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Growth and existence of analytic in a bidisc functions of bounded $\mathbf{L}$-index in joint variables
Bandura Andriy Ivanovych 1 , Kryshtopa Lyudmila 1 , Mazur Tetiana 1 , Ivasiv N. V. 2 , Skaskiv Oleg Bogdanovich 3
1 Department of Physical and Mathematical Sciences, Ivano-Frankivsk National Technical University of Oil and Gas, Ivano-Frankivsk, 76019, Ukraine
2 Boryslav Secondary School, No. 7, Lvivska, Borislav, 82300, Ukraine
3 Department of theory of functions and functional analysis, Ivan Franko National University of Lviv, Lviv, 79000, Ukraine
Keywords: growth estimate, analytic function, bidisc, bounded $\mathbf{L}$-index in joint variables, existence theorem, zero points with bounded multiplicities
Abstract

We obtained growth estimates for bivariate functions which are analytic in the unit bidisc and have bounded $\mathbf{L}$-index in joint variables.
The positive continuous function $\mathbf{L}(z_1,z_2)=(l_1(z_2,z_2),l_2(z_1,z_2))$ satisfies additional behavior condition:
for every point $z=(z_1,z_2)$ belonging the unit bidisc $\mathbb{D}^2$ the appropriate value of the function $l_j$ at this point is greater than the reciprocal to
$1-|z_j|$ multiplied by $\beta$, i.e. $l_j(z)>{\beta}/{(1-|z_j|)}$ for each $j\in\{1,2\}$
and some constant $\beta>1.$ Also  we prove that for every analytic functions in the unit bidisc with bounded multiplciities of zero points there exists a positive continuous function
$\mathbf{L}(z_1,z_2)=(l_1(z_2,z_2),l_2(z_1,z_2))$ providing boundedness of the $\mathbf{L}$-index in joint variables for primary analytic function.

References

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Published Online 12/11/2025
Cite
ACS Style
Bandura, A.I.; Kryshtopa , L.; Mazur , T.; Ivasiv , N.V.; Skaskiv, O.B. Growth and existence of analytic in a bidisc functions of bounded $\mathbf{L}$-index in joint variables. Bukovinian Mathematical Journal. 2025, 13 https://doi.org/https://doi.org/10.31861/bmj2025.02.09
AMA Style
Bandura AI, Kryshtopa L, Mazur T, Ivasiv NV, Skaskiv OB. Growth and existence of analytic in a bidisc functions of bounded $\mathbf{L}$-index in joint variables. Bukovinian Mathematical Journal. 2025; 13(2). https://doi.org/https://doi.org/10.31861/bmj2025.02.09
Chicago/Turabian Style
Andriy Ivanovych Bandura, Lyudmila Kryshtopa , Tetiana Mazur , N. V. Ivasiv , Oleg Bogdanovich Skaskiv. 2025. "Growth and existence of analytic in a bidisc functions of bounded $\mathbf{L}$-index in joint variables". Bukovinian Mathematical Journal. 13 no. 2. https://doi.org/https://doi.org/10.31861/bmj2025.02.09
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