Comments on higher-spin symmetries

The unconstrained frame-like formulation of an infinite tower of completely symmetric tensor gauge fields is reviewed and examined in the limit where the cosmological constant goes to zero. By partially fixing the gauge and solving the torsion constraints, the form of the gauge transformations in the unconstrained metric-like formulation are obtained till first order in a weak field expansion. The algebra of the corresponding gauge symmetries is shown to be equivalent, at this order and modulo (unphysical) gauge parameter redefinitions, to the Lie algebra of Hermitian differential operators on R^n, the restriction of which to the spin-two sector is the Lie algebra of infinitesimal diffeomorphisms.Comment: 53+1 pages, erratum: a minor error in corollary 3 remove