Sub-Lorentzian Coarea Formula for Mappings of Carnot Groups.

Considering the class of contact mappings of Carnot groups with a multidimensional sub-Lorentzian structure on the preimages, we prove that the tangent plane approximates the level sets to a higher order than in the classical case. We also obtain a coarea formula for such mappings with a sub-Lorentzian measure on the level sets. [ABSTRACT FROM AUTHOR]