Investigating Cosmological Models and the Hubble Tension Using Localized Fast Radio Bursts

We use the dispersion measure (DM) and redshift measurements of 24 localized fast radio bursts (FRBs) to compare cosmological models and investigate the Hubble tension. Setting a flat prior on the DM contribution from the Milky Way's halo, DMhaloMW is an element of [5,80]pc cm(-3) , the best fit for flat Lambda CDM is obtained with a Hubble constant H-0=95.8(-9.2)(+7.8)km s(-1) Mpc(-1) and a median matter density Omega(m) approximate to 0.66. The best fit for the R-h = ct universe is realized with H-0=94.2(-6.2)(+5.6)km s(-1) Mpc(-1) . We emphasize that the H-0 measurement depends sensitively on the DMhaloMW prior. Since flat Lambda CDM has one more free parameter, R-h = ct is favored by the Bayesian Information Criterion (BIC) with a likelihood of similar to 73% versus similar to 27%. Through simulations, we find that if the real cosmology is Lambda CDM, a sample of similar to 1150 FRBs in the redshift range 0 < z < 3 would be sufficient to rule out R-h = ct at a 3 sigma confidence level, while similar to 550 FRBs would be necessary to rule out Lambda CDM if the real cosmology is instead R-h = ct. The required sample sizes are different, reflecting the fact that the BIC imposes a severe penalty on the model with more free parameters. We further adopt a straightforward method of deriving an upper limit to H-0, without needing to consider the poorly known probability distribution of the DM contributed by the host galaxy. The theoretical DM contribution from the intergalactic medium (DMIGM) at any z is proportional to H-0. Thus, requiring the extragalactic DMext to be larger than DMIGM delimits H-0 to the upside. Assuming flat Lambda CDM, we have H-0 < 89.0 km s(-1) Mpc(-1) at a 95% confidence level.