A Dynamical Scalar Field Model for Dark Energy: Addressing the Hubble Tension and Cosmic Evolution

Abstract

We propose a dynamical dark energy model based on a canonical scalar field with a hybrid potential of the form $V(\phi) = V_{0}e^{-\lambda\phi} + V_{1}\phi^{n}$. We constrain the model's 11-dimensional parameter space using a comprehensive combination of cosmological data, including the Planck 2018 Cosmic Microwave Background (CMB) power spectra, Baryon Acoustic Oscillations (BAO), the Pantheon+ supernova sample, SH0ES and the matter power spectrum from SDSS. The model provides an excellent fit to the data, with a reduced chi-squared of $\chi^2_{\text{red}} = 0.989$, while successfully alleviating the Hubble constant tension. Our analysis yields a Hubble constant of $H_0 \approx 72.820$ km/s/Mpc, reducing the discrepancy between early and late-universe measurements. We find that the data favors a 'thawing' quintessence scenario, characterized by a potential slope parameter $\lambda \approx 0.056$. This small but non-zero slope drives a late-time deviation from $\Lambda$CDM ($w(z=0) \approx -0.85$) while preserving the standard expansion history at high redshifts. A model comparison using the Bayesian Information Criterion finds that the standard $\Lambda$CDM model is still slightly preferred ($\Delta\text{BIC} = 2.178$) due to its fewer parameters. Nevertheless, our results demonstrate that this hybrid potential model is a compelling, physically motivated alternative to a cosmological constant.