Unified field theory
- 1: a mathematical theory of fields developed by Einstein and involving Maxwell's electromagnetic theory and Einstein's mathematical theory of gravitation as special cases.
In physics, a unified field theory (UFT), occasionally referred to as a uniform field theory, is a type of field theory that allows all that is usually thought of as fundamental forces and elementary particles to be written in terms of a single field. There is no accepted unified field theory, and thus it remains an open line of research. The term was coined by Einstein, who attempted to unify the general theory of relativity with electromagnetism. The "theory of everything" and Grand Unified Theory are closely related to unified field theory, but differ by not requiring the basis of nature to be fields, and often by attempting to explain physical constants of nature.
This article describes unified field theory as it is currently understood in connection with quantum theory. Earlier attempts based on classical physics are described in the article on classical unified field theories.
There may be no a priori reason why the correct description of nature has to be a unified field theory. However, this goal has led to a great deal of progress in modern theoretical physics and continues to motivate research.
According to the current understanding of physics, forces are not transmitted directly between objects, but instead are described by intermediary entities called fields. All four of the known fundamental forces are mediated by fields, which in the Standard Model of particle physics result from exchange of gauge bosons. Specifically the four interactions to be unified are:
- Strong interaction: the interaction responsible for holding quarks together to form neutrons and protons, and holding neutrons and protons together to form nuclei. The exchange particle that mediates this force is the gluon.
- Electromagnetic interaction: the familiar interaction that acts on electrically charged particles. The photon is the exchange particle for this force.
- Weak interaction: a repulsive short-range interaction responsible for some forms of radioactivity, that acts on electrons, neutrinos, and quarks. It is governed by the W and Z bosons.
- Gravitational interaction: a long-range attractive interaction that acts on all particles. The postulated exchange particle has been named the graviton.
Modern unified field theory attempts to bring these four interactions together into a single framework.