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 $\hat{I}›$ cold dark matter ($\hat{I}›$CDM) 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 $\hat{I}›$CDM 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 $\hat{I}{\text{c◯}}_{\mathrm{b}}$ or $\hat{I}{\text{c◯}}_{\mathrm{b}}{h}^2$, indicating contradiction to the core postulate of $\hat{I}›$CDM. 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 $w_0{w}_a$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 $\hat{I}›$CDM model, supporting the need for a more flexible cosmological framework.

15 pages with 7 figures and 1 table; accepted for publication in ApJ