%0 Journal Article %T On isoperimetric inequalities with respect to infinite measures %A F. Brock %A A. Mercaldo %A M. R. Posteraro %J Mathematics %D 2011 %I arXiv %X We study isoperimetric problems with respect to infinite measures on $R ^n$. In the case of the measure $\mu$ defined by $d\mu = e^{c|x|^2} dx$, $c\geq 0$, we prove that, among all sets with given $\mu-$measure, the ball centered at the origin has the smallest (weighted) $\mu-$perimeter. Our results are then applied to obtain Polya-Szego-type inequalities, Sobolev embeddings theorems and a comparison result for elliptic boundary value problems. %U http://arxiv.org/abs/1108.0863v1