Chaotic initial conditions for nonminimally coupled inflation via a conformal factor with a zero

TL;DR

This paper explores how introducing a conformal factor with a zero in nonminimally coupled inflation models affects initial conditions and observable predictions, potentially leading to measurable changes in the spectral index and tensor-to-scalar ratio.

Contribution

It demonstrates that a conformal factor zero can enable inflation models to have high potential energy at large fields and predicts correlated increases in spectral index and tensor-to-scalar ratio.

Findings

Models predict increased spectral index and tensor-to-scalar ratio.

Modification can lead to measurable changes in CMB polarization.

Potential for next-generation satellite detection.

Abstract

Nonminimally coupled inflation models based on a nonminimal coupling $\xi \phi^{2} R$ and a $\phi^{4}$ potential are in excellent agreement with the scalar spectral index observed by Planck. Here we consider the modification of these models by a conformal factor with a zero. This enables a nonminimally coupled model to have a Planck-scale potential energy density at large values of the inflaton field, which can account for the smooth, potential-dominated volume that is necessary for inflation to start. We show that models with a conformal factor zero generally predict a correlated increase of the spectral index $n_{s}$ and tensor-to-scalar ratio $r$. For values of $n_{s}$ that are within the present $2-\sigma$ bounds from Planck, modification by $\Delta r$ as large as 0.0013 is possible, which is large enough to be measured by next generation cosmic microwave background polarization satellites.