Heidelberg University

Thermal Field Theory

Alexander Rothkopf, University of Stavanger


Thermal field theory lies at the heart of many phenomena studied in frontier experiments, ranging from the production of the quark-gluon plasma in relativistic heavy-ion collisions to understanding the phases in ultracold quantum gases and the design of materials capable of high-temperature superconductivity. Field theory in thermal equilibrium, while being an idealized concept, offers valuable insight into phenomenologically relevant static properties of quantum systems, as well as their real-time dynamics, all affected by the presence of the heat bath environment. Last but not least it provides the base-line from which to embark on the study and characterization of out-of-equilibrium phenomena.

Thermal fluctuations are not only able to generate macroscopic pressure in a quantum system but may lead to a characteristic modification of the carriers of interactions, endowing them with a thermal mass, referred to as Debye or screening mass. In this lecture we will explore the basics of thermal field theory, working our way from scalar fields to gauge theory, exploring how to theoretically implement the effects of thermal fluctuations and how to concretely compute relevant system properties with analytic and numeric methods.