Abstract
We consider a general chaotic inflation model with non-canonical kinetic term, resulting in attractor solutions for the inflation of quadratic or other monomial type. In particular, the form of the kinetic term and the potential is fixed due to the requirement that the inflation model is a quadratic form in the large field values of the inflaton. We show that a large coupling in the non-canonical kinetic term allows for the slow-roll inflation with sub-Planckian field values of the inflaton and the successful predictions of the quadratic or other monomial type chaotic inflation in light of BICEP2 results are maintained in our model. We find that due to the large rescaling of the inflaton field in the vacuum, there is no unitarity problem below the Planck scale.
Highlights
The BICEP2 collaboration [1] has recently announced the evidence for B-modes in the CMB polarization, which are presumably originated from the primordial gravitational waves of cosmic inflation
Variations of quadratic inflation with a polynomial potential can be consistent with Planck + BICEP2 [32], we focus on the simplest case with attractor solutions for the quadratic inflation
We have proposed the general chaotic inflation models that share the predictions of the usual chaotic inflation with canonically normalized inflaton field and are favored by the recent BICEP2 observation of a large tensor-to-scalar ratio
Summary
The BICEP2 collaboration [1] has recently announced the evidence for B-modes in the CMB polarization, which are presumably originated from the primordial gravitational waves of cosmic inflation. A large r suggests that the inflaton field with canonical kinetic term must have traveled to trans-Planckian field values during inflation, so there is a concern about how to address the quantum gravity effects suppressed by the Planck scale from the pointview of the effective field theory. In our general quadratic inflation, the field value of the noncanonical inflaton remains sub-Planckian during inflation, thanks to a large coupling in the non-canonical kinetic term [15,24–26]. There were previous discussions on more general polynomial chaotic inflation models obtaining a large tensor-to-scalar ratio with sub-Planckian inflation field values [27–30]. We begin with a model description of the general chaotic inflation focusing on the quadratic form and discuss the inflation constraints on the model in view of Planck and BICEP2.
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