Cosmological constraints on holographic dark energy models under the energy conditions

TL;DR

This paper investigates holographic and agegraphic dark energy models using observational data and energy conditions, analyzing their viability and constraints on model parameters, and comparing different cosmic cut-offs.

Contribution

It provides a comprehensive analysis of non-interacting holographic and agegraphic dark energy models with various cut-offs, using latest observational data and energy conditions to constrain parameters and assess model viability.

Findings

Matter density parameter around 0.26 across models

Agegraphic models recover standard cosmology as parameter c approaches infinity

Conformal time model is least favored among scenarios

Abstract

We study the holographic and agegraphic dark energy models without interaction using the latest observational Hubble parameter data (OHD), the Union2.1 compilation of type Ia supernovae (SNIa), and the energy conditions. Scenarios of dark energy are distinguished by the cut-off of cosmic age, conformal time, and event horizon. The best-fit value of matter density for the three scenarios almost steadily located at $\Omega_{m0}=0.26$ by the joint constraint. For the agegraphic models, they can be recovered to the standard cosmological model when the constant $c$ which presents the fraction of dark energy approaches to infinity. Absence of upper limit of $c$ by the joint constraint demonstrates the recovery possibility. Using the fitted result, we also reconstruct the current equation of state of dark energy at different scenarios, respectively. Employing the model criteria $\chi^2_{\textrm{min}}/dof$, we find that conformal time model is the worst, but they can not be distinguished clearly. Comparing with the observational constraints, we find that SEC is fulfilled at redshift $0.2 \lesssim z \lesssim 0.3$ with $1\sigma$ confidence level. We also find that NEC gives a meaningful constraint for the event horizon cut-off model, especially compared with OHD only. We note that the energy condition maybe could play an important role in the interacting models because of different degeneracy between $\Omega_m$ and constant $c$.