Michel Le Bellac, a renowned physicist from the Université de Nice, Sophia Antipolis , is well known for his research in this area, which gives the text a strong foundation in the latest developments of the time. The book has stood the test of time, establishing itself as a "standard reference," particularly for topics like real-time observables in thermal field theory.

While the imaginary-time formalism is powerful for equilibrium thermodynamics, it struggles with dynamic, time-dependent processes like transport coefficients, particle production rates, and relaxation times. To address this, Le Bellac introduces the Real-Time Formalism (RTF).

Thermal Field Theory (often referred to as Finite Temperature Field Theory) is the essential framework for studying physical systems where quantum effects and thermal fluctuations coexist. One of the most authoritative and widely cited textbooks in this field is .