Role of anisotropy in the expansion-free plane gravitational collapse

In this paper, we study the instability range of the collapsing fluid bounded by the plane geometry. For this purpose, the expansion-free dynamical equations in Newtonian and post-Newtonian regimes are obtained through perturbation scheme. We investigate the role of pressure anisotropy and energy density inhomogeneity in the instability ranges of expansion-free fluid. It is concluded that the instability regions for the plane geometry turns out to be large than the spherical case.