Gravitational waves of a first-order QCD phase transition at finite coupling from holography

We consider a holographic study of coupling dependent gravitational waves produced by the cosmic first order QCD phase transition at finite baryochemical potential. In the dual description, the first-order QCD phase transition corresponds to the first-order Hawking-Page phase transition in Gauss-Bonnet gravity. At intermediate coupling, we obtain key quantities characterizing the gravitational wave energy density spectrum. We then find that the gravitational waves might be detected for sufficiently large Gauss-Bonnet coupling, while sound waves play an important role in the spectrum. We also consider a supercooling scenario during the QCD phase transition and show that the gravitational waves generated during this period can be detected by pulsar timing array experiments.