Bounce Inflation with Dynamical Dark Energy in Light of DESI DR2

TL;DR

This work investigates whether a non-singular Bounce Inflation (BI) scenario can be reconciled with late-time dynamical dark energy described by the CPL parameterization in light of DESI DR2, Planck PSA, and Pantheon+. The authors perform MCMC analyses with CLASS/MontePython, comparing BI and power-law (PL) primordial spectra under ΛCDM and CPL, and study the role of DESI DR2, weak lensing amplitude $A_L$, and spatial curvature $\Omega_k$. They find that DESI DR2 alone tends to raise $H_0$ in CPL-based fits, while BI with combined CPL and DESI DR2 yields $H_0 \approx 65.2^{+1.8}_{-2.2}$ km s$^{-1}$ Mpc$^{-1}$ (PL: $64.0 \pm 2.1$), and with Pantheon+ the BI case increases to $H_0 \approx 68.66^{+0.63}_{-0.73}$ km s$^{-1}$ Mpc$^{-1}$, with BI preferring evolving dark energy ($w_0 \approx -0.919$, $w_a \approx -0.37$) vs PL ($w_0 \approx -0.960$, $w_a \approx -0.15$). The study highlights that DESI DR2 constrains the CPL parameters tightly and that BI can alleviate, but not fully resolve, the Hubble tension, underscoring the continued tension with ΛCDM in the presence of Pantheon+. Overall, the results motivate further joint theoretical and observational efforts to unify early- and late-time cosmic evolution under BI and dynamical dark energy.

Abstract

Recently, the Dark Energy Spectroscopic Instrument Data Release 2 (DESI DR2) suggests that the dark energy in our universe might be evolving, favoring the Chevallier-Polarski-Linder (CPL) parameterization and a lower Hubble constant. In our previous work, it has been reported that cosmological model with the non-singular bounce inflation (BI) scenario and $Λ$CDM might alleviate the Hubble tension into 3$σ$ confidence. In this paper, we study the cosmological model of BI with a dynamical dark energy. We find that individual consideration of the CPL parameterization and the data \texttt{DESI DR2} tend to larger Hubble constants for both BI and power law (PL) case with cosmic microwave background (CMB) data. Employing BI with combined CPL parameterization and \texttt{DESI DR2}, we obtain the Hubble constant $H_ 0 = 65.2^{ + 1.8}_{ - 2.2} \ \mathrm{km} \cdot \mathrm{s}^{ -1 } \cdot \mathrm{Mpc}^{ -1 }$, which is larger than $H_ 0 = 64.0 \pm 2.1 \ \mathrm{km} \cdot \mathrm{s}^{ -1 } \cdot \mathrm{Mpc}^{ -1 }$ for the PL case. After considering nontrivial weak lensing effect and spatial curvature as well as adding \texttt{Pantheon+}, BI fits 3.1$σ$ confidence of $Λ$CDM with $w_ 0 = -0.919 \pm 0.038$ and $w_{ \mathrm{a}} = -0.37 \pm 0.12$, and it prefers evolving dark energy than the PL case with $w_ 0 = -0.960 \pm 0.074$ and $w_{ \mathrm{a}} = -0.15^{ +0.28}_{ -0.25}$.

Figures (4)

• Figure 1: The best-fit results of the BI and PL power spectrum using Planck 2018 + Planck_lensing, PSA + DESI DR2 and PSA + DESI DR2 + P (P stands for Pantheon+). The oscillating behavior of BI power spectrum is suppressed when fitting to PSA + DESI DR2 data and has a lower index $n_{ \mathrm{s}} \approx 0.97$ than the BI scenario using Planck 2018 + Planck_lensing, similar to the spectral index in power law case with PSA + DESI DR2.
• Figure 2: Correlations of cosmological parameters of BI and PL with PSA + DESI DR2 based on $\Lambda$CDM or PSA based on CPL parameterization. The DESI DR2 favors a larger $r_ *$ and thus a larger $H_ 0$ than CMB results. On the other hand, because PSA could not constrain the CPL parameters, cases of PSA based on CPL parameterization have larger $H_ 0$ and less $S_ 8$.
• Figure 3: Contours of $w_ 0$, $w_{ \mathrm{a}}$, $\Omega_{ \mathrm{k}}$, $A_{ \mathrm{L}}$, $H_ 0$, $S_ 8$ and $n_{ \mathrm{s}}$ of BI and PL with PSA + DESI DR2. $d_{ \mathrm{M}}( z_ *)$ in BI and PL are similar, thus a less $w_ 0$ is consistent with a larger $H_ 0$ in BI with $A_{ \mathrm{L}}$ and $\Omega_{ \mathrm{k}}$.
• Figure 4: Contours of CPL dark energy of BI and PL with PSA + DESI DR2 + Pantheon+. These two cases fit similar $H_0$, but the BI scenario prefers a evolving dark energy.