  We use non-perturbative lattice calculations to investigate the
finite-temperature confinement transition of stealth dark matter, focusing on
the regime in which this early-universe transition is first order and would
generate a stochastic background of gravitational waves. Stealth dark matter
extends the standard model with a new strongly coupled SU(4) gauge sector with
four massive fermions in the fundamental representation, producing a stable
spin-0 'dark baryon' as a viable composite dark matter candidate. Future
searches for stochastic gravitational waves will provide a new way to discover
or constrain stealth dark matter, in addition to previously investigated
direct-detection and collider experiments. As a first step to enabling this
phenomenology, we determine how heavy the dark fermions need to be in order to
produce a first-order stealth dark matter confinement transition.
