The no-ghost theorem for AdS3 and the stringy exclusion principle Original Research Article

A complete proof of the no-ghost theorem for bosonic and fermionic string theories on AdS3, or the group manifold of SU(1, 1), is given. It is then shown that the restriction on the spin (in terms of the level) that is necessary to obtain a ghost-free spectrum corresponds to the stringy exclusion principle of Maldacena and Strominger.