Speaker: Marco Bruni
Location: 28th Texas Symposium, Geneva
I introduce new exact solutions of the Szekeres-Szafron type describing voids on a Friedmann-Roberson-Walker background with w=constant equation of state. At least in the linear regime the inhomogeneities can be thought of as large scale perturbations of the background. Using these exact solutions the averaged quantities of the Buchert scheme can be calculated exactly. I show that in general the late-time evolution is dominated by the voids: these back-react in such a way that the average expansion is significantly different from the background one, I will describe how.