Fermion Propagator in Cosmological Spaces with Constant Deceleration

Understand

We calculate the fermion propagator in FLRW spacetimes with constant deceleration $q=\epsilon-1$, $\epsilon=-\dot{H}/H^{2}$ for excited states.

• For fermions whose mass is generated by a scalar field through a Yukawa coupling $m=g_{\mathrm{\scriptscriptstyle{Y}}} \phi$, we assume $\phi \propto H$.
• We first solve for the mode functions by splitting the spinor into a direct product of helicity and chirality spinors.
• We also allow for non-vacuum states.