representative dark energy models. Our conclusion is that a model-independent mapping of the expansion of the universe from redshift z = 0 to z = 4 – a challenging but feasible goal for the next generation of astrophysical facilities – can have a significant impact on fundamental cosmology.

The accelerating universe and dark energy

2014 ◽  
Vol 23 (06) ◽  
pp. 1430012 ◽  
Author(s):  
Charles Baltay
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Parameters ◽  
Accelerating Universe ◽  
Heavy Particles ◽  
Familiar World ◽  
Acceleration Of The Universe ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Present Understanding

The recent discovery by Riess et al.1 and Perlmutter et al.2 that the expansion of the universe is accelerating is one of the most significant discoveries in cosmology in the last few decades. To explain this acceleration a mysterious new component of the universe, dark energy, was hypothesized. Using general relativity (GR), the measured rate of acceleration translates to the present understanding that the baryonic matter, of which the familiar world is made of, is a mere 4% of the total mass-energy of the universe, with nonbaryonic dark matter making up 24% and dark energy making up the majority 72%. Dark matter, by definition, has attractive gravity, and even though we presently do not know what it is, it could be made of the next heavy particles discovered by particle physicists. Dark energy, however, is much more mysterious, in that even though we do not know what it is, it must have some kind of repulsive gravity and negative pressure, very unusual properties that are not part of the present understanding of physics. Investigating the nature of dark energy is therefore one of the most important areas of cosmology. In this review, the cosmology of an expanding universe, based on GR, is discussed. The methods of studying the acceleration of the universe, and the nature of dark energy, are presented. A large amount of experimentation on this topic has taken place in the decade since the discovery of the acceleration. These are discussed and the present state of knowledge of the cosmological parameters is summarized in Table 7 below. A vigorous program to further these studies is under way. These are presented and the expected results are summarized in Table 10 below. The hope is that at the end of this program, it would be possible to tell whether dark energy is due to Einstein's cosmological constant or is some other new constituent of the universe, or alternately the apparent acceleration is due to some modification of GR.

ENTROPY CORRECTED HOLOGRAPHIC DARK ENERGY f(T) GRAVITY MODEL

2014 ◽  
Vol 29 (02) ◽  
pp. 1450015 ◽  
Author(s):  
M. SHARIF ◽  
SHAMAILA RANI
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Phase Plane ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Statefinder Parameters ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Evolution Trajectory

This paper is devoted to study the power-law entropy corrected holographic dark energy (ECHDE) model in the framework of f(T) gravity. We assume infrared (IR) cutoff in terms of Granda–Oliveros (GO) length and discuss the constructed f(T) model in interacting as well as in non-interacting scenarios. We explore some cosmological parameters like equation of state (EoS), deceleration, statefinder parameters as well as ωT–ωT′ analysis. The EoS and deceleration parameters indicate phantom behavior of the accelerated expansion of the universe. It is mentioned here that statefinder trajectories represent consistent results with ΛCDM limit, while evolution trajectory of ωT–ωT′ phase plane does not approach to ΛCDM limit for both interacting and non-interacting cases.

scholarly journals ADDRESSING THE CRISIS IN FUNDAMENTAL PHYSICS

2007 ◽  
Vol 16 (12a) ◽  
pp. 1947-1952
Author(s):  
CHRISTOPHER W. STUBBS
Keyword(s):  
Dark Energy ◽  
State Parameter ◽  
New Physics ◽  
Fundamental Physics ◽  
Accelerating Expansion ◽  
Cosmological Observations ◽  
Real Risk ◽  
Expansion Of The Universe ◽  
The One ◽  
The Universe

The observation that the expansion of the Universe is proceeding at an ever-increasing rate, i.e. the "dark energy" problem, constitutes a crisis in fundamental physics that is as profound as the one that preceded the advent of quantum mechanics. Cosmological observations currently favor a dark energy equation-of-state parameter w = P/ρ = -1. Awkwardly, this is the value that has the least ability to discriminate between alternatives for the physics that produces the observed accelerating expansion. If this result persists we therefore run a very real risk of stagnation in our attempt to better understand the nature of this new physics, unless we uncover another piece of the dark energy puzzle. I argue that precision fundamental measurements in space have an important role in addressing this crisis.

scholarly journals Barrow HDE model for statefinder diagnostic in FLRW universe

2021 ◽  
pp. 2150030
Author(s):  
Anirudh Pradhan ◽  
Archana Dixit ◽  
Vinod Kumar Bhardwaj
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Density Parameter ◽  
Phantom Divide ◽  
Phantom Divide Line ◽  
Expansion Of The Universe ◽  
Flrw Universe ◽  
The Universe

We have analyzed the Barrow holographic dark energy (BHDE) in the framework of flat FLRW universe by considering the various estimations of Barrow exponent △. Here, we define BHDE, by applying the usual holographic principle at a cosmological system, for utilizing the Barrow entropy rather than the standard Bekenstein–Hawking. To understand the recent accelerated expansion of the universe, consider the Hubble horizon as the IR cutoff. The cosmological parameters, especially the density parameter [Formula: see text], the equation of the state parameter [Formula: see text], energy density [Formula: see text] and the deceleration parameter [Formula: see text] are studied in this paper and found the satisfactory behaviors. Moreover we additionally focus on the two geometric diagnostics, the statefinder [Formula: see text] and [Formula: see text] to discriminant BHDE model from the [Formula: see text]CDM model. Here we determined and plotted the trajectories of evolution for statefinder [Formula: see text], [Formula: see text] and [Formula: see text] diagnostic plane to understand the geometrical behavior of the BHDE model by utilizing Planck 2018 observational information. Finally, we have explored the new Barrow exponent △, which strongly affects the dark energy equation of state that can lead it to lie in the quintessence regime, phantom regime and exhibits the phantom-divide line during the cosmological evolution.

scholarly journals Observational constraints and stability in viscous gravity

2020 ◽  
Vol 98 (12) ◽  
pp. 1119-1124
Author(s):  
T. Mirzaei Rezaei ◽  
Alireza Amani ◽  
E. Yusofi ◽  
S. Rouhani ◽  
M.A. Ramzanpour
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Teleparallel Gravity ◽  
System Stability ◽  
Accelerated Expansion ◽  
Tetrad Field ◽  
Dark Energy Component ◽  
Walker Metric ◽  
Expansion Of The Universe ◽  
The Universe

In this paper, we study the [Formula: see text] gravity model in the presence of bulk viscosity by the flat Friedmann–Robertson–Walker metric. The field equation is obtained by teleparallel gravity with a tetrad field. The universe components are considered matter and dark energy, with the dark energy component associated with viscous [Formula: see text] gravity. After calculating the Friedmann equations, we obtain the energy density, pressure, and equation of state of dark energy in terms of the redshift parameter. Afterward, we plot the corresponding cosmological parameters versus the redshift parameter and examine the accelerated expansion of the universe. In the end, we explore the system stability using a function called the speed sound parameter.

scholarly journals Using a multi-messenger and multi-wavelength observational strategy to probe the nature of dark energy through direct measurements of cosmic expansion history

2021 ◽  
Vol 2021 (12) ◽  
pp. 042
Author(s):  
Jing-Zhao Qi ◽  
Shang-Jie Jin ◽  
Xi-Long Fan ◽  
Jing-Fei Zhang ◽  
Xin Zhang
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Data Sets ◽  
Energy Parameters ◽  
Energy Models ◽  
Redshift Drift ◽  
Multi Wavelength ◽  
Weak Constraints ◽  
Almost All ◽  
Observational Strategy

Abstract In the near future, the redshift drift observations in optical and radio bands will provide precise measurements on H(z) covering the redshift ranges of 2<z<5 and 0<z<0.3. In addition, gravitational wave (GW) standard siren observations could make measurements on the dipole anisotropy of luminosity distance, which will also provide the H(z) measurements in the redshift range of 0<z<3. In this work, we propose a multi-messenger and multi-wavelength observational strategy to measure H(z) based on the three next-generation projects, E-ELT, SKA, and DECIGO, and we wish to see whether the future H(z) measurements could provide tight constraints on dark-energy parameters. The dark energy models we consider include ΛCDM, wCDM, CPL, HDE, and IΛCDM models. It is found that E-ELT, SKA1, and DECIGO are highly complementary in constraining dark energy models. Although any one of these three data sets can only give rather weak constraints on each model we consider, the combination of them could significantly break the parameter degeneracies and give much tighter constraints on almost all the cosmological parameters. Moreover, we find that the combination of E-ELT, SKA1, DECIGO, and CMB could further improve the constraints on dark energy parameters, e.g., σ(w 0)=0.024 and σ(w a)=0.17 in the CPL model, which means that these three promising probes will play a key role in helping reveal the nature of dark energy.

scholarly journals Study of growth matter index and cosmic implications in dynamical Chern–Simons modified gravity

2021 ◽  
Vol 81 (8) ◽  
Author(s):  
Abdul Jawad ◽  
Shamaila Rani ◽  
Saba Qummer ◽  
Amir Sharif
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Growth Index ◽  
Simons Theory ◽  
Cosmic Expansion ◽  
Acceleration Of The Universe ◽  
Expansion Of The Universe ◽  
Chern Simons ◽  
The Universe

AbstractIn the framework of dynamical Chern–Simons theory of gravity, we study the recent cosmic expansion with acceleration of the universe. We take interacting scenario of dark energy and dark matter with three cutoffs like Granda–Oliveros, higher order derivative of Hubble parameter and generalized holographic dark energy model. In the flat Friedmann–Robertson–Walker universe, well-known cosmological parameters have been calculated. We study the perturbation of matter density growth, growth factor and growth index behavior for the underlying framework. The cosmological parameters like equation of state parameter, deceleration parameter, and stability of each model are discussed. The outcomes of these models represent the cosmic expansion of the universe with acceleration.

Kantowski–Sachs universe with dark energy fluid and massive scalar field

2020 ◽  
Vol 98 (11) ◽  
pp. 993-998
Author(s):  
K. Deniel Raju ◽  
M.P.V.V. Bhaskara Rao ◽  
Y. Aditya ◽  
T. Vinutha ◽  
D.R.K. Reddy
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Massive Scalar ◽  
Field Equations ◽  
Massive Scalar Field ◽  
Anisotropic Dark Energy ◽  
Expansion Of The Universe ◽  
The Universe

This study is mainly concerned with a spatially homogeneous and anisotropic Kantowski–Sachs cosmological model with anisotropic dark energy fluid and massive scalar field. We solve the field equations using (i) the shear scalar proportionality to the expansion scalar and (ii) a mathematical condition that is a consequence of the power law between the scalar field and the average scale factor of the universe, and the corresponding dark energy model is presented. The cosmological parameters of the model are computed and discussed, as well as the relevance of its dynamical aspects to the recent scenario of the accelerated expansion of the universe.

Sharma–Mittal holographic dark energy model in conharmonically flat space-time

2020 ◽  
Vol 18 (01) ◽  
pp. 2150002
Author(s):  
Vipin Chandra Dubey ◽  
Umesh Kumar Sharma ◽  
Anirudh Pradhan
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Field Potential ◽  
Flat Space ◽  
Accelerated Expansion ◽  
Frw Universe ◽  
Eos Parameter ◽  
Expansion Of The Universe ◽  
Quintessence Field ◽  
The Universe

In this work, we explore the accelerated expansion of the conharmonically flat space in relation to an isotropic and spatially homogeneous Friedmann–Robertson–Walker (FRW) universe through a newly proposed dark energy (DE) model namely Sharma–Mittal holographic DE (SMHDE) by taking Hubble horizon as an IR cut-off and also by considering the deceleration parameter as a linear function of Hubble parameter as [Formula: see text], where [Formula: see text] and [Formula: see text] are arbitrary constants. The analysis of different cosmological parameters, equation of state (EoS) parameter, squared speed of sound, statefinder, [Formula: see text] pair, and quintessence field model has been calculated and discussed in detail. Analyzing the behavior of such cosmological parameters graphically, it is found that the SMHDE model can lead to the accelerated expansion of the universe at present epoch. We have also reconciled the DE with scalar field potential. For this analysis, we take into account the quintessence field for this reconstruction.

scholarly journals Cosmic Consequences of Kaniadakis and Generalized Tsallis Holographic Dark Energy Models in the Fractal Universe

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Abdul Jawad ◽  
Abdul Malik Sultan
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Apparent Horizon ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Accelerated Expansion ◽  
Energy Models ◽  
Expansion Of The Universe ◽  
The Stability ◽  
The Universe

We investigate the recently proposed holographic dark energy models with the apparent horizon as the IR cutoff by assuming Kaniadakis and generalized Tsallis entropies in the fractal universe. The implications of these models are discussed for both the interacting ( Γ = 3 H b 2 ρ m ) and noninteracting ( b 2 = 0 ) cases through different cosmological parameters. Accelerated expansion of the universe is justified for both models through deceleration parameter q . In this way, the equation of state parameter ω d describes the phantom and quintessence phases of the universe. However, the coincidence parameter r ~ = Ω m / Ω d shows the dark energy- and dark matter-dominated eras for different values of parameters. It is also mentioned here that the squared speed of sound gives the stability of the model except for the interacting case of the generalized Tsallis holographic dark energy model. It is mentioned here that the current dark energy models at the apparent horizon give consistent results with recent observations.

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