Let $M_\mu $ be the uncentered Hardy–Littlewood maximal operator with a Borel measure $\mu $ on $\mathbb {R}$. In this note, we verify that the norm of $M_\mu $ on $L^p(\mathbb {R},\mu )$ with $p\in (1,\infty )$ is just the upper bound $\theta _p$ obtained by Grafakos and Kinnunen and reobtain the norm of $M_\mu $ from $L^1(\mathbb {R},\mu )$ to $L^{1,\infty }(\mathbb {R},\mu )$. Moreover, the norm of the “strong” maximal operator $N_{\vec {\mu }}^{n}$ on $L^p(\mathbb {R}^n, \vec {\mu })$ is also given.

Recently, the discrete reversed Hardy–Littlewood–Sobolev inequality with infinite terms was proved. In this article, we study the attainability of its best constant. For this purpose, we introduce a discrete reversed Hardy–Littlewood–Sobolev inequality with finite terms. The constraint of parameters of this inequality is more relaxed than that of parameters of inequality with infinite terms. We here show the limit relations between their best constants and between their extremal sequences. Based on these results, we obtain the attainability of the best constant of the inequality with infinite terms in the noncritical case.

We investigate the continuity and differentiability of the Hardy constant with respect to perturbations of the domain in the case where the problem involves the distance from a boundary submanifold. We also investigate the case where only the submanifold is deformed.

We prove a reversed Hardy–Littlewood–Pólya inequality with finite terms. We also give the limit of the best constant.

The article is devoted to Hardy type inequalities on closed manifolds. By means of various weighted Ricci curvatures, we establish several sharp Hardy type inequalities on closed weighted Riemannian manifolds. Our results complement in several aspects those obtained recently in the non-compact Riemannian setting.