On Fano Manifolds of large index.
If a smooth projective variety admits a non-degenerate holomorphic map from the complex plane , then for any finite dimensional linear representation of the fundamental group of the image of this representation is almost abelian. This supports a conjecture proposed by F. Campana, published in this journal in 2004.
In this short note we utilize the Borsuk-Ulam Anitpodal Theorem to present a simple proof of the following generalization of the “Ham Sandwich Theorem”: Let be subsets with finite Lebesgue measure. Then, for any sequence of -linearly independent polynomials in the polynomial ring there are real numbers , not all zero, such that the real affine variety simultaneously bisects each of subsets , . Then some its applications are studied.
We introduce and study the k-jet ampleness and the k-jet spannedness for a vector bundle, E, on a projective manifold. We obtain different characterizations of projective space in terms of such positivity properties for E. We compare the 1-jet ampleness with different notions of very ampleness in the literature.
We investigate projective varieties which are binary symmetric models of trivalent phylogenetic trees. We prove that they have Gorenstein terminal singularities and are Fano varieties of index 4 and dimension equal to the number of edges of the tree in question. Moreover any two such varieties which are of the same dimension are deformation equivalent, that is, they are in the same connected component of the Hilbert scheme of the projective space. As an application we provide a simple formula for...