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Quantum electrodynamics is an abelian gauge theory with the symmetry group U(1) and has one gauge field, ... A quantity which is gauge-invariant (i.e., ...
The line is the equivalent of a gauge function; it need not be straight. Almost any line is a valid gauge fixing, i.e., there is a large gauge freedom. In summary, to tell whether the rod is twisted, the gauge must be known. Physical quantities, such as the energy of the torsion, do not depend on the gauge, i.e., they are gauge invariant.
The condition is Lorentz invariant. The Lorenz gauge condition does not completely determine the gauge: one can still make a gauge transformation +, where is the four-gradient and is any harmonic scalar function: that is, a scalar function obeying =, the equation of a massless scalar field.
A gauge theory is a type of theory in physics.The word gauge means a measurement, a thickness, an in-between distance (as in railroad tracks), or a resulting number of units per certain parameter (a number of loops in an inch of fabric or a number of lead balls in a pound of ammunition). [1]
In theoretical physics, scalar electrodynamics is a theory of a U(1) gauge field coupled to a charged spin 0 scalar field that takes the place of the Dirac fermions in "ordinary" quantum electrodynamics. The scalar field is charged, and with an appropriate potential, it has the capacity to break the gauge symmetry via the Abelian Higgs mechanism.
In contrast to the Berry connection, which is physical only after integrating around a closed path, the Berry curvature is a gauge-invariant local manifestation of the geometric properties of the wavefunctions in the parameter space, and has proven to be an essential physical ingredient for understanding a variety of electronic properties. [4] [5]
If we were using one gauge for all fields, X X would be gauge invariant. However, we need to convert gauge I to gauge II, transforming X to (e −V) q X. So, the gauge invariant quantity is X e −qV X. In gauge I, we still have the residual gauge e Λ where ¯ ˙ = and in gauge II, we have the residual gauge e Λ satisfying d α Λ = 0. Under ...
Any such term must be both gauge and reference-frame invariant, otherwise the laws of physics would depend on an arbitrary choice or the frame of an observer. Therefore, the global Poincaré symmetry , consisting of translational symmetry , rotational symmetry and the inertial reference frame invariance central to the theory of special ...