Abstract
We consider a simple inflation model with a complex scalar field coupled to gravity non-minimally. Both the modulus and the angular directions of the complex scalar are slowly rolling, leading to two-field inflation. The modulus direction becomes flat due to the non-minimal coupling, and the angular direction becomes a pseudo-Goldstone boson from a small breaking of the global U(1) symmetry. We show that large non-Gaussianity can be produced during slow-roll inflation under a reasonable assumption on the initial condition of the angular direction. This scenario may be realized in particle physics models such as the Standard Model with two Higgs doublets.
Highlights
Cosmic inflation [1] has been the cornerstone beyond the standard big bang cosmology
We have studied a simple multi-field inflation model by introducing a complex scalar field with non-minimal coupling to gravity
We have considered the general action for the complex scalar field with dimension-4 interactions in the potential
Summary
Cosmic inflation [1] has been the cornerstone beyond the standard big bang cosmology It makes the present observable universe homogeneous and isotropic on large scales and gives rise to the primordial perturbations [2]. The potential of the modulus of the complex scalar becomes flat at large field value due to the non-minimal coupling. This is comparable to √a similar observation in Higgs inflation that the gauge boson mass during inflation is of O(1/ ξ), which is identified with the ultraviolet cutoff during inflation [14] This is a simple Lagrangian [19] which has been studied in models motivated from string theory: it includes a non-canonical kinetic term with e2b(φ) ≡ 1 − e−2φ/ 6 ,. As will be shown later, the above product form of the potential makes it easy to study two-field inflation, for the background evolution and for the explicit computations of the perturbations using the δN formalism
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