Imprint of entanglement entropy in the power spectrum of inflationary fluctuations

Understand

If the inflaton couples to other degrees of freedom that populate the post-inflationary stage, such coupling modifies the dynamics of the inflaton \emph{during} inflation.

• We consider light fermions Yukawa coupled to the inflaton as "unobserved" degrees of freedom integrated out of the total density matrix.
• Tracing out these degrees of freedom yields a \emph{mixed} density matrix whose time evolution is described by an effective field theory.
• We show that the coupling leads to profuse fermion pair production for super-Hubble inflaton fluctuations which lead to the \emph{growth of entanglement entropy during inflation}.