Cosmic chronometers to calibrate the ladders and measure the curvature of the Universe. A model-independent study

Abstract

We use the state-of-the-art data on cosmic chronometers (CCH) and the Pantheon+ compilation of supernovae of Type Ia (SNIa) to test the constancy of the SNIa absolute magnitude, M, and the robustness of the cosmological principle (CP) at z ≲ 2 with a model-agnostic approach. We do so by reconstructing M(z) and the curvature parameter Ωk(z) using Gaussian Processes. Moreover, we use CCH in combination with data on baryon acoustic oscillations (BAO) from various galaxy surveys (6dFGS, BOSS, eBOSS, WiggleZ, DES Y3) to measure the sound horizon at the baryon-drag epoch, rd, from each BAO data point and check their consistency. Given the precision allowed by the CCH, we find that M(z), Ωk(z) and rd(z) are fully compatible (at $<68~{{\%}}$ C.L.) with constant values. This justifies our final analyses, in which we put constraints on these constant parameters under the validity of the CP, the metric description of gravity and standard physics in the vicinity of the stellar objects, but otherwise in a model-independent way. If we exclude the SNIa contained in the host galaxies employed by SH0ES, our results read $M=(-19.314^{+0.086}_{-0.108})$ mag, rd = (142.3 ± 5.3) Mpc and $\Omega _k=-0.07^{+0.12}_{-0.15}$, with H0 = (71.5 ± 3.1) km s−1 Mpc−1 (68% C.L.). These values are independent from the main data sets involved in the H0 tension, namely, the cosmic microwave background and the first two rungs of the cosmic distance ladder. If, instead, we also consider the SNIa in the host galaxies, calibrated with Cepheids, we measure $M=(-19.252^{+0.024}_{-0.036})$ mag, $r_d=(141.9^{+5.6}_{-4.9})$ Mpc, $\Omega _k=-0.10^{+0.12}_{-0.15}$ and $H_0=(74.0^{+0.9}_{-1.0})$ km s−1 Mpc−1.

Geometric perspective for explaining Hubble tension: theoretical and observational aspects

“…The predicted value of Ω K = −1/18 is also aligned to the estimations of Ω K = −0.07 +0.12 −0. 15 and Ω K = −0.076 ± 0.012 found by combining CCs and BAO data [29,30].…”

“…These values are comparable with the CMB polarisation power spectrum (EE), because they are non-linear (non-Gaussian) and do not depend on the coordinates (global-like approach) (figure 1). Particularly, CMB EE power spectra showed higher values of dark energy Ω Λ = 0.711 (30) with Hubble parameter about 69.9 ± 2.7 km s −1 Mpc −1 and the corresponding value from the linear hyperconical model (H 0 = 1/t 0 ) is 71.69 ± 0.65 km s −1 Mpc −1 (table 2), which are compatible with the values estimated with Large Magellanic Cloud (LMC) Cepheid samples, of about H 0 = 73 ± 1 km s −1 Mpc −1 (SH0ES [2,3,38]). In fact, the SH0ES estimation leads to an independent-scale ratio of 1.037 ± 0.036 and a time factor of F t = 0.97 ± 0.05.…”

Checking the second law at cosmic scales

“…However, no appreciable differences was found regardless of the kernel choice. Another effort was carried out in [31] with similar conclusion.…”

The state of the dark energy equation of state circa 2023

“…The presence of the lensing anomaly may hold significant implications when constraining other cosmological parameters beyond the standard ΛCDM model. One notable example pertains to the curvature parameter: since more lensing is expected with a higher abundance of dark matter, the observed lensing anomaly can be recast into a preference for a closed Universe, well documented and discussed in several recent works [231,300,[306][307][308][309][310][311][312][313][314][315][316][317][318][319][320][321][322][323][324].…”