Aligned Natural Inflation: Monodromies of two Axions

Abstract

Natural (axionic) inflation can accommodate sizeable primordial tensor modes but suffers from the necessity of trans-Planckian variations of the inflaton field. This problem can be solved via the mechanism of aligned axions arXiv:hep-ph/0409138, where the aligned axion spirals down in the potential of other axions. We elaborate on the mechanism in view of the recently reported observations of the BICEP2 collaboration arXiv:1403.3985.

Figures (3)

• Figure 1: The potential for parameters $f_1=f_2=g_1=0.5 M_{\text{Pl}}$ and the values $\alpha=0,$$\alpha=0.1,$ and $\alpha=0.3.$
• Figure 2: Parametric plot of the potential for parameters $f_1=f_2=g_1=0.5 M_{\text{Pl}}$ and $\alpha=0.1$ starting from $\xi=10.$ The $(x,y)$-coordinates are parametrised by $\cos{(\theta/M_{\rm Pl})}$ and $\sin{(\rho/M_{\rm Pl})}$ to visualise the axionic shift symmetries in the $\theta$ and $\rho$ directions.
• Figure 3: $n_s-r-$plane profile for aligned natural inflation. The green band shows the parameter-region which is obtained in the aligned natural inflation model for parameters $\alpha=0.01\ldots 0.2 M_{\rm Pl},$$f_1=f_2=g_1=0.5 M_{\rm Pl}$ and $N_E=50\ldots 60.$ The red line corresponds to the measured value by BICEP2 after reducing dust, the grey band indicates the 68 percent confidence level Ade:2014xna. The blue regions correspond to the parameter space allowed by combined data from Planck, WMAP polarisation, lensing, ACT and SPT at the 68 and 95 percent confidence level Ade:2013uln. The dotted regions correspond to the parameter space allowed by combined data from Planck, WMAP polarisation, lensing and BAO at the 68 and 95 percent confidence level Ade:2013uln. The potential plots show the range where inflation takes place for $\alpha=0.01$ and $\alpha=0.1.$