Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Dark Energy with Constant Inertial Mass Density: Updated Constraints and Curvature-Induced Sign Transitions in $ρ_{\rm DE}$ and $ρ_{\rm DE}+p_{\rm DE}$

Luis A. Escamilla, Berat Karadavut, Nihan Katırcı

Abstract

We present updated observational constraints on the simple-gDE model, characterized by a constant inertial mass density (IMD) $ρ_{\rm DE}+p_{\rm DE}$,which belongs to the broader graduated dark energy family, and compare its cosmological implications with those of the $w$CDM and the $Λ$CDM models. This parametrization provides a physically motivated, one-parameter extension of $Λ$CDM, perspective on DE dynamics beyond the usual equation-of-state approach. We use the newly released DESI DR2 BAO data in combination with either CMB measurements from Planck 2018 or late-time probes, CC and the Pantheon+ SNe Ia sample, considered both with and without SH0ES calibration in this analysis. The data favor a small positive IMD, and Bayesian evidence indicates that the models remain statistically indistinguishable within spatially flat scenarios. Consequently, none of these models exhibits a sign transition in the DE energy density, and no improvement in $H_0$ tension. Allowing spatial curvature qualitatively enlarges the phenomenology of the dark sector. In particular, the interplay between spatial curvature and a nonzero IMD permits sign transitions in both the effective dark-energy density and the IMD during cosmic evolution. For the BAO+CC+SN+SH0ES dataset, the $o$Simple-gDE model yields a transition redshift $z^\dagger = 1.51^{+0.68}_{-0.34}$, while the crossing of the Null Energy Condition boundary (NECB), defined by $ρ_{\rm DE}+p_{\rm DE}=0$, occurs at $z_{\rm NECB}=2.36^{+1.48}_{-1.48}$. The model is statistically favored over $oΛ$CDM and $ow$CDM. These results highlight the potential role of IMD as a fundamental parameter in DE phenomenology and demonstrate that geometric effects, such as spatial curvature, can reveal dynamical features of the dark sector that remain hidden within the spatially flat $Λ$CDM framework.

Dark Energy with Constant Inertial Mass Density: Updated Constraints and Curvature-Induced Sign Transitions in $ρ_{\rm DE}$ and $ρ_{\rm DE}+p_{\rm DE}$

Abstract

We present updated observational constraints on the simple-gDE model, characterized by a constant inertial mass density (IMD) ,which belongs to the broader graduated dark energy family, and compare its cosmological implications with those of the CDM and the CDM models. This parametrization provides a physically motivated, one-parameter extension of CDM, perspective on DE dynamics beyond the usual equation-of-state approach. We use the newly released DESI DR2 BAO data in combination with either CMB measurements from Planck 2018 or late-time probes, CC and the Pantheon+ SNe Ia sample, considered both with and without SH0ES calibration in this analysis. The data favor a small positive IMD, and Bayesian evidence indicates that the models remain statistically indistinguishable within spatially flat scenarios. Consequently, none of these models exhibits a sign transition in the DE energy density, and no improvement in tension. Allowing spatial curvature qualitatively enlarges the phenomenology of the dark sector. In particular, the interplay between spatial curvature and a nonzero IMD permits sign transitions in both the effective dark-energy density and the IMD during cosmic evolution. For the BAO+CC+SN+SH0ES dataset, the Simple-gDE model yields a transition redshift , while the crossing of the Null Energy Condition boundary (NECB), defined by , occurs at . The model is statistically favored over CDM and CDM. These results highlight the potential role of IMD as a fundamental parameter in DE phenomenology and demonstrate that geometric effects, such as spatial curvature, can reveal dynamical features of the dark sector that remain hidden within the spatially flat CDM framework.
Paper Structure (19 sections, 36 equations, 13 figures, 7 tables)

This paper contains 19 sections, 36 equations, 13 figures, 7 tables.

Table of Contents

  1. Introduction
  2. Non-null DE Inertial mass density
  3. $w$CDM: Constant EoS parameter having dynamical non-null IMD
  4. Simple Graduated Dark Energy: Constant IMD
  5. Spatial curvature together with non-null constant IMD of DE
  6. $o\Lambda$CDM and $ow$CDM models
  7. Sign transition in DE energy density
  8. Sign transition in DE IMD
  9. o-Simple gDE
  10. Sign transition in DE energy density
  11. Sign transition in DE IMD
  12. Observational Data Analysis
  13. Methodology of Cosmological Data Analysis
  14. Data sets
  15. Bayesian Model Comparison
  16. ...and 4 more sections

Figures (13)

  • Figure 1: One- and two-dimensional ($68\%$ and $95\%$ CLs) marginalized posterior distributions for the free parameters of $\Lambda$CDM model using the combined datasets.
  • Figure 2: One- and two-dimensional ($68\%$ and $95\%$ CLs) marginalized posterior distributions for the free parameters of $w$CDM model using the combined datasets.
  • Figure 3: Joint constraints in the $(\varrho,H_0)$ plane for the Simple-gDE (solid blue) and $w$CDM (dashed green) models from BAO+CMB+SN dataset. Contours represent the $1\sigma$ confidence regions. The grey point with error bars indicates the reference $\Lambda$CDM value (fixed $\varrho=0$), $H_0=68.15\pm0.44\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$.
  • Figure 4: One- and two-dimensional ($68\%$ and $95\%$ CLs) marginalized posterior distributions for the free parameters of Simple-gDE model using the combined datasets.
  • Figure 5: Joint constraints in the $(\varrho,H_0)$ plane for the Simple-gDE (solid blue) and $w$CDM (dashed green) models from BAO+CC+SN+SH0ES dataset. Contours represent the $1\sigma$ confidence regions. The grey point with error bars indicates the reference $\Lambda$CDM value (fixed $\varrho=0$), $H_0=70.57\pm0.96\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$.
  • ...and 8 more figures