Observational constraints on a nonlinear spinor field quintessence model in an FLRW universe

In the framework of a spherically symmetric Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime, we construct a quintessence model driven by a nonlinear, massless spinor field in an open-universe scenario. The model parameters are constrained using recent cosmological observations, including the distance modulus from type Ia supernovae (binned Pantheon sample), Hubble parameter measurements from cosmic chronometers (CC) and the Sloan Digital Sky Survey (SDSS), and baryon acoustic oscillation (BAO) data. A comprehensive Markov chain Monte Carlo (MCMC) analysis yields best-fit estimates for a relatively lower present-day Hubble constant, and the equation-of-state parameter. The best-fit theoretical predictions are compared with observational data for both the Hubble parameter and the distance modulus. Furthermore, the deceleration parameter and the statefinder pair {r,s} are evaluated to demonstrate the model’s effectiveness in describing the universe’s late-time acceleration. The resulting lower value of H0=66.9kms-1Mpc-1 is consistent with the Planck cosmic microwave background (CMB) measurements and suggests a possible route toward alleviating the current Hubble tension. Overall, the spinor field quintessence model with wde=-0.814 and Ωm0=0.264 emerges as a statistically viable and physically consistent alternative to the standard ΛCDM cosmology and conventional scalar-field quintessence frameworks. © The Author(s) 2026.