Cosmological Dynamics of Exponential Quintessence Constrained by BAO, Cosmic Chronometers, and DES-SN5YR/Pantheon+ Data

Abstract

We perform a comprehensive observational test of a canonical quintessence model driven by an exponential potential, motivated by its emergence in higher-dimensional theories, string-inspired scenarios, and modified gravity. Using a Markov Chain Monte Carlo framework, we constrain the model with the latest high-precision observational datasets including Cosmic Chronometers, Baryon Acoustic Oscillation, Pantheon+, and DES-SN5YR Type Ia Supernovae. The combined data significantly tighten the parameter bounds on (H0, Omega_m0, eta0, gamma) and yield predictions for the Hubble parameter H(z), the distance modulus mu(z), and the scaled comoving angular diameter distance that remain in excellent agreement with observations and closely follow the LCDM baseline. An information-theoretic model comparison using the Akaike Information Criterion shows that the exponential quintessence model remains statistically comparable with LCDM despite having additional parameters. The model successfully reproduces the transition from matter domination to late-time acceleration, maintains w_tot > -1, and provides an age of the universe consistent with Planck 2018. Statefinder diagnostics indicate trajectories approaching the LCDM fixed point with small deviations, and energy condition analysis confirms physical viability, with only the Strong Energy Condition violated at late times as required for acceleration.

40 pages, 13 figures, 6 tables

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