Nongauge

Nongauge is a term that appears occasionally in physics and mathematics to describe quantities or objects that are not associated with gauge degrees of freedom. It is not a standard or widely adopted term; in most literature the concept is expressed using phrases like gauge-invariant or physical quantities rather than the noun nongauge.

In gauge theories, many fields carry redundant degrees of freedom introduced by the gauge symmetry. Nongauge quantities refer to observables or constructions that remain unchanged under gauge transformations. Examples include gauge-invariant combinations such as traces of field strengths or Wilson loops, and, in some contexts, the S-matrix elements. However, the precise usage can vary, and some authors would simply say “gauge-invariant” or “physical” quantities rather than employing nongauge.

In mathematical contexts related to connections on fiber bundles, the term nongauge may appear informally to distinguish objects that depend only on base-space data rather than on the choice of connection or gauge. This usage is informal and not standard, and it is generally clearer to use established terminology from gauge theory and differential geometry.

Limitations and caveats: because nongauge is not a formal technical term in most scholarly sources, its meaning is highly dependent on context. Readers are advised to interpret it from accompanying definitions and contrast it with standard notions such as gauge invariance and gauge freedom.

See also: gauge theory, gauge invariance, gauge symmetry.