0 60 70 90 v 2 7 A ug 2 00 6 Λ effect in the cosmological expansion of voids

The dynamical effect of the cosmological constant Λ on a single spherical void evolving in a the universe is investigated within a non linear perturbation of Newton-Friedmann models. The void expands with a huge initial burst which freezes asymptotically with time up to matching Hubble flow. For Ω◦ ∼ 0.3, Λ-effect on the kinematics intervenes significantly by amplifying the expansion rate at redshift z ∼ 1.7. As a result, the size increases with the background density and with Λ, what interprets by the gravitational attraction of borders from outside regions and the gravitational repulsion of borders. The velocity flow within the void region depends solely on Λ, it reads ~v = √ Λ/3~r. Hence, the empty regions are swept out for spatially closed Friedmann models what provides us with a stability criterion.