Density of states for gravitational waves

We present ongoing investigations of the first-order confinement transition of a composite dark matter model, to predict the resulting spectrum of gravitational waves. To avoid long autocorrelations at the first-order transition, we employ the Logarithmic Linear Relaxation (LLR) density of states algorithm. After testing our calculations by reproducing existing results for compact U(1) lattice gauge theory, we focus on the pure-gauge SU(4) theory related to the Stealth Dark Matter model.