Higgs G-inflation

TL;DR

The paper addresses the challenge of Higgs-driven inflation within the Standard Model by introducing a Galileon-like derivative interaction (G-terms) to form potential-driven G-inflation. It develops a general slow-roll framework, derives perturbation properties, and identifies a model-independent consistency relation $r = -\frac{32\sqrt{6}}{9} n_T$, enabling discrimination from canonical inflation. As a concrete realization, it shows Higgs G-inflation can yield $n_s\approx0.967$ and $r\approx0.14$ for ${\cal N}\approx60$, with a COBE/WMAP-compatible normalization fixing the inflationary scale, $M\sim10^{13}$ GeV. The work highlights that Galileon interactions broaden inflationary possibilities while keeping non-Gaussianity modest, and it posits observational tests (e.g., Planck-era data) to distinguish this scenario from standard models.

Abstract

A new class of inflation models within the context of G-inflation is proposed, in which the standard model Higgs boson can act as an inflaton thanks to Galileon-like non-linear derivative interaction. The generated primordial density perturbation is shown to be consistent with the present observational data. We also make a general discussion on potential-driven G-inflation models, and find a new consistency relation between the tensor-to-scalar ratio $r$ and the tensor spectral index $n_T$, $r = -32 \sqrt{6}n_T / 9$, which is crucial in discriminating the present models from standard inflation with a canonical kinetic term.

Figures (4)

• Figure 1: The Galileon effect operates above the magenta line, and the slow-roll condition $\epsilon <1$ is satisfied above the cyan line. Chaotic G-inflation therefore takes place in the shaded region, while in the dotted region standard chaotic inflation occurs. In particular, in the green region the potential is rather steep and hence standard inflation would not proceed, but G-inflation can. For $M>M_c$ it can be seen that a standard inflationary phase follows G-inflation.
• Figure 2: The same diagram as Fig. \ref{['fig:chaotic.eps']}, but for new and hybrid inflation with $|\eta_{\rm std}|<1$. The Galileon effect operates above the magenta line, the slow-roll condition $\epsilon < 1$ is satisfied below the cyan line, and the constant piece $V_0$ dominates the potential below the green line.
• Figure 3: The same diagram as Fig. \ref{['fig:chaotic.eps']}, but for new and hybrid inflation with $|\eta_{\rm std}|> 1$. The slow-roll conditions are satisfied below the $\epsilon=1$ line and above the $\eta=1$ line. Therefore, even though $\eta_{\rm std}>1$, G-inflation can occur in the green, shaded region.
• Figure 4: The evolution of $|\phi|$ (blue, oscillating line) and $\rho$ (purple line) in the very final stage of Higgs G-inflation and in the reheating stage thereafter. We set $a(t_{\rm end})=1$ with $\epsilon(t_{\rm end})=1$. The parameters are given by $\lambda=0.1$ and $M=0.01\times M_c$.