Mapping the shape of the scalar potential with gravitational waves

Understand

We study the dependence of the observable stochastic gravitational wave background induced by a first-order phase transition on the global properties of the scalar effective potential in particle physics.

• The scalar potential can be that of the Standard Model Higgs field, or more generally of any scalar field responsible for a spontaneous symmetry breaking in beyond-the-Standard-Model settings thatprovide for a first-order phase transition in the early universe.Characteristics of the effective potential include the relative depth of the true minimum ($E_\alpha^4$), the height of the barrier that separates it from the false one ($E_m^4$) and the separation between the two minima in field space ($v$), all at the bubble nucleation temperature.
• We focus on a simple yet quite general class of single-field polynomial potentials, with parameters being varied over several orders of magnitude.
• It is then shown that gravitational wave observatories such as aLIGO O5, BBO, DECIGO and LISA are mostly sensitive to values of these parameters in the region $E_\alpha \sim (0.1-10) \times E_m$.