Stable Massive States in 1+1 Dimensional NCOS
  We study the case of open string theory on a D1-brane in a critical electric field. It was argued in hep-th/0006085 that the massless open string modes of this theory decouple from the massive modes, corresponding to a decoupling of the U(1) degrees of freedom in the U(N) gauge theory dual. To provide further support for the decoupling, we present several examples of open string disk amplitudes. Because of the decoupling, many of the massive open string states are stable, indicating the presence of a number of correspondingly stable states in the gauge theory. We provide a lengthy list of these stable states. However, when the theory is compactified in the spatial direction of the electric field, we demonstrate that sufficiently massive such states may decay into wound closed strings. 
Christopher P. Herzog and Igor R. Klebanov