Gravitational Wave Signatures of Particle Physics Models with Extended Gauge Symmetries*

The Standard Model of elementary particles describes remarkably well the physics at the most fundamental scale, but it leaves several questions unanswered: What is the nature of dark matter? What is the origin of the matter-antimatter asymmetry of the Universe? How do neutrinos become massive? Finding answers to those questions requires an understanding of what happened when high energy physics effects were prevalent in the Universe, i.e., a small fraction of a second after the Big Bang. Diving this far back into the Universe's history has become possible thanks to the recent first detection of gravitational waves. A primordial stochastic gravitational wave background, although not yet discovered, is expected to carry information precisely about the very early stages of the evolution of the Universe. Those gravitational waves could have been generated through a variety of processes, including first order phase transitions, cosmic strings, and domain walls. Their expected spectrum is within the reach of upcoming gravitational wave experiments, such as LISA, DECIGO, Big Bang Observer, Cosmic Explorer and Einstein Telescope. I will discuss how to use such signals to probe particle physics theories with extended gauge symmetries broken at high energy scales, otherwise completely inaccessible in conventional particle physics experiments.