Search results for "Canonical bundle"
showing 3 items of 3 documents
The cup product of Hilbert schemes for K3 surfaces
2003
To any graded Frobenius algebra A we associate a sequence of graded Frobenius algebras A [n] so that there is canonical isomorphism of rings (H *(X;ℚ)[2]) [n] ≅H *(X [n] ;ℚ)[2n] for the Hilbert scheme X [n] of generalised n-tuples of any smooth projective surface X with numerically trivial canonical bundle.
Theta-characteristics on singular curves
2007
On a smooth curve a theta–characteristic is a line bundle L with square that is the canonical line bundle ω. The equivalent conditionHom(L, ω) ∼= L generalizes well to singular curves, as applications show. More precisely, a theta–characteristic is a torsion–free sheaf F of rank 1 with Hom(F , ω) ∼= F . If the curve has non ADE–singularities then there are infinitely many theta–characteristics. Therefore, theta–characteristics are distinguished by their local type. The main purpose of this article is to compute the number of even and odd theta–characteristics (i.e. F with h(C,F) ≡ 0 resp. h(C,F) ≡ 1 modulo 2) in terms of the geometric genus of the curve and certain discrete invariants of a …
Subharmonic variation of the leafwise Poincar� metric
2003
Let X be a compact complex algebraic surface and let F be a holomorphic foliation, possibly with singularities, on X. On each leaf of F we put its Poincare metric (this will be defined below in more precise terms). We thus obtain a (singular) hermitian metric on the tangent bundle TF of F , and dually a (singular) hermitian metric on the canonical bundle KF = T ∗ F of F . The main aim of this paper is to prove that this metric on KF has positive curvature, in the sense of currents. Of course, the positivity of the curvature in the leaf direction is an immediate consequence of the definitions; the nontrivial fact is that the curvature is positive also in the directions transverse to the leaf…