Li\'{e}nard Type Nonlinear Oscillators and Quantum Solvability

TL;DR

This paper explores Liénard-type nonlinear oscillators, analyzing their classical and quantum behaviors, solutions, and generalizations, revealing their diverse dynamical properties and solvability in both regimes.

Contribution

It provides a comprehensive analysis of various Liénard-type oscillators, including their classical solutions, quantum solvability, and generalizations, highlighting new solvable models and complex dynamics.

Findings

Liénard-type-I oscillators are often exactly solvable quantum systems.

Classical solutions include elliptic functions and quasi-exact solutions in quantum mechanics.

Three-dimensional and isotonic generalizations exhibit complex dynamics and solvability.

Abstract

Li\'{e}nard-type nonlinear oscillators with linear and nonlinear damping terms exhibit diverse dynamical behavior in both the classical and quantum regimes. In this paper, we consider examples of various one-dimensional Li\'{e}nard type-I and type-II oscillators. The associated Euler-Lagrange equations are divided into groups based on the characteristics of the damping and forcing terms. The Li\'{e}nard type-I oscillators often display localized solutions, isochronous and non-isochronous oscillations and are also precisely solvable in quantum mechanics in general, where the ordering parameters play an important role. These include Mathews-Lakshmanan and Higgs oscillators. However, the classical solutions of some of the nonlinear oscillators are expressed in terms of elliptic functions and have been found to be quasi-exactly solvable in the quantum region. The three-dimensional generalizations of these classical systems add more degrees of freedom, which show complex dynamics. Their quantum equivalents are also explored in this article. The isotonic generalizations of the non-isochronous nonlinear oscillators have also been solved both classically and quantum mechanically to advance the studies. The modified Emden equation categorized as Li\'{e}nard type-II exhibits isochronous oscillations at the classical level. This property makes it a valuable tool for studying the underlying nonlinear dynamics. The study on the quantum counterpart of the system provides a deeper understanding of the behavior in the quantum realm as a typical PT-symmetric system.