DESI DR2 reduces the exclusion of the non-interacting scenario to below 1σ in vacuum decay models

We analyze two vacuum decay cosmological models using baryon acoustic oscillation (BAO) measurements from DESI DR2 in combination with cosmic microwave background (CMB), cosmic chronometer (CC), and multiple Type Ia supernova samples (Pantheon[Formula: see text], DES-Dovekie, and Union3). In contrast to previous DESI DR1-based studies, which reported moderate to strong evidence against the non-interacting case, our results show that DESI DR2 substantially weakens this level of exclusion. For both vacuum decay models, the interaction parameter is consistent with zero at a significance level of less than [Formula: see text] for all combinations of datasets considered, implying that the non-interacting scenario cannot be ruled out. We further examine the implications for cosmological parameters. While the vacuum decay models mildly shift the Hubble parameter toward higher values compared to [Formula: see text]CDM, leading to a modest alleviation of the [Formula: see text] tension, they do not fully resolve the discrepancy with the SH0ES measurement. The matter density parameter [Formula: see text], as well as the baryon and radiation density parameters, remain consistent across models within [Formula: see text]. Model comparison using [Formula: see text] shows only weak preference ([Formula: see text]) for the vacuum decay models, while Bayesian evidence remains inconclusive and, in most cases, mildly favors [Formula: see text]CDM. Our analysis demonstrates that the DESI DR2 data substantially reduce the previously reported exclusion of the non-interacting scenario in vacuum decay models, bringing the results into consistency with the standard non-interacting [Formula: see text]CDM framework.