The characteristics of the cosmic microwave background provide circumstantial evidence that the hot radiation-dominated epoch in the early Universe was preceded by a period of inflationary expansion. Here, we show how a measurement of the stochastic gravitational wave background can reveal the cosmic history and the physical conditions during inflation, subsequent pre- and reheating, and the beginning of the hot big bang era. This is exemplified with a particularly well-motivated and predictive minimal extension of the Standard Model, which is known to provide a complete model for particle physics—up to the Planck scale—and for cosmology—back to inflation.

• Received 21 March 2022
• Accepted 10 August 2022

DOI:https://doi.org/10.1103/PhysRevD.106.063027

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society