We compute explicitly the limits of tangents of a quasi-ordinary singularity in terms of its special monomials. We show that the set of limits of tangents of Y is essentially a topological invariant of Y .
We study spaces of lines that meet a smooth hypersurface X in P^n to high order. As an application, we give a polynomial upper bound on the number of planes contained in a smooth degree d hypersurface in P^5 and provide a proof of a result of Landsberg without using moving frames.
We study the behaviour of rational curves tangent to a hypersurface under degenerations of the hypersurface. Working within the framework of logarithmic Gromov-Witten theory, we extend the degeneration formula to the logarithmically singular setting, producing a virtual class on the space of maps to the degenerate fibre. We then employ logarithmic deformation theory to express this class as an obstruction bundle integral over the moduli space of ordinary stable maps. This produces new refinements of the logarithmic Gromov-Witten invariants, encoding the degeneration behaviour of tangent curves…
Extending previous results, we prove that for $n \ge 5$ all hypersurfaces of degree $n+1$ in ${\mathbb P}^{n+1}$ with isolated ordinary double points are birational superrigid and K-stable, hence admit a weak Kähler--Einstein metric.
The purpose of this paper is to investigate the geometric properties of real hypersurfaces of D'Angelo infinite type in ${\mathbb C}^n$. In order to understand the situation of flatness of these hypersurfaces, it is natural to ask whether there exists a nonconstant holomorphic curve tangent to a given hypersurface to infinite order. A sufficient condition for this existence is given by using Newton polyhedra,which is an important concept in singularity theory. More precisely,equivalence conditions are given in the case of some model hypersurfaces.
We extend the approach Abbott, Kedlaya and Roe to computation of the zeta function of a projective hypersurface with $τ$ isolated ordinary double points over a finite field $\mathbb{F}_q$ given by the reduction of a homogeneous polynomial $f \in \mathbb{Z}[x_0, \ldots, x_n]$, under the assumption of equisingularity over $\mathbb{Z}_q$. The algorithm is based on the results of Dimca and Saito (over the field $\mathbb{C}$ of complex numbers) on the pole order spectral sequence in the case of ordinary double points. We give some examples of explicit computations for surfaces in $\mathbb{P}^3$.
Toric embedded resolutions of quasi-ordinary hypersurface singularities
利用复解析超曲面的复环态射,建立了复解析超曲面的拟寻常奇点的两个嵌入式分解过程,其中复环态射只依赖于奇点的拟寻常投影的特征单项式.这个结果回答了Lipman在Equisingularity and simultaneous奇点的分解,奇点的分解,Progress in Mathematics No.181,2000,485-503中的一个公开问题。在第一个过程中,奇异性被嵌入为超曲面。在第二个过程中,这是灵感的工作戈尔丁和Teissier的平面曲线(见解决奇异的平面解析分支与一个环面态射,loc。引用,第315-340页),我们以一个环面态射提供其嵌入分辨率的方式将奇点重新嵌入到更大维度的仿射空间中。我们比较这两个程序,我们表明,他们符合适当的假设。
Let Y be a hypersurface in projective space having only ordinary double points as singularities. We prove a variant of a conjecture of L. Wotzlaw on an algebraic description of the graded quotients of the Hodge filtration on the top cohomology of the complement of Y except for certain degrees of the graded quotients, as well as its extension to the Milnor cohomology of a defining polynomial of Y for degrees a little bit lower than the middle. These partially generalize theorems of Griffiths and Steenbrink in the Y smooth case, and enable us to determine the structure of the pole order spectral…
Decomposition in bunches of the critical locus of a quasi-ordinary map
复解析超曲面芽f=0的极超曲面P可以通过分析与P的像相关联的某些牛顿多面体关于适当坐标的不变性,通过与f适当关联的某些态射来研究。我们发展了泰西耶的这个一般原理(见Variable Polaires。I.不变量polaires des singularites d 'hypersurfaces,Invent. Math.40(1977),3,267-292),其中f=0是拟普通超曲面芽,P是与f=0的任何拟普通投影相关联的极超曲面。我们建立了一个分解的P在束的分支特征的嵌入拓扑型的不可约成分f=0。这种分解的特点也是一些性质的严格变换P的复曲面嵌入决议的f=0的第二作者在一份文件中将出现在Annal。傅立叶研究所(格勒诺布尔)。在平面曲线的情况下,该结果提供了Le、Michel和Weber在“Sur le comportement des polaires associees aux germes de courbes planes”,Compositio Math,72,(1989),1,87-113中的主要定理的简单代数证明。
Instituto de Matemáticas, Universidad Nacional Autónoma de México(墨西哥国立自治大学数学研究所);Escuela de Ciencias Físicas y Matemáticas, Universidad de San Carlos de Guatemala(危地马拉圣卡洛斯大学物理与数学院);Aix Marseille Univ, CNRS, I2M(艾克斯-马赛大学,法国国家科学研究中心,I2M)
We investigate the problem of the number of flats simultaneously tangent to several convex hypersurfaces in real projective space from a random point of view. More precisely, we say that smooth convex hypersurfaces $X_1, \ldots, X_{d_{k,n}}\subset \mathbb{R}\textrm{P}^n$, where $d_{k,n}=(k+1)(n-k)$, are in random position if each one of them is randomly translated by elements $g_1, \ldots, g_{d_{k,n}}$ sampled independently and uniformly from the Orthogonal group; we denote by $τ_k(X_1, \ldots, X_{d_{k,n}})$ the average number of $k$-dimensional projective subspaces (flats) which are simultane…
The biduality and reflexivity theorems are known to hold for projective varieties defined over fields of characteristic zero, and to fail in positive characteristic. In this article, we construct a notion of reflexivity and biduality in positive characteristic by generalizing the ordinary tangent space to the notion of $h$-tangent spaces. The ordinary reflexivity theory can be recovered as the special case $h=0$, of our theory. Several varieties that are not ordinary reflexive or bidual become reflexive in our extended theory.
We give an algorithm to compute the periods of smooth projective hypersurfaces of any dimension. This is an improvement over existing algorithms which could only compute the periods of plane curves. Our algorithm reduces the evaluation of period integrals to an initial value problem for ordinary differential equations of Picard-Fuchs type. In this way, the periods can be computed to extreme-precision in order to study their arithmetic properties. The initial conditions are obtained by an exact determination of the cohomology pairing on Fermat hypersurfaces with respect to a natural basis.