Robust model comparison disfavors power law cosmology

Abstract

Late-time power law expansion has been proposed as an alternative to the standard cosmological model and shown to be consistent with some low-redshift data. We test power law expansion against the standard flat ΛCDM cosmology using goodness-of-fit and model comparison criteria. We consider Type Ia supernova (SN Ia) data from two current compilations (JLA and Union2.1) along with a current set of baryon acoustic oscillation (BAO) measurements that includes the high-redshift Lyman-α forest measurements from BOSS quasars. We find that neither power law expansion nor ΛCDM is strongly preferred over the other when the SN Ia and BAO data are analyzed separately but that power law expansion is strongly disfavored by the combination. We treat the R h = ct cosmology (a constant rate of expansion) separately and find that it is conclusively disfavored by all combinations of data that include SN Ia observations and a poor overall fit when systematic errors in the SN Ia measurements are ignored, despite a recent claim to the contrary. We discuss this claim and some concerns regarding hidden model dependence in the SN Ia data.

Strong evidence for an accelerating Universe

“…In Melia (2015) several claims against R h = ct were refuted, and a list of works favouring R h = ct over ΛCDM was compiled in Melia (2017). Power-law cosmologies with n ≥ 1 have been explored against data in several works such as Gehlaut et al (2003), Dev et al (2008), Sethi et al (2005), Zhu et al (2008), Shafer (2015), Rani et al (2015), Dolgov et al (2014), finding n ∼ 1.5 consistently. In a more recent work (Shafer 2015), power-law and R h = ct models were tested with SN Ia and BAO datasets and were found to be highly disfavoured against ΛCDM.…”

Classification of gamma-ray burst durations using robust model-comparison techniques

“…Frequentist model comparison after binning the data has been used by Zitouni et al (2015); Tarnopolski (2015). More information about AIC and BIC and its application to a variety of astrophysical problems can be found in Liddle (2004Liddle ( , 2007; Tan & Biswas (2012); Shi et al (2012);Shafer (2015). We should point that these are not the only possibilities for model comparison.…”

The linear growth of structure in theRh=ctuniverse

“…SNe by Wei et al (2015c), Shafer (2015) compared cosmological models using both the Union2.1 (Suzuki et al 2012) and JLA (Betoule et al 2014) SN samples and argued that ΛCDM was strongly favoured by these data. However, he appears to have incorrectly estimated the intrinsic dispersion of each sub-sample, and additionally failed to include them in his maximum likelihood estimation, which greatly biased his analysis.…”

“…However, he appears to have incorrectly estimated the intrinsic dispersion of each sub-sample, and additionally failed to include them in his maximum likelihood estimation, which greatly biased his analysis. Shafer (2015) also analyzed measurements of H(z) versus z, but here too he avoided using truly model-independent cosmic chronometer measurements, opting instead to use heavily biased BAO estimates. He appears to have been unaware of the significant limitations of all but the most recent 2 or 3 BAO scale determinations.…”