Gravitational waves from first-order cosmological phase transitions

A first-order cosmological phase transition that proceeds through the nucleation and collision of true-vacuum bubbles is a potent source of gravitational radiation. Possibilities for such include first-order inflation, grand-unified-theory-symmetry breaking, and electroweak-symmetry breaking. We have calculated gravity-wave production from the collision of two scalar-field vacuum bubbles, and, using an approximation based upon these results, from the collision of 20 to 30 vacuum bubbles. We present estimates of the relic background of gravitational waves produced by a first-order phase transition; in general, ${\mathrm{\Omega }}_{\mathrm{GW}}$∼${10}^{\mathrm{-}9}$ and f∼(${10}^{\mathrm{-}6}$ Hz) (T/1 GeV).