Abstract
In this paper we examine the viability of inflation models with a spectator axion field coupled to both gravitational and SU(2) gauge fields via Chern-Simons couplings. Requiring phenomenological success of the axion-SU(2) sector constrains the coupling strength of the gravitational Chern-Simons term. We find that the impact of this term on the production and propagation of gravitational waves can be as large as fifty percent enhancement for the helicity that is not sourced by the gauge field, if the cut-off scale is as low as Λ = 20H. The effect becomes smaller for a larger value of Λ, while the impact on the helicity sourced by the gauge field is negligible regardless of Λ.
Highlights
Background Evolutionwe describe the evolution of the background
The right-handed helicity gravitational wave grows around the horizon crossing and stays constant afterwards. (Right panel) The ratios of the right- and left-handed helicity mode functions for ξ2 = 4.5 × 10−6 with respect to those for ξ2 = 0
The right-handed helicity mode of the tensor perturbations of the SU(2) gauge field tR is amplified unlike the gravitational waves
Summary
The spectator sector action SSP EC contains axion and SU(2) gauge fields, where χ is an axion field with potential U (χ) and a decay constant f : SSP EC =. Is the field strength tensor of the SU(2) gauge fields, with gA being the self-coupling constant and abc the three dimensional anti-symmetric symbol. The last term in SSP EC is the Chern-Simons interaction, where λ1/f parametrizes its coupling strength and Faμν ≡. F Fis a total derivative and for χ = const, it reduces to a surface term. We can write F Fas. The last term in (2.1) is the gravitational Chern-Simons term coupled to the axion, with coupling strength of λ2/f : SGCS =. The gravitational Chern-Simons term is a total derivative. For χ = const, it reduces to a surface term
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
