Quasi-Conformal Models and the Early Universe

Abstract

Extensions of the Standard Model and general relativity featuring a UV fixed point can leave observable implications at accessible energies. Although mass parameters such as the Planck scale can appear through dimensional transmutation, all fundamental dimension-4 operators can (at least approximately) respect Weyl invariance at finite energy. An example is the Weyl-squared term, whose consistency and observational consequences are studied. This quasi-conformal scenario emerges from the UV complete quadratic gravity and is a possible framework for inflation. We find two realizations. In the first one the inflaton is a fundamental scalar with a quasi-conformal non-minimal coupling to the Ricci scalar. In this case the field excursion must not exceed the Planck mass by far. An example discussed in detail is hilltop inflation. In the second realization the inflaton is a pseudo-Goldstone boson (natural inflation). In this case we show how to obtain an elegant UV completion within an asymptotically free QCD-like theory, in which the inflaton is a composite scalar due to new strong dynamics. We also show how efficient reheating can occur. Unlike the natural inflation based on Einstein gravity, the tensor-to-scalar ratio is well below the current bound set by Planck. In both realizations mentioned above, the basic inflationary formulae are computed analytically and, therefore, these possibilities can be used as simple benchmark models.

25 pages, 9 figures. Version published in EPJC

References in corpus (17)

• The Standard Model Higgs boson as the inflaton
• Inflation scenario via the Standard Model Higgs boson and LHC
• Higgs inflation at the critical point
• Higgs inflation still alive
• Higgs inflation from Standard Model criticality
• Gravitational corrections to Standard Model vacuum decay
• Causality as an emergent macroscopic phenomenon: The Lee-Wick O(N) model
• Metastability in Quadratic Gravity
• A Simple Motivated Completion of the Standard Model below the Planck Scale: Axions and Right-Handed Neutrinos
• Softened Gravity and the Extension of the Standard Model up to Infinite Energy
• On the Quantisation of Complex Higher Derivative Theories and Avoiding the Ostrogradsky Ghost
• Inflation in models with Conformally Coupled Scalar fields: An application to the Noncommutative Spectral Action
• Rapid roll Inflation with Conformal Coupling
• Stable Asymptotically Free Extensions (SAFEs) of the Standard Model
• Non-Abelian dynamics in the resonant decay of the Higgs after inflation
• Fakeons and the classicization of quantum gravity: the FLRW metric
• Conformal Inflation, Modulated Reheating, and WMAP5

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