Polarized gravitational waves from cosmological phase transitions

We estimate the degree of circular polarization for the gravitational waves generated during the electroweak and QCD phase transitions from the kinetic and magnetic helicity generated by bubble collisions during those cosmological phase transitions.

Figure 1

The GW polarization degree ${\mathcal{P}}^{\mathrm{GW}}(K)$ ($K=k/k_0$) in terms of the model parameter $h=1.0$, 0.5, 0.1.