Gauge Miura and Backlund Transformations for Generalized $A_n$-KdV Hierarchies

The construction of Miura and B\"acklund transformations for $A_n$ mKdV and KdV hierarchies are presented in terms of gauge transformations acting upon the zero curvature representation. As in the well known $sl(2)$ case, we derive and relate the equations of motion for the two hierarchies. Moreover, the Miura-gauge transformation is not unique, instead, it is shown to be connected to a set of generators labeled by the exponents of $A_n$ The construction of generalized gauge-B\"acklund transformation for the $A_n$-KdV hierarchy is obtained as a composition of Miura and B\"acklund-gauge transformations for $A_n$-mKdV hierarchy. The zero curvature representation provide a framework which is universal within all flows and generate systematically B\"acklund transformations for the entirely hierarchy.