Open strings on AdS(2) branes

We study the spectrum of open strings on AdS(2) branes in AdS(3) in an NS-N S background, using the SL(2, R) WZW model. When the brane carries no funda mental string charge, the open string spectrum is the holomorphic square ro ot of the spectrum of closed strings in AdS(3). It contains short and long strings, and is invariant under spectral flow. When the brane carries funda mental string charge, the open string spectrum again contains short and lon g strings in all winding sectors. However, branes with fundamental string c harge break half the spectral flow symmetry. This has different implication s for short and long strings. As the fundamental string charge increases, t he brane approaches the boundary of AdS(3). In this limit, the induced elec tric field on the worldvolume reaches its critical value, producing noncomm utative open string theory on AdS(2). (C) 2001 Elsevier Science B.V. All ri ghts reserved.