Lightsheets, Branes and the Covariant Entropy Bound
  We investigate the geometry of lightsheets comprised of null geodesics near a brane. Null geodesics which begin parallel to a brane a distance d away are typically gravitationally bound to the brane, so that the maximum distance from the geodesic to the brane never exceeds d. The geometry of resulting lightsheets is similar to that of the brane if one coarse grains over distances of order d. We discuss the implications for the covariant entropy bound applied to brane worlds. 
Deog Ki Hong (Pusan Nat'l Univ.), Stephen D. H. Hsu (U. of Oregon)