Occurrence of Tachyonic Preheating in the Mixed Higgs-$R^2$ Model

Understand

It has recently been suggested that at the post-inflationary stage of the mixed Higgs-$R^2$ model of inflation efficient particle production can arise from the tachyonic instability of the Higgs field.

• It might complete the preheating of the Universe if appropriate conditions are satisfied, especially in the Higgs-like regime.
• In this paper, we study this behavior in more depth, including the conditions for occurrence, analytical estimates for the maximal efficiency, and the necessary degree of fine-tuning among the model parameters to complete preheating by this effect.
• We find that the parameter sets that cause the most efficient tachyonic instabilities obey simple laws in both the Higgs-like regime and the $R^2$-like regime, respectively.