Inhomogeneous preheating in multi-field models of cosmological perturbation

We consider inhomogeneous preheating in multi-field models of cosmological perturbation. After preheating, two fields are trapped at an enhanced symmetric point. One field is an oscillating field and the other is a light field that plays an important role in generating perturbation. In this presentation, we consider two types of potential for the light field. Submitted for the SUSY07 proceedings. [email protected] 1 1 Motivation for the “Alternatives” to the traditional inflation We consider the following: • Traditional Inflaton According to the traditional inflationary scenario, the spectrum of the curvature perturbation is generated by the inflaton field. Therefore, the spectrum is essentially determined by the inflation model alone. • Alternatives to the traditional inflation The traditional scenario is not the only way to generate the cosmological perturbation. The primordial density perturbation may instead originate from the vacuum fluctuation of a “non-inflaton” field. Considering alternatives to the traditional scenario, the inflation model can be eliminated as the source of the generation of the curvature perturbation. Hence, we can expect that inflation may be separated from the problems related to the generation of the cosmological perturbation. For the treatment of nontraditional cosmological perturbation, we introduce “φ2” as the non-inflaton field . 1.1 Problem in low-scale inflation (typical example) For traditional inflation, the spectrum of the curvature perturbation is given by PR(k) = 1 24π2M4 p VI ǫI (Traditional Inflation) (1.1) Assuming that the scale of the inflation is much smaller than the Planck scale, serious fine-tuning is required. For example: V 1/4 I < 10 GeV → ǫI < 10 . (1.2) Since a low-scale gravity model is still an important possibility that could be tested in future experiments, it is important to consider how low-scale inflation takes place. Future experiments may or may not put a bound on H 1/4 I , such as HI ≤ O(TeV).