The devil in the transition: NLO nucleation and the particle physics behind the PTA signal
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⋆ and β/H.
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BibTeX
@misc{puchadesibanez2026devil,
title = {{The devil in the transition: NLO nucleation and the particle physics behind the PTA signal}},
author = {Cristina Puchades-Ibáñez and Pedro Schwaller},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.12098},
eprint = {2609.12098},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.12098},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The devil in the transition: NLO nucleation and the particle physics behind the PTA signal
AU - Cristina Puchades-Ibáñez
AU - Pedro Schwaller
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.12098
UR - https://arxiv.org/abs/2609.12098
AB - 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_⋆ and β/H.
ER -