Natural Inflation From Fermion Loops

Abstract

``Natural'' inflationary theories are a class of models in which inflation is driven by a pseudo-Nambu-Goldstone boson. In this paper we consider two models, one old and one new, in which the potential for inflation is generated by loop effects from a fermion sector which explicitly breaks a global $U(1)$ symmetry. In both models, we retrieve the ``standard'' natural inflation potential, $V\left(\theta \right)={\Lambda }^4\left[1+\cos \left(\theta /\mu \right)\right]$, as a limiting case of the exact one-loop potential, but we carry out a general analysis of the models including the limiting case. Constraints from the COBE DMR observation and from theoretical consistency are used to limit the parameters of the models, and successful inflation occurs without the necessity of fine-tuning the parameters.

(Revised) 15 pages, LaTeX (revTeX), 8 figures in uuencoded PostScript format. Version accepted for publication in Phys. Rev. D 15. Corrected definition of power spectrum and added three references

References in corpus (4)

• A more accurate analytic calculation of the spectrum of cosmological perturbations produced during inflation
• Natural Inflation: Particle Physics Models, Power Law Spectra for Large Scale Structure, and Constraints from COBE
• Cosmic Temperature Fluctuations from Two Years of COBE DMR Observations
• Reconstructing the Inflaton Potential---in Principle and in Practice

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