Causal geometries and third-order ordinary differential equations

Abstract

We discuss contact invariant structures on the space of solutions of a third-order ordinary differential equation. Associated to any third-order differential equation modulo contact transformations, Chern introduced a degenerate conformal Lorentzian metric on the space of 2-jets of functions of one variable. When the Wuenschmann invariant vanishes, the degenerate metric descends to a proper conformal Lorentzian metric on the space of solutions. In the general case, when the Wuenschmann invariant is not zero, we define the notion of a causal geometry, and show that the space of solutions supports one. The Wuenschmann invariant is then related to the projective curvature of the indicatrix curve cut out by the causal geometry in the projective tangent space. When the Wuenschmann vanishes, the causal structure is then precisely the sheaf of null geodesics of the Chern conformal structure. We then introduce a Lagrangian and associated Hamiltonian from which the degenerate conformal Lorentzian metric are constructed. Finally, necessary and sufficient conditions are given for a rank three degenerate conformal Lorentzian metric in four dimensions to correspond to a third-order differential equation.

References in corpus (6)

• Differential equations and conformal structures
• 3-dimensional Cauchy-Riemann structures and 2nd order ordinary differential equations
• Differential Geometry from Differential Equations
• A holonomy characterisation of Fefferman spaces
• Geometry of Third-Order Ordinary Differential Equations and Its Applications in General Relativity
• GL(2,R) geometry of ODE's

Cited by in corpus (3)

• Differential Geometric Aspects of Causal Structures
• GL(2)-geometry and complex structures
• Causal geometries, null geodesics, and gravity