Monodromy of elliptic surfaces

Moduli of elliptic $K3$ surfaces: monodromy and Shimada root lattice strata

In this paper we investigate two stratifications of the moduli space of elliptically fibred K3 surfaces. The first comes from Shimada's classification of connected components of elliptically fibred K3 surfaces and is closely related to the root lattice of the fibration. The second is the monodromy stratification defined by Bogomolov, Petrov and Tschinkel. The main result of the paper is a classification of all positive-dimensional ambi-typical strata, that is strata which are both Shimada root strata and monodromy strata. We further discuss the connection with moduli spaces of lattice-polarise…

On monodromy in families of elliptic curves over $\mathbb C$

We show that if we are given a smooth non-isotrivial family of elliptic curves over~$\mathbb C$ with a smooth base~$B$ for which the general fiber of the mapping $J\colon B\to\mathbb A^1$ (assigning $j$-invariant of the fiber to a point) is connected, then the monodromy group of the family (acting on $H^1(\cdot,\mathbb Z)$ of the fibers) coincides with $\mathrm{SL}(2,\mathbb Z)$; if the general fiber has $m\ge2$ connected components, then the monodromy group has index at most~$2m$ in $\mathrm{SL}(2,\mathbb Z)$. By contrast, in \emph{any} family of hyperelliptic curves of genus $g\ge3$, the mon…

椭圆对数的单值性：若干拓扑方法与有效结果

Monodromy of elliptic logarithms: some topological methods and effective results

本文研究椭圆对数的相对单值群，提出构造保持周期但使对数非平凡变化的显式环路的方法，并给出处理截面分歧轨迹的拓扑工具与有效结果。

双椭圆对数的单演群

Monodromy of double elliptic logarithms

本文确定了椭圆概形纤维积中阿贝尔对数的相对单演群，推广了André及Corvaja-Zannier的结果，并猜想任意相对维数情形的类似结论。

Hirzebruch Surfaces: Degenerations, Related Braid Monodromy, Galois Covers

We describe various properties of Hirzebruch surfaces and related constructions: degenerations, braid monodromy, Galois covers and their Chern classes.

Monodromy of a Class of Logarithmic Connections on an Elliptic Curve

The logarithmic connections studied in the paper are direct images of regular connections on line bundles over genus-2 double covers of the elliptic curve. We give an explicit parametrization of all such connections, determine their monodromy, differential Galois group and the underlying rank-2 vector bundle. The latter is described in terms of elementary transforms. The question of its (semi)-stability is addressed.

Monodromy of rational curves on K3 surfaces of low genus

In many situations, the monodromy group of enumerative problems will be the full symmetric group. In this paper, we study a similar phenomenon on the rational curves in $|\mathcal{O}(1)|$ on a generic K3 surface of fixed genus over $\mathbb{C}$ as the K3 surface varies. We prove that when the K3 surface has genus $g$, $1\leq g\leq 3$, the monodromy group is the full symmetric group.

Monodromy groups of real Enriques surfaces

We compute the monodromy groups of real Enriques surfaces of hyperbolic type. The principal tools are the deformation classification of such surfaces and a modified version of Donaldson's trick, relating real Enriques surfaces and real rational surfaces.

P-torsion monodromy representations of elliptic curves over geometric function fields

Given a complex quasiprojective curve $B$ and a non-isotrivial family $\mathcal{E}$ of elliptic curves over $B$, the $p$-torsion $\mathcal{E}[p]$ yields a monodromy representation $ρ_\mathcal{E}[p]:π_1(B)\rightarrow \mathrm{GL}_2(\mathbb{F}_p)$. We prove that if $ρ_{\mathcal E}[p]\cong ρ_{\mathcal E'}[p]$ then $\mathcal{E}$ and $\mathcal E'$ are isogenous, provided $p$ is larger than a constant depending only on the gonality of $B$. This can be viewed as a function field analog of the Frey--Mazur conjecture, which states that an elliptic curve over $\mathbb{Q}$ is determined up to isogeny by i…

叠、单值与对称三次曲面

Stacks, Monodromy and Symmetric Cubic Surfaces

本文在模叠框架下研究枚举几何中受预设对称性影响的单值群，并以容许给定对称群的对称三次曲面上27条直线为例说明该视角的广泛用途。

Zeta functions and monodromy for surfaces that are general for a toric idealistic cluster

In this article we consider surfaces that are general with respect to a 3- dimensional toric idealistic cluster. In particular, this means that blowing up a toric constellation provides an embedded resolution of singularities for these surfaces. First we give a formula for the topological zeta function directly in terms of the cluster. Then we study the eigenvalues of monodromy. In particular, we derive a useful criterion to be an eigenvalue. In a third part we prove the monodromy and the holomorphy conjecture for these surfaces.

The monodromy property for K3 surfaces allowing a triple-point-free model

The aim of this thesis is to study under which conditions $K3$ surfaces allowing a triple-point-free model satisfy the monodromy property. This property is a quantitative relation between the geometry of the degeneration of a Calabi-Yau variety $X$ and the monodromy action on the cohomology of $X$: a Calabi-Yau variety $X$ satisfies the monodromy property if poles of the motivic zeta function $Z_{X,ω}(T)$ induce monodromy eigenvalues on the cohomology of $X$. In this thesis, we focus on $K3$ surfaces allowing a triple-point-free model, i.e., $K3$ surfaces allowing a strict normal crossings mod…

On the Monodromy and Galois Group of Conics Lying on Heisenberg Invariant Quartic K3 Surfaces

In "Curves on Heisenberg invariant quartic surfaces in projective 3-space", Eklund showed that a general $(\mathbb{Z}/2\mathbb{Z})^{4}$-invariant quartic K3 surface contains at least $320$ conics. In this paper we analyse the field of definition of those conics as well as their Monodromy group. As a result, we prove that the moduli space $(\mathbb{Z}/2\mathbb{Z})^{4}$-invariant quartic K3 surface with a marked conic has $10$ irreducible components.

Monodromy of plane curves and quasi-ordinary surfaces

We develop recursive formulas for the horizontal and vertical monodromies of a quasi-ordinary surface. These are monodromies associated to the Milnor fiber of a slice transverse to a component of the singular locus. In the course of working out these recursions, we have discovered what appears to be a new way to express the monodromy associated to the Milnor fibration of a singular plane curve.

Families of lattice polarized K3 surfaces with monodromy

We extend the notion of lattice polarization for K3 surfaces to families over a (not necessarily simply connected) base, in a way that gives control over the action of monodromy on the algebraic cycles, and discuss the uses of this new theory in the study of families of K3 surfaces admitting fibrewise symplectic automorphisms. We then give an application of these ideas to the study of Calabi-Yau threefolds admitting fibrations by lattice polarized K3 surfaces.

The Regeneration Of A 5-Point

The braid monodromy factorization of the branch curve of a surface of general type is known to be an invariant that completely determines the diffeomorphism type of the surface. Calculating this factorization is of high technical complexity; computing the braid monodromy factorization of branch curves of surfaces uncovers new facts and invariants of the surfaces. Since finding the branch curve of a surface is very difficult, we degenerate the surface into a union of planes. Thus, we can find the braid monodromy of the branch curve of the degenerated surface, which is a union of lines. The rege…

Braid monodromy factorization for a non-prime $K3$ surface branch curve

This paper is the second in a series. The first one describes pillow degenerations of a $K3$ surface with genus $g$. In this paper we study the $(2,2)$-pillow degeneration of a non-prime $K3$ surface and the braid monodromy of the branch curve of the surface with respect to a generic projection onto $\C¶^2$. In future papers we study the fundamental group of the complement of the branch curve and the fundamental group of the Galois cover of the surface with respect to this generic projection.

On the monodromy group of desingularised moduli spaces of sheaves on K3 surfaces

We compute the monodromy group of irreducible holomorphic symplectic manifolds of OG10 type, confirming a conjecture of Markman.

Monodromy of complete intersections and surface potentials

Following Newton, Ivory and Arnold, we study the Newtonian potentials of algebraic hypersurfaces in $R^n$. The ramification of (analytic continuations of) these potential depends on a monodromy group, which can be considered as a proper subgroup of the local monodromy group of a complete intersection (acting on a {\em twisted} vanishing homology group if $n$ is odd). Studying this monodromy group we prove, in particular, that the attraction force of a hyperbolic layer of degree $d$ in $R^n$ coincides with appropriate algebraic vector-functions everywhere outside the attracting surface if $n=2$…

阿贝尔曲面上层模空间局部平凡单值群

Locally trivial monodromy of moduli spaces of sheaves on Abelian surfaces

本文研究了阿贝尔曲面上非原始 Mukai 向量对应的半稳定层模空间，证明其奇异模空间的局部平凡单值群同构于光滑模空间的单值群，并由此证明了 SYZ 猜想。

紧致拉格朗日纤维化的monodromy

The monodromy of compact Lagrangian fibrations

研究紧致拉格朗日纤维化的monodromy表示，证明在周期映射通常浸没时表示是不可约的，在纤维为isotrivial时恢复Kim-Laza-Martin的结果，证明其纤维是椭圆曲线幂的isogeneous。

K3曲面上层模空间的局部平凡单值性

Locally trivial monodromy of moduli spaces of sheaves on K3 surfaces

本文通过将本原Mukai向量对应的层模空间作为最奇异轨迹嵌入非本原模空间，证明了二者单值群同构，从而把Markman的结果推广到非本原情形。

Monodromy representations and surfaces with maximal Albanese dimension

We relate the existence of some surfaces of general type and maximal Albanese dimension to the existence of some monodromy representations of the braid group $\mathsf{B}_2(C_2)$ in the symmetric group $\mathsf{S}_n$. Furthermore, we compute the number of such representations up to $n=9$, and we analyze the cases $n \in \{2, \, 3, \, 4\}$. For $n=2, \, 3$ we recover some surfaces with $p_g=q=2$ recently studied (with different methods) by the author and his collaborators, whereas for $n=4$ we obtain some conjecturally new examples.

Monodromy of rational curves on toric surfaces

For an ample line bundle $\mathcal{L}$ on a complete toric surface $X$, we consider the subset $V_{\mathcal{L}} \subset \vert \mathcal{L} \vert$ of irreducible, nodal, rational curves contained in the smooth locus of $X$. We study the monodromy map from the fundamental group of $V_{\mathcal{L}}$ to the permutation group on the set of nodes of a reference curve $C \in V_{\mathcal{L}}$. We identify a certain obstruction map $\varPsi_{X}$ defined on the set of nodes of $C$ and show that the image of the monodromy is exactly the group of deck transformations of $\varPsi_{X}$, provided that $\mathc…

Semistable fibrations over an elliptic curve with only one singular fibre

In this work we describe a construction of semistable fibrations over an elliptic curve with one unique singular fibre and we give effective examples using monodromy of curves.

关于 $K3$ 曲面的代数单步群的分量群

On the component group of the algebraic monodromy group of a $K3$ surface

本文为数域上的 $K3$ 曲面代数单步群分量数提供了下界，在 CM 情况下该界紧且据此用自同态域与几何 Picard 秩完整描述了跳跃特征。

Monodromy Relations in Higher-Loop String Amplitudes

New monodromy relations of loop amplitudes are derived in open string theory. We particularly study N-point one-loop amplitudes described by a world-sheet cylinder (planar and non-planar) and derive a set of relations between subamplitudes of different color orderings. Various consistency checks are performed by matching alpha'-expansions of planar and non-planar amplitudes involving elliptic iterated integrals with the resulting periods giving rise to two sets of multiple elliptic zeta values. The latter refer to the two homology cycles on the once-punctured complex elliptic curve and the mon…

Cubic threefolds, Fano surfaces and the monodromy of the Gauss map

The Tannakian formalism allows to attach to any subvariety of an abelian variety an algebraic group in a natural way. The arising groups are closely related to moduli questions such as the Schottky problem, but their geometric interpretation is still mysterious. We show that for the theta divisor on the intermediate Jacobian of a cubic threefold, the Tannaka group is an exceptional group of type E_6. This is the first known exceptional case, and it suggests a connection with the monodromy of the Gauss map.

Arithmetic monodromy actions on pro-metabelian fundamental groups of once-punctured elliptic curves

We prove structure theorems for the moduli stack of elliptic curves equipped with $G$-structures, where $G$ is a finite 2-generated metabelian group. In particular, we show that if $G$ has exponent $e$, then there is a subgroup $H\le GL_2(\mathbb{Z}/e)$ such that $G$-structures on elliptic curves $E$ are equivalent to "congruence structures of level $H$". Our methods are almost entirely group theoretic. Let $\widehat{M}$ denote the free profinite metabelian group of rank 2, then along the way we prove a decomposition of $Out(\widehat{M})$ as an internal semi-direct product of the subgroup of "…

On the monodromy of moduli spaces of sheaves on K3 surfaces

Let S be a K3 surface and Aut D(S) the group of auto-equivalences of the derived category of S. We construct a natural representation of Aut D(S) on the cohomology of all moduli spaces of stable sheaves (with primitive Mukai vectors) on S. The main result of this paper is the precise relation of this action with the monodromy of the Hilbert schemes S^[n] of points on the surface. A formula is provided for the monodromy representation, in terms of the Chern character of the universal sheaf. Isometries of the second cohomology of S^[n] are lifted, via this formula, to monodromy operators of the …

对称三次曲面空间中的monodromy研究

Monodromy in the space of symmetric cubic surfaces with a line

研究对称三次曲面中直线的monodromy群，发现其Galois群为克莱因四元群，揭示了对称性对计数问题的影响。

On the monodromy of moduli spaces of sheaves on K3 surfaces II

Let S be a K3 surface. In part I of this paper, we constructed a representation of the group Aut D(S), of auto-equivalences of the derived category of S. We interpreted this infinite dimensional representation, as the natural action of Aut D(S) on the cohomology of all moduli spaces of stable sheaves (with primitive Mukai vectors) on S. The main result, of part I, is the precise relation of this action with the monodromy of the Hilbert schemes S^[n] of points on the surface. The proof of the above result was reduced, in part I, to the case of two monodromy operators of S^[n], associated with c…

Monodromy Criterion for the Good Reduction of K3 Surfaces

We give a criterion for the good reduction of semistable $K3$ surfaces over $p$-adic fields using purely $p$-adic methods. We use neither $p$-adic Hodge theory nor transcendental methods as in the analogous proofs of criteria for good reduction of curves or $K3$ surfaces. We achieve our goal by realizing the special fiber $X_s$ of a semistable model $X$ of a $K3$ surface over the $p$-adic field $K$, $X_K$ as a special fiber of a log-family in characteristic $p$ and use an arithmetic version of the Clemens-Schimd exact sequence in order to obtain a Kulikov-Persson-Pinkham classification theorem…

Petersen图与Clebsch曲面上27条线的单值性

Petersen graph and monodromy of the 27 lines on the Clebsch surface

通过计算10个显式生成元的作用，用Petersen图描述了Clebsch曲面上27条线的单值性，该单值群是E6型Weyl群。

Algebraic functions with even monodromy

Let $X$ be a compact Riemann surface of genus $g$ and $d\geq 12g+4$ be an integer. We show that $X$ admits meromorphic functions with monodromy group equal to the alternating group $A_d.$

Igusa's p-adic local zeta function and the Monodromy Conjecture for non-degenerated surface singularities

In 2011 Lemahieu and Van Proeyen proved the Monodromy Conjecture for the local topological zeta function of a non-degenerated surface singularity. We start from their work and obtain the same result for Igusa's p-adic and the motivic zeta function. In the p-adic case, this is, for a polynomial f in Z[x,y,z] satisfying f(0,0,0)=0 and non-degenerated with respect to its Newton polyhedron, we show that every pole of the local p-adic zeta function of f induces an eigenvalue of the local monodromy of f at some point of the complex zero locus of f close to the origin. Essentially the entire paper is…

具有坏约化的阿贝尔曲面与K3曲面的单值性结果

Monodromy results for abelian surfaces and K3 surfaces with bad reduction

本文证明了特征p下具有坏约化的常阿贝尔曲面与K3曲面的局部p进单值性定理，并由此在II型超奇异约化情形下得到Hecke轨道约化的有限性结果。

Isotrivially fibred isles in the moduli space of surfaces of general type

We complement Catanese's results on isotrivially fibred surfaces by completely describing the components containing an isotrivial surface with monodromy group $\ZZ/2\ZZ$. We also give an example for deformation equivalent isotrivial surfaces with different monodromy group.

A special Calabi-Yau degeneration with trivial monodromy

A well-known theorem of Kulikov, Persson and Pinkham states that a degeneration of a family of K3-surfaces with trivial monodromy can be completed to a smooth family. We give a simple example that an analogous statement does not hold for Calabi-Yau threefolds.

Integral constraints on the monodromy group of the hyperkahler resolution of a symmetric product of a K3 surface

Let M be a 2n-dimensional Kahler manifold deformation equivalent to the Hilbert scheme of length n subschemes of a K3 surface S. Let Mon be the group of automorphisms of the cohomology ring of M, which are induced by monodromy operators. The second integral cohomology of M is endowed with the Beauville-Bogomolov bilinear form. We prove that the restriction homomorphism from Mon to the isometry group O[H^2(M)] is injective, for infinitely many n, and its kernel has order at most 2, in the remaining cases. For all n, the image of Mon in O[H^2(M)] is the subgroup generated by reflections with res…

On the degeneration, regeneration and braid monodromy of $T \times T$

This paper is the first in a series of three papers concerning the surface T times T. In this paper we study the degeneration of T times T and the regeneration of its degenerated object. We study the braid monodromy and its regeneration.

Monodromy and vanishing cycles in toric surfaces

Given an ample line bundle on a toric surface, a question of Donaldson asks which simple closed curves can be vanishing cycles for nodal degenerations of smooth curves in the complete linear system. This paper provides a complete answer. This is accomplished by reformulating the problem in terms of the mapping class group-valued monodromy of the linear system, and giving a precise determination of this monodromy group.

关于椭圆K3曲面与儿童画

On Elliptic K3 Surfaces and Dessins d'Enfants

本文通过分解函数不变量并利用儿童画分类椭圆K3曲面的单值群，提出了一种基于Bogomolov-Tschinkel策略的系统方法。

Moduli spaces of surfaces and monodromy invariants

This paper is a survey of the authors' recent results on "abc-surfaces" and the monodromy of their natural Lefschetz fibrations and projections to P^1 x P^1, see (arXiv:0910.2142). The results being surveyed explore various fundamental questions about complex deformation vs. symplectomorphism vs. diffeomorphism from the perspective of one explicit family of examples; the paper also contains some remarks which were not in earlier papers.

椭圆纤维化的辫子单项群中的挠元

Torsion in the Braid Monodromy of Elliptic Fibrations

本文研究了椭圆纤维化的辫子单项群，通过将其共轭类与$\operatorname{SL}_2$-特征簇上的特殊点相联系，分类了其中的 $n$ 阶元素，并证明了该群中不存在 $n-1$ 或 $n-2$ 阶元素。

单例和消失环对于足够 ample 线性系统在单连通表面上的 Monodromy

Monodromy and vanishing cycles for sufficiently ample linear systems on simply connected surfaces

研究了单连通表面中足够 ample 线性系统的 Monodromy 与 r-spin 映射类群的关系，并探讨了消失环在节点退化中的应用。

Monodromy of Fermat Surfaces and Modular Symbols for Fermat curves

Let $F_n$ denote the Fermat curve given by $x^n+y^n=z^n$ and let $μ_n$ denote the Galois module of $n$th roots of unity. It is known that the integral homology group $H_1(F_n,\Z)$ is a cyclic $\Z[μ_n\times μ_n]$ module. In this paper, we prove this result using modular symbols and the modular description of Fermat curves; moreover we find a basis for the integral homology group $H_1(F_n,\Z)$. We also construct a family of Fermat curves using the Fermat surface and compute its monodromy.

对称性与可解性：等变枚举问题的伽罗瓦群

Symmetry and solvability: Galois groups of equivariant enumerative problems

本文研究等变枚举问题的伽罗瓦群，刻画四种单值群关系，并证明在存在对称性时，求解三次曲面直线和平面四次曲线双切线问题可解。

K3曲面的Virasoro约束与单值化算子

Virasoro constraints for K3 surfaces and monodromy operators

本研究利用Markman单值化算子证明K3曲面的Virasoro约束，将问题约化到秩1情形，同时证明秩0的新Virasoro约束，并引入负次数新型Virasoro算子，与已有算子共同构成中心荷为24的Virasoro代数表示。

Dihedral Monodromy and Xiao Fibrations

We construct three new families of fibrations $π: S \to B$ where $S$ is an algebraic complex surface and $B$ a curve that violate Xiao's conjecture relating the relative irregularity and the genus of the general fiber. The fibers of $π$ are certain étale cyclic covers of hyperelliptic curves that give coverings of $P^1$ with dihedral monodromy. As an application, we also show the existence of big and nef effective divisors in the Brill-Noether range.

关于单值群曲面的单值性

On monodromy of monodromy surfaces

该研究将Painlevé方程关联的单值群曲面实现为仿射del Pezzo曲面，明确其单值群为对应仿射外尔群的有限部分，还给出Painlevé方程参数空间的模空间解释。

Monodromy and normal forms

We discuss the history of the monodromy theorem, starting from Weierstraß, and the concept of monodromy group. From this viewpoint we compare then the Weierstraß, the Legendre and other normal forms for elliptic curves, explaining their geometric meaning and distinguishing them by their stabilizer in P SL(2,Z) and their monodromy. Then we focus on the birth of the concept of the Jacobian variety, and the geometrization of the theory of Abelian functions and integrals. We end illustrating the methods of complex analysis in the simplest issue, the difference equation $f(z) = g(z+1) - g(z)$ on $\…

Monodromy of Kodaira Fibrations of Genus $3$

A Kodaira fibration is a non-isotrivial fibration $f\colon S\rightarrow B$ from a smooth algebraic surface $S$ to a smooth algebraic curve $B$ such that all fibers are smooth algebraic curves of genus $g$. Such fibrations arise as complete curves inside the moduli space $\mathcal{M}_g$ of genus $g$ algebraic curves. We investigate here the possible connected monodromy groups of a Kodaira fibration in the case $g=3$ and classify which such groups can arise from a Kodaira fibration obtained as a general complete intersection curve inside a subvariety of $\mathcal{M}_3$ parametrizing curves whose…

Big symplectic or orthogonal monodromy modulo l

Let k be a field not of characteristic two and L be a set of almost all rational primes invertible in k. Suppose we have a variety X/k and strictly compatible system {M_ell -> X : ell in L} of constructible F_ell-sheaves. If the system is orthogonally or symplectically self-dual, then the geometric monodromy group of M_ell is a subgroup of a corresponding isometry group G_ell over F_ell, and we say it has big monodromy if it contains the derived subgroup DG_ell=[G_ell,G_ell]. We prove a theorem which gives sufficient conditions for M_ell to have big monodromy. We apply the theorem to explicit …