Rigidity of Nilpotent Lie Foliations: Cohomological Obstructions and Classification

Abstract

In this article, we develop a systematic cohomological framework for the study of the rigidity of nilpotent Lie foliations with respect to solvable deformations. We introduce the deformation complex associated to a pair of Lie algebras $(\mathfrak{g}, \mathfrak{h})$ and show that the main obstruction to deforming a nilpotent Lie foliation into a non-nilpotent solvable foliation lies in the cohomology group $H^2(\mathfrak{g},\mathfrak{g}/[\mathfrak{g},\mathfrak{g}])$. We establish a necessary and sufficient algebraic criterion for rigidity within the family of foliations modelled on the generalized Heisenberg groups $H_{2k+1}$. This result unifies and generalizes the construction of Dathe--Ndiaye (2012) as well as its subsequent extensions. We complete the article with a full classification of nilpotent Lie foliations of codimension at most six according to their deformation behaviour.