A Novel Phenomenological Ansatz for Dynamical Dark Energy: Resolving Cosmological Tensions via Cosmic-Time Exponentials

Abstract

We introduce a novel three-parameter phenomenological ansatz for the dark energy equation of state (EoS) parametrized as w(t) = w_inf - exp(K t)/V_0, where t denotes the cosmic time measured relative to the current epoch. We confront this formulation against the latest Baryon Acoustic Oscillations (BAO) data matrix from the Dark Energy Spectroscopic Instrument (DESI) DR2 combined with the Planck 2018 compressed Cosmic Microwave Background (CMB) prior. Our data-driven optimization uncovers a significant statistical preference for the dynamical ansatz over the flat ΛCDM baseline, achieving a total chi-squared reduction of Δχ² = -7.566 and an Akaike Information Criterion improvement of ΔAIC = -1.566.