We use observational data from Type Ia Supernovae (SN), Baryon Acoustic Oscillations (BAO), Cosmic Microwave Background (CMB) and observational Hubble data (OHD), and the Markov Chain Monte Carlo (MCMC) method, to constrain the cosmological scenario of holographic dark energy with varying gravitational constant. We consider both flat and non-flat background geometry, and we present the corresponding constraints and contour-plots of the model parameters. We conclude that the scenario is compatible with observations. In 1$σ$ we find $Ω_{\Lambda0}=0.72^{+0.03}_{-0.03}$, $Ω_{k0}=-0.0013^{+0.0130}_{-0.0040}$, $c=0.80^{+0.19}_{-0.14}$ and $Δ_G\equiv G'/G=-0.0025^{+0.0080}_{-0.0050}$, while for the present value of the dark energy equation-of-state parameter we obtain $w_0=-1.04^{+0.15}_{-0.20}$.
We use observational data from Supernovae (SNIa) Pantheon sample, as well as from direct measurements of the Hubble parameter from the cosmic chronometers (CC) sample, in order to extract constraints on the scenario of Barrow holographic dark energy. The latter is a holographic dark energy model based on the recently proposed Barrow entropy, which arises from the modification of the black-hole surface due to quantum-gravitational effects. We first consider the case where the new deformation exponent $Δ$ is the sole model parameter, and we show that although the standard value $Δ=0$, which corr…
A novel fractal structure for the cosmological horizon, inspired by COVID-19 geometry, which results in a modified area entropy, is applied to cosmology in order to serve dark energy. The constraints based on a complete set of observational data are derived. There is a strong Bayesian evidence in favor of such a dark energy in comparison to a standard $Λ$CDM model and that this energy cannot be reduced to a cosmological constant. Besides, there is a shift towards smaller values of baryon density parameter and towards larger values of the Hubble parameter, which reduces the Hubble tension.
Holographic Ricci dark energy: Current observational constraints, quintom feature, and the reconstruction of scalar-field dark energy
在这项工作中,我们考虑的宇宙学约束的全息里奇暗能量提出的高等。[Phys. Rev. D 79,043511(2009)],利用现有的观测数据。全息Ricci暗能量的主要特征由模型中的正数值参数$α$决定。当$α<1/2$时,全息里奇暗能量将表现出类似五等分的行为;即,它的状态方程将跨越宇宙常数边界$w=-1$。参数$α$只能通过观察确定。因此,利用观测数据约束参数$α$,对于刻画暗能量的演化特征和预测宇宙的命运具有非常重要的意义。本文利用307颗Ia型超新星的Union样本、Wilkinson微波各向异性探测器5年观测给出的宇宙微波背景位移参数和Sloan数字巡天的重子声学振荡测量结果,导出了全息Ricci暗能量模型的约束条件。联合分析给出了最佳拟合结果($σ$不确定度为1):$α=0.359^{+0.024}_{-0.025}$和$Ω_{\rm m0}=0.318^{+0.026}_{-0.024}$。也就是说,根据观测,全息利玛窦暗能量呈现出五分之一的特征。最后,根据宇宙学约束的结果,我们讨论了基于全息Ricci真空能量的标量场暗能量重构问题。
We consider the holographic Friedman-Robertson-Walker (hFRW) universe on the 4-dimensional membrane embedded in the 5-dimensional bulk spacetime and fit the parameters with the observational data. In order to fully account for the phenomenology of this scenario, we consider the models with the brane cosmological constant and the negative bulk cosmological constant. The contribution from the bulk is represented as the holographic dark fluid on the membrane. We derive the universal modified Friedmann equation by including all of these effects in both braneworld and holographic cutoff approaches.…
Four-dimensional cosmological models are studied on a boundary of a five-dimensional Anti-de Sitter (AdS_5) black hole with AdS Reissner-Nordstrom and scalar charged Reissner- Nordstrom black hole solutions, where we call the former a "Hairless" black hole and the latter a "Hairy" black hole. To obtain the Friedmann-Robertson-Walker (FRW) spacetime metric on the boundary of the AdS_5 black hole, we employ Eddington-Finkelstein (EF) coordinates to the bulk geometry. We then derive modified Friedmann equations on a boundary of the AdS_5 black hole via AdS/CFT correspondence and discuss its cosmo…
In this paper, we investigate a recent proposed model - so called the Tsallis holographic dark energy (THDE) model. In this case, we consider the non-gravitational and phenomenological interaction between dark sectors. We fit the free parameters of the model using Pantheon Supernovae Type Ia data, Baryon Acoustic Oscillations, Cosmic Microwave Background, Gamma-Ray burst and the the local value of the Hubble constant. We examine the THDE model to check its compatibility with observational data using objective Information Criterion (IC). We find that the THDE model cannot be supported by observ…
We investigate Kaniadakis-holographic dark energy by confronting it with observations. We perform a Markov Chain Monte Carlo analysis using cosmic chronometers, supernovae type Ia, and Baryon Acoustic Oscillations data. Concerning the Kaniadakis parameter, we find that it is constrained around zero, namely around the value in which Kaniadakis entropy recovers standard Bekenstein-Hawking one. Additionally, for the present matter density parameter $Ω_m^{(0)}$, we obtain a value slightly smaller compared to $Λ$CDM scenario. Furthermore, we reconstruct the evolution of the Hubble, deceleration and…
The holographic space-time approach to inflation provides a well defined and self-contained framework to study the early universe. Based on a quasi-local quantum gravity theory generalizing string theory beyond AdS backgrounds, it addresses fundamental questions like the arrow of time and the entropy of the initial cosmological state. It was recently argued that it also provides a naturel explanation for dark matter in the form of primordial black holes. The orignal idea however suffers from troubles that can be cured by considering instead Planck relics. This possibility is investigated and p…
In this research, we are interested in constraining the nonlinear interacting and noninteracting Tsallis holographic dark energy (THDE) with Ricci horizon cutoff by employing three observational datasets. To this aim, the THDE with Ricci horizon considering the noninteraction and nonlinear interaction terms will be fitted by the SNe Ia, SNe Ia+H(z), and SNe Ia+H(z)+GRB samples to investigate the Hubble ($H(z)$), dark energy equation of state ($ω_{DE}$), effective equation of state ($ω_{eff}$), and deceleration ($q$) parameters. Investigating the $H(z)$ parameter illustrates that our models are…
Observations restrict the parameter space of Holographic Dark Energy (HDE) so that a turning point in the Hubble parameter $H(z)$ is inevitable. Concretely, cosmic microwave background (CMB), baryon acoustic oscillations (BAO) and Type Ia supernovae (SNE) data put the turning point in the future, but removing SNE results in an observational turning point at positive redshift. From the perspective of theory, not only does the turning point violate the Null Energy Condition (NEC), but as we argue, it may be interpreted as an evolution of the Hubble constant $H_0$ with redshift, which is at odds …