In physics, a gauge principle specifies a
procedure for obtaining an interaction term
from a free Lagrangian which is symmetric
with respect to a continuous symmetry—the
results of localizing (or gauging) the global
symmetry group must be accompanied by the
inclusion of additional fields (such as the
electromagnetic field), with appropriate kinetic
and interaction terms in the action, in such
a way that the extended Lagrangian is covariant
with respect to a new extended group of local
transformations.
== See 
also ==
Gauge theory
Gauge covariant derivative
Gauge fixing
Gauge gravitation theory
Kaluza–Klein theory
Lie algebra
Lie group
Lorenz gauge
Quantum chromodynamics
Quantum electrodynamics
Quantum field theory
Quantum gauge theory
Standard Model
Standard Model (mathematical formulation)
Symmetry breaking
Symmetry in physics
Yang–Mills theory
Yang–Mills existence and mass gap
1964 PRL symmetry breaking papers
