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Algebraic Geometry papers — page 43

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Spin polynomial invariants for Dolgachev surfaces
We consider the spin polynomial invariants for bundles with c2=2 and c1 = KS + 2nk a rational mutiple of the canonical divisor on a Dolgacev surface. It is shown that the chamber structure can be…
S. Bauer, V. PidstrigatchNov 23, 1993
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On the Picard Number of Fano 3-Folds with Terminal Singularities
We prove the following main result: Let X be a Fano 3-fold with terminal Q-factorial singularities and X does not have a small extremal ray and a face of Kodaira dimension 1 or 2 for Mori polyhedron…
Viacheslav V. NikulinNov 19, 1993
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Surfaces of Degree 10 in the Projective Fourspace via Linear Systems and Linkage
The paper discusses the classification of surfaces of degree 10 and sectional genus 9 and 10. The surfaces of degree at most 9 are described through classical work dating from the last century up to…
Sorin Popescu, Kristian RanestadNov 16, 1993
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Irreducibility of Moduli Spaces of Vector Bundles on Birationally Ruled Surfaces
Let S be a birationally ruled surface. We show that the moduli schemes MS(r,c1,c2) of semistable sheaves on S of rank r and Chern classes c1 and c2 are irreducible for all…
Charles WalterNov 16, 1993
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On discrete Zariski-dense subgroups of algebraic groups
We investigate for which linear-algebraic groups (over the complex numbers or any local field) there exists subgroups which are dense in the Zariski topology, but discrete in the Hausdorff topology.…
J. WinkelmannNov 14, 1993
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Geometric height inequality on varieties with ample cotangent bundles
Let F be a function field of one variable over an algebraically closed field of characteristic zero, X a geometrically irreducible smooth projective variety over F, and L a line bundle on X. In this…
Atsushi MoriwakiNov 10, 1993
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Projective Degenerations of K3 Surfaces, Gaussian Maps, and Fano Threefolds
In this article we exhibit certain projective degenerations of smooth K3 surfaces of degree 2g-2 in Pg (whose Picard group is generated by the hyperplane class), to a union of two…
Ciro Ciliberto, Angelo Lopez, Rick MirandaNov 9, 1993
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On Banica sheaves and Fano manifolds
In the present paper we discuss coherent sheaves of rank > 1 whose projectivization gives rise to smooth varieties - varieties of this type are also called smooth scrolls. We prove some basic…
Edoardo Ballico, Jaroslaw WisniewskiNov 7, 1993
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A Propos de l'Existence de Fibrés Stables sur les Surfaces
We prove the existence (in characteristic 0) on every polarized (smooth, projective and connected) surface of stable bundles of rank r≥ 2, arbitrary first Chern class and large enough c2.
André Hirschowitz, Yves LaszloOct 29, 1993
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Initial ideals, Veronese subrings, and rates of algebras
We show that high Veronese subrings of any commutative graded ring have a Grobner basis with all relations of degree 2. (The d-th Veronese subring of a ring A0 + A1 + A2 + ... is the ring A0 +…
David Eisenbud, Alyson Reeves, Burt TotaroOct 11, 1993
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Teichmüller Theory and the Universal Period Mapping via Quantum Calculus and the H1/2 Space on the Circle
The Universal Teichmüller Space, T(1), is a universal parameter space for all Riemann surfaces. In earlier work of the first author it was shown that one can canonically associate infinite-…
Subhashis Nag, Dennis SullivanOct 7, 1993
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Torsion Sections of Elliptic Surfaces
Given a torsion section of a semistable elliptic surface, we prove equidistribution results for the components of singular fibers which are hit by the section, and for the root of unity (identifying…
Rick Miranda, Peter F. StillerOct 7, 1993
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Quantum Cohomology Rings of Toric Manifolds
We compute the quantum cohomology ring H*φ( P, C) of an arbitrary d-dimensional smooth projective toric manifold PΣ associated with a fan Σ. The multiplicative structure…
Victor V. BatyrevOct 5, 1993
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Dual Polyhedra and Mirror Symmetry for Calabi-Yau Hypersurfaces in Toric Varieties
We consider families F(Δ) consisting of complex (n-1)-dimensional projective algebraic compactifications of Δ-regular affine hypersurfaces Zf defined by Laurent polynomials f with a…
Victor V. BatyrevOct 5, 1993
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General hyperplane sections of nonsingular flops in dimension 3
We give a simple proof of a theorem of Katz and Morrison.
Yujiro KawamataOct 5, 1993
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Towards the Mirror Symmetry for Calabi-Yau Complete intersections in Gorenstein Toric Fano Varieties
We propose a combinatorical duality for lattice polyhedra which conjecturally gives rise to the pairs of mirror symmetric families of Calabi-Yau complete intersections in toric Fano varieties with…
Lev BorisovOct 2, 1993
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The Monomial-Divisor Mirror Map
For each family of Calabi-Yau hypersurfaces in toric varieties, Batyrev has proposed a possible mirror partner (which is also a family of Calabi-Yau hypersurfaces). We explain a natural construction…
Paul S. Aspinwall, Brian R. Greene, David R. MorrisonSep 30, 1993
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Conic bundles in projective fourspace
P. Ellia and G.Sacchiero have shown that if S is a smooth surface in 4 which is ruled in conics, then S has degree 4 or 5. In this paper we give a proof of this result combining the ideas…
Robert Braun, Kristian RanestadSep 27, 1993
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Differential-geometric methods for the lifting problem and linear systems on plane curves
Let X be an integral projective variety of codimension two, degree d and dimension r and Y be its general hyperplane section. The problem of lifting generators of minimal degree σ from the…
Emilia MezzettiSep 23, 1993
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Generic Singularities of Holomorphic Foliations
A holomorphic foliation is defined as an integrable coherent subsheaf of the tangent sheaf. The structure of the leaves around a singularity is read off from the structure of the stalks. This was…
Sinan SertozSep 21, 1993
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Conformal blocks and generalized theta functions
Let M(r) be the moduli space of rank r vector bundles with trivial determinant on a Riemann surface X . This space carries a natural line bundle, the determinant line bundle L . We describe a…
Arnaud Beauville, Yves LaszloSep 15, 1993
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A family of étale coverings of the affine line
In the note we construct a family of étale coverings of the affine line. More specifically, let F be a finite field of characteristic p and suppose that the cardinality of F is at least 4. Let…
Kirti JoshiSep 2, 1993
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Theoremes de connexites et varietes abeliennes
We prove a connexity theorem for abelian varieties in characteristic 0: if X is an abelian variety and V→ X and W→ X two morphisms, then, under certain hypotheses, the…
Olivier DebarreSep 1, 1993
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Unobstructedness of Calabi-Yau OrbiKleinfolds
We show that Calabi-Yau spaces with certain types of hypersurface- quotient singularities have unobstructed deformations. This applies in particular to all Calabi-Yau orbifolds nonsingular in…
Z. RanAug 31, 1993
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The existence of higher logarithms
In this paper we prove the existence of all higher logarithms as multivalued and ordinary Deligne cohomology classes.
Richard HainAug 31, 1993
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