Nonlinear self-adjointness;
Lagrangian with an auxiliary function;
Conservation law;
PARTIAL-DIFFERENTIAL EQUATIONS;
DIRECT CONSTRUCTION METHOD;
THIN-FILM EQUATIONS;
EVOLUTION-EQUATIONS;
MODEL;
D O I:
10.1016/j.nonrwa.2015.04.005
中图分类号:
O29 [应用数学];
学科分类号:
070104 ;
摘要:
In this work we study the conservation laws of a modified lubrication equation, which describes the dynamics of the interfacial motion in phase transition. We show that the equation is nonlinear self-adjoint and has an exact Lagrangian with an auxiliary function. As a result, by a general theorem on conservation laws proved by Nail Ibragimov recently and Noether's theorem, some new conservation laws for the equation are obtained. Our results show that the non-locally defined conservation laws generated by Noether's theorem are equivalent to the local ones given by Ibragimov's theorem. (C) 2015 Elsevier Ltd. All rights reserved.