W algebra from boundary action of higher spin gravity on AdS

Higher spin gravity theories (in 3 dimensions with negative cosmological constant) can be expressed as an SL(n)\\times SL(n) Chern Simons theory. The theory in pure gauge (allowed by the bulk topology) reduces to a WZW action. Choice of asymptotic boundary conditions again transfers the whole dynamics to a conformal boundary theory. Symmetries of this theory turn out to be W_3 \\times W_3 (for spin 3 system).