Invariant divisors, equivariant line bundles and global relative differential invariants

Invariants of Lie pseudogroup actions are important in solving the equivalence problem for geometric structures, such as vector distributions or CR geometries. Differential invariants arise as those for the lifted action to the space of jets, and relative invariants describe singular orbits (differential equations). Scalar relative invariants correspond to invariant divisors, while their weights to equivariant line bundles. These stabilize in jets and we discuss the basic question of finite generation of the algebra of relative differential invariants.
The work is joint with Eivind Schneider.