Higgs inflation and general initial conditions

Abstract

A Higgs field of particle physics can play the role of the inflaton in the early universe if it is non-minimally coupled to gravity. The Higgs inflation scenario predicts a small tensor to scalar ratio: r 0.003. Although this value is consistent with the upper bound r < 0.12 given by the BICEP2/Keck Array and Planck data, it is not at their maximum likelihood point: r 0.05. Inflationary observables depend not only on the inflationary models, but they also depend on the initial conditions of inflation. Changing the initial state of inflation can improve the value of r . In this work, we study the Higgs inflation model under general initial conditions and show that there is a subset of these general initial conditions which leads to enhancement of r . Then we show that this region of parameter space is consistent with a non-Gaussianity bound.

Ultraviolet behaviour of Higgs inflation models

“…Among the existing inflationary models, Higgs Inflation is particularly attractive since it aims to explain cosmological inflation in terms of a scalar field that plays a central role in conventional particle physics, namely the standard Higgs boson that realises electroweak symmetry breaking at low energies [1]. The model, although in very good agreement with cosmological observations [2], requires a non-minimal coupling of the inflaton/Higgs to the Ricci scalar ξ|H| 2 R with rather large values of the corresponding dimensionless parameter ξ ∼ O(10 4 − 10 9 ), which through the derivative interactions induced in the Einstein frame seems to cause a tree-level unitarity violation at a scale much below the Planck mass M P [3][4][5][6][7][8][9][10][11][12][13][14].…”

Mimetic gravity: mimicking the dynamics of the primeval universe in the context of loop quantum cosmology

“…The Higgs field playing the role of inflaton, the usual scalar field associated with the standard slow-roll inflation, is an idea that has been discussed since the first inflationary models were developed, as can be seen in [40]. Notwithstanding, HI describes inflation as a chaotic scenario in which a Higgs field is coupled with the curvature through large values of self-coupling λ and non-minimal coupling ξ parameters [41][42][43]. Basically, HI reproduces the successful flat potential of slow-roll approximation by coupling a primordial version of the current Higgs field with the Ricci scalar.…”

“…with u = ξ h/M Pl . Since HI is built under the requirement ξ 1, if the non-minimal coupling is chosen to be in the range 1 ξ M 2 Pl /v 2 then equation (42) corresponds to the conformal transformation Ω 2 = e 2χ/ √ 6M Pl . Thus, the potential V (χ) is given by…”

Predictions of Spectral Parameters by Several Inflationary Universe Models in Light of the Planck Results

“…Higgs inflation has recently been considered by Bezrukov et al [125,126], by Gorbunov and Tokareva [127] and by Zeynizadeh and Akbarieh [128] in connection with observations of spectral properties of the cosmic microwave background radiation. Rubio [129] has given the Higgs potential as …”