 1e-10  1e-08  1e-06  1e-04  0.01  1  5  10  15  20  25  30  35  40  45 energy/ 0 mt tachyonic growth bubble collisions turbulence total kinetic gradient potential 12 23 31 gw v=0.001 M$_{p}$ $_{gw}$/10 $^{4}$ v=0.1 M$_{p}$ $_{gw}$/10 2 v=0.01 M$_{p}$ FIG. 17: The time evolution of the different types of energy (kinetic, gradient, potential, anisotropic components and gravitational waves for different lattices), normalized to the initial vacuum energy, after hybrid inflation, for a model with v = 10 − $^{3}$M$_{P}$ . One can clearly distinguish here three stages: tachyonic growth, bubble collisions and turbulence. The plot is taken from [779]. The initial energy density at the end of hybrid inflation is given by: ρ$_{0}$ = m $^{2}$v$^{2}$/ 4, with m 2 = λv $^{2}$, where v is the VEV of the Higgs field (water-field), so the fractional energy density in gravitational waves is r is roughly given by [779]: where 〈 ˙ h$_{ij}$ ˙ h ij 〉 $_{V}$, defined as a volume average like 1 V ∫ d $^{3}$x ˙ h$_{ij}$ ˙ h $^{ij}$, is extracted from the nu- merical simulations. There are three stages of preheating which contribute to gravity waves. First, an expo- nential growth driven by the tachyonic instability of the long-wave modes of the Higgs field. Second, the Higgs field oscillates around the true vacuum, as the Higgs’ bubbles collide and scatter off each other. Third, a period of turbulence is reached, during which the inflaton oscillates around its minimum and the Higgs is already settled in its vacuum [725, 779, 796]. In Ref. [808], it was pointed out that the turbulence phase does not contribute to any en- hancement in gravity waves, but if one includes the gauge fields in the stress-energy tensor it is possible to mimic the results of [779]. Gravity wave production has also been studied in a potential given by Eq. (395). The 187 ρ$_{GW}$ ρ$_{0}$ = 4 t$_{00}$ v $^{2}$m2 = 1 8 π Gv $^{2}$m2 〈 ˙ h$_{ij}$ ˙ h ij 〉 V , (406)