Speaker
Description
Thermal correlation functions depend on widely separated scales: the temperature, particle masses, and the external kinematics. In vacuum, the method of regions organises such expansions and tells us which modes an effective theory must contain. At finite temperature the picture is incomplete. Beyond the familiar hard and soft contributions, thermal correlators contain terms exponentially suppressed in m/T, precisely the terms which are not captured by a naive expansion by regions. I will introduce the method of regions on simple examples, then apply it to thermal correlators and present recent progress towards a systematic classification of their regions. The emphasis is on the exponentially suppressed contributions: where they originate and how they can be extracted.