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Properties of solutions of a heterogeneous differential equation of the second order
Author(s) -
O. M. Mulyava,
M. M. Sheremeta,
Yu.S. Trukhan
Publication year - 2019
Publication title -
carpathian mathematical publications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.63
H-Index - 4
eISSN - 2313-0210
pISSN - 2075-9827
DOI - 10.15330/cmp.11.2.379-398
Subject(s) - mathematics , order (exchange) , convexity , power series , combinatorics , radius of convergence , differential equation , beta (programming language) , convergence (economics) , mathematical analysis , series (stratigraphy) , unit disk , biology , programming language , economic growth , paleontology , finance , computer science , financial economics , economics
Suppose that a power series $A(z)=\sum_{n=0}^{\infty}a_n z^{n}$ has the radius of convergence \break $R[A]\in [1,+\infty]$. For a heterogeneous differential equation $$ z^2 wu0027u0027+(\beta_0 z^2+\beta_1 z) wu0027+(\gamma_0 z^2+\gamma_1 z+\gamma_2)w=A(z) $$ with complex  parameters geometrical properties of its solutions (convexity, starlikeness and close-to-convexity) in the unit disk are investigated. Two cases are considered: if $\gamma_2\neq0$ and $\gamma_2=0$. We also consider cases when parameters of the equation are real numbers. Also, we prove that for a solution $f$ of this equation the radius of convergence $R[f]$ equals to $R[A]$ and the recurrent formulas for the coefficients of the power series of $f(z)$ are found. For entire solutions it is proved that the order of a solution $f$ is not less than the order of $A$ ($\varrho[f]\ge\varrho[A]$) and the estimate is sharp. The same inequality holds for generalized orders ($\varrho_{\alpha\beta}[f]\ge \varrho_{\alpha\beta}[A]$). For entire solutions of this equation the belonging to convergence classes  is studied. Finally, we consider a linear differential equation of the endless order $\sum\limits_{n=0}^{\infty}\dfrac{a_n}{n!}w^{(n)}=\Phi(z),$ and study a possible growth of its solutions.

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