Double-graviton production from Standard Model plasma
Jacopo Ghiglieri, M. Laine, J. Schütte-Engel, Enrico Speranza
Abstract
Abstract The thermal plasma filling the early universe generated a stochastic gravitational wave background that peaks in the microwave frequency range today. If the graviton production rate is expressed as a series in a fine-structure constant, α , and the temperature over the Planck mass, T 2 / m pl 2 , then the lowest-order contributions come from single (∼ αT 2 / m pl 2 ) and double (∼ T 4 / m pl 4 ) graviton production via 2 → 2 scatterings. We show that in the Standard Model, single-graviton production dominates if the maximal temperature is smaller than 4 × 10 18 GeV. This justifies previous calculations which relied solely on single-graviton production. We mention Beyond the Standard Model scenarios in which the single and double-graviton contributions could be of comparable magnitudes. Finally, we elaborate on what these results imply for the range of applicability of General Relativity as an effective theory.