Uniqueness of positive radial solutions of superlinear elliptic equations in annuli.

We present a generalized comparison identity for a two point boundary value problem, and we apply it to show the uniqueness of positive radial solutions of { Δ u (x) + f (u (x)) = 0 in A a , b , u (x) = 0 on ∂ A a , b , where n ∈ N with n ≥ 2 , 0 < a < b < ∞ , A a , b = { x ∈ R N : a < | x | < b } and f ∈ C 1 [ 0 , ∞) is a superlinear function. [ABSTRACT FROM AUTHOR]