Revisiting the Matter Creation Process: Observational Constraints on Gravitationally Induced Dark Energy and the Hubble Tension

TL;DR

The paper addresses the Hubble tension and the nature of dark energy by revisiting gravitationally induced particle creation as a late-time open-system phenomenon. It introduces four phenomenological PC models (PC1–PC4) with a created species of constant EOS $w_E$, each specified by a distinct particle-creation rate $\Gamma$, and constrains them against a joint dataset including Cosmic Chronometers, PantheonPlus SNe, DESI DR2 BAO, a compressed CMB likelihood, and SH0ES. The results show that PC models fit as well as $\Lambda$CDM, with $H_0$ around $69.3$ km s$^{-1}$ Mpc$^{-1}$ and $w^{\rm eff}_{\rm DE}(0)$ near $-1$, while reducing the Hubble tension to roughly $2.4$–$3\sigma$ without a clear Bayesian preference over $\Lambda$CDM$. This establishes gravitationally induced particle creation as a viable late-time extension that reproduces acceleration and offers a controlled framework to explore departures from $\Lambda$CDM, meriting further study of perturbations and microphysical underpinnings.

Abstract

The persistent Hubble tension and the lack of a fundamental explanation for dark energy motivate the exploration of alternative mechanisms capable of reproducing late-time cosmic acceleration. In this work, we revisit gravitationally induced particle creation as a phenomenological non-equilibrium process that can effectively mimic a dynamical dark-energy component. Within the thermodynamic framework of open systems, we model the production of an unspecified particle species with constant intrinsic equation-of-state parameter and consider four phenomenological parametrisations of the particle-creation rate. The modified continuity and Friedmann equations lead to an effective negative pressure and a redshift-dependent effective equation of state, which we constrain using Cosmic Chronometers, Pantheon+ supernovae, DESI DR2 BAO, a compressed CMB likelihood, and SH0ES data. Using the full dataset combination, we find that particle-creation models provide fits comparable to $Λ$CDM, yielding $H_0 \simeq 69.3\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$ and present-day effective dark-energy equation-of-state values close to $w^{\rm eff}_{\rm DE}(0)\simeq -1$, with all models predicting an accelerating Universe ($q_0\simeq -0.55$). When the Hubble tension is assessed using early- and late-time dataset splits, particle-creation scenarios reduce its statistical significance to the $\simeq 2.4σ$--$3σ$ level, compared to the $4.3σ$ discrepancy obtained in $Λ$CDM. Although deviations from $Λ$CDM remain mild and Bayesian model comparison indicates no statistical preference between models, gravitationally induced particle creation emerges as a viable late-time extension of the standard cosmological model and provides a consistent phenomenological framework for exploring departures from $Λ$CDM.

Figures (9)

• Figure 1: Triangular plots showing the 1D and 2D posterior distributions for the $\Lambda$CDM (left panels) and $w_0w_a$CDM (right panels) models, obtained using the CC+SN+SH0ES, BAO+CMB, and full CC+SN+SH0ES+BAO+CMB dataset combinations.
• Figure 2: Triangular plots showing the 1D and 2D posterior distributions for the PC models using the CC+SN+SH0ES, BAO+CMB, and full CC+SN+SH0ES+BAO+CMB dataset combinations. The panels correspond to PC1 (top left), PC2 (top right), PC3 (bottom left), and PC4 (bottom right).
• Figure 3: Plots of the function $H(z)/(1+z)$ for the PC models. The upper panels show the PC1 (left) and PC2 (right) models, while the lower panels show the PC3 (left) and PC4 (right) models. The functional posterior distributions are shown up to the $2\,\sigma$ level, based on the parameter constraints reported in Table \ref{['TableConstraintsFull']} for the CC+SN+SH0ES+BAO+CMB dataset combination. For comparison, the dashed curve corresponds to the $\Lambda$CDM model, using the best-fit parameter values from Table \ref{['TableConstraintsFull']}. The blue data points with error bars indicate the DESI DR2 BAO measurements, included as an illustrative subset of the data to demonstrate the agreement with observations.
• Figure 4: Plots of the deceleration parameter $q(z)$ for the PC models. The upper panels show the PC1 (left) and PC2 (right) models, while the lower panels show the PC3 (left) and PC4 (right) models. The functional posterior distributions are shown up to the $2\,\sigma$ level, based on the parameter constraints reported in Table \ref{['TableConstraintsFull']} for the CC+SN+SH0ES+BAO+CMB dataset combination. For comparison, the dashed curve corresponds to the $\Lambda$CDM model, using the best-fit parameter values from Table \ref{['TableConstraintsFull']}.
• Figure 5: Redshift evolution of the cosmological components in the PC1 model, computed using the best-fit parameter values from Table \ref{['TableConstraintsFull']} obtained in the joint CC+SN+SH0ES+BAO+CMB analysis. The fractional energy densities $\Omega_m(z)$, $\Omega_r(z)$, and $\Omega_E(z)$ are shown by the blue, red, and black curves, respectively.