## Dissertations, Theses, and Capstone Projects

#### Date of Degree

6-2017

#### Document Type

Dissertation

#### Degree Name

Ph.D.

#### Program

Mathematics

#### Advisor

Alexey Ovchinnikov

#### Committee Members

Alexey Ovchinnikov

Richard Churchill

Benjamin Steinberg

#### Subject Categories

Algebra | Partial Differential Equations

#### Keywords

algebraic differential equations, differential elimination algorithms, effective differential Nullstellensatz

#### Abstract

We develop new upper bounds for several effective differential elimination techniques for systems of algebraic ordinary and partial differential equations. Differential elimination, also known as decoupling, is the process of eliminating a fixed subset of unknown functions from a system of differential equations in order to obtain differential algebraic consequences of the original system that do not depend on that fixed subset of unknowns. A special case of differential elimination, which we study extensively, is the question of consistency, that is, if the given system of differential equations has a solution. We first look solely at the ``algebraic data" of the system of differential equations through the theory of differential kernels to provide a new upper bound for proving the consistency of the system. We then prove a new upper bound for the effective differential Nullstellensatz, which determines a sufficient number of times to differentiate the original system in order to prove its inconsistency. Finally, we study the Rosenfeld-Gröbner algorithm, which approaches differential elimination by decomposing the given system of differential equations into simpler systems. We analyze the complexity of the Rosenfeld-Gröbner algorithm by computing an upper bound for the orders of the derivatives in all intermediate steps and in the output of the algorithm.

#### Recommended Citation

Gustavson, Richard, "Elimination for Systems of Algebraic Differential Equations" (2017). *CUNY Academic Works.*

https://academicworks.cuny.edu/gc_etds/1970