Minimal warm inflation with complete medium response

Abstract If a homogeneous field evolves within medium, with the latter gradually picking up temperature, then friction felt by depends on how its evolution rate compares medium time scales. We suggest framework which permits to incorporate contributions from all As an example, we illustrate warm axion inflation can be described inputting retarded pseudoscalar correlator of thermal Yang-Mills plasma. Adopting semi-realistic model for latter, and starting at almost vanishing show system heats enters “weak” or “strong” regime inflation. Previous approximate treatments are scrutinized.