Speaker
Description
Gravitational waves (GWs) from first-order cosmological phase transitions provide a powerful probe of physics beyond the Standard Model, and upcoming space-based GW observatories necessitate greater precision in theoretical predictions for these signals. In this work, we present a systematic framework for consistently predicting the GW spectra for such transitions.
We first outline the standard calculation of the GW spectrum utilising a fitting formula. In this approach, the physics of bubble nucleation and GW production is compressed into a small set of thermal parameters. This provides limited physical insight and introduces significant degeneracy in the GW inverse problem. We improve upon this approach by directly linking each calculation step to the effective potential, thereby establishing a pipeline that maintains consistency across the entire computational framework and provides a more robust GW spectrum. Our framework consistently couples the effective potential to the equation of state, bubble nucleation history, hydrodynamics, and bubble wall velocity.
We demonstrate this pipeline on the scalar-singlet extension of the Standard Model as a benchmark. Enforcing consistency throughout the calculation systematically shifts the predicted GW amplitude relative to the standard fitting-formula approach. More importantly, the resulting spectral shape departs from the broken-power-law form conventionally assumed in GW template fitting. Such templates may be insufficient for characterising signals and inferring BSM parameters from future LISA data.
| I am the presenting author | Yes |
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