Graviton- and inflaton-mediated dark matter production after large field polynomial inflation

Polynomial inflation is a simple cosmological scenario, which fits the cosmic microwave background data well. It provides testable predictions for the tensor-to-scalar ratio and the running of the spectral index. In this work, we investigate the production of Dirac dark matter (DM) within the framework of large-field polynomial inflation. We study all relevant production channels including (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>i</a:mi></a:math>) nonthermal production through inflaton decays and scatterings, and (<c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>i</c:mi><c:mi>i</c:mi></c:math>) thermal production from scattering of standard model particles mediated by inflatons and gravitons. In contrast to small-field polynomial inflation, where inflaton decay dominates DM production, we find that graviton-mediated processes can be dominant in the large-field scenario. For DM lighter than the inflaton, we demonstrate that the interplay between graviton- and inflaton-mediated production channels give rise to nontrivial relations between the DM mass and the reheating temperature required to account for the DM relic abundance.