The sum of the Betti numbers of smooth Hilbert schemes

迫使弱莱夫谢茨性质失效的Betti表

Betti tables forcing failure of the Weak Lefschetz Property

该研究聚焦点配置的Artinian约化的弱莱夫谢茨性质，证明某类Betti表会迫使WLP失效，且该失效无法通过希尔伯特函数检测，拓展了相关几何与代数性质关联的研究。

光滑的Calabi-Yau变种与大指数和贝蒂数

Smooth Calabi-Yau varieties with large index and Betti numbers

本文构造了在每维中具有双指数增长指数的光滑射影Calabi-Yau变种，并探讨了其拓扑不变量的极端性质，认为这些变种在每维中可能是极值的。

Reduced arithmetically Gorenstein schemes and simplicial polytopes with maximal Betti numbers

An SI-sequence is a finite sequence of positive integers which is symmetric, unimodal and satisfies a certain growth condition. These are known to correspond precisely to the possible Hilbert functions of Artinian Gorenstein algebras with the Weak Lefschetz Property, a property shared by most Artinian Gorenstein algebras. Starting with an arbitrary SI-sequence, we construct a reduced, arithmetically Gorenstein configuration $G$ of linear varieties of arbitrary dimension whose Artinian reduction has the given SI-sequence as Hilbert function and has the Weak Lefschetz Property. Furthermore, we s…

Betti numbers in three dimensional minimal model program

Let $X$ be a smooth projective threefold. We prove that, among the process of minimal model program, the variance of the third Betti number can be bounded by some integer depends only on the Picard number of $X$.

Logarithmic De Rham, Infinitesimal and Betti Cohomologies

In this article, we analyze the connection between the Log De Rham Cohomology of an fs (not necessary log smooth) log scheme $Y$ over $\mathbb C$ (for $Y$ admitting an exact closed immersion into an fs log smooth log scheme over $\mathbb C$), its Log Infinitesimal Cohomology $H^{^.}(Y^{log}_{inf}, \mathcal O_{Y^{log}_{inf}})$, and its Log Betti Cohomology, which is the Cohomology of its associated Kato-Nakayama topological space $Y^{an}_{log}$, and we prove that they are isomorphic. These results are the log scheme analogues of two classical comparison theorems.

Limiting Betti distributions of Hilbert schemes on $n$ points

Hausel and Rodriguez-Villegas recently observed that work of Göttsche, combined with a classical result of Erdős and Lehner on integer partitions, implies that the limiting Betti distribution for the Hilbert schemes $(\mathbb{C}^2)^{[n]}$ on $n$ points, as $n\rightarrow +\infty,$ is a \textit{Gumbel distribution}. In view of this example, they ask for further such Betti distributions. We answer this question for the quasihomogeneous Hilbert schemes $((\mathbb{C}^2)^{[n]})^{T_{α,β}}$ that are cut out by torus actions. We prove that their limiting distributions are also of Gumbel type. To obtain…

Hilbert schemes of a surface and Euler characteristics

We use basic algebraic topology and Ellingsrud-Stromme results on the Betti numbers of punctual Hilbert schemes of surfaces to compute a generating function for the Euler characteristic numbers of the Douady spaces of "n-points" associated with a complex surface. The projective case was first proved by L. Göttsche.

关于光滑曲面上点的Hilbert方案乘积的分类

On the classification of products of Hilbert schemes of points over a surface

本文通过Betti数、Hodge数和欧拉特征等不变量，证明了光滑曲面上的点Hilbert方案乘积在特定条件下不等价，并对K3表面和一般化Kummer变分进行了完整分类。

模面上一维斜稳定层模空间的交贝蒼地数稳定化

Stabilization of intersection Betti numbers for moduli spaces of one-dimensional sheaves on surfaces

本文研究光滑射影表面的一维斜稳定层模空间的交贝蒼地数，证明在特定度数范围内与点希尔伯特方案的稳定贝蒼地数一致，并在表面具有 nef 反可以能除数时证明这些交贝蒼地数在每个固定度数中稳定化。

Relative Hilbert Scheme of Points

Let $D$ be a smooth divisor on a non singular surface $S$. We compute Betti numbers of the relative Hilbert scheme of points of $S$ relative to $D$. In the case of $\PP^2$ and a line in it, we give an explicit set of generators and relations for the cohomology groups of this space.

Betti numbers of smooth Schubert varieties and the remarkable formula of Kostant,Macdonald,Shapiro and Steinberg

The purpose of this note is to give a refinement of the product formula proved in [1] for the Poincare polynomial of a smooth Schubert variety in the flag variety of an algebraic group G over C. This yields a factorization of the number of elements in a Bruhat interval [e,w] in the Weyl group W of G provided the Schubert variety associated to w is smooth. This gives an elementary necessary condition for a Schubert variety in the flag variety to be smooth.

What is the total Betti number of a random real hypersurface?

We bound from above the expected total Betti number of a high degree random real hypersurface in a smooth real projective manifold. This upper bound is deduced from the equirepartition of critical points of a real Lefschetz pencil restricted to the complex domain of such a random hypersurface, equirepartition which we first establish. Our proofs involve Hörmander's theory of peak sections as well as the formula of Poincaré-Martinelli.

Deformation equivalence classes of complex surfaces with the first Betti number one, and the second Betti number zero

We will prove that the number of deformation equivalence classes of surfaces homotopy equivalent to a smooth, closed 4-manifold is finite, if the first Betti number is equal to one, and the second Betti number is equal to zero.

On the first infinitesimal neighborhood of a linear configuration of points in $\mathbb P^2$

We consider the following open questions. Fix a Hilbert function, $h$, that occurs for a reduced zero-dimensional subscheme of $\mathbb P^2$. Among all subschemes, $X$, with Hilbert function $h$, what are the possible Hilbert functions and graded Betti numbers for the first infinitesimal neighborhood, $Z$, of $X$ (i.e. the double point scheme supported on $X$)? Is there a minimum ($h^{\min}$) and maximum ($h^{\max}$) such function? The numerical information encoded in $h$ translates to a {\it type vector}, which allows us to find unions of points on lines, called {\it linear configurations}, w…

On the Betti numbers of compact holomorphic symplectic orbifolds of dimension four

We extend a result of Guan by showing that the second Betti number of a 4-dimensional primitively symplectic orbifold is at most 23 and there are at most 91 singular points. The maximal possibility 23 can only occur in the smooth case. In addition to the known smooth examples with second Betti numbers 7 and 23, we provide examples of such orbifolds with second Betti numbers 3, 5, 6, 8, 9, 10, 11, 14 and 16. In an appendix, we extend Salamon's relation among Betti/Hodge numbers of symplectic manifolds to symplectic orbifolds.

Families of reduced zero-dimensional schemes

A great deal of recent activity has centered on the question of whether, for a given Hilbert function, there can fail to be a unique minimum set of graded Betti numbers, and this is closely related to the question of whether the associated Hilbert scheme is irreducible or not. We give a broad class of Hilbert functions for which we show that there is no minimum set of graded Betti numbers, and hence that the associated Hilbert scheme is reducible. Furthermore, we show that the Weak Lefschetz Property holds for the general element of one component, while it fails for every element of another co…

Betti Tables of MCM Modules Over the Cone of a Plane Cubic

We show that for maximal Cohen-Macaulay modules over a homogeneous coordinate rings of smooth Calabi-Yau varieties $X$ computation of Betti numbers can be reduced to computations of dimensions of certain $\operatorname{Hom}$ groups in the bounded derived category $D^b(X)$. In the simplest case of a smooth elliptic curve $E$ imbedded into $\mathbb{P}^2$ as a smooth cubic we use our formula to get explicit answers for Betti numbers. Description of the automorphism group of the derived category $D^b(E)$ in terms of the spherical twist functors of Seidel and Thomas plays a major role in our approa…

Betti numbers of Brill-Noether varieties on a general curve

We compute the rational cohomology groups of the smooth Brill-Noether varieties $G^r_d(C)$, parametrizing linear series of degree $d$ and dimension exactly $r$ on a general curve $C$. As an application, we determine the whole intersection cohomology of the singular Brill-Noether loci $W^r_d(C)$, parametrizing complete linear series on $C$ of degree $d$ and dimension at least $r$.

Some Questions in $l-$adic Cohomology

The comparison theorem for a smooth projective variety $X$ over $\mathbb{C}$ tells us that the Betti numbers are independent of $l$. We aim to understand the $l$ independence of Betti numbers for smooth projective varieties $X$ over $k$, where $k$ is an algebraic extension of $\mathbb{F}_p$.

关于界定具有$b_2=1$的光滑4-流形的透镜空间

On lens spaces bounding smooth 4-manifolds with $\boldsymbol{b_2=1}$

该文研究不同拓扑下可界定b₂=1的光滑4-流形的透镜空间，构造出两类无穷族透镜空间并证明其拓扑性质，研究受有理同调射影平面相关问题启发。

Betti numbers of toric varieties and eulerian polynomials

It is well-known that the Eulerian polynomials, which count permutations in $S_n$ by their number of descents, give the $h$-polynomial/$h$-vector of the simple polytopes known as permutohedra, the convex hull of the $S_n$-orbit for a generic weight in the weight lattice of $S_n$. Therefore the Eulerian polynomials give the Betti numbers for certain smooth toric varieties associated with the permutohedra. In this paper we derive recurrences for the $h$-vectors of a family of polytopes generalizing this. The simple polytopes we consider arise as the orbit of a non-generic weight, namely a weight…

On the Topology of Birational Minimal Models

We show that birational smooth complex projective varieties with numerically effective canonical bundles along the exceptional loci have the same Betti numbers. In particular, birational smooth minimal models share the same Betti numbers. Our methods indicate a link between $p$-adic measure and the minimal model theory.

The Hilbert Scheme of Buchsbaum space curves

We consider the Hilbert scheme H(d,g) of space curves C with homogeneous ideal I(C):=H_{*}^0(\sI_C) and Rao module M:=H_{*}^1(\sI_C). By taking suitable generizations (deformations to a more general curve) C' of C, we simplify the minimal free resolution of I(C) by e.g. making consecutive free summands (ghost-terms) disappear in a free resolution of I(C'). Using this for Buchsbaum curves of diameter one (M_v \ne 0 for only one v), we establish a one-to-one correspondence between the set \sS of irreducible components of H(d,g) that contain (C) and a set of minimal 5-tuples that specializes in a…

Betti Numbers of Syzygies and Cohomology of Coherent Sheaves

The Betti numbers of a graded module over the polynomial ring form a table of numerical invariants that refines the Hilbert polynomial. A sequence of papers sparked by conjectures of Boij and Söderberg have led to the characterization of the possible Betti tables up to rational multiples---that is, to the rational cone generated by the Betti tables. We will summarize this work by describing the cone and the closely related cone of cohomology tables of vector bundles on projective space, and we will give new, simpler proofs of some of the main results. We also explain some of the applications o…

Irreducible components of the equivariant punctual Hilbert schemes

Let H_{ab} be the equivariant Hilbert scheme parametrizing the 0-dimensional subschemes of the affine plane invariant under the natural action of the one-dimensional torus T_{ab}:={(t^{-b},t^a), t\in k^*}. We compute the irreducible components of H_{ab}: they are in one-one correspondence with a set of Hilbert functions. As a by-product of the proof, we give new proofs of results by Ellingsrud and Stromme, namely the main lemma of the computation of the Betti numbers of the Hilbert scheme H^l parametrizing the 0-dimensional subschemes of the affine plane of length l and a description of Bialyn…

Intersection Poincare polynomial for Nagaraj-Seshadri moduli space

We compute Betti numbers of both the components of the moduli space of rank 2 semi-stable torsion-free sheaves with fixed determinant over a reducible nodal curve with two smooth components intersecting at a node. We also compute the intersection Betti numbers of the moduli space.

Stable Betti numbers of (partial) toroidal compactifications of the moduli space of abelian varieties

We present an algorithm for explicitly computing the number of generators of the stable cohomology algebra of any rationally smooth partial toroidal compactification of ${\mathcal A}_g$, satisfying certain additivity and finiteness properties, in terms of the combinatorics of the corresponding toric fans. In particular the algorithm determines the stable cohomology of the matroidal partial compactification, in terms of simple regular matroids that are irreducible with respect to the 1-sum operation, and their automorphism groups. The algorithm also applies to compute the stable Betti numbers i…

Topological properties of punctual Hilbert schemes of almost-complex fourfolds (I)

In this article, we study topological properties of Voisin's punctual Hilbert schemes of an almost-complex fourfold $X$. In this setting, we compute their Betti numbers and construct Nakajima operators. We also define tautological bundles associated with any complex bundle on $X$, which are shown to be canonical in $K$-theory.

带有系数的de Rham-贝蒂类

De Rham-Betti classes with coefficients

本文证明了椭圆曲线积上的L-德拉姆-贝蒂类是L线性组合的代数类，并给出了K3表面的全局德拉姆-贝蒂托里利定理。

Birational Calabi--Yau n-folds have equal Betti numbers

Let X and Y be two smooth projective n-dimensional algebraic varieties X and Y over C with trivial canonical line bundles. We use methods of p-adic analysis on algebraic varieties over local number fields to prove that if X and Y are birational, they have the same Betti numbers.

Consecutive cancellations in Betti numbers of local rings

Let I be a homogeneous ideal in a polynomial ring P over a field. By Macaulay's Theorem, there exists a lexicographic ideal L=Lex(I) with the same Hilbert function as I. Peeva has proved that the Betti numbers of P/I can be obtained from the graded Betti numbers of P/L by a suitable sequence of consecutive cancellations. We extend this result to any ideal I in a regular local ring (R,m) by passing through the associated graded ring. To this purpose it will be necessary to enlarge the list of the allowed cancellations. Taking advantage of Eliahou-Kervaire's construction, several applications ar…

Koszul duality between Betti and Cohomology numbers in Calabi-Yau case

Let $X$ be a smooth projective Calabi-Yau variety and $L$ a Koszul line bundle on $X$. We show that for Betti numbers of a maximal Cohen-Macaulay module over the homogeneous coordinate ring $A$ of $X$ there are formulas similar to the formulas for cohomology number. This similarity is realized via the box-product resolution of the diagonal $Δ_X \subset X \times X$.

A few remarks about the Hilbert scheme of smooth projective curves

We discuss two conjectures by Francesco Severi and Joe Harris about the irreducibility and the dimension of the Hilbert scheme parameterizing smooth projective curves of given degree and genus.

Canonical syzygies of smooth curves on toric surfaces

In a first part of this paper, we prove constancy of the canonical graded Betti table among the smooth curves in linear systems on Gorenstein weak Fano toric surfaces. In a second part, we show that Green's canonical syzygy conjecture holds for all smooth curves of genus at most 32 or Clifford index at most 6 on arbitrary toric surfaces. Conversely we use known results on Green's conjecture (due to Lelli-Chiesa) to obtain new facts about graded Betti tables of projectively embedded toric surfaces.

超凯勒六重流形的第二贝蒂数的一个精确界

A Sharp Bound for the Second Betti Number of Hyperkähler Sixfolds

该研究针对六维光滑紧不可约超凯勒流形，证明其第二贝蒂数的精确上界为23，还得出相关上同调消失条件及第二贝蒂数的可能取值，所用方法涉及分解定理、曲率不等式与双线性关系。

Powers of complete intersections: graded Betti numbers and applications

Let I = (F_1,...,F_r) be a homogeneous ideal of R = k[x_0,...,x_n] generated by a regular sequence of type (d_1,...,d_r). We give an elementary proof for an explicit description of the graded Betti numbers of I^s for any s \geq 1. These numbers depend only upon the type and s. We then use this description to: (1) write H_{R/I^s}, the Hilbert function of R/I^s, in terms of H_{R/I}; (2) verify that the k-algebra R/I^s satisfies a conjecture of Herzog-Huneke-Srinivasan; and (3) obtain information about the numerical invariants associated to sets of fat points in P^n whose support is a complete in…

On automorphisms of Hilbert squares of smooth hypersurfaces

Let $X$ be a smooth projective hypersurface of dimension at least three. We show that every automorphism of the Hilbert square $X^{[2]}$ of $X$ is induced by some automorphism of $X$.

Incidence stratifications on Hilbert schemes of smooth surfaces, and an application to Poisson structures

Given a smooth curve on a smooth surface, the Hilbert scheme of the surface is stratified according to the length of the intersection with the curve. The strata are highly singular. We show that this stratification admits a natural log-resolution, namely the stratified blowup. As a consequence, the induced Poisson structure on the Hilbert scheme of a Poisson surface has unobstructed deformations.

The Hilbert compactification of the universal moduli space of semistable vector bundles over smooth curves

We construct the Hilbert compactification of the universal moduli space of semistable vector bundles over smooth curves. The Hilbert compactification is the GIT quotient of some open part of an appropriate Hilbert scheme of curves in a Grassmannian. It has all the properties asked for by Teixidor.

Betti numbers of holomorphic symplectic quotients via arithmetic Fourier transform

A Fourier transform technique is introduced for counting the number of solutions of holomorphic moment map equations over a finite field. This in turn gives information on Betti numbers of holomorphic symplectic quotients. As a consequence simple unified proofs are obtained for formulas of Poincare polynomials of toric hyperkahler varieties, Poincare polynomials of Hilbert schemes of points and twisted ADHM spaces of instantons on C^2 and Poincare polynomials of all Nakajima quiver varieties. As an application, a proof of a conjecture of Kac on the number of absolutely indecomposable represent…

The Ubiquity of Smooth Hilbert Schemes

We investigate the geography of Hilbert schemes parametrizing closed subschemes of projective space with specified Hilbert polynomials. We classify Hilbert schemes with unique Borel-fixed points via combinatorial expressions for their Hilbert polynomials. These expressions naturally lead to an arrangement of nonempty Hilbert schemes as the vertices of an infinite full binary tree. Here we discover regularities in the geometry of Hilbert schemes. Specifically, under natural probability distributions on the tree, we prove that Hilbert schemes are irreducible and nonsingular with probability grea…

Incidence Hilbert schemes and infinite dimensional Lie algebras

Given a projetive surface $S$, using correspondences, we construct an infinite dimensional Lie algebra that acts on the direct sum $\Wfock$ of the cohomology groups of the incidence Hilbert schemes $S^{[n,n+1]}$ over all $n$. The algebra is related to an extension of an infinite dimensional Heisenberg algebra. The space $\Wfock$ is a highest weight representation of this algebra. Our result provides a representation-theoretic interpretation of Cheah's generating function of Betti numbers of the incidence Hilbert schemes. As a consequence, an additive basis of the cohomology group of the incide…

On the moduli scheme of stable sheaves supported on cubic space curves

We investigate the geometry of the Simpson moduli space M of stable sheaves on P_3 with Hilbert polynomial H(m)=3m+1 and describe explicitly the two smooth, rational components, their 11-dimensional smooth, transversal intersection and the relation between M and the Hilbert scheme Hilb_H(P_3) of cubic space curves. We also compute the Betti numbers of the Chow groups of the moduli space M.

关于超Kähler流形上反演的极大性及曲面点希尔伯特方案

On maximality of involutions of hyper-Kähler manifolds and punctual Hilbert schemes of surfaces

本文研究了超Kähler流形和曲面点希尔伯特方案上反演的极大性，推导出极大反演的条件并证明了某些流形不存在极大反演。

Smooth components on special iterated Hilbert schemes

Let $S$ be a smooth projective surface with $p_g=q=0$. We show how to use derived categorical methods to study the geometry of certain special iterated Hilbert schemes associated to $S$ by showing that they contain a smooth connected component isomorphic to $S$.

Fundamental Group Schemes of Hilbert Scheme of $n$ Points on a Smooth Projective Surface

Let $k$ be an algebraically closed field of characteristic $p > 3$. Let $X$ be an irreducible smooth projective surface over $k$. Fix an integer $n \geq 1$ and let ${\mathcal{H}{\it ilb}}_X^n$ be the Hilbert scheme parameterizing effective $0$-cycles of length $n$ on $X$. The aim of the present article is to find the $S$-fundamental group scheme and Nori's fundamental group scheme of the Hilbert scheme $\mathcal{H}{\it ilb}_X^n$.

关于光滑曲线Hilbert概型的非约化分支

On generically non-reduced components of Hilbert schemes of smooth curves

本文利用Hodge理论技术，构造了光滑曲线Hilbert概型的泛非约化分支的新例子，突破了超曲面次数限制，并获得了某些Hodge轨迹的泛非约化分支。

立方四维流形上线的Fano簇商的终端化

Terminalizations of quotients of Fano varieties of lines on cubic fourfolds

本文研究了立方四维流形上线的Fano簇商的终端化，计算了相关拓扑不变量，并识别出新的四维不可约解析辛流形变形类。

三维空间中曲面的雅可比代数的分层贝蒂数

Graded Betti numbers of the Jacobian algebra of surfaces in $\mathbb P^3$

本文基于雅可比代数的分层贝蒂数，推导了三维空间中曲面的希尔伯特多项式闭合公式，并讨论了孤立奇点曲面的分层贝蒂数必要条件及平面曲线与节点曲面的比较。

Computable Białynicki-Birula decomposition of the Hilbert scheme

We call the scheme parameterizing homogeneous ideals with fixed initial ideal the Gröbner scheme. We introduce a Białynicki-Birula decomposition of the Hilbert scheme $\mathrm{Hilb}^{P}_n$ for any Hilbert polynomial $P$ such that the cells are the Gröbner schemes in set-theoretically. Then we obtain a computable homology formula for smooth Hilbert schemes. As a corollary of our argument, we show that the Gröbner scheme for a monomial ideal defining a smooth point in the Hilbert scheme is smooth.

关于复解析空间芽的粘合、Betti数及其结构

On the Gluing of germs of complex analytic spaces, Betti numbers and their structure

本文引入复解析空间芽的三种新粘合类，通过其Poincaré级数与Betti数给出判断光滑、奇异、完全交集及Gorenstein性质的数值判据，并证明沿任意子空间粘合同一空间芽必为奇异芽。

Picard-graded Betti numbers and the defining ideals of Cox rings

Let X be a smooth projective variety with torsion-free Picard group. We introduce complexes of vector spaces whose homology determines the structure of the minimal free resolution of the Cox ring of X over the polynomial ring and show how the homology of these complexes can be studied by purely geometric methods. As an application of these techniques we give a simple new proof of a characterization of the Cox rings of Del Pezzo surfaces (of degree >1) conjectured by Batyrev and Popov.

Irreducibility of the Hilbert scheme of smooth curves in $\Bbb P^4$ of degree $g+2$ and genus $g$

We denote by $\mathcal{H}_{d,g,r}$ the Hilbert scheme of smooth curves, which is the union of components whose general point corresponds to a smooth irreducible and non-degenerate curve of degree $d$ and genus $g$ in $\PP^r$. In this note, we show that any non-empty $\mathcal{H}_{g+2,g,4}$ is irreducible without any restriction on the genus $g$. Our result augments the irreducibility result obtained earlier by Hristo Iliev(2006), in which several low genus $g\le 10$ cases have been left untreated.

低度希尔伯特方案的组成部分和平滑可变形代数

Components of Hilbert Schemes of low degree and smoothable algebras

本文研究了低度希尔伯特方案的不可约成分，并证明了特定条件下的局部代数可平滑，同时建立了两种Grassmann变种的等价性。