Revisiting the cosmological phase transitions on the inflationary gravitational waves with BKP18

Abstract

The effects of the electroweak and the quark-gluon plasma phase transitions are considered in the course of evolution of the universe and the resulting spectrum of primordial gravitational waves normalized with the BICEP/Keck and Planck joint data is obtained. The QGP index n=0.203 leads to a step reduction of ∼17.6% in the amplitude and a step of ∼35% in the energy density spectrum for frequency >1.36×10−8Hz. On the other hand, the EW index w=0.0147 leads to a step of ∼1.47% in the amplitude and a step of ∼2.9% in the energy density spectrum for frequency >10−5Hz. The combined effect of phase transitions on the inflationary gravitational waves leads to about ∼19% reduction in the amplitude and an overall reduction of ∼38% in the energy density as compared to the spectrum without considering these phase transitions. The resulting spectrum for R2 inflation model is found to be well within the BBN bound and its potential detectability is tested with the power-law integrated sensitivity curves of the future LISA, DECIGO, BBO, SKA and IPTA experiments.