Late-time backreaction from inflationary fluctuations of a non-minimally coupled massless scalar

Understand

We consider the late time one-loop quantum backreaction from inflationary fluctuations of a non-minimally coupled, massless scalar field.

• The scalar is assumed to be a spectator field in an inflationary model with a constant principal slow roll $\epsilon$ parameter.
• We regulate the infrared by matching onto a pre-inflationary radiation era.
• We find a large late time backreaction when the nonminimal coupling $\xi$ is negative (in which case the scalar exhibits a negative mass term during inflation).