Strongly lensed repeating Fast Radio Bursts as precision probes of the universe

TL;DR

This paper proposes using strongly lensed repeating Fast Radio Bursts as highly precise cosmological probes, capable of constraining the Hubble constant and cosmic curvature with unprecedented accuracy within a decade.

Contribution

It introduces a novel method utilizing strongly lensed FRBs to measure cosmological parameters with high precision, including model-independent constraints on cosmic curvature.

Findings

H_0 can be constrained to 0.91% uncertainty with 10 systems.

Cosmic curvature can be measured to a precision of 0.076.

Method can test the cosmological principle and break degeneracies.

Abstract

Fast Radio bursts (FRBs), bright transients with millisecond durations at $\sim$ GHz and typical redshifts probably $>0.8$, are likely to be gravitationally lensed by intervening galaxies. Since the time delay between images of strongly lensed FRB can be measured to extremely high precision because of the large ratio $\sim10^9$ between the typical galaxy-lensing delay time $\sim\mathcal{O}$(10 days) and the width of bursts $\sim\mathcal{O}$(ms), we propose strongly lensed FRBs as precision probes of the universe. We show that, within the flat $\Lambda$CDM model, the Hubble constant $H_0$ can be constrained with a $\sim0.91\%$ uncertainty from 10 such systems probably observed with the Square Kilometer Array (SKA) in $<$ 30 years. More importantly, the cosmic curvature can be model-independently constrained to a precision of $\sim0.076$. This constraint can directly test the validity of the cosmological principle and break the intractable degeneracy between the cosmic curvature and dark energy.