scholarly journals Cosmological constraints from unWISE and Planck CMB lensing tomography

2021 ◽  
Vol 2021 (12) ◽  
pp. 028
Author(s):  
Alex Krolewski ◽  
Simone Ferraro ◽  
Martin White
Keyword(s):  
Dark Energy ◽  
Cross Correlation ◽  
Cosmological Parameters ◽  
Model Fit ◽  
Cosmological Constraints ◽  
A Value ◽  
Λcdm Model ◽  
The Universe

Abstract A number of recent, low-redshift, lensing measurements hint at a universe in which the amplitude of lensing is lower than that predicted from the ΛCDM model fit to the data of the Planck CMB mission. Here we use the auto- and cross-correlation signal of unWISE galaxies and Planck CMB lensing maps to infer cosmological parameters at low redshift. In particular, we consider three unWISE samples (denoted as "blue", "green" and "red") at median redshifts z ∼ 0.6, 1.1 and 1.5, which fully cover the Dark Energy dominated era. Our cross-correlation measurements, with combined significance S/N ∼ 80, are used to infer the amplitude of low-redshift fluctuations, σ8; the fraction of matter in the Universe, Ω m ; and the combination S8 ≡ σ8 (Ω m /0.3)0.5 to which these low-redshift lensing measurements are most sensitive. The combination of blue, green and red samples gives a value S m  = 0.784 ± 0.015, that is fully consistent with other low-redshift lensing measurements and in 2.4σ tension with the CMB predictions from Planck. This is noteworthy, because CMB lensing probes the same physics as previous galaxy lensing measurements, but with very different systematics, thus providing an excellent complement to previous measurements.

scholarly journals Physical Acceptability of the Renyi, Tsallis and Sharma-Mittal Holographic Dark Energy Models in the f(T,B) Gravity under Hubble’s Cutoff

Universe ◽  
2021 ◽  
Vol 7 (3) ◽  
pp. 67
Author(s):  
Salim Harun Shekh ◽  
Pedro H. R. S. Moraes ◽  
Pradyumn Kumar Sahoo
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Field Equations ◽  
Eos Parameter ◽  
Two Fluids ◽  
Gravitational Field Equations ◽  
Energy Models ◽  
Different Types ◽  
The Universe

In the present article, we investigate the physical acceptability of the spatially homogeneous and isotropic Friedmann–Lemâitre–Robertson–Walker line element filled with two fluids, with the first being pressureless matter and the second being different types of holographic dark energy. This geometric and material content is considered within the gravitational field equations of the f(T,B) (where T is the torsion scalar and the B is the boundary term) gravity in Hubble’s cut-off. The cosmological parameters, such as the Equation of State (EoS) parameter, during the cosmic evolution, are calculated. The models are stable throughout the universe expansion. The region in which the model is presented is dependent on the real parameter δ of holographic dark energies. For all δ≥4.5, the models vary from ΛCDM era to the quintessence era.

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.

GROWTH INDEX AND MODIFIED GRAVITY

2011 ◽  
Vol 01 ◽  
pp. 228-233
Author(s):  
YUNGUI GONG
Keyword(s):  
Growth Rate ◽  
Dark Energy ◽  
Modified Gravity ◽  
Growth Index ◽  
Accurate Approximation ◽  
Energy Models ◽  
Λcdm Model ◽  
The Universe ◽  
Matter Energy ◽  
Matter Perturbation

The growth rate of matter perturbation and the expansion rate of the Universe can be used to distinguish modified gravity and dark energy models. Remarkably, the growth rate can be approximated as Ωγ. We discuss the dependence of the growth index γ on the dimensionless matter energy density Ω for a more accurate approximation of the growth factor. The observational data are used to fit different models. The data strongly disfavor the Dvali-Gabadadze-Porrati model. For the ΛCDM model, we find that [Formula: see text]. For the Dvali-Gabadadze-Porrati model, we find that [Formula: see text].

Testing anisotropy and comparison of various supernova data constraints on dark energy model

2019 ◽  
Vol 34 (34) ◽  
pp. 1950276 ◽  
Author(s):  
H. Hossienkhani ◽  
H. Yousefi ◽  
N. Azimi
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Cosmological Parameters ◽  
Acoustic Oscillation ◽  
Maximum Likelihood Analysis ◽  
Accelerating Expansion ◽  
Combining Data ◽  
Likelihood Analysis ◽  
Data Constraints ◽  
The Universe

We study the possibly existing anisotropy in the accelerating expansion Universe with various supernovae data, the baryon acoustic oscillation and the observational Hubble data. We present combined results from these probes, deriving constraints on the equation of state (EoS), [Formula: see text], of dark energy (DE) and its energy density in the Universe. We fit the cosmological parameters simultaneously employing the maximum likelihood analysis. By combining data and considering anisotropy effects, we find that the EoS of DE are [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] within [Formula: see text] confidence level. Finally, introducing an anisotropy appears to improve the fit to observations with respect to that provided by an isotropic [Formula: see text]CDM model.

scholarly journals UNIVERSE WITH HOLOGRAPHIC DARK ENERGY

MOMENTO ◽  
2020 ◽  
pp. 1-10
Author(s):  
Carlos Rodriguez-Benites ◽  
Mauricio Cataldo ◽  
Marcial Vásquez-Arteaga
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Cold Dark Matter ◽  
Holographic Dark Energy ◽  
Cosmological Parameters ◽  
Holographic Dark Energy Model ◽  
Dark Sector ◽  
Algebraic Expressions ◽  
Proposed Model ◽  
Λcdm Model

In this work we explore a Holographic Dark Energy Model in a flat Friedmann-LemaÎtre-Robertson-Walker Universe, which contains baryons, radiation, cold dark matter and dark energy within the framework of General Relativity. Furthermore, we consider three types of phenomenological interactions in the dark sector. With the proposed model we obtained the algebraic expressions for the cosmological parameters of our interest: the deceleration and coincidence parameters. Likewise, we graphically compare the proposed model with the ΛCDM model.

scholarly journals The dark sector cosmology

2020 ◽  
Vol 29 (14) ◽  
pp. 2030014
Author(s):  
Elcio Abdalla ◽  
Alessandro Marins
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Acoustic Oscillations ◽  
Dark Sector ◽  
Fundamental Physics ◽  
Observational Techniques ◽  
Distance Indicators ◽  
The Universe ◽  
Theoretical Developments

The most important problem in fundamental physics is the description of the contents of the Universe. Today, we know that 95% thereof is totally unknown. Two thirds of that amount is the mysterious Dark Energy described in an interesting and important review [E. J. Copeland, M. Sami and S. Tsujikawa, Int. J. Mod. Phys. D 15 (2006) 1753]. We briefly extend here the ideas contained in that review including the more general Dark Sector, that is, Dark Matter and Dark Energy, eventually composing a new physical Sector. Understanding the Dark Sector with precision is paramount for us to be able to understand all the other cosmological parameters comprehensively as modifications of the modeling could lead to potential biases of inferred parameters of the model, such as measurements of the Hubble constant and distance indicators such as the Baryon Acoustic Oscillations. We discuss several modern methods of observation that can disentangle the different possible descriptions of the Dark Sector. The possible applications of some theoretical developments are also included in this paper as well as a more thorough evaluation of new observational techniques at lower frequencies and gravitational waves.

scholarly journals Constraints on barotropic dark energy models by a new phenomenological q(z) parameterization

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Jaime Román-Garza ◽  
Tomás Verdugo ◽  
Juan Magaña ◽  
Verónica Motta
Keyword(s):  
Dark Energy ◽  
Joint Analysis ◽  
Effective Equation ◽  
Phantom Divide ◽  
Plane Analysis ◽  
Energy Models ◽  
A Value ◽  
Type Ia ◽  
Ia Supernovae ◽  
The Universe

Abstract In this paper, we propose a new phenomenological two parameter parameterization of q(z) to constrain barotropic dark energy models by considering a spatially flat Universe, neglecting the radiation component, and reconstructing the effective equation of state (EoS). This two free-parameter EoS reconstruction shows a non-monotonic behavior, pointing to a more general fitting for the scalar field models, like thawing and freezing models. We constrain the q(z) free parameters using the observational data of the Hubble parameter obtained from cosmic chronometers, the joint-light-analysis Type Ia Supernovae (SNIa) sample, the Pantheon (SNIa) sample, and a joint analysis from these data. We obtain, for the joint analysis with the Pantheon (SNIa) sample a value of q(z) today, $$q_0=-0.51\begin{array}{c} +0.09 \\ -0.10 \end{array}$$q0=-0.51+0.09-0.10, and a transition redshift, $$z_t=0.65\begin{array}{c} +0.19 \\ -0.17 \end{array}$$zt=0.65+0.19-0.17 (when the Universe change from an decelerated phase to an accelerated one). The effective EoS reconstruction and the $$\omega '$$ω′–$$\omega $$ω plane analysis point towards a transition over the phantom divide, i.e. $$\omega =-1$$ω=-1, which is consistent with a non parametric EoS reconstruction reported by other authors.

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.

scholarly journals Interactions in the dark sector of the Universe

2014 ◽  
Vol 11 (02) ◽  
pp. 1460014 ◽  
Author(s):  
Winfried Zimdahl
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Dark Sector ◽  
Future Evolution ◽  
Evolution Of The Universe ◽  
Λcdm Model ◽  
The Future ◽  
The Universe

Interactions inside the cosmological dark sector influence the cosmological dynamics. As a consequence, the future evolution of the Universe may be different from that predicted by the ΛCDM model. We review main features of several recently studied models with nongravitational couplings between dark matter and dark energy.

Observational and astrophysical cosmology: 1980–2018

2019 ◽  
pp. 375-423
Author(s):  
Malcolm S. Longair
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Cosmological Constant ◽  
Large Scale ◽  
Cosmological Parameters ◽  
Semiconductor Detectors ◽  
Empirical Knowledge ◽  
Global Geometry ◽  
The Universe ◽  
Large Scale Structure Formation

Since 1980, our empirical knowledge of the universe has advanced tremendously and precision cosmology has become a reality. These developments have been largely technology-driven, the result of increased computer power, new generations of telescopes for all wavebands, new types of semiconductor detectors, such as CCDs, and major investments by many nations in superb observing facilities. The discipline also benefitted from the influx of experimental and theoretical physicists into the cosmological arena. The accuracy and reliability of the values of the cosmological parameters has improved dramatically, many of them now being known to about 1%. The ΛCDM model provides a remarkable fit to all the observational data, demonstrating that the cosmological constant is non-zero and that the global geometry of the universe is flat. The underlying physics of galaxy and large-scale structure formation has advanced dramatically and demonstrated the key roles played by dark matter and dark energy.

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