Research Article
Location of the Zeros of Certain Complex-Valued
Harmonic Polynomials
Hunduma Legesse Geleta and Oluma Ararso Alemu
Department of Mathematics, Addis Ababa University, Addis Ababa, Ethiopia
Correspondence should be addressed to Hunduma Legesse Geleta; hunduma.legesse@aau.edu.et
Received 28 March 2022; Accepted 18 July 2022; Published 11 August 2022
Academic Editor: Firdous A. Shah
Copyright © 2022 Hunduma Legesse Geleta and Oluma Ararso Alemu. is is an open access article distributed under the
Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided
the original work is properly cited.
Finding the approximate region containing all the zeros of analytic polynomials is a well-studied problem. But the number of the
zeros and regions containing all the zeros of complex-valued harmonic polynomials is relatively a fresh research area. It is well
known that all the zeros of analytic trinomials are enclosed in some annular sectors that take into account the magnitude of the
coefficients. Following Kennedy and Dehmer, we provide the zero inclusion regions of all the zeros of complex-valued harmonic
polynomials in general, and in particular, we bound all the zeros of some families of harmonic trinomials in a certain
annular region.
1. Introduction
e location of the zeros of analytic polynomials has been
studied by many researchers (see Brilleslyper and Schaubroeck
[1], Dhemer [2], Frank [3], Gilewicz and Leopold [4], Howell
and Kyle [5], Johnson and Tucker [6], Kennedy [7], and
Melman [8]). Recently, researching the number of the zeros of
general analytic trinomials and the regions in which the zeros
are located has become of interest due to their application in
other fields. For example, the roots of the trinomial equations
can be interpreted as the equilibrium points of unit masses that
are located at the vertices of two regular concentric polygons
centered at the origin in the complex plane [9]. A useful result
in determining the location of the zeros of analytic polynomials
is the argument principle. Recall that if f is analytic inside and
on positively oriented rectifiable Jordan curve C and f(z) ≠ 0
on C, then the winding number of the image curve f(C) about
the origin (1/2π)Δ
C
argf(z) equals the total number of zeros
of f in D, counted according to multiplicity where D is a plane
domain bounded by C. In 1940, Kennedy [7] showed that the
roots of analytic trinomial equations of the form
z
n
+ az
k
+ b 0, where ab ≠ 0, have certain bounds to their
respective absolute values. In 2006, Dehmer [2] proved that all
the zeros of complex-valued analytic polynomials lie in certain
closed disk. In 2012, Melman [8] investigated the regions in
which the zeros of analytic trinomials of the
formp(z) z
n
− αz
k
− 1, with integers n ≥ 3 and
1 ≤ k ≤ n − 1withgcd(k, n) 1, andα ∈ C, lie. He determined
the zero inclusion regions for the following cases: (a for any
value of |α|; (b) |α| > σ (n, k); and (c |α| < σ n (), k (), where
σ (n, k) n/n − k(n − k/k)
k/n
. In each case, Melman provided
useful information on the location of the zeros of p.
One area of investigation that has recently become of
interest is the number and location of zeros of complex-
valued harmonic polynomials. In 1984, Clunie and Sheil-
Small [10] introduced the family of complex-valued har-
monic functions f u + iv defined in the unit disk
D z: |z| < 1 { }, where u and v are real harmonic in D.A
continuous function f u + iv defined in a domain G ⊂ C is
harmonic in G if u and v are real harmonic in G. In any
simply connected subdomain of G, we can decompose f as
f h + g, where g and h are analytic and g denotes the
function z↦ g(z) (see Duren [11]). is family of complex-
valued harmonic functions is a generalization of analytic
mappings studied in geometric function theory, and much
research has been done investigating the properties of these
harmonic functions. For an overview of the topic, see Duren
[12] and Dorff and Rolf [13]. It was shown by Bshouty et al.
Hindawi
Journal of Mathematics
Volume 2022, Article ID 4886522, 5 pages
https://doi.org/10.1155/2022/4886522