Dynamics of quiet universes

We study the stability of a contracting silent universe, which is a spacetime with irrotational dust and vanishing magnetic part of the Weyl tensor, [Formula presented]. Two general relativistic backgrounds are analyzed: one is an attractor of silent universes, i.e., a locally Kasner spacetime, and the other is a particular class of inhomogeneous Szekeres solutions. In both cases their stabilities against perturbations with a nonzero magnetic part depend on a contraction configuration; a spindlelike collapse is unstable, while a pancakelike collapse is still stable. We also find that a similar instability exists in spindle collapse for a Newtonian case. We conclude that [Formula presented] is not a generic ansatz even in general relativistic dust collapse.