Echoes of $R^3$ modification and Goldstone preheating in the CMB-BAO landscape

Abstract

The $R^2$ and the single-field-like regime of $R^2$-Higgs inflation are disfavored by the observed high spectral index $n_s$ from the combined cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements at the $\sim2σ$ level. The addition of a dimension-six $R^3$ term in the action helps alleviate this tension. We show that the parameter space accounting for the observed high $n_s$ also induces rapid Goldstone and Higgs preheating. The preheating, especially from Goldstone modes, helps match the CMB and inflationary scales, which in turn supports the observed $n_s$.

Figures (2)

• Figure 1: The evolution of $M_{\phi_2}^2$ and $m_{\mathrm{eff},(h)}^2$ for the BPs.
• Figure 2: The $\rho^q_{(h)}$ (blue) and $\rho^q_{(\phi_2)}$ (red) along with $\rho_{\rm inf}$ (black) for BP$a$ (upper panel) and BP$b$ (lower panel) respectively.