Resonant particle production with non-minimally coupled scalar fields in preheating after inflation

Abstract

We investigate a resonant particle production of a scalar field $χ$ coupled non-minimally to a spacetime curvature $R$ ($ξR χ^2$) as well as to an inflaton field $ϕ$ ($g^2ϕ^2χ^2$). In the case of $g < 3 \times 10^{-4}$, $ξ$ effect assists $g$-resonance in certain parameter regimes. However, for $g > 3 \times 10^{-4}$, $g$-resonance is not enhanced by $ξ$ effect because of $ξ$ suppression effect as well as a back reaction effect. If $ξ\approx -4$, the maximal fluctuation of produced $χ$-particle is $\sqrt{< χ^2 >}_{max} \approx 2 \times 10^{17}$ GeV for $g < 1 \times 10^{-5}$, which is larger than the minimally coupled case with $g \approx 1 \times 10^{-3}$.