- Μία κατηγορία Πεδίων.
The transformations between possible gauges, called gauge transformations, form a Lie group-referred to as the symmetry group or the gauge group of the theory.
For each group generator there necessarily arises a corresponding field (usually a vector field) called the gauge field.
When such a theory is quantized, the quanta of the gauge fields are called gauge bosons.
Many powerful theories in physics are described by Lagrangians that are invariant under some symmetry transformation groups. When they are invariant under a transformation identically performed at every point in the spacetime in which the physical processes occur, they are said to have a global symmetry.
Local symmetry, the cornerstone of gauge theories, is a stricter constraint. In fact, a global symmetry is just a local symmetry whose group's parameters are fixed in spacetime (the same way a constant value can be understood as a function of a certain parameter, but which output is always the same).
Gauge theories are important as the successful field theories explaining the dynamics of elementary particles.
- three weak bosons and
- eight gluons.
Gauge theories are also important in explaining gravitation in the theory of general relativity. Its case is somewhat unique in that the gauge field is a tensor, the Lanczos tensor. Theories of quantum gravity, beginning with gauge gravitation theory, also postulate the existence of a gauge boson, known as the graviton.
Gauge symmetries can be viewed as analogues of the principle of general covariance of general relativity in which the coordinate system can be chosen freely under arbitrary diffeomorphisms of spacetime. Both gauge invariance and diffeomorphism invariance reflect a redundancy in the description of the physical system.
An alternative theory of gravitation, gravity gauge theory, replaces the principle of general covariance with a true gauge principle with new gauge fields.
Historically, these ideas were first stated in the context of classical electromagnetism and later in general relativity. However, the modern importance of gauge symmetries appeared first in the relativistic quantum mechanics of electrons, quantum electrodynamics, elaborated on below.
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