Yonghwa Cho, Double Point Divisors from Projections

Consider a smooth projective variety of codimension e. A general projection from a linear subspace of dimension (e-2) is birational, hence the non-isomorphic locus forms a proper closed subset of X. Mumford showed that this non-isomorphic locus is not merely a closed subset, but is naturally endowed with a divisor structure. We call it a double point divisor from outer projection. In this talk I will discuss the positivity property of double point divisors including our recent proof of very ampleness, except for some exceptional cases. This work is based on a joint work with Jinhyung Park.