To every morphism $\chi :L\to M$ of differential graded Lie algebras we associate a functors of artin rings ${Def}_{\chi }$ whose tangent and obstruction spaces are respectively the first and second cohomology group of the suspension of the mapping cone of $\chi$. Such construction applies to Hilbert and Brill-Noether functors and allow to prove with ease that every higher obstruction to deforming a smooth submanifold of a Kähler manifold is annihilated by the semiregularity map.

We study liftings or deformations of $D$-modules ($D$ is the ring of differential operators from EGA IV) from positive characteristic to characteristic zero using ideas of Matzat and Berthelot’s theory of arithmetic $D$-modules. We pay special attention to the growth of the differential Galois group of the liftings. We also apply formal deformation theory (following Schlessinger and Mazur) to analyze the space of all liftings of a given $D$-module in positive characteristic. At the end we compare the problems...