Geometric torsion Galois representations and ramification theory

In this two-year study period, I had investigated a ramification theory of torsion Galois representations of local fields of mixed characteristic (0,p). It is well-known that there exists an inclusion from the category of finite flat group schemes killed by p over the ring of integers of such a local field into a similar category for equal characteristic p. In this research project, I proved that this inclusion preserves ramification of both sides. This enables us to reduce the study of ramification to the much easier case of equal characteristic. As an application of this result, I also proved a new existence theorem of canonical subgroups of Abelian varieties, which is one of the key ingredients of the theory of p-adic Siegel modular forms.