UC Irvine

We derive cosmological parameter constraints from the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) galaxy clustering data, based on a joint full-shape analysis of the power spectrum multipoles and the bispectrum monopole using the ShapeFit framework [1]. This work is the follow-up of [2], which obtains for the first time constraints on the ShapeFit parameters using the bispectrum of DESI DR1, for the luminous red galaxy (LRG) and quasar (QSO) samples. Here we present the first ShapeFit cosmological inference results using the bispectrum of DESI DR1. For the baseline flat ΛCDM model, our analysis yields results broadly in agreement with previous studies of the DESI DR1 data-set. In particular, we recover values for the matter density parameter and Hubble constant of respectively Ω m =0.310±0.012 and H0 =[68.92±0.97] km s-1 Mpc-1, consistent with previous results from the full DESI DR1 dataset that did not use the bispectrum signal [3]. The inclusion of the bispectrum significantly tightens the constraints on the amplitude of fluctuations, reducing the error-bars in ln(A_s×1010) by approximately 20%, compared to using the power spectrum alone. We also explore extended cosmological models by performing fits for the evolving dark energy equation of state w0wa , and the sum of neutrino masses ∑ mν . In these cases, we obtain constraints slightly larger than the ones from previous works from the DESI collaboration [4], due to not combining the full-shape results with other probes in all tracers. We find no strong evidence of deviations from standard ΛCDM, with the dark energy equation-of-state remaining within 2σ from a cosmological constant Λ, and the neutrino mass being consistent with the normal hierarchy, ∑ mν <0.1 [eV] at 95% confidence limit. These constraints are broadly consistent with other DESI DR1 analyses, thus validating the robustness of the ShapeFit compression approach and the inclusion of the bispectrum for cosmological inference.