Many-Body Perturbation Theory

Many-Body Perturbation Theory (MBPT) is a method in physics used to analyze complex systems with many interacting particles, like electrons in an atom or molecules. Instead of solving exact equations, which is often impossible, MBPT starts with a simple approximation and then systematically includes the effects of interactions as small corrections. This approach allows scientists to predict properties such as energy levels and response behaviors more accurately by accounting for the collective influence of particles without requiring an exact solution of the entire system.