Respondent

Petrechko Nataliia Vasylivna

Theme

Properties of functions of bounded index in the unit bidisc

Defence Date

02.05.2019

Annotation

The dissertation consists of an introduction, 4 chapters, conclusions to each secti-
on and general conclusions, list of sources used. The introduction substantiates the
relevance of the research topic, formulates the purpose, task, subject, object and
methods of the research, presents the scientific novelty, the practical significance of
the results obtained, the relationship of work with scientific themes and the personal
contributions of the author of the dissertation, a list of conferences and scientific semi-
nars, on which the results of the dissertation research are tested; List of publications
in which the main results of the dissertation are published.
In the dissertation, the main object of investigations is a class of analytic functions
in the unit polydisc — so-called functions of bounded L-index in joint variables.
There were obtained the criteria of boundedness of L-index in joint variables for
analytic functions in a polydisc. Particularly, the statements describe estimates of the
behavior of the maximum modulus of the function on polydiscs of various radii, local
behavior of the maximum modulus of partial derivatives on polydiscs of various radii.
We found sufficient conditions of boundedness of the L-index in joint variables for
the solutions of some higher-order linear systems of partial differential equations with
analytic coefficients in the polydisc. The properties of the power expansion for entire
functions in complex plane and analytic functions in the unit bidisc of bounded L-index
in joint variables are investigated. We also indicate growth estimates of logarithm of
maximum modulus on a bidisc for this class of analytic functions. The logarithm
behave as some integral from the vector-function L in the worst case. In any compact
embedding domain in the unit bidisc an analytic functions in the bidisc has bounded
L-index in joint variables for every positive continuous vector-function L, which is
greater than some constant depending of the domain. All results of the thesis are new.
They have theoretical meaning and can be used both in multidimensional complex
analysis and in the analytic theory of differential equations.
Keywords: entire function, analytic function, polydisc, bounded L-index in joint
variables, system of linear partial differential equations.

Dissertation File

Autosummary File