Gauge Theory Gauge theory is concerned with the problem of comparing physical states at different space-time locations. To get a feel for the problem, it is best to begin with a simple example. Quantum chromodynamics is the theory of the force that...

Modern particle theories, such as the Standard Model, are quantum Yang-Mills theories. In a quantum field theory, space-time fields with relativistic field equations are quantized and, in many calculations, the quanta of the fields are interpreted as...

In the last half of the twentieth century, physicists succeeded in unifying three of the four fundamental forces of nature: electromagnetism, the "weak force" responsible for radioactive decay, and the "strong force" responsible for holding the nuclei...

If a field theory possesses a gauge symmetry, then the theory is invariant under certain local transformations of the fields. The description of the system has a built-in redundancy corresponding to the action of a gauge transformation, which is...

In physics, gauge theories are a class of physical theories based on the idea that symmetry transformations can be performed locally as well as globally. This idea applies not only to field theories, but to finite-dimensional systems as well (i.e.,...