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Paper IPM / P / 11248  


Abstract:  
We study the tachyonic resonance preheating generated from the bosonic trilinear ϕχ^{2} interactions following inflation period caused by the quartic inflationary potential λϕ^{4}/4. In particular, we focus on the effects of expansion of the Universe during the preheating era. The trilinear interaction, in contrast to the fourleg ϕ^{2}χ^{2},
breaks the conformal symmetry explicitly and the resonant source term becomes nonperiodic, making the Floquet theorem inapplicable. We find that the occupation number of the produced χparticles has a nonlinear exponential growth with exponent ∼ x^{3/2}, where x is the conformal time.
This should be contrasted with preheating from a periodic resonant source, arising for example from fourlegs ϕ^{2}χ^{2} interaction, where the occupation number has a linear exponential growth. We present an analytic method to compute the interference term coming from phases accumulated in nontachyonic scattering regions and show that the effects of
the interference term causes ripples on x^{3/2} curve, a result which is
confirmed by numerical analysis. Studying the effects of backreaction of the χparticles, we show that tachyonic resonance preheating in our model can last long enough to transfer most of the energy from the background inflation field ϕ, providing an efficient model for preheating in the chaotic inflation models.
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