Quasi-spherical collapse with cosmological constant
  The junction conditions between static and non-static space-times are studied for analyzing gravitational collapse in the presence of a cosmological constant. We have discussed about the apparent horizon and their physical significance. We also show the effect of cosmological constant in the collapse and it has been shown that cosmological constant slows down the collapse of matter. 
Ujjal Debnath, Soma Nath and Subenoy Chakraborty