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 $V(φ) = V_{0}e^{-λφ} + V_{1}φ^{n}$. 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, and the matter power spectrum from SDSS. The model provides an excellent fit to the data, with a reduced chi-squared of $χ^2_{\text{red}} = 0.987$, while successfully alleviating the Hubble constant tension. Our analysis yields a Hubble constant of $H_0 = 70.0$ km/s/Mpc, reducing the discrepancy between early and late-universe measurements. The data favor a negative power-law index of $n \approx -0.92$. A model comparison using the Bayesian Information Criterion finds that the standard $Λ$CDM model is still slightly preferred ($Δ\text{BIC} = 2.178$) due to its fewer parameters. Nevertheless, our results demonstrate that this hybrid potential model is a compelling, physically motivated alternative to a cosmological constant.