Abstract: As our observational capabilities advance with stage-IV surveys such as DESI, now is a key moment to push beyond traditional two-point statistics to extract more information from the cosmic density field. We present the first joint analysis involving power spectrum and bispectrum of the DESI Data Release 1. We are able to constrain the logarithmic growth rate of structure f and the amplitude of matter fluctuations sigma_s8 separately, which are degenerate in analyses only involving two-point statistics. By fitting the full-shape of the power spectrum and bispectrum on observations of Luminous Red Galaxies and quasars, spanning a redshift range of 0.4<z<2.1, we obtain cumulative constraints of ~10% and of ~8% for respectively f and sigma_s8. To achieve this, we use the GEO-FPT bispectrum model, which we developed by extending perturbation theory into the mildly non-linear regime by incorporating geometrical features in the bispectrum observed in simulations. We also validate and use for the bispectrum the DESI official catalogue-level blinding scheme, and the ShapeFit compression. Our results are consistent with Planck ΛCDM and with the official DESI ShapeFit power spectrum-only analysis, while improving on the latter through the additional information coming from the bispectrum.

Tribunal:

President: Dr. Julián Bautista

Secretary: Dr. Fréderic Courbin

Vocal: Dr. José Luis Bernal Mera

Suplents:

Dr. Andreu Font Ribera

Dr. Álex Alarcón González

Directors: Dra. Licia Verde i Dr. Héctor Gil Marín

Tutor: Dr. Alberto Manrique Oliva