Groups of loops and hoops

The approaches to quantum field theories based in the so-called loop representation deserved much attention recently. In it, closed curves and holonomies around them play a central role. In this framework the group of loops and the group of hoops have been defined, the first one consisting in closed curves quotient with the equivalence relation that identifies curves differing in retraced segments, and the second one consisting in closed curves quotient with the equivalence relation that identifies curves having the same holonomy for every connection in a fiber bundle. The purpose of this paper is to clarify the relation between hoops and loops, or in other words, to give a description of the class of holonomy equivalent curves. (orig.)