Title: Constraining inflation and light relics with the DESI Lyman-alpha forest
Place: Seminar del DAA. Jeroni Muñoz Research Building, fourth floor, in Burjassot.
Day: Monday, march 2 , 2026. Time: 12.00.
Abstract:
The Lyman-alpha forest refers to absorption lines in the spectra of high redshift quasars caused by neutral hydrogen in the intergalactic medium, making the Lyman-alpha forest a powerful cosmological probe at higher redshift than galaxy clustering or weak gravitational lensing. In this talk, I present the cosmological analysis of the one-dimensional flux power spectrum of the Lyman-alpha forest from the first data release of the Dark Energy Spectroscopic Instrument (DESI). Using a model calibrated on cosmological hydrodynamical simulations with corrections for astrophysical contaminants and observational systematics, I analyze DESI measurements from z=2.2 to 4.2 to constrain the small-scale amplitude and logarithmic slope of the linear matter power spectrum at z=3. The robustness of the results is assessed through extensive tests on mock data and multiple analysis variations, with cosmological parameters blinded throughout. I then combine these constraints with baryon acoustic oscillation measurements from DESI and cosmic microwave background temperature, polarization, and lensing data from Planck, ACT, and SPT. While the addition of Lyman-alpha data does not significantly improve current limits on the sum of neutrino masses, it tightens constraints on the effective number of relativistic species, the running of the spectral index, and the running of the running by factors of 1.18, 1.27, and 1.90, respectively.
