Building Gauge Theories: The Natural Way
The construction of a gauge field theory for elementary particles usually starts by promoting global invariance of the matter action to a local one, this in turn implying the introduction of gauge fields. We present here a procedure that runs the other way: starting from the action for gauge fields, matter is gauge invariantly coupled on the basis of Lorentz invariance and charge conservation. This natural approach prevents using the concept of particles separated from gauge fields that mediate interactions.