Resonant decay of Bose condensates

Abstract

We present results of fully non-linear calculations of decay of the inflaton interacting with another scalar field X. Combining numerical results for cosmologically interesting range of resonance parameter, q \leq 10^6, with analytical estimates, we extrapolate them to larger q. We find that scattering of X fluctuations off the Bose condensate is a very efficient mechanism limiting growth of X fluctuations. For a single-component X, the resulting variance, at large q, is much smaller than that obtained in the Hartree approximation.

Figures (4)

• Figure 1: Variances of the fields $X$ (solid curve) and $\phi$ (dotted curve) in Model 1 in flat space-time. The filled square marks the spike value of $\langle X^2 \rangle$ at the end of resonance.
• Figure 2: Filled squares and crosses are the spike values, $\langle X^2 \rangle_{\rm s}$, at the end of resonance obtained in fully non-linear simulations of Model 1 (flat space-time) and Model 2; empty boxes are the spike values at the first plateau in the Hartree approximation. Stars correspond to $\langle X^2 \rangle$ at the moment when zero mode decayed in Model 1 in expanding universe.
• Figure 3: Variances of fields $X$ and $\phi$, together with the inflaton zero-momentum mode, in Model 1 in expanding universe.
• Figure 4: Power spectrum of the field $X$ in Model 1 in expanding universe, output every period at maxima of $\phi_0(\tau)$.