# Quantum Field Theory

Quantum field theory is a part of theoretical physics, a framework for the construction of quantum mechanical models of various subatomic particles. In quantum field theory, these particles are views as excited states of underlying physical fields. Unlike quantum mechanical systems, in quantum field theory the excited states can represent any number of subatomic particles.

Quantum field theory began with the work of Paul Dirac in the 1920s. Dirac (1902-1984) predicted the existence of antimatter and formulated the Dirac equation, which describes the behavior of fermions, which are elementary particles. Further advances came in the 1950s, when scientists understood that Einstein’s theory of relativity needed to be incorporated into the field of electromagnetism. This led to the development of quantum electrodynamics. Through the 1970s, this field expanded to include gauge theory and movement towards a grand synthesis of all theoretical physics.

Quantum field theory provides a framework for describing forces such as an electromagnetic field and particle objects such as electrons. Most scientists believe that quantum field theory explains what identical particles are. For example, the electron field is fundamental, but it is wrong to regard individual electrons as fundamental objects. Currently, physicists have been unable to apply quantum theory to gravity.