Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 7, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/1475-7516/2022/07/046
Keywords
axions; inflation; primordial gravitational waves (theory)
Funding
- JSPS [18K13537, 20J20248]
- World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan
- Program of Excellence in Photon Science
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This study proposes a modified chromo-natural inflation model, which considers the enhanced gravitational wave effect and identifies a parameter space that avoids violating the constraints of cosmic microwave background (CMB) observations.
Chromo-natural inflation (CNI) is an inflationary model where an axion coupled with SU(2) gauge fields acts as the inflaton. In CNI, the gauge fields have nonzero vacuum expectation values (VEVs), which results in the enhancement of gravitational waves (GWs). The original CNI is ruled out by the Planck observations due to the overproduction of GWs. In this work, we consider an inflationary model where the gauge fields acquire nonzero VEVs after the CMB modes exit the horizon. Moreover, we add to the model another field that dominates the universe and drives inflation after the axion starts to oscillate and the gauge field VEVs vanish. By performing numerical simulations, we find a parameter space where the enhanced GWs do not violate the CMB constraints and can be detected by the future GWs observations such as BBO and ET.
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