Production of gravitational waves during preheating in the Starobinsky inflationary model

Abstract

Abstract The production of GWs during preheating in the Starobinsky model with a nonminimally coupled auxiliary scalar field is studied through the lattice simulation in this paper. We find that the GW spectrum $$\Omega _{\mathrm{gw}}$$ Ωgw grows fast with the increase of the absolute value of coupling parameter $$\xi $$ ξ . This is because the resonant bands become broad with the increase of $$|\xi |$$ |ξ| . When $$\xi 0$$ ξ>0 . $$\Omega _{\mathrm{gw}}$$ Ωgw reaches the maximum at $$\xi =-20$$ ξ=-20 ($$\xi =42$$ ξ=42 for the case $$\xi >0$$ ξ>0 ) and then decreases with slight oscillation. Furthermore we find that the GWs produced in the era of preheating satisfy the limits from the Planck and next-generation CMB experiments.