Weighted norm inequalities in Lebesgue spaces with Muckenhoupt weights and some applications to operators

Abstract

In the present work we give a simple method to obtain weighted norm inequalities in Lebesgue spaces $L_{p,\gamma }$ with Muckenhoupt weights $\gamma $. This method is different from celebrated Extrapolation or Interpolation Theory. In this method starting point is uniform norm estimates of special form. Then a procedure give desired weighted norm inequalities in $L_{p,\gamma }.$ We apply this method to obtain several convolution type inequalities. As an application we consider a difference operator of type $\Delta _{v}^{r}:=\left( \mathbb{I}-\mathfrak{T}_{v}\right) ^{r}$ where $\mathbb{I}$ is the identity operator, $r\in \mathbb{N}$ and \begin{equation*} \mathfrak{T}_{v}f\left( x\right) :=\frac{1}{v}\int\nolimits_{x}^{x+v}f\left(t\right) dt,\quad x\in \left[ -\pi ,\pi \right] ,\quad v>0,\quad \mathfrak{T}_{0}:=\mathbb{I}. \end{equation*} We obtain main properties of $\Delta _{v}^{r}f$ for functions $f$ given in $L_{p,\gamma }$, $1\leq p<\infty $, with weights $\gamma $ satisfying the Muckenhoupt's $A_{p}$ condition. Also we consider some applications of difference operator $\Delta _{v}^{r}$ in these spaces. In particular, we obtain that difference $\left\Vert \Delta _{v}^{r}f\right\Vert _{p,\gamma }$ is a useful tool for computing the smoothness properties of functions these spaces. It is obtained that $\left\Vert \Delta _{v}^{r}f\right\Vert_{p,\gamma }$ is equivalent to Peetre's K-functional.