NULL LAGRANGIAN FORMS ON 2ND ORDER JET BUNDLES

The paper analyzes the null Lagrangian forms on the second order jet bundles, extending the results in [11]. The term null Lagrangian is associated to a Lagrangian whose Euler-Lagrange PDEs are identically satisfied. §1 refers to the Lagrange 1-forms of the second order in both cases, single and multi-time. §2 finds the Euler-Lagrange PDEs associated to path independent curvilinear functionals. §3 presents equivalent conditions for null Lagrangians in the single-time and multitime cases. §4 deals with null Lagrange 1-forms and total derivatives.