One-sided versions of maximal functions for suitable defined distributions are considered. Weighted norm equivalences of these maximal functions for weights in the Sawyer's Aq+ classes are obtained.

We obtain the equivalence of the properties $\left(\beta \right)$ and (NUC) in Orlicz function spaces. This answers a question raised by Y. Cui, R. Pluciennik and T. Wang.

We consider (p,q)-multi-norms and standard t-multi-norms based on Banach spaces of the form $L^r\left(\Omega \right)$, and resolve some question about the mutual equivalence of two such multi-norms. We introduce a new multi-norm, called the [p,q]-concave multi-norm, and relate it to the standard t-multi-norm.

We discuss the validity of the Helmholtz decomposition of the Muckenhoupt $A_p$-weighted $L^p$-space ${\left(L_w^p\left(\Omega \right)\right)}^n$ for any domain $\Omega$ in ${ℝ}^n$, $n\in \mathbb{Z}$, $n\ge 2$, $1<p<\infty$ and Muckenhoupt $A_p$-weight $w\in A_p$. Set $p^{\text{'}}:=p/(p-1)$ and $w^{\text{'}}:=w^{-1/(p-1)}$. Then the Helmholtz decomposition of ${\left(L_w^p\left(\Omega \right)\right)}^n$ and ${\left(L_{w^{\text{'}}}^{p^{\text{'}}}\left(\Omega \right)\right)}^n$ and the variational estimate of $L_{w,\pi }^p\left(\Omega \right)$ and $L_{w^{\text{'}},\pi }^{p^{\text{'}}}\left(\Omega \right)$ are equivalent. Furthermore, we can replace $L_{w,\pi }^p\left(\Omega \right)$ and $L_{w^{\text{'}},\pi }^{p^{\text{'}}}\left(\Omega \right)$ by $L_{w,\sigma }^p\left(\Omega \right)$ and $L_{w^{\text{'}},\sigma }^{p^{\text{'}}}\left(\Omega \right)$, respectively. The proof is based on the reflexivity and orthogonality of $L_{w,\pi }^p\left(\Omega \right)$ and $L_{w,\sigma }^p\left(\Omega \right)$ and the Hahn-Banach theorem. As a corollary of our main result, we obtain the extrapolation theorem with...

The main object of this work is to describe such weight functions w(t) that for all elements $f\in L_{p,\Omega }$ the estimate $\parallel wf{\parallel }_p\ge K\left(\Omega \right)\parallel f{\parallel }_p$ is valid with a constant K(Ω), which does not depend on f and it grows to infinity when the domain Ω shrinks, i.e. deforms into a lower dimensional convex set ${\Omega }_{\infty }$. In one-dimensional case means that $K\left(\sigma \right):=K\left({\Omega }_{\sigma }\right)\to \infty$ as σ → 0. It should be noted that in the framework of the signal transmission problem such estimates describe a signal’s behavior under the influence of detection and amplification. This work...

Recently, the weak Triebel-Lizorkin space was introduced by Grafakos and He, which includes the standard Triebel-Lizorkin space as a subset. The latter has a wide applications in aspects of analysis. In this paper, the authors firstly give equivalent quasi-norms of weak Triebel-Lizorkin spaces in terms of Peetre's maximal functions. As an application of those equivalent quasi-norms, an atomic decomposition of weak Triebel-Lizorkin spaces is given.

Utilizing elementary properties of convergence of numerical sequences we prove Nikodym, Banach, Orlicz-Pettis type theorems