Decay of f⁡(R) quintessence into dark matter: mitigating the Hubble tension?

We propose a revised cosmological scenario that extends the Λ cold dark matter (ΛCDM) framework by incorporating metric f(R) gravity in the Jordan frame. In this model, the dark energy component arises from a nonminimally coupled scalar field, decomposed into a smooth background [set to unity to recover general relativity (GR)] and a rapidly varying, massive fluctuation that decays into the dark matter sector. In the near-GR limit, this setup provides a phenomenological extension of ΛCDM characterized by two additional parameters: the present-day value of the scalar fluctuation and a normalized decay rate. Using a Markov chain Monte Carlo analysis of low-redshift cosmological data, comprising Type Ia supernovae, baryon acoustic oscillation (BAO), and cosmic chronometer measurements, we find that the proposed model achieves a better overall fit than ΛCDM, while the Bayesian evidence remains statistically inconclusive given the inclusion of two extra parameters. The model predicts a moderate increase in the inferred value of H0 and an improved consistency with Dark Energy Spectroscopic Instrument BAO data when adopting the SH0ES prior. Furthermore, describing dark matter particle creation as a transition phase in the late Universe offers an intriguing physical interpretation, potentially capturing features already present in current data and providing a promising avenue to explore extensions of the standard cosmological model within modified gravity frameworks.