Gravitational Waves at Strong Coupling from an Effective Action

Using a holographic derivation of a quantum effective action for a scalar operator at strong coupling, we compute quasiequilibrium parameters relevant for the gravitational wave signal from a first-order phase transition in a simple dual model. We discuss how the parameters of the phase transition vary with the effective number of degrees of freedom of the dual field theory. Our model can produce an observable signal at LISA if the critical temperature is around a TeV, in a parameter region where the field theory has an approximate conformal symmetry.