A stochastic background of gravitational waves from hybrid preheating

TL;DR

The power spectrum of the stochastic background of gravitational waves produced at reheating after hybrid inflation is studied and it is found that the amplitude could be significant for high-scale models, although the typical frequencies are well beyond what could be reached by planned gravitational wave observatories.

Abstract

The process of reheating the universe after hybrid inflation is extremely violent. It proceeds through the nucleation and subsequent collision of large concentrations of energy density in bubble-like structures, which generate a significant fraction of energy in the form of gravitational waves. We study the power spectrum of the stochastic background of gravitational waves produced at reheating after hybrid inflation. We find that the amplitude could be significant for high-scale models, although the typical frequencies are well beyond what could be reached by planned gravitational wave observatories like LIGO, LISA or BBO. On the other hand, low-scale models could still produce a detectable stochastic background at frequencies accesible to those detectors. The discovery of such a background would open a new window into the very early universe.

Figures (3)

• Figure 1: 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.
• Figure 2: We show here the comparison between the power spectrum of gravitational waves obtained with increasing lattice resolution, to prove the robustness of our method. The different realizations are characterized by the number of lattice points (N), the minimum lattice momentum (p$_{\rm min}$) and the lattice spacing (ma). The growth is shown in steps of $m\Delta t = 1$ for the lower spectra and $m\Delta t = 5$ for the rest.
• Figure 3: The sensitivity of the different gravitational wave experiments, present and future, compared with the possible stochastic backgrounds; we include the White Dwarf Binaries (WDB) WDB and chaotic preheating ($\lambda\phi^4$) TkachevGW for comparison. Note the two well differentiated backgrounds from high-scale and low-scale hybrid inflation.