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**Second-order systems of ODEs admitting three-dimensional Lie algebras and integrability.**
*(English)*
Zbl 1266.34054

Summary: We present a systematic procedure for the determination of a complete set of \(k\)th-order (\(k \geq 2\)) differential invariants corresponding to vector fields in three variables for three-dimensional Lie algebras. In addition, we give a procedure for the construction of a system of two \(k\)th-order ODEs admitting three-dimensional Lie algebras from the associated complete set of invariants and show that there are 29 classes for the case of \(k = 2\) and 31 classes for the case of \(k \geq 3\). We discuss the singular invariant representations of canonical forms for systems of two second-order ODEs admitting three-dimensional Lie algebras. Furthermore, we give an integration procedure for canonical forms for systems of two second-order ODEs admitting three-dimensional Lie algebras which comprises of two approaches, namely, division into four types I, II, III, and IV and that of integrability of the invariant representations. We prove that if a system of two second-order ODEs has a three-dimensional solvable Lie algebra, then, its general solution can be obtained from a partially linear, partially coupled or reduced invariantly represented system of equations. A natural extension of this result is provided for a system of two \(k\)th-order (\(k \geq 3\)) ODEs. We present illustrative examples of familiar integrable physical systems which admit three-dimensional Lie algebras such as the classical Kepler problem and the generalized Ermakov systems that give rise to closed trajectories.

### MSC:

34C14 | Symmetries, invariants of ordinary differential equations |

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\textit{M. Ayub} et al., J. Appl. Math. 2013, Article ID 147921, 15 p. (2013; Zbl 1266.34054)

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### References:

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