Sub-Lorentzian coarea formula for mappings of Carnot groups (Q2671979)

In this paper the author considers the class of contact mappings of Carnot groups with a multidimensional sub-Lorentzian structure on the preimages and proves that the tangent plane approximates the level sets to a higher order than in the classical case. Also, he establishes a coarea formula for the mappings on Carnot groups with sub-Lorentzian structure with values in another Carnot group. In particular, it is deduces some space-likeness conditions for level surfaces in this case and finds an adequate parametrization for them.