Comments on Galileons

Understand

The recent progress in the study of Galileons, i.e.

• equations of second order with an action invariant under a Galilean transformation is related to work on `Universal Field Equations' \cite{dbfgov} which are second order equations arising by an iterative procedure from arbitrary Lagrangians of weight one in their first derivatives.
• It is pointed out that the Galileon is simply a Kaluza-Klein reduction of a Universal Field Equation.
• An implicit solution to the equation of motion is presented, and a class of explicit solutions pointed out.