2025/11/03 by Malcolm Fairbairn, Fairbairn, Malcolm, Lucien Heurtier +3 · 1 voice
Physics and Astronomy · #Cosmology and Gravitation Theories #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #High Energy Physics - Phenomenology (hep-ph) #Particle physics theoretical and experimental studies #astro-ph.CO #hep-ph
paper · pdf · doi:10.48550/arxiv.2511.01612
openalex publication_date 2025/11/03 · arxiv published 2025/11/03 · openalex created_date 2025/11/06 · arxiv updated 2026/06/18 · openalex updated_date 2026/08/03
We investigate the scale dependence of the primordial power spectrum by combining \Planck, ACT DR6, SPT-3G, and eBOSS Lyman-α forest data, extending sensitivity to smaller comoving scales than those probed by the CMB alone. Within a parametrisation based on a Taylor expansion around the pivot scale, we constrain the running of the spectral index αs and its running βs. By using eBOSS likelihoods exhibiting a suppression of small-scale power either in amplitude or spectral index, we show that the latter can be accommodated by correlated variations of (αs,βs), leading to a preference for non-zero running. We show that inflationary potentials with localised features -- such as Gaussian dips, bumps, or axion-monodromy modulations -- can reproduce the inferred scale dependence while remaining compatible with current CMB constraints. We release the public \tt PIPE code to enable systematic tests of inflationary potentials against current CMB datasets.