We study the scenario of Kaniadakis horizon-entropy cosmology, which arises from the application of the gravity-thermodynamics conjecture using the Kaniadakis modified entropy. The resulting modified Friedmann equations contain extra terms that constitute an effective dark energy sector. We use data from cosmic chronometers, Type Ia supernova, H ii galaxies, strong lensing systems, and baryon acoustic oscillation observations, and we apply a Bayesian Markov chain Monte Carlo analysis to construct the likelihood contours for the model parameters. We find that the Kaniadakis parameter is constrained around 0, namely around the value where the standard Bekenstein–Hawking is recovered. Concerning the normalized Hubble parameter, we find |$h=0.708^{+0.012}_{-0.011}$|⁠, a result that is independently verified by applying the |$\mathbf {\mathbb {H}}0(z)$| diagnostic and, thus, we conclude that the scenario at hand can alleviate the H₀ tension problem. Regarding the transition redshift, the reconstruction of the cosmographic parameters gives |$z_{\rm T}=0.715^{+0.042}_{-0.041}$|⁠. Furthermore, we apply the Akaike, Bayesian, and deviance information criteria, and we find that in most data sets the scenario is statistical equivalent to Λ cold dark matter one. Moreover, we examine the big bang nucleosynthesis, and we show that the scenario satisfies the corresponding requirements. Additionally, we perform a phase-space analysis, and we show that the Universe past attractor is the matter-dominated epoch, while at late times the Universe results in the dark-energy-dominated solution. Finally, we show that Kaniadakis horizon-entropy cosmology accepts heteroclinic sequences, but it cannot exhibit bounce and turnaround solutions.

In this work we explore an alternative phenomenological model to Chaplygin gas proposed by Hova et al. (Int J Mod Phys D 26:1750178, 2017), consisting on a modification of a perfect fluid, to explain...

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

Recently, a phenomenologically emergent dark energy (PEDE) model was presented with a dark energy density evolving as |$\widetilde{\Omega }_{\rm {DE}}(z)\, =\, \Omega _{\rm {DE,0}}\left[ 1 - {\rm {tanh}}\left( {\log }_{10}(1+z) \right) \right]$|⁠, i.e. with no degree of freedom. Later on, a generalized model was proposed by adding one degree of freedom to the PEDE model, encoded in the parameter Δ. Motivated by these proposals, we constrain the parameter space (⁠|$h,\Omega _m^{(0)}$|⁠) and (⁠|$h,\Omega _m^{(0)}, \Delta$|⁠) for PEDE and Generalized Emergent Dark Energy (GEDE) respectively, by employing the most recent observational (non-)homogeneous and differential age Hubble data. Additionally, we reconstruct the deceleration and jerk parameters and estimate yield values at z = 0 of |$q_0 = -0.784^{+0.028}_{-0.027}$| and |$j_0 = 1.241^{+0.164}_{-0.149}$| for PEDE and |$q_0 = -0.730^{+0.059}_{-0.067}$| and |$j_0 = 1.293^{+0.194}_{-0.187}$| for GEDE using the homogeneous sample. We report values on the deceleration-acceleration transition redshift with those reported in the literature within 2σ CL. Furthermore, we perform a stability analysis of the PEDE and GEDE models to study the global evolution of the Universe around their critical points. Although the PEDE and GEDE dynamics are similar to the standard model, our stability analysis indicates that in both models there is an accelerated phase at early epochs of the Universe evolution.

In this work, we use an observational approach and dynamical system analysis to study the cosmological model recently proposed by Saridakis (2020), which is based on the modification of the entropy-area black hole relation proposed by Barrow (2020). The Friedmann equations governing the dynamics of the Universe under this entropy modification can be calculated through the gravity-thermodynamics conjecture. We investigate two models, one considering only a matter component and the other including matter and radiation, which have new terms compared to the standard model sourcing the late cosmic acceleration. A Bayesian analysis is performed in which using five cosmological observations (observational Hubble data, type Ia supernovae, HII galaxies, strong lensing systems, and baryon acoustic oscillations) to constrain the free parameters of both models. From a joint analysis, we obtain constraints that are consistent with the standard cosmological paradigm within 2σ confidence level. In addition, a complementary dynamical system analysis using local and global variables is developed which allows obtaining a qualitative description of the cosmology. As expected, we found that the dynamical equations have a de Sitter solution at late times.

Fractional cosmology modifies the standard derivative to Caputo’s fractional derivative of order μ, generating changes in General Relativity. Friedmann equations are modified, and the evolution of the species densities depends on μ and the age of the Universe t_U. We estimate stringent constraints on μ using cosmic chronometers, Type Ia supernovae, and joint analysis. We obtain |$\mu =2.839^{+0.117}_{-0.193}$| within the 1σ confidence level providing a non-standard cosmic acceleration at late times; consequently, the Universe would be older than the standard estimations. Additionally, we present a stability analysis for different μ values. This analysis identifies a late-time attractor corresponding to a power-law decelerated solution for μ < 2. Moreover, a non-relativistic critical point exists for μ > 1 and a sink for μ > 2. This solution is a decelerated power-law if 1 < μ < 2 and an accelerated power-law solution if μ > 2, consistent with the mean values obtained from the observational analysis. Therefore, for both flat FLRW and Bianchi I metrics, the modified Friedmann equations provide a late cosmic acceleration under this paradigm without introducing a dark energy component. This approach could be a new path to tackling unsolved cosmological problems.