Hardy's inequality in a limiting case on general bounded domains.

In this paper, we study Hardy's inequality in a limiting case: ∫ Ω | ∇ u | N d x ≥ C N (Ω) ∫ Ω | u (x) | N | x | N (log R | x |) N d x for functions u ∈ W 0 1 , N (Ω) , where Ω is a bounded domain in ℝ N with R = sup x ∈ Ω | x |. We study the attainability of the best constant C N (Ω) in several cases. We provide sufficient conditions that assure C N (Ω) > C N (B R) and C N (Ω) is attained, here B R is the N -dimensional ball with center the origin and radius R. Also, we provide an example of Ω ⊂ ℝ 2 such that C 2 (Ω) > C 2 (B R) = 1 / 4 and C 2 (Ω) is not attained. [ABSTRACT FROM AUTHOR]