112 research outputs found
Ruled Fano fivefolds of index two
No full textWe classify Fano fivefolds of index two which are projectivization of rank two vector bundles over four dimensional manifolds
Double covers of some Fano manifolds as hyperplane sections
No full textLet Y be a Fano manifold of dimension n \geq 3 with b_2(Y)=1 and index n-1, and let A be a double cover of Y. We determine which complex projective manifolds can admit A among their hyperplane sections
Projective manifolds containing a large linear subspace with nef normal bundle
No full textWe classify smooth complex projective varieties of dimension in containing a linear subspace of dimension whose normal bundle is numerically effective
Rational curves and bounds on the Picard number of Fano manifolds
No full textWe prove that Generalized Mukai Conjecture holds for Fano manifolds of pseudoindex . We also give different proofs of the conjecture for Fano fourfolds and fivefolds
Manifolds covered by lines and extremal rays
No full textLet X be a smooth complex projective variety and let H be an ample line bundle.
Assume that X is covered by rational curves with degree one with respect to H and with anticanonical degree greater than or equal to (dim X -1)/2.
We prove that there is a covering family of such curves whose numerical class spans an extremal ray in the cone of curves NE(X)
Connections between the geometry of a projective variety and of an ample section
No full textLet be a smooth complex projective variety and let be a smooth submanifold which is the zero locus of a section of an ample vector bundle of rank with .
We show with some examples that in general the Kleiman--Mori cones and are different. We then give a necessary and sufficient condition for an extremal ray in to be also extremal in .
We apply this result to the case and a Fano manifold of high index; in particular we classify all with an ample divisor which is a Mukai manifold of dimension .
In the last section we prove a general result in case is a minimal variety with
Primary hyperparathyroidism and arrhythmic storm in a patient with an implantable cardioverter defibrillator for primary prevention of sudden death.
No full text
Small modifications of Mori dream spaces arising from C*-actions
No full textWe link small modifications of projective varieties with a C*-action to their GIT quotients. Namely, using flips with centers in closures of Bialynicki-Birula cells, we produce a system of birational equivariant modifications of the original variety, which includes those on which a quotient map extends from a set of semistable points to a regular morphism. The structure of the modifications is completely described for the blowup along the sink and the source of smooth varieties with Picard number one with a C*-action which has no finite isotropy for any point. Examples can be constructed upon homogeneous varieties with a C*-action associated to short grading of their Lie algebras
Inappropriate implantable cardioverter-defibrillator discharges unrelated to supraventricular tachyarrhythmias
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