Extension of Floquet's theory to nonlinear quasiperiodic differential equations

In this paper, we consider the following autonomous system of differential equations: x = Ax f(x,θ), θ = ω, where θ∈Rm, ω = (ω1,…,ωm) ∈ Rm, x ∈ Rn, A ∈ Rn×n is a constant matrix and is hyperbolic, f is a C∞ function in both variables and 2π-periodic in each component of the vector e which satisfies f = O(||x||2) as x → 0. We study the normal form of this system and prove that under some proper conditions this system can be transformed to an autonomous system: x = Ax g(x), θ = ω. Additionally, the proof of this paper naturally implies the extension of Chen's theory in the quasi-periodic case.

Extension of floquet’s theory to nonlinear quasiperiodic differential equations

In this paper, we consider the following autonomous system of differential equations: . where θ ∈ ℝ^m, ω=(ω₁...,ω_m) ∈ ℝ^m, x ∈ ℝⁿ, A ∈ ℝ^n×n is a constant matrix and is hyperbolic, f is a C^∞ function in both variables and 2π-periodic in each component of the vector θ which satisfies f-O(‖x‖²) as x → 0. We study the normal form of this system and prove that under some proper conditions this system can be transformed to an autonomous system: Additionally, the proof of this paper naturally implies the extension of Chen’s theory in the quasiperiodic case.