The inside story: Quasilocal tachyons and black holes

We analyze the fate of excitations in regions of closed string tachyoncondensate, a question crucial for understanding unitarity in a class of blackholes in string theory. First we introduce a simple new example of {\itquasilocal} tachyon condensation in a globally stable AdS/CFT background, andreview tachyons' appearance in black hole physics. Then we calculate forces onparticles and fields in a tachyon phase using a field theoretic model withspatially localized exponentially growing time dependent masses. This modelreveals two features, both supporting unitary evolution in the bulk ofspacetime. First, the growing energy of fields sourced by sets of (real andvirtual) particles in the tachyon phase yields outward forces on them, leavingbehind only combinations which do not source any fields. Secondly, requiringthe consistency of perturbative string theory imposes cancellation of a BRSTanomaly, which also yields a restricted set of states. Each of these effectssupports the notion of a black hole final state arising from string-theoreticdynamics replacing the black hole singularity.Comment: 32 pages, harvmac big, 2 figure