[Paper Review] Self-complete chaotic inflation

Hyun Min Lee|arXiv (Cornell University)|Mar 22, 2014

Cosmology and Gravitation Theories3 references3 citations

TL;DR

This paper proposes a self-complete chaotic inflation model with a non-canonical kinetic term that stabilizes quadratic inflationary dynamics, enabling slow-roll inflation with sub-Planckian inflaton field values. The model maintains successful BICEP2-compatible predictions while resolving unitarity violations below the Planck scale through large field rescaling.

ABSTRACT

We consider a general chaotic inflation model with non-canonical kinetic term, resulting in attractor solutions for the quadratic inflation. The form of the kinetic term and the potential is fixed due to the requirement that the inflation model is a quadratic form in the large field values of the inflaton. We show that a large coupling in the non-canonical kinetic term allows for the slow-roll inflation with sub-Planckian field values of the inflaton and the successful predictions of the quadratic inflation in light of BICEP2 results are maintained in our model. We find that due to the large rescaling of the inflaton field in the vacuum, there is no unitarity problem below the Planck scale.

Motivation & Objective

• To address the unitarity problem in chaotic inflation by introducing a non-canonical kinetic term.
• To maintain the successful predictions of quadratic inflation, particularly those aligned with BICEP2 results.
• To enable slow-roll inflation with sub-Planckian inflaton field values through field rescaling.
• To derive a self-complete inflation model where the kinetic term and potential are fixed by large-field quadratic behavior.

Proposed method

• Introduce a non-canonical kinetic term in the inflaton Lagrangian to modify the dynamics in large field regimes.
• Derive the effective potential and kinetic term under the constraint that the model reduces to a quadratic form at large field values.
• Apply attractor solution techniques to show stability of slow-roll conditions despite non-canonical structure.
• Perform field rescaling analysis to demonstrate that unitarity is preserved below the Planck scale.
• Use the requirement of quadratic behavior in the large-field limit to uniquely fix the form of the kinetic term and potential.

Experimental results

Research questions

• RQ1 Can a non-canonical kinetic term stabilize slow-roll inflation with sub-Planckian inflaton values while preserving quadratic inflation predictions?
• RQ2 How does a large coupling in the non-canonical kinetic term affect the unitarity of the model below the Planck scale?
• RQ3 What constraints does the requirement of quadratic behavior at large field values impose on the form of the kinetic term and potential?
• RQ4 To what extent can the attractor solution mechanism ensure robustness of inflationary dynamics in this setup?

Key findings

• The model achieves slow-roll inflation with sub-Planckian inflaton field values due to a large coupling in the non-canonical kinetic term.
• The attractor solution mechanism stabilizes the inflationary trajectory, ensuring robustness of the slow-roll conditions.
• The model successfully reproduces the BICEP2-compatible predictions of quadratic inflation, including the tensor-to-scalar ratio.
• Due to large field rescaling in the vacuum, the model avoids unitarity violation below the Planck scale.