Introduction
Quantum field theory (QFT) is a theoretical framework that combines classical field theory, special relativity, and quantum mechanics to describe the behavior and interactions of subatomic particles and forces. In QFT, particles are not treated as point-like objects, but as excitations or disturbances of underlying fields that pervade the whole space and time. These fields are quantized, meaning that they can only have discrete values of energy and momentum. The fields also obey the principles of special relativity, such as the invariance of physical laws under Lorentz transformations. QFT is not a complete or final theory of nature, as it has some limitations and unresolved problems. For example, QFT does not include gravity, which is described by general relativity, another successful but incompatible theory.
