Minimal rCVGT as a One-Parameter Deformation of ΛCDM: Background Cosmology and BAO Constraints from DESI DR2

We investigate the minimal realization of Relativistic Coherent Vacuum Gravity Theory (rCVGT) as a one-parameter extension of ΛCDM. The model introduces a coherent vacuum sector characterized by scalar fields that modify the effective energy density driving cosmic expansion. We demonstrate that the theory admits a well-defined General Relativity (GR) limit, recovering ΛCDM at the background and perturbation levels. We then introduce a controlled one-parameter deviation and compute its impact on the expansion history and baryon acoustic oscillation (BAO) observables. Using recent DESI DR2 measurements, we compare the model predictions for and to observational data. We show that rCVGT naturally produces an effective time-evolving dark energy component, qualitatively consistent with the preference for dynamical dark energy indicated by DESI. This work establishes a minimal, testable baseline for rCVGT and provides a framework for future constraints using large-scale structure data.