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Published online by Cambridge University Press: 20 November 2018
In this paper, we introduce two quantities defined on a surface in a contact manifold. The first one is called degree of transversality $(\text{DOT})$, which measures the transversality between the tangent spaces of a surface and the contact planes. The second quantity, called curvature of transversality $(\text{COT})$, is designed to give a comparison principle for $\text{DOT}$ along characteristic curves under bounds on $\text{COT}$. In particular, this gives estimates on lengths of characteristic curves, assuming $\text{COT}$ is bounded below by a positive constant.
We show that surfaces with constant $\text{COT}$ exist, and we classify all graphs in the Heisenberg group with vanishing $\text{COT}$. This is accomplished by showing that the equation for graphs with zero $\text{COT}$ can be decomposed into two first order PDEs, one of which is the backward invisicid Burgers’ equation. Finally we show that the p-minimal graph equation in the Heisenberg group also has such a decomposition. Moreover, we can use this decomposition to write down an explicit formula of a solution near a regular point.