Minimal Models in Homotopy Theory.
Morales-Ramis Theorems via Malgrange pseudogroup
In this article we give an obstruction to integrability by quadratures of an ordinary differential equation on the differential Galois group of variational equations of any order along a particular solution. In Hamiltonian situation the condition on the Galois group gives Morales-Ramis-Simó theorem. The main tools used are Malgrange pseudogroup of a vector field and Artin approximation theorem.
m-Reduction of ordinary differential equations
Multistructures determined by differential rings
Multivariable dimension polynomials and new invariants of differential field extensions.