Nonlocal transformations of the generalized Liénard type equations and dissipative Ermakov-Milne-Pinney systems

We employ the method of nonlocal generalized Sundman transformations to formulate the linearization problem for equations of the generalized Liénard type and show that they may be mapped to equations of the dissipative Ermakov-Milne-Pinney type. We obtain the corresponding new first integrals of these derived equations, this method yields a natural generalization of the construction of Ermakov–Lewis invariant for a time-dependent oscillator to (coupled) Liénard and Liénard type equations. We also study the linearization problem for the coupled Liénard equation using nonlocal transformations and derive coupled dissipative Ermakov-Milne-Pinney equation. As an offshoot of this nonlocal transformation method when the standard Liénard equation, [Formula: see text], is mapped to that of the linear harmonic oscillator equation, we obtain a relation between the functions [Formula: see text] and [Formula: see text] which is exactly similar to the condition derived in the context of isochronicity of the Liénard equation.

A note on generalization of the Ermakov–Lewis invariant and its demystification

Recently, a physical basis for the Ermakov–Lewis invariant has been pointed out by Padmanabhan [Mod. Phys. Lett. A 33, 1830005 (2018)] and the most general form of the equations admitting such an invariant has been identified. Further generalizations to other equations beyond the Ermakov–Lewis system are derived by considering a more general form of a nonlocal transformation of the Sundman type and the corresponding invariants are derived. Reductions to the time-dependent isotonic oscillator are also obtained.

Linearization properties, first integrals, nonlocal transformation for heat transfer equation

We examine first integrals and linearization methods of the second-order ordinary differential equation which is called fin equation in this study. Fin is heat exchange surfaces which are used widely in industry. We analyze symmetry classification with respect to different choices of thermal conductivity and heat transfer coefficient functions of fin equation. Finally, we apply nonlocal transformation to fin equation and examine the results for different functions.

Nonlocal Symmetries of Systems of Evolution Equations

We prove that any potential symmetry of a system of evolution equations reduces to a Lie symmetry through a nonlocal transformation of variables. This fact is in the core of our approach to computation of potential and more general nonlocal symmetries of systems of evolution equations having nontrivial Lie symmetry. Several examples are considered.

FIRST-ORDER ACTIONS AND DUALITY

We consider some aspects of classical S-duality transformations in first-order actions taking into account the general covariance of the Dirac algorithm and the transformation properties of the Dirac bracket. By classical S-duality transformations we mean a field redefinition that interchanges the equations of motion and its associated Bianchi identities. By working from a first-order variational principle and performing the corresponding Dirac analysis we find that the standard electromagnetic duality can be reformulated as a canonical local transformation. The reduction from this phase space to the original phase space variables coincides with the well-known result about duality as a canonical nonlocal transformation. We have also applied our ideas to the bosonic string. These dualities are not canonical transformations for the Dirac bracket and relate actions with different kinetic terms in the reduced space.