Probing cosmic curvature with fast radio bursts and DESI DR2 data

Abstract

The spatial curvature of the Universe remains a central question in modern cosmology. In thiswork, we explore the potential of localized Fast Radio Bursts (FRBs) as a novel tool to constrainthe cosmic curvature parameter Ωk in a cosmological model–independent way. Using a sample of120 FRBs with known redshifts and dispersion measures, we reconstruct the Hubble parameterH(z) via artificial neural networks, and use it to obtain angular–diameter distances DA(z) throughtwo complementary approaches. First, we derive the comoving distance DC(z) and DA(z) directlyfrom FRBs without assuming a fiducial cosmology. Then, we combine the FRB-based H(z) withBaryon Acoustic Oscillation (BAO) DESI DR2 measurements to infer DA(z). By comparing theFRB-derived and BAO+FRB-derived DA(z), we constrain spatial curvature. Our covariance-basedlikelihood (accounting for correlated uncertainties) yields Ωk = −0.31 ± 0.57, while a diagonal(Gaussian) treatment gives Ωk = −0.13±0.46. Both estimations are consistent with spatial flatnessat the 1σ level, albeit with a mild preference for negative curvature. Explicitly accounting for thefull covariance broadens the intervals and avoids underestimation of uncertainties. These resultshighlight the growing relevance of FRBs in precision cosmology and their synergy with BAO as apowerful, cosmological model–independent probe of the large–scale geometry of the Universe.