Suppression without Thawing: Constraining Structure Formation and Dark Energy with Galaxy Clustering (2406.13388v2)

Abstract: We present a new perturbative full-shape analysis of BOSS galaxy clustering data, including the full combination of the galaxy power spectrum and bispectrum multipoles, baryon acoustic oscillations, and cross-correlations with the gravitational lensing of cosmic microwave background measured from \textit{Planck}. Assuming the $\Lambda$CDM model, we constrain the matter density fraction $\Omega_m = 0.3138\pm 0.0086$, the Hubble constant $H_0=68.23\pm 0.78\,\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$, and the mass fluctuation amplitude $\sigma_8=0.688\pm 0.026$ (equivalent to $S_8 = 0.703\pm 0.029$). Cosmic structure at low redshifts appears suppressed with respect to the Planck $\Lambda$CDM concordance model at $4.5\sigma$. We explore whether this tension can be explained by the recent DESI preference for dynamical dark energy (DDE): the BOSS data combine with DESI BAO and PantheonPlus supernovae competitively compared to the CMB, yielding no preference for DDE, but the same $\sim 10\%$ suppression of structure, with dark energy being consistent with a cosmological constant at 68\% CL. Our results suggest that either the data contains residual systematics, or more model-building efforts may be required to restore cosmological concordance.

• The paper integrates BOSS clustering data with CMB lensing, revealing a 4.5σ suppression of cosmic structure growth relative to the Planck model.
• It employs an effective field theory framework to analyze galaxy power spectrum and bispectrum multipoles, tightly constraining Ωm, H0, and σ8.
• Despite testing dynamical dark energy scenarios, the analysis shows no strong preference over the cosmological constant, underscoring persistent σ8 tensions.

Analyzing Galaxy Clustering for Cosmological Insights

The paper "Suppression without Thawing: Constraining Structure Formation and Dark Energy with Galaxy Clustering" by Shi-Fan Chen et al. presents a comprehensive analysis using perturbative full-shape analysis of the Baryon Oscillation Spectroscopic Survey (BOSS) galaxy clustering data, linking it with cosmic microwave background (CMB) lensing from Planck. This paper aims to shed light on the parameters of the Lambda Cold Dark Matter ($\Lambda$CDM) model and the dynamical dark energy (DDE) hypothesis by intricately correlating multiple cosmological datasets.

Methodology

In their analysis, the authors utilized a suite of statistical tools to analyze two key components: the galaxy power spectrum and bispectrum multipoles, in addition to baryon acoustic oscillations (BAO), against the background of CMB lensing data. They adopted an effective field theory (EFT)-based framework, noted for its ability to handle non-linearities inherent in the large-scale structure of the universe. Their primary dataset stems from the BOSS survey, enriched with cross-correlation metrics between BOSS galaxies and Planck CMB lensing reconstructions.

Key Findings

• Cosmological Parameter Constraints: The paper reaffirmed the $\Lambda$CDM model with notable precision. The matter density fraction, $\Omega_{\rm m}$, was constrained to $0.3138\pm 0.0086$, with a Hubble constant $H_0$ of $$68.23\pm 0.78\,\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$$ and the mass fluctuation amplitude $\sigma_8$ as $0.688\pm 0.026$. Interestingly, their results indicated a suppression in cosmic structure growth at low redshifts, departing significantly by $4.5\sigma$ from the Planck concordance model.
• Analysis of the $\sigma_8$ Tension: This tension has been a pivotal point of discussion, suggesting potential discrepancies in structure growth as predicted by the standard model. The paper shows the robustness of this anomaly across various constraints coming from the dataset, presenting it as a significant observational feature rather than a product of modeling choices or data anomalies.
• Dynamical Dark Energy: The research investigates the DDE paradigm in light of recent findings suggesting its potential through BAO and supernovae data. While individual datasets hinted towards DDE, the integration of BOSS data displayed no substantial preference over a cosmological constant model. However, a consistent suppression of structure by ~10% was observed.

Implications

The consistent suppression of $\sigma_8$ calls for deeper investigation. The research suggests potential modifications or expansions to existing theoretical frameworks. The non-preference for DDE in this combined analysis implies that existing tensions within standard cosmology might not be eased by traditional dark energy extensions, necessitating alternative approaches or complementary explanations such as new physics or systematic corrections.

Future Outlook

The paper emphasizes the need for finer calibrations in lensing-galaxy cross-correlations and a broader exploration of galaxy clustering analytics. As future surveys, like the Dark Energy Spectroscopic Instrument (DESI), promise richer datasets with enhanced precision, they will be crucial in illuminating these tensions further. As theoretical and observational methodologies evolve, the inherent complexities of galaxy clustering will likely surface richer insights into the universe’s evolving tapestry.

Overall, Chen et al.'s paper stands as a meticulous exploration into subtle cosmic features that challenge our understanding, steering the field towards rigorous inquiry and interdisciplinary advances in cosmology.