Gravitational Waves from the Very Early Universe – Arthur Kosowsky

The recent signal detection by pulsar timing arrays has renewed interest in stochastic backgrounds of gravitational waves. Two promising possibilities are gravitational waves generated during an initial period of inflationary expansion, and gravitational waves generated during a first-order phase transition. I will review the signals which may arise from these processes, and prospects for detection with a range of upcoming experiments. Such signals hold the promise of obtaining direct information about the universe from its earliest moments at energy scales far beyond the reach of any envisioned terrestrial experiments.