Double monodromy inflation: Gravitational wave factory for CMB-S4, LiteBIRD, and LISA

We consider a short rollercoaster cosmology based on two stages of monodromy inflation separated by a stage ofmatter domination, generated after the early inflaton falls out of slow roll. If the first stage is controlled by a flat potential, V similar to phi(p) withp < 1 and lasts N similar to 30-40 e-folds, the scalar and tensor perturbations at the largest scales will fit the CMB perfectly, and produce relic gravity waves with 0.02 less than or similar to r less than or similar to 0.06, which can be tested by LiteBIRD and CMB-S4 experiments. If in addition the first inflaton is strongly coupled to a hidden sector U(1), there will be an enhanced production of vector fluctuations near the end of the first stage of inflation. These modes convert rapidly to tensors during the short epoch of matter domination, and then get pushed to superhorizon scales by the second stage of inflation, lasting another 20-30 e-folds. This band of gravity waves is chiral, arrives today with wavelengths in the range of 10(8) km, and with amplitudes greatly enhanced compared to the long wavelength CMB modes by vector sources. It is therefore accessible to LISA. Thus our model presents a rare early universe theory predicting several simultaneous signals testable by a broad range of gravity wave searches in the very near future.

Automated summary

The short rollercoaster cosmology model based on two stages of inflation separated by matter domination predicts enhanced production of gravity waves, particularly when the first inflaton is strongly coupled to a hidden sector. This unique model offers multiple signals simultaneously testable by a variety of gravity wave searches in the near future, including CMB experiments and LISA.