Extranatural inflation redux
Abstract
The success of a given inflationary model crucially depends upon two features: its predictions for observables such as those of the cosmic microwave background (CMB) and its insensitivity to the unknown UV physics such as quantum gravitational effects. Extranatural inflation is a wellmotivated scenario that is insensitive to UV physics by construction. In this fivedimensional model, the fifth dimension is compactified on a circle, and the zero mode of the fifth component of a bulk U (1 ) gauge field acts as the inflaton. In this work, we study simple variations of the minimal extranatural inflation model in order to improve its CMB predictions while retaining its numerous merits. We find that it is possible to obtain CMB predictions identical to those of, e.g., the R +R^{2} Starobinsky model of inflation and show that this can be done in the most minimal way by having two additional light fermionic species in the bulk, with the same U (1 ) charges. We then find the constraints that CMB observations impose on the parameters of the model.
 Publication:

Physical Review D
 Pub Date:
 October 2017
 DOI:
 10.1103/PhysRevD.96.083529
 arXiv:
 arXiv:1705.11071
 Bibcode:
 2017PhRvD..96h3529D
 Keywords:

 High Energy Physics  Phenomenology;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 Journal version (to appear in Phy. Rev. D)