Remark about the maximum of the modulus of an analytic function on the boundary
Zapiski Nauchnykh Seminarov POMI, Investigations on linear operators and function theory. Part 32, Tome 315 (2004), pp. 149-154
N. A. Shirokov. Remark about the maximum of the modulus of an analytic function on the boundary. Zapiski Nauchnykh Seminarov POMI, Investigations on linear operators and function theory. Part 32, Tome 315 (2004), pp. 149-154. http://geodesic.mathdoc.fr/item/ZNSL_2004_315_a10/
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     title = {Remark about the maximum of the modulus of an analytic function on the boundary},
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     year = {2004},
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     url = {http://geodesic.mathdoc.fr/item/ZNSL_2004_315_a10/}
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Voir la notice du chapitre de livre provenant de la source Math-Net.Ru

Let $\Lambda^{\alpha}$ be the analytic Hölder class in the unit disc $\mathbb D$. For $f\in \Lambda^{\alpha}$ and $I\subset\partial\mathbb D$, let $M_f(I)=\max_I|f|$. Assume that $I$, $J$ are arcs such that $|J|=2|I|$, $J$ and $I$ have common middle point. Then $$ M_f(J)\le C(\alpha,f)\frac{|I|^{\alpha}+M_f(I)}{\log^{\alpha}\Bigl(\frac{|I|^{\alpha}}{M_f(I)}+2\Bigr)}. $$ It is proved that this estimate cannot be improved.

[1] N. A. Shirokov, Analytic functions smooth up to the boundary, Lecture Notes in Mathematics, 1312, 1988 | MR | Zbl