The Ermakov-Pinney Equation: its varied origins and the effects of the introduction of symmetry-breaking functions
The Ermakov-Pinney Equation, $$\ddot{x}+ω^2 x=\frac{h^2}{x^3},$$ has a varied provenance which we briefly delineate. We introduce time-dependent functions in place of the $ω^2$ and $h^2$. The former has no effect upon the algebra of the Lie point symmetries of the equation. The latter destroys the $sl(2,\Re)$ symmetry and a single symmetry persists only when there is a specific relationship between the two time-dependent functions introduced. We calculate the form of the corresponding autonomous equation for these cases.
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