Charles Cadman, Radu Laza
We use three different methods to count the number of lines in the plane whose intersection with a fixed general quintic has fixed cross-ratios. We compare and contrast these methods, shedding light on some classical ideas which underly modern techniques.
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Li-Zinger's hyperplane theorem states that the genus one GW-invariants of the quintic threefold is the sum of its reduced genus one GW-invariants and 1/12 multiplies of its genus zero GW-invariants. We apply the Guffin-Sharpe-Witten's theory (GSW theory) to give an algebro-geometric proof of the hyperplane theorem, including separation of contributions and computation of 1/12.
We introduce certain rational functions on a smooth projective surface X in IP^3 which facilitate counting the lines on X. We apply this to smooth quintics in characteristic zero to prove that they contain no more than 127 lines, and that any given line meets at most 28 others. We construct examples which demonstrate that the latter bound is sharp.
Let $X$ be a smooth quintic hypersurface in $\mathbb{P}^3$, let $C$ be a smooth hyperplane section of $X$, and let $H=\mathcal{O}_X(C)$. In this paper, we give a necessary and sufficient condition for the line bundle given by a non-zero effective divisor on $X$ to be initialized and aCM with respect to $H$.
Motivic counting of curves on split quintic del Pezzo surfaces
本文证明了分裂五次德尔皮佐表面的Batyrev-Manin-Peyre猜想的'所有高度'版本，涵盖了正特征全局函数域上的有理点计数及一般基域上的动机版本。
For each $1\leq n\leq6$ we present formulas for the number of $n-$nodal curves in an $n-$dimensional linear system on a smooth, projective surface. This yields in particular the numbers of rational curves in the system of hyperplane sections of a generic $K3-$surface imbedded in \p{n} by a complete system of curves of genus $n$ as well as the number {\bf17,601,000} of rational ({\em singular}) plane quintic curves in a generic quintic threefold.
We explain a classical construction of a del Pezzo surface of degree d = 4 or 5 as a smooth order two congruence of lines in 3-space whose focal surface is a quartic surface $X_{20-d}$ with 20-d ordinary double points. We also show that $X_{15}$ can be realized as a hyperplane section of the Castelnuovo-Richmond-Igusa quartic hypersurface. This leads to the proof of rationality of the moduli space of 15-nodal quartic surfaces. We discuss some other birational models of $X_{15}$: quartic symmetroids, 5-nodal quartic surfaces, 10-nodal sextic surfaces in $P^4$ and nonsingular surfaces of degree …
The trigonal curves of genus 5 can be represented by projective plane quintics that have 1 singularity of delta invariant 1. Combining this with a partial sieve method for plane curves we count the number of such curves over any finite field. The main application is that this then gives the motivic Euler characteristic of the moduli space of trigonal curves of genus 5.
Points of bounded height on quintic del Pezzo surfaces over number fields
该研究证明了任意数域上分裂光滑五次 del Pezzo 曲面关于一般反典范高函数的 Manin 猜想，通过泛挠子限制变量至典型大小并在 o-极小结构框架下解决计数问题。
In this paper, we investigate the space of certain weak stability conditions on the triangulated category of D0-D2-D6 bound states on a smooth projective Calabi-Yau 3-fold. In the case of a quintic 3-fold, the resulting space is interpreted as a universal covering space of an infinitesimal neighborhood of the conifold point in the stringy Kahler moduli space. We then construct the DT type invariants counting semistable objects in our triangulated category, which are new curve counting invariants on a Calabi-Yau 3-fold. We also investigate the wall-crossing formula of our invariants and their i…
Given any polynomial system with fixed monomial term structure, we give explicit formulae for the generic number of roots with specified coordinate vanishing restrictions. For the case of affine space minus an arbitrary union of coordinate hyperplanes, these formulae are also the tightest possible upper bounds on the number of isolated roots. We also characterize, in terms of sparse resultants, precisely when these upper bounds are attained. Finally, we reformulate and extend some of the prior combinatorial results of the author on which subsets of coefficients must be chosen generically for o…
Given a real algebraic curve, embedded in projective space, we study the computational problem of deciding whether there exists a hyperplane meeting the curve in real points only. More generally, given any divisor on such a curve, we may ask whether the corresponding linear series contains an effective divisor with totally real support. This translates into a particular type of parametrized real root counting problem that we wish to solve exactly. On the other hand, it is known that for a given genus and number of real connected components, any linear series of sufficiently large degree contai…
Jacobian algebras and variation of hyperplane sections
通过 Milnor 代数研究至多孤立奇点超曲面的超平面截面模空间的变分，给出超平面截面映射为有限态的无穷小商判据，并推广了光滑情形的 Beauville-Patel-Riedl-Tseng 理论。
Curve counting and S-duality
研究项目性三维流形上二维 torsion sheaves 的模空间，证明其为理想 sheaves 的希尔伯特方案的光滑纤维，并探讨Calabi-Yau情形下的曲线计数与D4-D2-D0膜不变量的Wall Crossing公式及S对称性。
Fix a Calabi-Yau 3-fold $X$ satisfying the Bogomolov-Gieseker conjecture of Bayer-Macrì-Toda, such as the quintic 3-fold. By two different wall-crossing arguments we prove two different explicit formulae relating rank 0 Donaldson-Thomas invariants (counting torsion sheaves on $X$ supported on ample divisors) in terms of rank 1 Donaldson-Thomas invariants (counting ideal sheaves of curves) and Pandharipande-Thomas invariants. In particular, we prove a slight modification of Toda's formulation of OSV conjecture for $X$. When $X$ is of Picard rank one, we also give an explicit formula for rank tw…
Rank $r$ DT theory from rank $1$
该研究针对满足特定猜想的Calabi-Yau 3-折叠，将任意秩r的Gieseker半稳定层的广义DT不变量用秩1层的不变量表示，且通过MNOP猜想证明其由Gromov-Witten不变量决定。
Counting rational points on non-uniruled surfaces
本文研究了光滑四次和五次曲面上有理点的计数问题，通过切割和法尔廷斯定理改进了已有界。
Two Formulas for the Number of Lines on Complex Projective Hypersurfaces
本文研究复射影一般超曲面上的经典直线数 $C_n$，通过分裂原理和随机代数几何给出两个新的组合公式，并重新得到其奇偶性、渐近上界及完全交推广。
We study the geometry of varieties parametrizing degree d rational and elliptic curves in P^n intersecting fixed general linear spaces and tangent to a fixed hyperplane H with fixed multiplicities along fixed general linear subspaces of H. As an application, we derive recursive formulas for the number of such curves when the number is finite. These recursive formulas require as ``seed data'' only one input: there is one line in P^1 through two points. These numbers can be seen as top intersection products of various cycles on the Hilbert scheme of degree d rational or elliptic curves in P^n, o…
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