  We study in more detail the dynamics of chiral primaries of the D1/D5 system.
  From the CFT given by the $S_{n}$ orbifold a study of correlators resulted in
an interacting (collective) theory of chiral operators. In $AdS_{3}\times
S^{3}$ SUGRA we concentrate on general 1/2 BPS configurations described in
terms of a fundamental string .We first establish a correspondence with the
linerized field fluctuations and then present the nonlinear analysis. We
evaluate in detail the symplectic form of the general degrees of freedom in
Sugra and confirm the appearance of chiral bosons. We then discuss the
apearance of interactions and the cubic vertex,in correspondence with the
$S_{N}$ collective field theory representation.
