#### Date of Award

2013

#### Degree Type

Dissertation

#### Degree Name

Doctor of Philosophy in Mathematics

#### Department

Mathematics

#### First Advisor

Gerasimos Ladas

#### Abstract

This dissertation is an exposition of systems of difference equations. I examine multiple examples of both piecewise and rational difference equations.

[Mathematical equations can not be displayed here, refer to PDF]

In the first two manuscripts, I share the published results of two members of the following family of 81 systems of piecewise linear difference equations:

where the initial condition (χ_{0}, γ_{0}) ∈**R**^{2}, and where the parameters *a b, c* and *d* are integers between -1 and 1, inclusively. Since each parameter can be one of three values, there are 81 members. Each system is designated a number. The system’s number N is given by

N = 27(*a* + 1) + 9(*b* +1) + 3(*c* + 1) + (*d* +1) + 1.

The first manuscript is a study of System(2). System(2) results when *a* = *b* = *c* = -1 and *d* = 0. For System(2), I show that there exists a unique equilibrium solution and exactly two prime period-5 solutions, and that every solution of the system is eventually one of the two prime period-5 solutions or unique equilibrium solution.

The second manuscript is a study of System(8). System(8) results when *a* = *b* = -1, *c* = 1 and *d* = 0. For System(8), I show that there exists a unique equilibrium solution and exactly two prime period-3 solutions, and that except for the equilibrium solution, every solution of the system is eventually one of the two prime period-3 solutions.

Of the 81 systems, 65 have been studies thoroughly. In Appendix .1, I give the unpublished results of the 21 systems that I studied. In Appendix .2, I list all 81 systems (studied by W. Tikjha, E. Grove, G. Ladas, and E. Lapierre) each with a theorem or conjecture about its global behavior.

In the third manuscript, I give the published results of the following system of rational difference equations:

[Mathematical equations can not be displayed here, refer to PDF]

where the parameters and initial conditions are positive real values. I show that the system is permanent and has a unique positive equilibrium which is locally asymptotically stable. I also find sufficient conditions to insure that the unique positive equilibrium is globally asymptotically stable.

In Appendix .3, I give the unpublished results of the following system of rational difference equations:

[Mathematical equations can not be displayed here, refer to PDF]

where the parameters and initial conditions are positive real values. I show that the system is permanent. I also find sufficient conditions to insure that the unique positive equilibrium is globally asymptotically stable.

#### Recommended Citation

Lapierre, Evalina G., "On the Global Behavior of Some Systems of Difference" (2013). *Open Access Dissertations.* Paper 6.

https://digitalcommons.uri.edu/oa_diss/6