Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userReconciling Hubble Constant Discrepancy from Holographic Dark Energy
180
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Holographic dark energy (HDE) describes the vacuum energy in a cosmic IR region whose total energy saturates the limit of avoiding the collapse into a black hole. HDE predicts that the dark energy equation of the state transiting from greater than the $-1$ regime to less than $-1$, accelerating the Universe slower at the early stage and faster at the late stage. We propose the HDE as a new {it physical} resolution to the Hubble constant discrepancy between the cosmic microwave background (CMB) and local measurements. With Planck CMB and galaxy baryon acoustic oscillation (BAO) data, we fit the HDE prediction of the Hubble constant as $H_0^{}!=, 71.54pm1.78,mathrm{km,s^{-1} Mpc^{-1}}$, consistent with local $H_0^{}$ measurements by LMC Cepheid Standards (R19) at $1.4sigma$ level. Combining Planck+BAO+R19, we find the HDE parameter $c=0.51pm0.02$ and $H_0^{}! = 73.12pm 1.14,mathrm{km ,s^{-1} Mpc^{-1}}$, which fits cosmological data at all redshifts. Future CMB and large-scale structure surveys will further test the holographic scenario.
rate research
Read More
We consider holographic cosmological models of dark energy in which the infrared cutoff is set by the Hubbles radius. We show that any interacting dark energy model with a matter like term able to alleviate the coincidence problem (i.e., with a positive interaction term, regardless of its detailed form) can be recast as a noninteracting model in which the holographic parameter evolves slowly with time. Two specific cases are analyzed. First, the interacting model presented in [1] is considered, and its corresponding noninteracting version found. Then, a new noninteracting model, with a specific expression of the time-dependent holographic parameter, is proposed and analyzed along with its corresponding interacting version. We constrain the parameters of both models using observational data, and show that they can be told apart at the perturbative level.
We consider holographic cosmological models of dark energy in which the infrared cutoff is set by the Hubbles radius. We show that any interacting dark energy model, regardless of its detailed form, can be recast as a non interacting model in which the holographic parameter $c^{2}$ evolves slowly with time. Two specific cases are analyzed. We constrain the parameters of both models with observational data, and show that they can be told apart at the perturbative level.
We investigate a generalized form of the phenomenologically emergent dark energy model, known as generalized emergent dark energy (GEDE), introduced by Li and Shafieloo [Astrophys. J. {bf 902}, 58 (2020)] in light of a series of cosmological probes and considering the evolution of the model at the level of linear perturbations. This model introduces a free parameter $Delta$ that can discriminate between the $Lambda$CDM (corresponds to $Delta=0$) or the phenomenologically emergent dark energy (PEDE) (corresponds to $Delta=1$) models, allowing us to determine which model is preferred most by the fit of the observational datasets. We find evidence in favor of the GEDE model for Planck alone and in combination with R19, while the Bayesian model comparison is inconclusive when Supernovae Type Ia or BAO data are included. In particular, we find that $Lambda$CDM model is disfavored at more than $2sigma$ CL for most of the observational datasets considered in this work and PEDE is in agreement with Planck 2018+BAO+R19 combination within $1sigma$ CL.
We use Pantheon Type Ia supernova (SN Ia) apparent magnitude, DES-3yr binned SN Ia apparent magnitude, Hubble parameter, and baryon acoustic oscillation measurements to constrain six spatially flat and non-flat cosmological models. These sets of data provide mutually consistent cosmological constraints in the six cosmological models we study. A joint analysis of these data sets provides model-independent estimates of the Hubble constant, $H_0=68.8pm1.8 rm{km s^{-1} Mpc^{-1}}$, and the non-relativistic matter density parameter, $Omega_{rm m_0}=0.294pm0.020$. Although the joint constraints prefer mild dark energy dynamics and a little spatial curvature, they do not rule out dark energy being a cosmological constant and flat spatial hypersurfaces. We also add quasar angular size and H II starburst galaxy measurements to the combined data set and find more restrictive constraints.
The Hubble tension can be significantly eased if there is an early component of dark energy that becomes active around the time of matter-radiation equality. Early dark energy models suffer from a coincidence problem -- the physics of matter-radiation equality and early dark energy are completely disconnected, so some degree of fine-tuning is needed in order for them to occur nearly simultaneously. In this paper we propose a natural explanation for this coincidence. If the early dark energy scalar couples to neutrinos then it receives a large injection of energy around the time that neutrinos become non-relativistic. This is precisely when their temperature is of order their mass, which, coincidentally, occurs around the time of matter-radiation equality. Neutrino decoupling therefore provides a natural trigger for early dark energy by displacing the field from its minimum just before matter-radiation equality. We discuss various theoretical aspects of this proposal, potential observational signatures, and future directions for its study.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
