Anisotropic power-law inflation for a model of two scalar and two vector fields

Tuan Q Do,W F Kao

doi:10.1140/epjc/s10052-021-09334-y

Tuan Q Do, W F Kao

Open Access

https://doi.org/10.1140/epjc/s10052-021-09334-y

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Abstract

Inspired by an interesting counterexample to the cosmic no-hair conjecture found in a supergravity-motivated model recently, we propose a multi-field extension, in which two scalar fields are allowed to non-minimally couple to two vector fields, respectively. This model is shown to admit an exact Bianchi type I power-law solution. Furthermore, stability analysis based on the dynamical system method is performed to show that this anisotropic solution is indeed stable and attractive if both scalar fields are canonical. Nevertheless, if one of the two scalar fields is phantom then the corresponding anisotropic power-law inflation turns unstable as expected.

Highlights

Observations of cosmic microwave background (CMB) anomalies, such as the hemispherical asymmetry and the cold spot observed by Wilkinson Microwave Anisotropy Probe (WMAP) and Planck, have been one of the great challenges of the standard inflationary models based on the cosmological principle [14]
It is straightforward to verify that we always have the result ζ κ1 for anisotropic powerlaw solutions, regardless of the nature of scalar fields as well as the number of scalar and vector fields counted in the Kanno–Soda– Watanabe (KSW) model
We have proposed a multi-field extension of the KSW anisotropic inflation, in which two scalar fields, φ and ψ, are allowed to non-minimally couple to two vector fields, Aμ and Aμ, respectively, through two corresponding couplings, f12(φ)Fμν Fμν and f22(ψ)Fμν F μν

Summary

Introduction

Observations of CMB anomalies, such as the hemispherical asymmetry and the cold spot observed by WMAP and Planck, have been one of the great challenges of the standard inflationary models based on the cosmological principle [14]. C (2021) 81:525 no-hair conjecture states that the late time universe should be inevitably homogeneous and isotropic consistent with the cosmological principle regardless of the early state of the universe If this conjecture is not valid, the observation shown in Ref. Non-trivial extensions with multi scalar fields coupled to one vector field have been proposed in Refs. There are other types of conformalviolating Maxwell coupling that lead to anisotropic inflation [105,106,107] Motivated by these observations, we would like to propose in this paper a non-trivial extension of the KSW model with multi scalar fields and multi vector fields.

The model

Anisotropic power-law solution

Stability analysis

A3 A4 A5 A6

Conclusions