Improved predictions on Higgs-Starobinsky inflation and reheating with ACT DR6 and primordial gravitational waves
Year: 2025
Type: article
Abstract: In this letter, we investigate the implications of recent CMB observations for Higgs–Starobinsky inflationary models and their associated reheating dynamics, utilising data from ACT DR6, Planck 2018, BICEP/Keck 2018, and DESI, collectively referred to as P-ACT-LB-BK18. In addition to direct CMB constraints, we incorporate indirect bounds arising from the potential overproduction of primordial gravitational waves (PGWs), particularly through limits on the effective number of relativistic species, Δ N e f f , during Big Bang Nucleosynthesis (BBN). These constraints become especially relevant in scenarios featuring a stiff post-inflationary equation of state w R H ≥ 0.58 . Our analysis shows that, when both P-ACT-LB-BK18 data and Δ N e f f bounds are considered, the viable number of inflationary e-folds is restricted to the range 57.9–62.2 at the 2 σ confidence level (C.L.). Correspondingly, the reheating temperature is constrained to lie between the BBN energy scale and 10 12 GeV, with the post-inflationary equation-of-state parameter satisfying w R H > 0.41 . However, no parameter space remains viable at the 1 σ C.L. once Δ N e f f constraints from PGWs are included, rendering the Higgs–Starobinsky model highly restricted.
Source: Physics Letters B
Authors: Md Riajul Haque, Sourav Pal, Debarun Paul
Institution: Indian Statistical Institute
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: diamond
Award: G4788381450
OpenAlex ID: W4413848340