Higgs inflation (1807.02376v3)

Abstract: The properties of the recently discovered Higgs boson together with the absence of new physics at collider experiments allows us to speculate about consistently extending the Standard Model of particle physics all the way up to the Planck scale. In this context, the Standard Model Higgs non-minimally coupled to gravity could be responsible for the symmetry properties of the Universe at large scales and for the generation of the primordial spectrum of curvature perturbations seeding structure formation. We overview the minimalistic Higgs inflation scenario, its predictions, open issues and extensions and discuss its interplay with the possible metastability of the Standard Model vacuum.

Analysis of "Higgs Inflation" by Javier Rubio

The paper "Higgs inflation," authored by Javier Rubio, pertains to the integration of the Higgs boson into the framework of cosmic inflation, which seeks to explain the early accelerated expansion of the Universe. Using the properties of the Higgs boson and leveraging the absence of new findings at collider experiments, the paper considers extending the Standard Model (SM) of particle physics to the Planck scale, thereby exploring whether the Higgs boson could drive inflation.

First and foremost, the paper examines the minimalistic scenario of Higgs inflation where the Higgs boson is non-minimally coupled to gravity. This coupling, parameterized by a dimensionless constant, enables the transformation from standard quantum field theory to general relativity through a dynamic, scale-dependent adaptation of field equations, thus offering a mechanism for maintaining perturbative unitarity up to the Planck scale.

In the introduction, the author articulates various facets of the inflationary paradigm, citing its capacity to address cosmic isotropy and homogeneity puzzles and engender primordial perturbations instrumental in structure formation. Despite inflation's success, the inflaton—essentially the particle effectuating this period—remains unidentified. Notably, the Large Hadron Collider's discovery of the Higgs boson yields a measured mass $m_H = 125.18 \pm 0.16$ GeV, which is particularly suited for high-energy scale stability under certain conditions relating to the top quark Yukawa coupling $y_t$.

The paper discusses the subtleties of SM vacuum stability and suggests that, in the absence of new physics, the Higgs boson could be the inflaton. Yet, under normal metrics, the Higgs self-interaction would be too substantial for a sufficiently prolonged inflation. Instead, the introduction of a non-minimal coupling to the Ricci scalar in the gravitational sector allows the effective kinetic term of the Higgs field to diversify in the high-field scenario. This procedure mirrors a chiral SM with modified inflationary capabilities.

Rubio explores the qualitative predictions stemming from Higgs inflation, adopting a robust effective field theory (EFT) approach. He resolves that quantum corrections heavily influence potential shapes and inflationary observables. Importantly, the renormalization group's running logarithmically alters the potential, fostering a flat inflationary trajectory—specifically, a plateau potentially adorned with an inflection point.

The implications of Higgs inflation extend far—whether in reinforcing the absolute necessity of new physics or providing profound insights should SM alone suffice, especially examining the intersection of reheating, metastability, and high-scale physics without novel particle detection. In addition, Rubio evaluates model variations such as the Palatini formulation, which proposes distinguishing characteristics from the traditional metric approach and discussing extensions toward a complete scale invariant theory.

The paper establishes parameters necessitating precision verifications, especially in inflation observables like $n_s$ (spectral index) and $r$ (tensor-to-scalar ratio), to distinguish among current cosmological models. Furthermore, rendering Higgs inflation more coherent requires reconciling it with metastability regions determined by $m_H$ and $y_t$ constraints.

Rubio’s work demonstrates that Higgs inflation can be more than a theoretical amusement; it connects cosmology with particle physics in a potentially observable manner. Higgs inflation holds places well beyond the present blank spaces of our cosmology and particle physics jigsaw puzzle, anticipating further exploration in the evolution and destiny of our Universe. The research calls for enhanced theoretical model-building and observational prospects, with a likely focus on critical examination of inflationary perturbations which could empirically align the inflationary plateau with future cosmological datasets.

In conclusion, the paper presents a substantive, technical exploration of Higgs inflation's feasibility and implications, iterating on theoretical constructs and confronting their alignment with the contiguous frontier of particle physics and cosmology. The comprehensive assessment from EFT principles underscores the intricate dance between quantum scales and cosmic macrodynamics, heralding a fertile ground for future theoretical and practical inquiries.