Gravitational Waves from Cosmological Phase Transitions
Moritz Breitbach (JGU Mainz)

In 2015, gravitational waves originating from a binary black hole merger were directly detected by the LIGO observatory, a revolutionary discovery which was awarded the 2017 Nobel Prize of Physics. The detection capabilities of planned pulsar timing arrays and space-based observatories herald a new era of astronomical and cosmological research, complementary to current and future collider experiments. Cosmological phenomena such as cosmic strings, the inflation and phase transitions are believed to generate a stochastic gravitational wave background.

We focus on cosmological phase transitions driven by the temperature dependence of the thermodynamical free energy density in the expanding and cooling universe. If such a transition occurs abruptly, i.e. if it is first-order, bubbles of the new phase nucleate, expand and finally collide. These collisions cause anisotropies acting as sources for gravitational radiation. After their production, the gravitational waves propagate through space undisturbed until they might be detected in the form of a redshifted stochastic background today. We present different models that feature dark matter candidates together with first-order phase transitions.