We might have observed \u201cthe end of the first act\u201d of the universe’s evolution in recent high-precision CMB observations. In a new paper, we show that ACT DR6 data provide evidence for an accelerated running of the primordial spectral index, which would imply a breakdown of the first stage of inflation and, at the same time, resolve the Hubble tension in the DRMD Hot NEDE model (see previous posts). <\/p>\n\n\n\n
Inflation occurs during the first period of the universe’s evolution after the Big Bang, and observing the breakdown in the first stage of inflation therefore amounts to observing the end of the first act of the universe’s evolution. The accelerated running compensates for the increased damping at small scales in the CMB and therefore allows for a larger N_eff in models with self-interacting dark radiation, such as Hot NEDE with DRMD. The idea that inflation occurred in several acts (or stages) has long been considered more natural than 60 e-folds of single-field slow-roll inflation. In our paper, we also discuss how the end of the first act could occur through gauge-field production in axion monodromy-like inflation or through a tachyonic instability. For more details, see our new paper: https:\/\/arxiv.org\/abs\/2604.26541<\/a><\/p>\n\n\n\n Work in collaboration with Mathias Garny (Technical University of Munich) and Florian Niedermann (Nordita).<\/p>\n\n\n\n We might have observed \u201cthe end of the first act\u201d of the universe’s evolution in recent high-precision CMB observations. In a new paper, we show that ACT DR6 data provide evidence for an accelerated running of the primordial spectral index, … Continue reading ![\"\"](\"https:\/\/universe-origins.dk\/sloth\/wp-content\/uploads\/2026\/04\/Screenshot-2026-04-30-at-08.09.37-1024x377.png\")
<\/a><\/figure>\n","protected":false},"excerpt":{"rendered":"