Exploring new physics in the late Universe’s expansion through non-parametric inference

Abstract

In this study, we investigate deviations from the Planck-ΛCDM model in the late universe (z ≲ 2.5) using the Gaussian Processes method, with minimal assumptions. Our goal is to understand where exploring new physics in the late universe is most relevant. We analyze recent Cosmic Chronometers (CC), Type Ia Supernovae (SN), and Baryon Acoustic Oscillations (BAO) data. Byexaminingreconstruc tions of the dimensionless parameter δ(z), which measures deviations of the Hubble parameter from the Planck-ΛCDM predictions, we identify intriguing features at low (z ≲ 0.5) and high (z ≳ 2) redshifts. Deviations from the Planck-ΛCDM model were not significant between 0.5 ≲ z ≲ 2. Using the combined CC+SN+BAO dataset, we gain insights into dark energy (DE) dynamics, resembling characteristics of omnipotent DE, extending beyond quintessence and phantom models. DE exhibits n-quintessence traits for z ≳ 2, transitioning with a singularity around z ∼ 2 to usual phantom traits in 1 ≲ z ≲ 2. DE characteristics differ between scenarios (H0-SH0ES and H0-&CMB), with H0-SH0ES leaning towards phantom traits and H0-&CMB towards quintessence. We suggest exploring new physics at z ≲ 0.5 and 1.5 ≲ z ≲ 2.5, particularly around z = 2, to understand cosmological tensions such as H0 and S8.