Chaplygin-Kalb-Ramond Quartessence
  Unified dark matter/energy models (quartessence) based upon the Chaplygin gas D-brane fail owing to the suppression of structure formation by the adiabatic speed of sound. Including string theory effects, in particular the Kalb-Ramond field which becomes massive via the brane, we show how nonadiabatic perturbations allow successful structure formation. 
Neven Bilic (1), Gary B. Tupper (2), and Raoul D. Viollier (2) ((1)   Rudjer Boskovic Institute, Zagreb, Croatia, (2) Univer...