Inflation from broken scale invariance.

Area of Science:

• Cosmology
• Theoretical Physics
• Particle Physics

Background:

• The standard model of cosmology requires an inflationary epoch to explain observations.
• Inflationary models often face challenges with quantum corrections and the slow-roll approximation.

Purpose of the Study:

• To construct a novel model of cosmic inflation.
• To protect the inflaton potential from quantum corrections using a shift symmetry.
• To ensure the validity of the slow-roll approximation over large field displacements.

Main Methods:

• Constructing an inflationary model based on a low-energy effective theory of spontaneously broken global scale invariance.
• Utilizing noncompact scale invariance to allow large inflaton field displacements.
• Introducing weak breaking of scale invariance by almost marginal operators to create a nontrivial inflaton minimum.

Main Results:

• The model provides a shift symmetry that shields the inflaton potential from quantum corrections.
• A nontrivial inflaton minimum is established, stabilizing the Planck scale.
• The slow-roll approximation remains valid for large inflaton displacements.
• A scale-invariant spectrum of perturbations is generated, consistent with cosmic microwave background data.

Conclusions:

• The proposed model offers a robust framework for cosmic inflation.
• Scale invariance provides a mechanism to protect the inflaton potential and ensure observational consistency.
• This approach successfully addresses key challenges in inflationary cosmology.