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Algebraic Geometry papers — page 7

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Exact Random Walk Distributions using Noncommutative Geometry
Using the results obtained by the non commutative geometry techniques applied to the Harper equation, we derive the areas distribution of random walks of length N on a two-dimensional square…
Jean Bellissard, Carlos J Camacho, Armelle Barelli et al.Aug 18, 1997
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A stratification of the moduli space of vector bundles on curves
Let E be a vector bundle of rank r≥ 2 on a smooth projective curve C of genus g ≥ 2 over an algebraically closed field K of arbitrary characteristic. For any integer with $1 k…
L. Brambila-Paz, H. LangeAug 18, 1997
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Bend, break and count II : elliptics, cuspidals, linear genera
Extending the method of Part I (alg-geom/9704004), we give recursive formulae for: the genus-1 Severi degree (formula first found by Getzler), the degree of the variety of 1-cuspidal curves of genus…
Ziv RanAug 15, 1997
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Euler number of the compactified Jacobian and multiplicity of rational curves
We show that the Euler number of the compactified Jacobian of a rational curve C with locally planar singularities is equal to the multiplicity of the δ-constant stratum in the base of a…
Barbara Fantechi, Lothar Göttsche, Duco van StratenAug 14, 1997
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Some finiteness results for Calabi-Yau threefolds
We investigate the moduli theory of Calabi--Yau threefolds, and using Griffiths' work on the period map, we derive some finiteness results. In particular, we confirm a prediction of…
Balazs SzendroiAug 12, 1997
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Limits in n-categories
We define notions of direct and inverse limits in an n-category. We prove that the n+1-category nCAT' of fibrant n-categories admits direct and inverse limits. At the end we speculate…
Carlos SimpsonAug 7, 1997
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Desingularized moduli spaces of sheaves on a K3, I
Moduli spaces of semistable torsion-free sheaves on a K3 surface X are often holomorphic symplectic varieties, deformation equivalent to a Hilbert scheme parametrizing zero-dimensional subschemes…
Kieran G. O'GradyAug 6, 1997
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Local structure of moduli spaces
We describe the algebra of a universal formal deformation as the zeroth cohomology of the dg Lie algebra corresponding to this deformation problem. A report at Arbeitstagung 1997 on the joint work…
Vadim SchechtmanAug 5, 1997
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Torsion of abelian varieties, Weil classes and cyclotomic extensions
Let K be a field finitely generated over the field of rational numbers, K(c) the extension of K obtained by adjoining all roots of unity, L an infinite Galois extension of K, X an abelian…
Yuri G. ZarhinAug 4, 1997
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Duality and flat base change on formal schemes
We give several related versions of global Grothendieck Duality for unbounded complexes on noetherian formal schemes. The proofs, based on a non-trivial adaptation of Deligne's method for the special…
Leovigildo Alonso, Ana Jeremias, Joseph LipmanAug 4, 1997
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A remark on virtual orientations for complete intersections
The aim of this note is to give a simple definition of genus zero virtual orientation classes (or fundamental classes) for projective complete intersections or, more generally, for complete…
Vadim SchechtmanAug 3, 1997
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Effective nonvanishing, effective global generation
We prove a multiple-points higher-jets nonvanishing theorem by the use of local Seshadri constants. Applications are given to effectivity problems such as constructing rational and birational maps…
Mark Andrea A. de CataldoAug 2, 1997
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Singular hermitian metrics on vector bundles
We introduce a notion of singular hermitian metrics (s.h.m.) for holomorphic vector bundles and define positivity in view of L2-estimates. Associated with a suitably positive s.h.m. there is a…
Mark Andrea A. de CataldoAug 2, 1997
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Discriminant Complements and Kernels of Monodromy Representations
We show that the kernel of the monodromy representation for hypersurfaces of degree d and dimension n is large for d at least three with the exception of the cases (d,n) = (3,0) and (3,1). For these…
James A. Carlson, Domingo ToledoAug 1, 1997
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Localization of virtual classes
We prove a localization formula for virtual fundamental classes in the context of torus equivariant perfect obstruction theories. As an application, the higher genus Gromov-Witten invariants of…
T. Graber, R. PandharipandeAug 1, 1997
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On Simplicial Commutative Rings with Vanishing André-Quillen Homology
We propose a generalization of a conjecture of D. Quillen, on the vanishing of André-Quillen homology, to simplicial commutative rings. This conjecture characterizes a notion of local complete…
James M. TurnerJul 31, 1997
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New evidence for Green's conjecture on syzygies of canonical curves
We prove that two weakened forms of Green's conjectures for canonical curves are equivalent when the genus g is odd.
A. Hirschowitz, S. RamananJul 31, 1997
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Rational Curves on Quasi-Projective Surfaces
The main result is that a quasi-projective surface has negative log Kodaira dimension (i.e. no log pluricanonical sections) iff it is dominated by images of the affine line. This follows from our…
Sean Keel, James McKernanJul 25, 1997
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Fano contact manifolds and nilpotent orbits
A contact structure on a complex manifold M is a corank 1 subbundle F of T(M) such that the bilinear form on F with values in the quotient line bundle L=T(M)/F deduced from the Lie bracket of vector…
Arnaud BeauvilleJul 24, 1997
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Borel-Weil-Bott theory for Loop Groups
This note outlines the Borel-Weil-Bott theory for (arbitrary-genus) flag varieties of loop groups, following ideas of G. Segal. Recent revivalist interest in the "WZW fusion rules" suggests…
Constantin TelemanJul 17, 1997
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Rational and Non-Rational Algebraic Varieties: Lectures of János Kollár
This is a detailed write-up of Kollár's course at the EMS summer school in Algebraic Geometry in Eger, Hungary, August 1996. The topics include definitions and examples of rational and…
Karen E. Smith, Joel RosenbergJul 15, 1997
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Weak semistable reduction in characteristic 0
Let X->B be a morphism of varieties in characteristic zero. Semistable reduction has been proved for dim(B)=1 (Kempf, Knudsen, Mumford, Saint-Donat), dim(X)=dim(B)-1 (de Jong) and dim(X)=dim(B)+2…
Dan Abramovich, Kalle KaruJul 13, 1997
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The tangent space at a special symplectic instanton bundle on P2n+1
Let MISimp,P2n+1(k) be the moduli space of stable symplectic instanton bundles on P2n+1 with second Chern class c2=k (it is a closed subscheme of the moduli space MIP2n+1(k)),…
Carla DionisiJul 10, 1997
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Semiinfinite Flags. I. Case of global curve P1
The Semiinfinite Flag Space appeared in the works of B.Feigin and E.Frenkel, and under different disguises was found by V.Drinfeld and G.Lusztig in the early 80-s. Another recent discovery…
Michael Finkelberg, Ivan MirkovićJul 9, 1997
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Flops, Type III contractions and Gromov-Witten invariants on Calabi-Yau threefolds
We investigate Gromov-Witten invariants associated to exceptional classes for primitive birational contractions on a Calabi-Yau threefold X. It was observed in a previous paper that these invariants…
P. M. H. WilsonJul 9, 1997
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