Jaquette, Jonathan Caleb. Counting and discounting slowly oscillating periodic solutions to Wright's equation. Retrieved from https://doi.org/doi:10.7282/T3GB27H8
DescriptionA classical example of a nonlinear delay differential equations is Wright's equation: y'(t) = −αy(t − 1)[1 + y(t)],, considering α > 0 and y(t) > −1. This thesis proves two conjectures associated with this equation: Wright's conjecture, which states that the origin is the global attractor for all α ∈ (0,π/2]; and Jones' conjecture, which states that there is a unique slowly oscillating periodic solution for α > π/2. Moreover, we prove there are no isolas of periodic solutions to Wright's equation; all periodic orbits arise from Hopf bifurcations. To prove Wright's conjecture our approach relies on a careful investigation of the neighborhood of the Hopf bifurcation occurring at α = π/2. Using a rigorous numerical integrator we characterize slowly oscillating periodic solutions and calculate their stability, proving Jones' conjecture for α ∈ [1.9, 6.0] and thereby all α ≥ 1.9. We complete the proof of Jones conjecture using global optimization methods, extended to treat infinite dimensional problems.