A characterization of bielliptic curves via syzygy schemes
Marian Aprodu, Andrea Bruno, Edoardo Sernesi
本文证明亏格至少为11的典范曲线为双椭圆曲线当且仅当其第二合冲概型与该曲线本身不同，从而给出双椭圆性的合冲概型判别准则。
我们证明：亏格 $\ge 11$ 的典范曲线 $C$ 是双椭圆的，当且仅当其第二合冲概型 $\mathrm{Syz}_2(C)$ 不同于 $C$。
We prove that a canonical curve $C$ of genus $\ge 11$ is bielliptic if and only if its second syzygy scheme $\mathrm{Syz}_2(C)$ is different from $C$.
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In this note, we prove that the syzygy bundle $M_L$ is cohomologically stable with respect to $L$ for any ample and globally generated line bundle $L$ on an Enriques (resp. bielliptic) surface over an algebraically closed field of characteristic $\neq 2$ (resp. $\neq 2,3$). In particular our result on complex Enriques surfaces improves a result of Torres-López and Zamora by removing a condition on Clifford index. Together with the results of Camere and Caucci--Lahoz, it implies that $M_L$ is stable with respect to $L$ for an ample and globally generated line bundle $L$ on any smooth minimal co…
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本文证明了亏格 $g \geq 11$ 的典范曲线 Hilbert 概型中双椭圆曲线轨迹的单有理性，并以此给出了亏格 $g \geq 11$ 曲线模空间中双椭圆轨迹单有理性的另一证明。
Raynaud has shown that over a general curve of genus $g \ge 2$, every semistable bundle of rank three and integral slope admits a theta divisor. We show that this can fail for special curves: Over any bielliptic curve of genus $g \ge 5$, we construct a stable rank three bundle of trivial determinant with no theta divisor. This gives a partial answer to a question of Beauville.
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Reduction of bielliptic hyperelliptic functions of genus 3
针对亏格3超椭圆函数的约化问题，受方程理论与超椭圆函数可积动力系统应用启发，研究人员将具有2次椭圆曲线态射的亏格3超椭圆曲线的对应超椭圆函数，用Weierstrass椭圆函数和亏格2超椭圆函数表示。
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The second syzygy schemes of curves of large degree
本文延续典范曲线第二合冲概型研究，给出次数不小于2g+2的亏格g曲线的第二合冲概型与曲线自身重合的充分条件，分满足和不满足性质(N₂)两种情形论证。
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Stability of syzygy bundles over certain curves of compact type
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The Syzygy Matrix and the Differential for Rational Curves in Projective Space
针对射影空间中有理曲线切丛限制所诱导的态射判别问题，本文借助 Mathematica 计算提出猜想，并对若干参数取值给出计算机辅助证明。
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本文研究双椭圆 Picard 曲线及其 Prym 阿贝尔曲面，证明 Torelli 定理并给出 QM 的几何证明，进而刻画 Galois 作用并分类有理 Mordell-Weil 挠子群。
We introduce the problem of GIT stability for syzygy points of canonical curves with a view toward a GIT construction of the canonical model of the moduli space of stable curves. As the first step in this direction, we prove semi-stability of the first syzygy point for a general canonical curve of odd genus.
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An answer for a Mistretta-Stoppino's conjecture
该研究围绕Mistretta-Stoppino猜想，通过Brill-Noether理论、Lazarsfeld-Mukai层等方法，建立了一般曲线及K3曲面上曲线的线性系列线性稳定性蕴含合冲层斜率稳定性的新情形，为二者等价关系提供了进一步证据。
Gromov-Witten Invariants of Bielliptic Surfaces
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Free plane curves with a linear Jacobian syzygy
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We consider the generic Green conjecture on syzygies of a canonical curve, and particularly the following reformulation thereof: {\it For a smooth projective curve $C$ of genus $g$ in characteristic 0, the condition ${\rm Cliff} C>l$ is equivalent to the fact that $K_{g-l'-2,1}(C,K_C)=0, \forall l'\leq l$.} We propose a new approach, which allows up to prove this result for generic curves $C$ of genus $g(C)$ and gonality ${\rm gon(C)}$ in the range $$\frac{g(C)}{3}+1\leq {\rm gon(C)}\leq\frac{g(C)}{2}+1.$$
Let X be a smooth complex projective curve of genus g bigger or equal to 1. If g is bigger than 1 assume further that X is either bielliptic or with general moduli. Under a natural condition on slopes, we prove that there exists a short exact sequence of semistable vector bundles with given ranks and degrees. The importance of the paper consists of the new method adopted for the proves.
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The Geometric Syzygy Conjecture in Positive Characteristic
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We show that for $5$-gonal curves of odd genus $g\geq 13$ and even genus $g\geq 28$ the $\lceil \frac{g-1}{2}\rceil$-th syzygy module of the curve is not determined by the syzygies of the scroll swept out by the special pencil of degree $5$.
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本文研究正特征中典范曲线的合冲，在 p≥(g+4)/2 时重新证明一般 Green 猜想，并在 p>g 时确立一般偶亏格曲线最后合冲空间的几何合冲猜想关键情形。
Generalizing Green's Syzygy Theorems to Symmetric Products of Curves
该研究将Mark Green的Koszul上同调经典定理推广到曲线的对称乘积，通过归纳法证明权1消失定理，得到重言线丛满足性质(N_p)的条件，为伴随合冲的民间猜想提供了证据。
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Jacobian schemes of conic-line arrangements and eigenschemes
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We introduce a relativization of the secant sheaves used by Ein, Green and Lazarsfeld and apply this construction to the study of syzygies of canonical curves. As a first application, we give a simpler proof of Voisin's Theorem for general canonical curves. This completely determines the terms of the minimal free resolution of the coordinate ring of such curves. Secondly, in the case of curves of even genus, we enhance Voisin's Theorem by providing a structure theorem for the last syzygy space, resolving the Geometric Syzygy Conjecture in even genus.
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The minimal resolution property for points on general curves
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We describe a systematic way of constructing effective divisors on the moduli space of stable curves of genus g having exceptionally small slope. We prove that any divisor on \bar{M}_g consisting of curves failing a certain Green-Lazarsfeld syzygy type condition, provides a counterexample to the Harris-Morrison Slope Conjecture. These divisors generalize our original isolated counterexample to the Slope Conjecture which was the divisor on M_{10} of curves lying on K3 surfaces. We also introduce a new stratification of M_g, somewhat similar to the classical stratification given by gonality, but…
This short note provides a quick introduction to relative canonical resolutions of curves on rational normal scrolls. We present our Macaulay2-package which computes the relative canonical resolution associated to a curve and a pencil of divisors. Most of our experimental data can be found on a dedicated webpage. We end with a list of conjectural shapes of relative canonical resolutions. In particular, for curves of genus $g=n\cdot k +1$ and pencils of degree $k$ for $n\ge 1$, we conjecture that the syzygy divisors on the Hurwitz space $\mathscr{H}_{g,k}$ constructed by Deopurkar and Patel all…
We show that if $R$ is a two dimensional standard graded ring (with the graded maximal ideal ${\bf m}$) of characteristic $p>0$ and $I\subset R$ is a graded ideal with $\ell(R/I) <\infty$ then the $F$-threshold $c^I({\bf m})$ can be expressed in terms of a strong HN (Harder-Narasimahan) slope of the canonical syzygy bundle on $\mbox{Proj}~R$. Thus $c^I({\bf m})$ is a rational number. This gives us a well defined notion, of the $F$-threshold $c^I({\bf m})$ in characteristic $0$, in terms of a HN slope of the syzygy bundle on $\mbox{Proj}~R$. This generalizes our earlier result (in [TrW]) where …
For any finite abelian group G, we study the moduli space of abelian $G$-covers of elliptic curves, in particular identifying the irreducible components of the moduli space. We prove that, in the totally ramified case, the moduli space has trivial rational Picard group, and it is birational to the moduli space M_{1,n}, where n is the number of branch points. In the particular case of moduli of bielliptic curves, we also prove that the boundary divisors are a basis of the rational Picard group of the admissible covers compactification of the moduli space. Our methods are entirely algebro-geomet…
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.
Representations on canonical models of generalized Fermat curves and their syzygies
本文研究了射影直线 $(\mathbb{Z}/k\mathbb{Z})^n$-覆盖的典范模型，显式确定了其齐次坐标环作为分次代数、群表示及分次模的结构，并给出一阶合冲模的生成元与不可约表示分解。
We explore the concept of projections of syzygies and prove two new technical results; we firstly give a precise characterization of syzygy schemes in terms of their projections, secondly, we prove a converse to Aprodu's Projection Theorem. Applying these results, we prove that extremal syzygies of general curves of non-maximal gonality embedded by a linear system of sufficiently high degree arise from scrolls. Lastly, we prove Green's Conjecture for general covers of elliptic curves (of arbitrary degree) as well as proving a new result for curves of even genus and maximal gonality.
We define syzygy points of projective schemes, and introduce a program of studying their GIT stability. Then we describe two cases where we have managed to make some progress in this program, that of polarized K3 surfaces of odd genus, and of genus six canonical curves. Applications of our results include effectivity statements for divisor classes on the moduli space of odd genus K3 surfaces, and a new construction in the Hassett-Keel program for the moduli space of genus six curves.
Based on a recent result of Voisin [2001] we describe the last nonzero syzygy space in the linear strand of a canonical curve C of even genus g=2k lying on a K3 surface, as the ambient space of a k-2-uple embedded P^{k+1}. Furthermore the geometric syzygies constructed by Green and Lazarsfeld [1984] from g^1_{k+1}'s form a non degenerate configuration of finitely many rational normal curves on this P^{k+1}. This proves a natural generalization of Green's conjecture [1984], namely that the geometric syzygies should span the space of all syzygies, in this case.
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