Speaker
Description
The detection of a stochastic gravitational wave background from the early Universe offers a unique window into beyond-the-Standard-Model physics. As we prepare for future space-based observatories such as LISA, TianQin, and others, precise theoretical predictions of the gravitational wave (GW) spectra generated by cosmological first-order phase transitions (FOPTs) are paramount. Conventional approaches often rely on the "bag model" approximation and fitting formulas, which can introduce substantial theoretical uncertainties and obscure model-dependent features.
In this talk, we present a self-consistent framework for calculating the GW spectrum sourced by sound waves during an FOPT, starting directly from the particle physics Lagrangian. By deriving the equation of state (EoS) and bubble nucleation rate directly from the effective potential, we accurately determine the hydrodynamic quantities and bubble wall velocity. This approach eliminates the need for simplified phenomenological parameters, such as the transition strength alpha, and allows for a congruous evaluation of the phase transition hydrodynamics.
We demonstrate the applicability of this framework using a well-motivated Beyond the Standard Model (BSM) scenario, the real scalar singlet extension of the Standard Model. Through generalised hybrid simulations that track fluid evolution after bubble collisions, we provide the first deterministic numerical calculations of GW spectra for these models. Our results highlight the importance of model-specific EoS in revealing complex spectral features, such as double broken power-laws, and establish a robust foundation for constraining BSM theories with upcoming gravitational wave data.
| I am the presenting author | Yes |
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