About Lebesgue inequalities on the classes of generalized Poisson integrals (2005.13849v1)

Abstract: For the functions $f$, which can be represented in the form of the convolution $f(x)=\frac{a_{0}}{2}+\frac{1}{\pi}\int\limits_{-\pi}^{\pi}\sum\limits_{k=1}^{\infty}e^{-\alpha k^{r}}\cos(kt-\frac{\beta\pi}{2})\varphi(x-t)dt$, $\varphi\perp1$, $\alpha>0, \ r\in(0,1)$, $\beta\in\mathbb{R}$, we establish the Lebesgue-type inequalities of the form \begin{equation*} |f-S_{n-1}(f)|{C}\leq e^{-\alpha n^{r}}\left(\frac{4}{\pi^{2}}\ln \frac{n^{1-r}}{\alpha r} + \gamma{n} \right) E_{n}(\varphi){C}. \end{equation*} These inequalities take place for all numbers $n$ that are larger than some number $n{1}=n_{1}(\alpha,r)$, which constructively defined via parameters $\alpha$ and $r$. We prove that there exists a function, such that the sign "$\leq$" in given estimate can be changed for "$=$".