In "Quantum Field Theory," the "Path Integral Formulation" introduced by Richard Feynman:
a) Provides a way to compute quantum amplitudes by summing over all possible paths a particle can take, each path being weighted by a phase factor related to the classical action. This formulation offers an alternative to the operator-based approach and is useful for understanding quantum mechanics, statistical mechanics, and quantum field theory in a unified manner. It also provides insights into the connection between classical and quantum physics.
b) Focuses on solving the Schrödinger equation in the position representation.
c) Describes the perturbative expansions for interactions between particles.
d) Offers exact solutions to the Dirac equation for relativistic electrons.