Double-graviton production from Standard Model plasma

J. Ghiglieri, M. Laine, J. Schütte-Engel, E. Speranza.


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, \alpha, and the temperature over the Planck mass, T^2_{ } / m_{\rm pl}^2, then the lowest-order contributions come from single (\sim \alpha T^2_{ }/m_{\rm pl}^2) and double (\sim T^4_{ }/m_{\rm pl}^4) graviton production via 2\to 2 scatterings. We show that in the Standard Model, single-graviton production dominates if the maximal temperature is smaller than 4\times 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.

Associated Fellows