What is a unified field theory in physics?

A unified field theory is a type of physical field theory that attempts to write all fundamental forces of nature and elementary particles in terms of a single physical field. Albert Einstein coined the term during his decades-long effort to combine general relativity and electromagnetism. Modern attempts incorporate quantum mechanics, though fully uniting gravity with the other forces remains an ongoing challenge.

What we know

• A unified field theory allows all fundamental forces of nature, including gravity, and all elementary particles to be expressed through a single physical field, while quantum field theory considers particles as quanta of fields. [2, 4]
• Albert Einstein coined the term unified field theory and attempted to create a classical version by uniting general relativity with electromagnetism starting in the 1920s. [2]
• Different types of fields in physics include vector fields, spinor fields, and tensor fields, which unified field theories attempt to organize into a single mathematical structure. [2]
• Unlike Grand Unified Theories, a unified field theory explicitly attempts to include the gravitational force. [2]

Still open

• Einstein's classical unified field theory attempts required explaining particles as singularities or solitons rather than field quanta, presenting ongoing difficulties.

Where to go next

• how it workedHow does quantum field theory combine relativity and quantum mechanics?
• the bigger pictureWhat is the Standard Model of particle physics?
• whoHow did Paul Dirac contribute to early quantum field theory?
• compared withWhat are the differences between a Theory of Everything and a Grand Unified Theory?
• how we knowHow do tensor fields describe spacetime curvature in general relativity?
• an unexpected connectionHow do weather maps relate to physical field theories?Just as a weather map uses numbers or arrows to assign values to spatial points, physical fields use scalar, vector, or tensor quantities to define properties at every point in space and time.

Sources

• [1]unified field theory (Wikidata Q1080745) · CC0 1.0
• [2]Unified field theory · CC BY-SA 4.0
• [3]Quantum field theory · CC BY-SA 4.0
• [4]Field (physics) · CC BY-SA 4.0
• [5]History of quantum field theory · CC BY-SA 4.0