Linearization criteria for second order systems of ODEs obtained from geometry
Abstract:
Lie provided criteria to determine what equations can be written,
by a suitable choice of transformation, to linear equations. More
specifically, he showed that a single 2nd order ODE must be (at most)
cubically semi-linear to be linearizable and stated the criteria to
determine linearizability. Considering quadratically semi-linear systems of
equations that could be regarded as geodesic equations it has been shown
that the criteria could be stated as well. Aminova and Aminov provided a
method for projecting a system of geodesic equations to a (one) lower
dimensional system of cubically semi-linear equations. Using this method the
criteria developed for quadratically semi-linear equations can be used to
develop criteria for cubically semi-linear 2nd order ODEs. Projecting a 2-d
system one obtains Lie's criteria. The procedure can also be used more
generally and provides an understanding of various specific results in a
more general context. The geometric method also allows one to provide some
(incomplete) linearization criteria for quintically semi-linear 3rd order
ODEs. In this talk the geometric methods will be reviewed and their
application for linearization criteria discussed.