About Lebesgue inequalities on the classes of generalized Poisson integrals

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 "$=$".