5 σ tension between Planck cosmic microwave background and eBOSS Lyman-alpha forest and constraints on physics beyond ΛCDM

We find that combined Planck cosmic microwave background, baryon acoustic oscillations and supernovae data analyzed under ΛCDM are in 4.9σ tension with eBOSS Lyα forest in inference of the linear matter power spectrum at wavenumber ∼ 1 h Mpc^-1 and redshift = 3. Model extensions can alleviate this tension: running in the tilt of the primordial power spectrum (α_s∼ -0.01); a fraction ∼ (1 - 5)% of ultra-light axion dark matter (DM) with particle mass ∼ 10^-25 eV or warm DM with mass ∼ 90 eV. The new DESI survey, coupled with high-accuracy modeling, will help distinguish the source of this discrepancy.