Results 1  10
of
1,336
Towards an enumerative geometry of the moduli space of curves
 in Arithmetic and Geometry
, 1983
"... The goal of this paper is to formulate and to begin an exploration of the enumerative geometry of the set of all curves of arbitrary genus g. By this we mean setting up a Chow ring for the moduli space M g of curves of genus g and its compactification.M 9, defining what seem to be ..."
Abstract

Cited by 336 (0 self)
 Add to MetaCart
(Show Context)
The goal of this paper is to formulate and to begin an exploration of the enumerative geometry of the set of all curves of arbitrary genus g. By this we mean setting up a Chow ring for the moduli space M g of curves of genus g and its compactification.M 9, defining what seem to be
Localization of virtual classes
"... We prove a localization formula for the virtual fundamental class in the general context of C∗equivariant perfect obstruction theories. Let X be an algebraic scheme with a C∗action and a C∗equivariant perfect obstruction theory. The virtual fundamental class [X] vir in ..."
Abstract

Cited by 260 (37 self)
 Add to MetaCart
(Show Context)
We prove a localization formula for the virtual fundamental class in the general context of C∗equivariant perfect obstruction theories. Let X be an algebraic scheme with a C∗action and a C∗equivariant perfect obstruction theory. The virtual fundamental class [X] vir in
A holomorphic Casson invariant for CalabiYau 3folds, and bundles on K3 fibrations
 J. DIFFERENTIAL GEOM
, 2000
"... We briefly review the formal picture in which a CalabiYau nfold is the complex analogue of an oriented real nmanifold, and a Fano with a fixed smooth anticanonical divisor is the analogue of a manifold with boundary, motivating a holomorphic Casson invariant counting bundles on a CalabiYau 3fol ..."
Abstract

Cited by 202 (8 self)
 Add to MetaCart
We briefly review the formal picture in which a CalabiYau nfold is the complex analogue of an oriented real nmanifold, and a Fano with a fixed smooth anticanonical divisor is the analogue of a manifold with boundary, motivating a holomorphic Casson invariant counting bundles on a CalabiYau 3fold. We develop the deformation theory necessary to obtain the virtual moduli cycles of [LT], [BF] in moduli spaces of stable sheaves whose higher obstruction groups vanish. This gives, for instance, virtual moduli cycles in Hilbert schemes of curves in P 3, and Donaldson – and GromovWitten – like invariants of Fano 3folds. It also allows us to define the holomorphic Casson invariant of a CalabiYau 3fold X, prove it is deformation invariant, and compute it explicitly in some examples. Then we calculate moduli spaces of sheaves on a general K3 fibration X, enabling us to compute the invariant for some ranks and Chern classes, and equate it to GromovWitten invariants of the “Mukaidual” 3fold for others. As an example the invariant is shown to distinguish Gross’ diffeomorphic 3folds. Finally the Mukaidual 3fold is shown to be CalabiYau and its cohomology is related to that of X.
Finite element exterior calculus, homological techniques, and applications
 ACTA NUMERICA
, 2006
"... ..."
Eigenvalues, invariant factors, highest weights, and Schubert calculus
 Bull. Amer. Math. Soc. (N.S
"... Abstract. We describe recent work of Klyachko, Totaro, Knutson, and Tao, that characterizes eigenvalues of sums of Hermitian matrices, and decomposition of tensor products of representations of GLn(C). We explain related applications to invariant factors of products of matrices, intersections in Gra ..."
Abstract

Cited by 176 (3 self)
 Add to MetaCart
(Show Context)
Abstract. We describe recent work of Klyachko, Totaro, Knutson, and Tao, that characterizes eigenvalues of sums of Hermitian matrices, and decomposition of tensor products of representations of GLn(C). We explain related applications to invariant factors of products of matrices, intersections in Grassmann varieties, and singular values of sums and products of arbitrary matrices. Contents 1. Eigenvalues of sums of Hermitian and real symmetric matrices 2. Invariant factors 3. Highest weights 4. Schubert calculus
Parallel spinors and connections with skewsymmetric torsion in string theory
, 2008
"... We describe all almost contact metric, almost hermitian and G2structures admitting a connection with totally skewsymmetric torsion tensor, and prove that there exists at most one such connection. We investigate its torsion form, its Ricci tensor, the Dirac operator and the ∇parallel spinors. In p ..."
Abstract

Cited by 153 (7 self)
 Add to MetaCart
We describe all almost contact metric, almost hermitian and G2structures admitting a connection with totally skewsymmetric torsion tensor, and prove that there exists at most one such connection. We investigate its torsion form, its Ricci tensor, the Dirac operator and the ∇parallel spinors. In particular, we obtain solutions of the type II string equations in dimension n = 5, 6 and 7.
Notes On Stable Maps And Quantum Cohomology
, 1996
"... Contents 0. Introduction 1 1. Stable maps and their moduli spaces 10 2. Boundedness and a quotient approach 12 5. The construction of M g;n (X; fi) 25 6. The boundary of M 0;n (X; fi) 29 7. GromovWitten invariants 31 8. Quantum cohomology 34 9. Applications to enumerative geometry 38 10. Varia ..."
Abstract

Cited by 141 (14 self)
 Add to MetaCart
Contents 0. Introduction 1 1. Stable maps and their moduli spaces 10 2. Boundedness and a quotient approach 12 5. The construction of M g;n (X; fi) 25 6. The boundary of M 0;n (X; fi) 29 7. GromovWitten invariants 31 8. Quantum cohomology 34 9. Applications to enumerative geometry 38 10. Variations 43 References 46 0. Introduction 0.1. Overview. The aim of these notes is to describe an exciting chapter in the recent development of quantum cohomology. Guided by ideas from physics (see [W]), a remarkable structure on the solutions of certain rational enumerative geometry problems has been found: the solutions are coefficients in the multiplication table of a quantum cohomology ring. Associativity of the ring yields nontrivial relations among the enumerative solutions. In many cases, these relations suffice to solve the enumerative problem. For example, let N d be the number of degree d, rational plane curves passing through 3d \Gamma 1 general points in P . Since there is a un
Hurwitz numbers and intersections on moduli spaces of curves
 Invent. Math
"... 1.1. Topological classification of ramified coverings of the sphere. For a compact connected genus g complex curve C let f: C → CP 1 be a meromorphic function. We treat this function as a ramified covering of the sphere. Two ramified coverings (C1; f1), (C2; f2) are called topologically ..."
Abstract

Cited by 118 (3 self)
 Add to MetaCart
(Show Context)
1.1. Topological classification of ramified coverings of the sphere. For a compact connected genus g complex curve C let f: C → CP 1 be a meromorphic function. We treat this function as a ramified covering of the sphere. Two ramified coverings (C1; f1), (C2; f2) are called topologically
Dynamics of bimeromorphic maps of surfaces
 Amer. J. Math
"... Abstract. We classify bimeromorphic selfmaps f: X of compact kähler surfaces X and classify them in terms of their actions f ∗ : H1,1(X) on cohomology. We observe that the growth rate of fn∗  is invariant under bimeromorphic conjugacy, and that by conjugating one can always arrange that fn ..."
Abstract

Cited by 112 (17 self)
 Add to MetaCart
(Show Context)
Abstract. We classify bimeromorphic selfmaps f: X of compact kähler surfaces X and classify them in terms of their actions f ∗ : H1,1(X) on cohomology. We observe that the growth rate of fn∗  is invariant under bimeromorphic conjugacy, and that by conjugating one can always arrange that fn ∗ = f∗n. We show that the sequence fn∗  can be bounded, grow linearly, grow quadratically, or grow exponentially. In the first three cases, we show that after conjugating, f is an automorphism virtually isotopic to the identity, f preserves a rational fibration, or f preserves an elliptic fibration, respectively. In the last case, we show that there is an unique (up to scaling) expanding eigenvector θ+ for f ∗, that θ+ is nef, and that f is bimeromorphically conjugate to an automorphism if and only if θ2+ = 0. We go on in this case to construct a dynamically natural positive current representing θ+, and we study the growth rate of periodic orbits of f. We conclude by illustrating our results with a particular family of examples.