Higgs G-inflation (1012.4238v1)

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.

Exploring Higgs G-inflation Models

This paper presents a comprehensive analysis of Higgs G-inflation, a subset within the framework of G-inflation models, focusing on incorporating the Standard Model (SM) Higgs boson as an inflaton. Traditionally, in the context of primordial inflation, the SM Higgs boson is deemed an inadequate inflaton due to shortcomings originating from strong self-interactions, which lead to primordial density fluctuations too large to match observational data. Previous models attempt to circumvent these issues by integrating non-standard kinetic terms or non-minimal coupling to gravity. Higgs G-inflation provides an alternative by leveraging the Galileon-like nonlinear derivative interaction to modify the kinetic term without imparting extra ghostly degrees of freedom.

A key innovation in Higgs G-inflation is using Galileon-type interactions to enable the Higgs boson to inflate by enhancing the kinetic term. This provides a distinctive consistency relation between the tensor-to-scalar ratio (r) and the tensor spectral index (nT), represented by $r = -32 \sqrt{6nT}/9$. This relationship is pivotal in distinguishing Higgs G-inflation models from standard inflation models that employ canonical kinetic terms.

Numerical Results and Claims:

The paper derives several salient results, notably predicting the scalar spectral index $n_s \approx 0.967$ and the tensor-to-scalar ratio $r \approx 0.14$ for $N = 60$ e-folds within Higgs G-inflation models. These values align closely with the observations made by cosmic microwave background experiments like WMAP and Planck, thereby offering a viable model for Higgs boson-driven inflation. Moreover, the proposed consistency equation suggests potential avenues for experimental verification, highlighting the model's practical relevance.

Implications and Future Developments:

Theoretically, Higgs G-inflation contributes to the broader cosmological discourse by expanding possible inflaton candidates within the SM, thereby addressing the limitations of canonical kinetic models. Practically, it provides a testable hypothesis that could be scrutinized by forthcoming high-precision cosmological observations targeting tensor perturbations. The provision of a novel consistency relation forms the basis for distinguishing G-inflation models in observational cosmology, effectively operationalizing Higgs G-inflation's claims.

Future work might explore extending these models to incorporate quantum corrections or interacting fields beyond the SM framework, considering how these might further nuance the understanding of inflationary dynamics. Additionally, investigating the role of higher-order Galileon terms could reveal further complexities in the interplay between kinetic terms and potential-driven inflation, potentially offering even greater flexibility in model building.

In conclusion, this paper delineates a substantive approach to utilizing the Higgs boson in inflation models by combining Galileon-induced kinetic enhancements, thus carving out space in the theoretical landscape for SM-compatible inflation scenarios. It sets a precedent for integrating complex kinetic terms into cosmological models—an endeavor promising novel insights into the primordial universe's dynamics.