Discrete Dynamics in Nature and Society

Volume 2018, Article ID 7052935, 22 pages

https://doi.org/10.1155/2018/7052935

## Global Asymptotic Stability and Naimark-Sacker Bifurcation of Certain Mix Monotone Difference Equation

^{1}Department of Mathematics, University of Rhode Island, Kingston, RI 02881, USA^{2}Department of Mathematics, University of Tuzla, 75000 Tuzla, Bosnia and Herzegovina

Correspondence should be addressed to M. R. S. Kulenović; ude.iru.liam@civonelukm

Received 18 July 2018; Accepted 17 October 2018; Published 8 November 2018

Guest Editor: Abdul Qadeer Khan

Copyright © 2018 M. R. S. Kulenović et al. This 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.

#### Abstract

We investigate the global asymptotic stability of the following second order rational difference equation of the form where the parameters , , , and and initial conditions and are positive real numbers. The map associated with this equation is always decreasing in the second variable and can be either increasing or decreasing in the first variable depending on the parametric space. In some cases, we prove that local asymptotic stability of the unique equilibrium point implies global asymptotic stability. Also, we show that considered equation exhibits the Naimark-Sacker bifurcation resulting in the existence of the locally stable periodic solution of unknown period.

#### 1. Introduction and Preliminaries

In this paper, we investigate the local and global dynamics of the following difference equation:where the parameters are positive real numbers and initial conditions and are arbitrary positive real numbers. Equation (1) is the special case of a general second order quadratic fractional equation of the formwith nonnegative parameters and initial conditions such that , and . Several global asymptotic results for some special cases of Equation (2) were obtained in [1–11]. Also, Equation (1) is a special case of the equationwith positive parameters and nonnegative initial conditions , . Local and global dynamics of Equation (3) was investigated in [12].

The special case of Equation (3) when , i.e.,was studied in [8]. The authors performed the local stability analysis of the unique equilibrium point and gave the necessary and sufficient conditions for the equilibrium to be locally asymptotically stable, a repeller or nonhyperbolic equilibrium. Also, it was shown that Equation (4) exhibits the Naimark-Sacker bifurcation.

The special case of Equation (3) (when and ) is the following equation:where the parameters , , and are nonnegative numbers with condition , and the initial conditions , arbitrary nonnegative numbers such that . Equation (5) is a perturbed Sigmoid Beverton-Holt difference equation and it was studied in [9]. The special case of Equation (5) for is the well-known Thomson equationwhere the parameters and are positive numbers and the initial conditions , are arbitrary nonnegative numbers, is used in the modelling of fish population [13].

The dynamics of (6) is very interesting and follows from the dynamics of related equationIndeed (6) is delayed version of (7) and so it exhibits the existence of period-two solutions.

Two interesting special cases of Equation (2) are the following difference equations:studied in [14], andstudied in [5]. In both equations, (8) and (9), the associated map changes its monotonicity with respect to its variable.

In this paper, in some cases when the associated map changes its monotonicity with respect to the first variable in an invariant interval, we will use Theorems 1 and 2 below in order to obtain the convergence results. However, if , we would not be able to use this method, so we will use the semicycle analysis; see [15] to show that each of the following four sequences , , , converges to the unique equilibrium point.

Also, we will show that Equation (1) exhibits the Naimark-Sacker bifurcation resulting in the existence of the locally stable periodic solution of unknown period.

Note that the problem of determining invariant intervals in the case when the associated map changes its monotonicity with respect to its variable has been considered in [17, 18].

In this paper, we will use the following well-known results, Theorem 2.22, in [16], and Theorem 1.4.7 in [19].

Theorem 1. *Let be a compact interval of real numbers and assume that is a continuous function satisfying the following properties:*(a)* is nondecreasing in for each , and is nonincreasing in for each ;*(b)*If is a solution of the system* *then .**Thenhas a unique equilibrium and every solution of Equation (11) converges to .*

*Theorem 2. Let be an interval of real numbers and assume that is a continuous function satisfying the following properties:(a) is nonincreasing in both variables(b)If is a solution of the system then .Then, (11) has a unique equilibrium and every solution of Equation (11) converges to .*

*Remark 3. *As is shown in [20] the unique equilibrium in Theorems 1 and 2 is globally asymptotically stable.

*The rest of this paper is organized as follows. The second section presents the local stability of the unique positive equilibrium solution and the nonexistence of the minimal period-two solution. The third section gives global dynamics in certain regions of the parametric space. The results and techniques depend on monotonic character of the transition function which is either decreasing in both arguments or increasing in first and decreasing in second argument. In simpler situations Theorems 1 and 2 are sufficient to prove global stability of the unique equilibrium. In more complicated situations we use the semicycle analysis, which is extensively used in [15, 19] for many linear fractional equations, to prove that every solution has four convergent subsequences, which leads to the conclusion that every solution converges to period-four solution. In some parts of parametric space we prove that there is no minimal period-four solution and so every solution converges to the equilibrium, while in other parts of parametric space we prove that the period-four solution exists. The semicycle analysis presented here uses innovative techniques based on analysis of systems of polynomial equations which coefficients depend on four parameters. Finally in the region of parameters complementary to the one where the period-four solution exists we prove that the Naimark-Sacker bifurcation takes place which produces locally stable periodic solution. All numerical simulations indicate that the equilibrium solution is globally asymptotically stable whenever it is locally asymptotically stable and that the dynamics is chaotic whenever the equilibrium is repeller. An interesting feature of Equation (1) is that it gives an example of second order difference equation with period-four solution for which period-two solution does not exist. The global dynamics of Equation (11) when the transition function is either increasing in both arguments or decreasing in the first and increasing in the second argument is fairly simple as every solution breaks into two eventually monotonic subsequences and ; see [21–23]. The global dynamics of Equation (11) when the transition function is either decreasing in both arguments or increasing in the first and decreasing in the second argument could be quite complicated ranging from global asymptotic stability of the equilibrium, see [19, 21, 22, 24–26] to conservative and nonconservative chaos, see [3, 19, 26]. Interesting applications can be found in [27].*

*2. Linearized Stability*

*2. Linearized Stability*

*In this section, we present the local stability of the unique positive equilibrium of Equation (1) and the nonexistence of the minimal period-two solution of Equation (1).*

*In view of the above restriction on the initial conditions of Equation (1), the equilibrium points of Equation (1) are the positive solutions of the equationor equivalentlyEquation (1) has the unique positive solution given aswhereNow, we investigate the stability of the positive equilibrium of Equation (1). Setand observe that The linearized equation associated with Equation (1) about the equilibrium point iswhere*

*Theorem 4. Let The unique equilibrium point of Equation (1) given by (15) is(i)locally asymptotically stable if ,(ii)a repeller if ,(iii)a nonhyperbolic point of elliptic type if .*

*Proof. *In view ofwe have thatandand so

Also, we haveSince , the equilibrium point will be nonhyperbolic if and . From we obtainand by using (14), we haveNow,and the characteristic equation of (19) is of the form from which that is, is nonhyperbolic equilibrium point. Let us denote Then,The condition is always satisfied. Hence, it holds: the equilibrium solution is locally asymptotically stable ifi.e., and a repeller if , which is equivalent with , i.e., . See Figure 1.