Model-agnostic interpretation of 10 billion years of cosmic evolution traced by BOSS and eBOSS data

Abstract

We present the first model-agnostic analysis of the complete set of Sloan Digital Sky Survey III (BOSS) and -IV (eBOSS) catalogues of luminous red galaxy and quasar clustering in the redshift range 0.2 ≤ z ≤ 2.2 (10 billion years of cosmic evolution), which consistently includes the baryon acoustic oscillations (BAO), redshift space distortions (RSD) and the shape of the transfer function signatures, from pre-and post-reconstructed catalogues in Fourier space. This approach complements the standard analyses techniques which only focus on the BAO and RSD signatures, and the full-modeling approaches which assume a specific underlying cosmology model to perform the analysis. These model-independent results can then easily be interpreted in the context of the cosmological model of choice. In particular, when combined with z > 2.1 Ly-α BAO measurements, the clustering BAO, RSD and Shape parameters can be interpreted within a flat-ΛCDM model yielding h = 0.6816±0.0067, Ω m = 0.3001±0.0057 and 10 9 ×A s = 2.43±0.20 (or σ 8 = 0.858±0.036) with a Big Bang Nucleosynthesis prior on the baryon density. Without any external dataset, the BOSS and eBOSS data alone imply Ω m = 0.2971 ± 0.0061 and 10 9 × A s = 2.39 +0.24 −0.43 (or σ 8 = 0.857 ± 0.040). For models beyond ΛCDM, eBOSS data alone (in combination with Planck) constrain the sum of neutrino mass to be Σm ν < 0.40 eV with a BBN prior (Σm ν < 0.082 eV) at 95% CL, the curvature energy density to Ω k = −0.022 +0.032 −0.038 (Ω k = 0.0015 ± 0.0016) and the dark energy equation of state parameter to w = −0.998 +0.085 −0.073 (w = −1.093 +0.048 −0.044 ) at 68% CL without a BBN prior. These results are the product of a substantial improvement of the state-of-the-art methodologies and represent the most precise model-agnostic cosmological constrains using spectroscopic large-scale data alone.

A non-linear solution to the $S_8$ tension?

“…The measurement at z = 0.15 is for the SDSS Main Galaxy Sample (Howlett et al 2015). The open circles show a reanalysis of the BOSS, eBOSS/LRG and eBOSS/QSO samples by Brieden et al (2022) using their ShapeFit methodology. The open diamond shows results from an effective field theory analysis of the eBOSS Emission Line Galaxy sample by Ivanov (2021).…”

“…Recently, Brieden et al (2021b,a) have developed an extension of the 'classical' BOSS/eBOSS analyses, by including an additional parameter that is sensitive to the parameter combination Ωmh. The constraints on f σ8 derived by applying their ShapeFit technique to the BOSS, eBOSS/LRG and eBOSS/QSO samples (Brieden et al 2022) are shown by the open symbols in Fig. 2.…”

Black holes as “time capsules”: A cosmological graviton background and the Hubble tension

“…While detecting these gravitons is an experimental challenge for the future, the above estimates provide an avenue to test our scenario rather soon. Improvements in theoretical reactions rates relevant to BBN calculations by the LUNA 8 project, as well as further analysis from a large-scale structure by the ShapeFit team Brieden et al (2022), will provide much tighter constrain on the allowed value of ΔN eff during BBN. This can either refute our scenario or support it.…”

Distinguishing Dirac vs. Majorana neutrinos: a cosmological probe

“…The most natural path to discover this is via the presence of neutrinoless double beta decay (which is only possible if the neutrinos are Majorana) [2,3]; several experimental efforts around the world, placed in underground laboratories, are trying to detect this signal [4]. However, if the total mass of neutrinos is as small as cosmology suggests (< 0.1 eV [5,6]), then the required size of the detector will be ∼1-10 tons of the double beta decay isotope, which will be challenging. It is therefore interesting to explore other experimental signatures to detect the physical nature of neutrinos.…”