Addressing the Hubble Tension: Insights from Reversible and Irreversible Thermodynamic Processes

Abstract

We investigate reversible and irreversible thermodynamic processes in cosmology and their impact on the Hubble tension. Gravitationally induced adiabatic matter creation/annihilation is treated as irreversible, while energy exchange between the cosmic bulk and horizon is modeled as reversible. Two scenarios are proposed: Model I features matter creation/annihilation across all species with energy transfer to effective entropic dark energy; Model II considers dark matter creation/annihilation with energy flow from baryonic matter and radiation. The creation rate is parameterized as $Γ(t)=Γ_0 H$, with energy transfer controlled by $γ$. We constrain both models using Pantheon$+$ supernovae, CMB distance priors, baryon acoustic oscillations, gamma-ray bursts, and cosmic chronometers, with and without SH$_0$ES. When SH$_0$ES is included, matter annihilation ($Γ_0<0$) is statistically preferred, yielding $H_0 = 71.75 \pm 0.79$ km s$^{-1}$ Mpc$^{-1}$ (Model I) and $H_0 = 71.06 \pm 0.81$ km s$^{-1}$ Mpc$^{-1}$ (Model II), corresponding to $1.2σ$ and $1.8σ$ consistency with the SH$_0$ES value $73.17 \pm 0.86$ km s$^{-1}$ Mpc$^{-1}$. Matter creation ($Γ_0>0$) or pure energy flow ($Γ=0$) do not improve the tension. Without SH$_0$ES, information criteria show no preference over $Λ$CDM. For the matter annihilation/creation with energy flow, the effective entropic dark energy evolves dynamically, mimicking radiation and matter before recombination and approaching a cosmological constant at late times. These results demonstrate that thermodynamically motivated interactions can alleviate the Hubble tension when calibrated with local measurements, while remaining consistent with cosmological data.

Figures (13)

• Figure 1: Contour plots representing $68\%$ and $95\%$ confidence regions for Models I, II, and $\Lambda$CDM with Pantheon$+$$\&$SH0ES+CMB+BAO+GRB+CC data. Priors: $\gamma > 0$ and $\Gamma_0$ free.
• Figure 2: Same as Fig. \ref{['contourPlot_1']} but with matter creation/annihilation function $\Gamma(t)=0$.
• Figure 3: Same as Fig. \ref{['contourPlot_1']} but with $\gamma=0$ and prior $\Gamma_0<0$.
• Figure 4: Same as Fig. \ref{['contourPlot_1']} but with $\gamma=0$ and prior $\Gamma_0>0$.
• Figure 5: Contour plots representing $68\%$ and $95\%$ confidence regions for Models I, II, and $\Lambda$CDM with Pantheon$+$+CMB+BAO+GRB+CC data (without SH0ES). Priors: $\gamma > 0$ and $\Gamma_0$ free.