Year: 2026
Type: preprint
Abstract: We quantify how the treatment of a strongly supercooled phase transition affects the particle-physics interpretation of a nanohertz gravitational-wave signal. For the classically conformal Abelian Higgs model, we calculate the nucleation rate at NLO in the dimensionally reduced theory and test the gradient expansion against explicit fluctuation determinants. A calibrated correction reproduces the determinant exponent with a mean absolute relative difference of $0.8\%$ and allows this information to be included throughout the parameter scan. We propagate the corrected rate through percolation, reheating and gravitational-wave production, and confront the resulting spectra with the NANOGrav 15-year and IPTA DR2 data. The corrected NLO calculation shifts the preferred gauge coupling by $9\%$ and $13\%$, respectively, and the input scale by $18\%$ for NANOGrav. After the determinant calibration, the largest theoretical uncertainties arise from uncertainties in the gravitational-wave spectra and the relation between $R_\star$ and $β/H$.
Source: arXiv (Cornell University)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: Deutsche Forschungsgemeinschaft
OpenAlex ID: W7212683602