Local obstructions to a conformally invariant equation on Möbius surfaces

Abstract

On a Möbius surface, as defined in [1], we study a variant of the Einstein–Weyl (EW) equation which we call scalar-flat Möbius EW (sf-MEW). This is a conformally invariant, finite type, overdetermined system of semi-linear partial differential equations. We derive local algebraic constraints for this equation to admit a solution and give local obstructions. In the generic case when a certain invariant of the Möbius structure given by a symmetric tensor Mab is non-zero, the obstructions are given by resultants of 3 polynomial equations whose coefficients are conformal invariants of the Möbius structure. The vanishing of the resultants is a necessary condition for there to be solutions to sf-MEW.