On recent claims concerning the R_h = ct Universe

The R_h = ct universe is a Friedmann-Robertson-Walker (FRW) cosmology which, like Λ cold dark matter (ΛCDM), assumes the presence of dark energy in addition to (baryonic and non-luminous) matter and radiation. Unlike ΛCDM, however, it is also constrained by the equation of state (EOS) p=-ρ/3, in terms of the total pressure p and energy density ρ. Oneon- one comparative tests between R_h = ct and ΛCDM have been carried out using over 14 different cosmological measurements and observations. In every case, the data have favoured R_h = ct over the standard model, with model selection tools yielding a likelihood ~90- 95 per cent that the former is correct, versus only ~5-10 per cent for the latter. In other words, the standard model without the EOS p=-ρ/3 does not appear to be the optimal description of nature. Yet in spite of these successes - or perhaps because of them - several concerns have been published recently regarding the fundamental basis of the theory itself. The latest paper on this subject even claims - quite remarkably - that R_h = ct is a vacuum solution, though quite evidently ρ ≠ 0. Here, we address these concerns and demonstrate that all criticisms levelled thus far against R_h = ct, including the supposed vacuum condition, are unwarranted. They all appear to be based on incorrect assumptions or basic theoretical errors. Nevertheless, continued scrutiny such as this will be critical to establishing R_h = ct as the correct description of nature.