Families of disjoint divisors on varieties
نویسندگان
چکیده
منابع مشابه
Canonical Divisors on T-varieties
Generalising toric geometry we study compact varieties admitting lower dimensional torus actions. In particular we describe divisors on them in terms of convex geometry and give a criterion for their ampleness. These results may be used to study Fano varieties with small torus actions. As a first result we classify log del Pezzo C∗-surfaces of Picard number 1 and Gorenstein index ≤ 3. In furthe...
متن کاملExistence of good divisors on Mukai varieties
A normal projective variety X is called Fano if a multiple of the anticanonical Weil divisor, −KX , is an ample Cartier divisor. The importance of Fano varieties is twofold, from one side they give, has predicted by Fano [Fa], examples of non rational varieties having plurigenera and irregularity all zero (cfr [Is]); on the other hand they should be the building block of uniruled variety. Indee...
متن کاملOn Projective Varieties with Nef Anticanonical Divisors
The aim of this note is to prove a structure theorem for projective varieties with nef anticanonical divisors (the Main Theorem). In [18], we showed that if X is smooth and −KX is nef, then the Albanese map AlbX : X → Alb(X) is surjective and has connected fibers (i.e., it is a fiberspace map). In this note we apply the techniques which have been developed in [2],[14] and [19] to prove the foll...
متن کاملEffective divisors on moduli spaces of curves and abelian varieties
The pseudo-effective cone Eff(X) of a smooth projective variety X is a fundamental, yet elusive invariant. On one hand, a few general facts are known: the interior of the effective cone is the cone of big divisors so, in particular, X is of general type if and only if KX ∈ int(Eff(X)); less obviously [4], a variety X is uniruled if and only if KX is not pseudo-effective and the dual of Eff(X) i...
متن کاملAlmost disjoint families on large underlying sets
We show that, for any poset P, the existence of a P-indestructible mad family F ⊆ [ω]א0 is equivalent to the existence of such a family over אn for some/all n ∈ ω. Under the very weak square principle ¤∗∗∗ ω1,μ of Fuchino and Soukup [7] and cf([μ]א0 ,⊆) = μ+ for all limit cardinals μ of cofinality ω, the equivalence for any proper poset P transfers to all cardinals. That is, under these assumpt...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: European Journal of Mathematics
سال: 2016
ISSN: 2199-675X,2199-6768
DOI: 10.1007/s40879-016-0109-1