Neumann Problems and Steiner Symmetrization.

In the present paper we prove some comparison results via Steiner symmetrization for solutions to the Neumann problem where T > 0, Ω is a smooth connected open bounded subset of ℝ n , the coefficients a ij ( x , y ) and the datum f are smooth functions such that a ij ( x , y )ξ i ξ j ≥ |ξ| 2 , for any ( x , y ) ∈ G , for any ξ ∈ ℝ n and ∈ t G f dx dy = 0. [ABSTRACT FROM AUTHOR]