Partial masslessness of higher spins in (A)dS

Massive spin s greater than or equal to 3/2 fields can become partially mas sless in cosmological backgrounds. In the plane spanned by m(2) and A, ther e are lines where new gauge invariances permit intermediate sets of higher helicities, rather than the usual flat space extremes of all 2S + 1 massive or just 2 massless helicities. These gauge lines divide the (m2, A) plane into unitarily allowed or forbidden intermediate regions where all 2s + 1 m assive helicities propagate but lower helicity states can have negative nor ms. We derive these consequences for s = 3/2, 2 by studying both their cano nical (anti)commutators and the transmutation of massive constraints to par tially massless Bianchi identities. For s = 2, a Hamiltonian analysis exhib its the absence of zero helicity modes in the partially massless sector. Fo r s = 5/2, 3 we derive Bianchi identities and their accompanying gauge inva riances for the various partially massless theories with propagating helici ties (+/-5/2, +/-3/2) and (+/-3, +/-2), (+/-3, +/-2, +/-1), respectively. O f these, only the s = 3 models are unitary. To these ends, we also provide the half integer generalization of the integer spin wave operators of Lichn erowicz. Partial masslessness applies to all higher spins in (A)dS as seen by their degree of freedom counts. Finally a derivation of massive d = 4 co nstraints by dimensional reduction from their d = 5 massless Bianchi identi ty ancestors is given. (C) 2001 Elsevier Science B.V. All rights reserved.