Cosmological constraints from the nonlinear galaxy bispectrum

We present the cosmological constraints from analyzing higher-order galaxy clustering on small nonlinear scales. We use SimBIG, a forward modeling framework for galaxy clustering analyses that employs simulation-based inference to perform highly efficient cosmological inference using normalizing flows. It leverages the predictive power of high-fidelity simulations and robustly extracts cosmological information from regimes inaccessible with current standard analyses. In this work, we apply SimBIG to a subset of the BOSS galaxy sample and analyze the redshift-space bispectrum monopole, B₀ (k₁, k₂, k₃), to k₌₀ₗ=0. 5 h/Mpc. We achieve 1 constraints of ₌=0. 293-₀. ₀₂₇^+0. 027 and ₈=0. 783-₀. ₀₃₈^+0. 040, which are more than 1. 2 and 2. 4 tighter than constraints from standard power spectrum analyses of the same dataset. We also derive 1. 4, 1. 4, 1. 7 tighter constraints on ₁, h, nₒ. This improvement comes from additional cosmological information in higher-order clustering on nonlinear scales and, for ₈, is equivalent to the gain expected from a standard analysis on a 4 larger galaxy sample. Even with our BOSS subsample, which only spans 10% of the full BOSS volume, we derive competitive constraints on the growth of structure: S₈=0. 774-₀. ₀₅₃^+0. 056. Our constraint is consistent with results from both cosmic microwave background and weak lensing. Combined with a ₁ prior from big bang nucleosynthesis, we also derive a constraint on H₀=67. 6-₁. ₈^+2. 2 km s^-1 Mpc^-1 that is consistent with early Universe constraints.