Author Type

Graduate Student

Date of Award

Spring 4-22-2026

Document Type

Dissertation

Publication Status

Version of Record

Submission Date

May 2026

Department

Mathematics and Statistics

College Granting Degree

Charles E. Schmidt College of Science

Department Granting Degree

Mathematics and Statistics

Degree Name

Doctor of Philosophy (PhD)

Thesis/Dissertation Advisor [Chair]

Vincent Naudot

Abstract

The field of delay differential equations (DDEs) concerns the study of systems whose evolution depends on certain past states of the system. Of particular interest are the state-dependent DDEs, whose delay terms are non-constant and depend on the current state itself. In this thesis, we provide rigorous solution-finding techniques for a certain class of one-dimensional state-dependent DDEs, as well as a state-dependent delayed Van der Pol equation. This technique is inspired by the classical Picard-Lindelof theorem and is successful in proving the existence and uniqueness of orbits in such systems under certain reasonable restrictions. We then employ the Lagrange-Chebyshev interpolating operator to frame our results in the computational setting, allowing us to algorithmically obtain periodic orbits of the systems in question. These algorithms are based on the Newton-Kantorovich theorem and the resulting illustrations and numerics are discussed in detail.

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