Revealing Limitation in the Standard Cosmological Model: A Redshift-dependent Hubble Constant from Fast Radio Bursts

Abstract A major issue in contemporary cosmology is the persistent discrepancy, known as the Hubble tension, between the Hubble constant ( H 0 ) estimates from local measurements and those inferred from early-Universe observations under the standard Lambda cold dark matter (ΛCDM) paradigm. Recent advances have identified fast radio bursts (FRBs), a class of extragalactic phenomena observable at considerable redshifts, as a promising observational tool for probing late-time cosmology. In this study, we incorporate two complementary methodologies, machine learning algorithms and Bayesian analysis, on a set of localized FRBs to rigorously test the consistency of the ΛCDM model at late cosmic epochs. Our results reveal a statistically significant redshift-dependent variation of H 0 when using separate priors on baryon density parameters Ω b or Ω b h 2 , indicating contradiction to the core postulate of ΛCDM. However, when the priors are combined, this redshift dependence disappears, yielding a consistent estimate of H 0 . We further validate that the redshift dependency of H 0 can be removed within the more flexible framework of the w 0 w a CDM model even without combining the priors. These findings highlight that the redshift evolution of H 0 is not merely an artifact of the standard model but an indication of a deeper inadequacy in the ΛCDM model, supporting the need for a more flexible cosmological framework.