Suppression without Thawing: Constraining Structure Formation and Dark Energy with Galaxy Clustering

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 Planck. Assuming the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, we constrain the matter density fraction ${\mathrm{\ensuremath{\Omega}}}_{\mathrm{m}}=0.3138\ifmmode\pm\else\textpm\fi{}0.0086$, the Hubble constant ${H}_{0}=68.23\ifmmode\pm\else\textpm\fi{}0.78\text{ }\text{ }\mathrm{km}\text{ }{\mathrm{s}}^{\ensuremath{-}1}\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$, and the mass fluctuation amplitude ${\ensuremath{\sigma}}_{8}=0.688\ifmmode\pm\else\textpm\fi{}0.026$ (equivalent to ${S}_{8}=0.703\ifmmode\pm\else\textpm\fi{}0.029$). Cosmic structure at low redshifts appears suppressed with respect to the Planck $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ concordance model at $4.5\ensuremath{\sigma}$. We explore the implications of this dataset for the recent DESI BAO 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 $\ensuremath{\sim}10%$ 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.

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