The off-shell behaviour of propagators and the Goldstone field in higher   spin gauge theory on $AdS_{d+1}$ space
  A detailed analysis of the structure and gauge dependence of the bulk-to-bulk propagators for the higher spin gauge fields in $AdS$ space is performed. The possible freedom in the construction of the propagators is investigated and fixed by the correct boundary behaviour and correspondence to the representation theory results for the $AdS$ space isometry group. The classical origin of the Goldstone mode and its connection with the gauge fixing procedure is considered. 
Ruben Manvelyan and Werner Ruehl