## On contact symmetries of evolution equations    [PDF]

Qing Huang, Renat Zhdanov, Changzheng Qu
In this paper, we develop an algebraic approach to classifying contact symmetries of the second-order nonlinear evolution equations. Up to contact isomorphisms, all inequivalent PDEs admitting semi-simple algebras, solvable algebras of dimension $n\leq4$, and algebras having nontrivial Levi factors, belonging to the class under consideration, and corresponding contact symmetries they admitted are listed.
View original: http://arxiv.org/abs/1301.2097