Radiation tails and boundary conditions for black hole evolutions
  In numerical computations of Einstein's equations for black hole spacetimes, it will be necessary to use approximate boundary conditions at a finite distance from the holes. We point out here that ``tails,'' the inverse power-law decrease of late-time fields, cannot be expected for such computations. We present computational demonstrations and discussions of features of late-time behavior in an evolution with a boundary condition. 
Elspeth W. Allen, Elizabeth Buckmiller, Lior M. Burko, Richard H.Price