Revealing Intrinsic Flat $Λ$CDM Biases with Standardizable Candles

Abstract

Emerging high redshift cosmological probes, in particular quasars (QSOs), show a preference for larger matter densities, Ω m ≈ 1, within the flat ΛCDM framework. Here, using the Risaliti-Lusso relation for standardizable QSOs, we demonstrate that the QSOs recover the same Planck-ΛCDM Universe as Type Ia supernovae (SN), Ω m ≈ 0.3 at lower redshifts 0 < z 0.7, before transitioning to an Einstein-de Sitter Universe (Ω m = 1) at higher redshifts z 1. We illustrate the same trend, namely increasing Ω m and decreasing H 0 with redshift, in SN but poor statistics prevent a definitive statement. We explain physically why the trend is expected in the flat ΛCDM cosmology, illustrate the intrinsic bias and non-Gaussian tails with mock Pantheon data, and identify a similar trend in BAO below z = 1. Our results highlight an intrinsic bias in the flat ΛCDM Universe, whereby Ω m increases, H 0 decreases and S 8 increases with effective redshift, thus providing a new perspective on ΛCDM tensions; even in a Planck-ΛCDM Universe the current tensions might have been expected.

Putting Flat $Λ$CDM In The (Redshift) Bin

“…On the other hand, note that at higher redshifts H(z) 2 ∼ B(1 + z) 3 , so the combination Ω m h 2 , with h := H 0 /100, is the relevant quantity. Exploiting these facts, it was recently argued that increases in Ω m (decreases in H 0 ) with effective redshift are inherent to the flat ΛCDM model [16]. Here, we demonstrate through ΛCDM mocks binned by redshift that the probability of Planck values Ω m ∼ 0.3 decreases as we increase bin redshift.…”

“…Next, we repeat the mocking and binning procedure outlined earlier with the new input parameters (H 0 , Ω m ) = (69.11, 0.299). Following [16] we impose a low redshift cutoff and isolate high redshift bins. In each bin we compare the best fit values from the real data and flat ΛCDM mocks in order to establish the probability of recovering the same or larger Ω m and the same or smaller H 0 values.…”

“…We revisit the analysis of the Pantheon data set [25] conducted in [16] (see also [13,14]) in order to introduce a high redshift Planck prior on Ω m h 2 [9]. Note, to do so, we treat the absolute magnitude of Type Ia SN M B as a nuisance parameter.…”

“…In particular, local H 0 values [4][5][6][7][8] are universally biased to larger values than Planck-ΛCDM [9]. Observations at different redshifts have shown that H 0 evolves with effective (binned) redshift in the flat ΛCDM model [10][11][12][13][14][15][16][17] (see also [18]. If true, this behaviour is indicative of model breakdown [19,20].…”

Gamma-ray burst data strongly favor the three-parameter fundamental plane (Dainotti) correlation relation over the two-parameter one

“…Farooq et al 2017;Scolnic et al 2018;Planck Collaboration 2020;eBOSS Collaboration 2021). The measurements, however, are not yet decisive enough (see, surements that reach to z ∼ 7.5 (Risaliti & Lusso 2015Khadka & Ratra 2020a,b, 2021Lusso et al 2020;Zhao & Xia 2021;Rezaei et al 2022;Luongo et al 2021;Leizerovich et al 2021;Colgáin et al 2022;Dainotti et al 2022a), 1 and -the main subject of our paper -gamma-ray burst (GRB) observations that reach to z ∼ 8.2 (Cardone et al 2009(Cardone et al , 2010Samushia & Ratra 2010;Dainotti et al 2013;Postnikov et al 2014;Wang et al 2015Wang et al , 2016Dainotti & Del Vecchio 2017;Dainotti & Amati 2018;Wang et al 2022;Fana Dirirsa et al 2019;Amati et al 2019;Khadka & Ratra 2020c;Hu et al 2021;Demianski et al 2021;Khadka et al 2021b;Luongo et al 2021;Luongo & Muccino 2021;Cao et al 2021a;Liu et al 2022). In this paper the highest redshift GRB we use is at z = 9.4 (Cucchiara et al 2011), but GRBs might be detectable to z = 20 (Lamb & Reichart 2000).…”