Speaker
Description
The persistent absence of non-gravitational dark matter signals has increased interest in candidates that interact extremely weakly with the Standard Model—if at all. (Non-perturbative) gravitational particle production provides an unavoidable mechanism for generating such dark matter via the expansion of spacetime. However, predicting the exact relic abundance is subject to significant theoretical ambiguities tied to the framework of QFT in curved spacetimes, as well as uncertainties coming from inflationary and reheating dynamics.
In this talk, I will present an overview of these uncertainties based on recent results for scalar and vector spectator fields across different inflationary backgrounds. These ambiguities become especially problematic for masses below the scale of inflation due to tachyonic instabilities and the non-adiabaticity of the field modes. Since this regime is of particular interest for other non-thermal production mechanisms, such as freeze-in, it is crucial to address these conceptual and technical challenges to ensure a robust phenomenological approach.