Randall-Sundrum Gauge in the Brane World

We discuss the Randall-Sundrum (RS) gauge in the brane-world. We begin with the de Donder gauge (transverse-tracefree) in five dimensions for comparison. One finds that $h_{55}=0$ and $h_{5\mu}$ has a tachyonic mass. Hence we have to set $h_{5\mu}=0$. This leads to the RS gauge. It appears that the RS gauge is so restrictive for the five massless states, whereas it is unique for describing the massive states. Furthermore, one can establish the stability of the RS solution with the RS gauge only.