Lukong Cornelius Fai is professor of theoretical physics at the Department of Physics, Faculty of Sciences, University of Dschang. He is Head of Condensed Matter and Nanomaterials as well as Mesoscopic and Multilayer Structures Laboratory. He was formerly a senior associate at the Abdus Salam International Centre for Theoretical Physics (ICTP), Italy. He holds a Masters of Science in Physics and Mathematics (June 1991) as well as a Doctor of Science in Physics and Mathematics (February 1997) from Moldova State University. He is an author of over a hundred scientific publications and three textbooks.

Chapter 1. Symmetry Requirements In Quantum Field Theory. Chapter 2. Coherent States. Chapter 3. Fermionic and Bosonic Path Integrals. Chapter 4. Perturbation Theory and Feynman Diagrams. Chapter 5. (Anti) Symmetrized Vertices. Chapter 6. Generating Functionals. Chapter 7. Random Phase Approximation (RPA). Chapter 8. Phase Transitions and Critical Phenomena. Chapter 9. Weakly Interacting Bose Gas. Chapter 10. Superconductivity Theory. Chapter 11. Path Integral Approach to the BCS Theory. Chapter 12. Green's Functions Averages Over Impurities. Chapter 13. Classical and Quantum Theory of Magnetism. Chapter 14. Nonequilibrium Quantum Field Theory.