On the classification of cubic plane Cremona maps

有限域上秩 2 的 Cremona 群的 Jordan 常数

Jordan constant for Cremona group of rank 2 over a finite field

本文确定了所有有限域上秩 2 的 Cremona 群的 Jordan 常数精确值，并构造了 $\mathbb{F}_2$ 上具有最大自同构群 $\mathrm{S}_6$ 的正则作用的三次曲面，且证明了其唯一性。

Monomial Cremona transformations and toric polar maps

Given a birational map in the three dimensional projective space defined by monomials of degree $d$, we prove that its inverse is defined by monomials of degree at most $d^2-d+1$.

Cremona transformations, surface automorphisms and plane cubics

We give a method for constructing many examples of automorphisms with positive entropy on rational complex surfaces. The general idea is to begin with a quadratic Cremona transformation that fixes a reduced cubic curve and then use the group structure on the cubic to understand when the indeterminacy and exceptional behavior of the transformation may be eliminated by repeated blowing up.

Classification of the monomial Cremona transformations of the plane

We classify all monomial planar Cremona maps by multidegree using recent methods developed by Aluffi. Following the main result, we prove several more properties of the set of these maps, and also extend the results to the more general `r.c. monomial' maps.

保持欧几里得体积形式的平面克雷莫纳映射

Plane Cremona maps preserving a Euclidean volume form

该研究给出了保持沿三重直线带极点微分形式的平面双有理变换群的生成元与关系表示，该群包含仿射平面自同构群。

Segre三次曲面和Cremona–Richmond构型的Pascal型构造

A Pascal-type construction of the Segre cubic and the Cremona--Richmond configuration

本文提出P^4中的Pascal型剩余构造，从两对超平面出发，证明十二个剩余平面位于一个三次三维流形上，一般情况为Segre三次曲面，并恢复其十五个平面和关联的Cremona–Richmond构型，同时给出该构型的点线实现。

Extremal varieties 3-rationally connected by cubics, quadro-quadric Cremona transformations and rank 3 Jordan algebras

For any $n\geq 3$, we prove that there exist equivalences between these apparently unrelated objects: irreducible $n$-dimensional non degenerate projective varieties $X\subset \mathbb P^{2n+1}$ different from rational normal scrolls and 3-covered by twisted cubic curves, up to projective equivalence; quadro-quadric Cremona transformations of $ \mathbb P^{n-1}$, up to linear equivalence; $n$-dimensional complex Jordan algebras of rank three, up to isotopy. We also provide some applications to the classification of particular classes of varieties in the class defined above and of quadro-quadric …

Cremona maps of de Jonquières type

This paper is concerned with suitable generalizations of a plane de Jonquières map to higher dimensional space $\mathbb{P}^n$ with $n\geq 3$. For each given point of $\mathbb{P}^n$ there is a subgroup of the entire Cremona group of dimension $n$ consisting of such maps. One studies both geometric and group-theoretical properties of this notion. In the case where $n=3$ one describes an explicit set of generators of the group and gives a homological characterization of a basic subgroup thereof.

关于次数为4且长度为2的平面Cremona映射

On plane Cremona maps of degree 4 and length 2

本文对次数为4且长度为2的平面Cremona映射在射影平面自同构作用下进行分类，并计算其普通二次长度，证明该长度至多为7且分类达到上界的映射。

四次平面 Cremona 映射的二次长度

On the quadratic length of plane Cremona maps of degree 4

本文研究四次平面 Cremona 映射的二次长度，证明非 de Jonquières 型长度为 2，de Jonquières 型长度为 3、4 或 5，并分类达到上界的映射。

组合Cremona自同构与Coxeter构形拟阵

Combinatorial Cremona automorphisms and Coxeter arrangement matroids

本文通过研究粗Bergman扇的自同构探索拟阵的双有理几何，分析了组合Cremona映射的结构，证明了可实现性判据，并确立了Coxeter构形拟阵的粗自同构群生成定理。

The group of Cremona transformations generated by linear maps and the standard involution

This article studies the group generated by automorphisms of the projective space of dimension $n$ and by the standard birational involution of degree $n$. Every element of this group only contracts rational hypersurfaces, but in odd dimension, there are simple elements having this property which do not belong to the group. Geometric properties of the elements of the group are given, as well as a description of its intersection with monomial transformations.

Cremona maps and involutions

We deal with the following question of Dolgachev : is the Cremona group generated by involutions ? Answer is yes in dimension $2$ (Cerveau-Deserti). We give an upper bound of the minimal number $\mathfrak{n}_φ$ of involutions we need to write a birational self map $φ$ of $\mathbb{P}^2_\mathbb{C}$. We prove that de Jonquières maps of $\mathbb{P}^3_\mathbb{C}$ and maps of small bidegree of $\mathbb{P}^3_\mathbb{C}$ can be written as a composition of involutions of $\mathbb{P}^3_\mathbb{C}$ and give an upper bound of $\mathfrak{n}_φ$ for such maps $φ$. We get similar results in particular for aut…

On the inertia group of elliptic curves in the Cremona group of the plane

We study the group of birational transformations of the plane that fix (each point of) a curve of geometric genus 1. A precise description of the finite elements is given; it is shown in particular that the order is at most 6, and that if the group contains a non-trivial torsion, the fixed curve is the image of a smooth cubic by a birational transformation of the plane. We show that for a smooth cubic, the group is generated by its elements of degree 3, and prove that it contains a free product of Z/2Z, indexed by the points of the curve.

Counting Square free Cremona monomial maps

We use combinatorics tools to reobtain the classification of monomial quadratic Cremona transformations in any number of variables given in \cite{SV2} and to classify and count square free cubic Cremona maps with at most six variables, up to isomorphism.

On degenerations of plane Cremona transformations

This article studies the possible degenerations of plane Cremona transformations of some degree into maps of smaller degree.

Counting square free monomial cremona maps

We give a complete list of square-free Cremona maps with at most six variables, up to equivalence classes. We also build an algorithm to count monomial square-free Cremona transformations. Using this algorithm, we obtain a complete list of monomial square-free Cremona transformations in seven variables.

Gluing determinantal Cremona maps

We study determinantal Cremona maps, i.e. birational maps whose base ideal is the maximal minors ideal of a given matrix $Φ$, via the resolution of the polynomials systems defined by $Φ$. Using convex geometry, this approach leads in particular to describe the projective degrees of some almost linear determinantal maps.

Bijective Cremona transformations of the plane

We study the birational self-maps of the projective plane over finite fields that induce permutations on the set of rational points. As a main result, we prove that no odd permutation arises over a non-prime finite field of characteristic two, which completes the investigation initiated by Cantat about which permutations can be realized this way. Main ingredients in our proof include the invariance of parity under groupoid conjugations by birational maps, and a list of generators for the group of such maps.

Cremona maps defined by monomials

Cremona maps defined by monomials of degree 2 are thoroughly analyzed and classified via integer arithmetic and graph combinatorics. In particular, the structure of the inverse map to such a monomial Cremona map is made very explicit as is the degree of its monomial defining coordinates. As a special case, one proves that any monomial Cremona map of degree 2 has inverse of degree 2 if and only if it is an involution up to permutation in the source and in the target. This statement is subsumed in a recent result of L. Pirio and F. Russo, but the proof is entirely different and holds in all char…

Special cubic birational transformations of projective spaces

We extend our classification of special Cremona transformations whose base locus has dimension at most three to the case when the target space is replaced by a (locally) factorial complete intersection.

Inverses of monomial Cremona maps

We show that monomial Cremona maps of degree d on P^n can have inverses whose degree d' is quite large (for d > 2, d' = ((d-1)^n - 1)/(d-2) occurs), and that the full list of degrees d' does not always form an interval. An easy method for inverting the maps is presented.

New Constructions of Cremona Maps

One defines two ways of constructing rational maps derived from other rational maps, in a characteristic-free context. The first introduces the Newton complementary dual of a rational map. One main result is that this dual preserves birationality and gives an involutional map of the Cremona group to itself that restricts to the monomial Cremona subgroup and preserves de Jonquières maps. In the monomial restriction this duality commutes with taking inverse in the group, but is a not a group homomorphism. The second construction is an iterative process to obtain rational maps in increasing dimen…

On planar Cremona maps of prime order

This paper contains a new proof of the classification of elements of prime order in the Cremona group Bir(P^2), up to conjugation. In addition, we give explicit geometric constructions of these Cremona transformations, and provide a parameterization of their conjugacy classes. Analogous constructions in higher dimensions are also discussed.

二元域上平面Cremona群的生成元

Generators of the plane Cremona group over the field with two elements

本文证明二元域上平面Cremona群由三个无限族及有限个双有理映射生成，并给出各族的参数化生成集及所需映射数上界，最终证明该群由对合生成。

Some remarks about the Zariski topology of the Cremona group

For an algebraic variety $X$ we study the behavior of algebraic morphisms from an algebraic variety to the group $\bir(X)$ of birational maps of $X$ and obtain, as application, some insight about the relationship between the so-called Zariski topology of $\bir(X)$ and the algebraic structure of this group, where $X$ is a rational variety.

Combinatorics of Cremona monomial maps

One studies Cremona monomial maps by combinatorial means. Among the results is a simple integer matrix theoretic proof that the inverse of a Cremona monomial map is also defined by monomials of fixed degree, and moreover, the set of monomials defining the inverse can be obtained explicitly in terms of the initial data. A neat consequence is drawn for the plane Cremona monomial group, in particular the known result saying that a plane Cremona (monomial) map and its inverse have the same degree. Included is a discussion about the computational side and/or implementation of the combinatorial inva…

Quadratic Planar Differential Systems with Algebraic Limit Cycles via Quadratic Plane Cremona Maps

In this paper we show how we can transform quadratic systems into new quadratic systems after some kind of birational transformations, the quadratic plane Cremona maps. We afterwards apply these transformations to the families of quadratic differential systems having an algebraic limit cycle. As a consequence, we provide a new family of quadratic systems having an algebraic limit cycle of degree 5. Moreover we show how the known families of quadratic differential systems having an algebraic limit cycle of degree greater than four are obtained using these transformations. We also provide the ph…

Severi-Brauer曲面的双有理映射及其在高秩Cremona群中的应用

Birational maps of Severi-Brauer surfaces, with applications to Cremona groups of higher rank

本研究通过刻画非平凡Severi-Brauer曲面的双有理变换群性质，推导得出秩≥4的Cremona群的商群结构、生成元性质、Hopfian性质及3-挠元不可数等关键群论结论。

Plane Cremona maps: saturation and regularity of the base ideal

One studies plane Cremona maps by focusing on the ideal theoretic and homological properties of its homogeneous base ideal ("indeterminacy locus"). The {\em leitmotiv} driving a good deal of the work is the relation between the base ideal and its saturation. As a preliminary one deals with the homological features of arbitrary codimension 2 homogeneous ideals in a polynomial ring in three variables over a field which are generated by three forms of the same degree. The results become sharp when the saturation is not generated in low degrees, a condition to be given a precise meaning. An implic…

Plane polar Cremona maps of arbitrarily large degree in positive characteristic

A result of I.V.Dolgachev states that the complex homaloidal polynomials in three variables, i.e. the complex homogeneous polynomials whose polar map is birational, are of degree at most three. In this note we describe homaloidal polynomials in three variables of arbitrarily large degree in positive characteristic. Using combinatorial arguments, we also classify line arrangements whose polar map is homaloidal in positive characteristic.

Simple relations in the Cremona group

We give a simple set of generators and relations for the Cremona group of the plane. Namely, we show that the Cremona group is the amalgamated product of the de Jonquières group with the group of automorphisms of the plane, divided by one relation which is $στ=τσ$, where $τ=(x:y:z)\mapsto (y:x:z)$ and $σ=(x:y:z)\dasharrow (yz:xz:xy)$.

Some properties of the Cremona group

We recall some properties, unfortunately not all, of the Cremona group. We first begin by presenting a nice proof of the amalgamated product structure of the well-known subgroup of the Cremona group made up of the polynomial automorphisms of $\mathbb{C}^2$. Then we deal with the classification of birational maps and some applications (Tits alternative, non-simplicity...) Since any birational map can be written as a composition of quadratic birational maps up to an automorphism of the complex projective plane, we spend time on these special maps. Some questions of group theory are evoked: the c…

A four-dimensional cousin of the Segre cubic

This note is devoted to a special Fano fourfold defined by a four-dimensional space of skew-symmetric forms in five variables. This fourfold appears to be closely related with the classical Segre cubic and its Cremona-Richmond configuration of planes. Among other exceptional properties, it is infinitesimally rigid and has Picard number six. We show how to construct it by blow-up and contraction, starting from a configuration of five planes in a four-dimensional quadric, compatibly with the symmetry group $S_5$. From this construction we are able to describe the Chow ring explicitly.

Length in the Cremona group

The Cremona group is the group of birational transformations of the plane. A birational transformation for which there exists a pencil of lines which is sent onto another pencil of lines is called a Jonquières transformation. By the famous Noether-Castelnuovo theorem, every birational transformation $f$ is a product of Jonquières transformations. The minimal number of factors in such a product will be called the length, and written $\mathrm{lgth}(f)$. Even if this length is rather unpredictable, we provide an explicit algorithm to compute it, which only depends on the multiplicities of the lin…

平面克雷莫纳群的\(p\)-元非循环子群

$p$-elementary non-cyclic subgroups of the Cremona group of the plane

研究平面克雷莫纳群中同构于\((\mathbb{Z}/p\mathbb{Z})^r\)（\(p\)素数，\(r \geq 2\)）的子群，在特定代数闭域上进行共轭分类，给出代表列表和共轭性研究，还给出特征等于\(p\)时的相关结果。

Abel-Jacobi maps associated to smooth cubic threefolds

We pose some questions about spaces parametrizing rational curves on rationally connected varieties. We give a partial answer for cubic threefolds. Many of our results were previously proved by Iliev, Markushevich and Tikhimirov by analyzing vector bundles on cubic threefolds. Our proofs use residuation rather than vector bundles.

On cubic birational maps of $\mathbb{P}^3_\mathbb{C}$

We study the birational maps of $\mathbb{P}^3_\mathbb{C}$. More precisely we describe the irreducible components of the set of birational maps of bidegree $(3,3)$ (resp. $(3,4)$, resp. $(3,5)$).

假设Segre-Harbourne-Gimigliano-Hirschowitz猜想成立的平面线性系统有界性结果

Boundedness Results for Planar Linear Systems Assuming The Segre-Harbourne-Gimigliano-Hirschowitz Conjecture

本文在Segre-Harbourne-Gimigliano-Hirschowitz猜想成立的前提下，研究胀开$n\geq10$个一般点的射影平面上的完全线性系统，完成相关分类并证明有界性等结果。

Classification of cubic homogeneous polynomial maps with Jacobian matrices of rank two

Let $K$ be any field with $\textup{char}K\neq 2,3$. We classify all cubic homogeneous polynomial maps $H$ over $K$ with $\textup{rk} JH\leq 2$. In particular, we show that, for such an $H$, if $F=x+H$ is a Keller map then $F$ is invertible, and furthermore $F$ is tame if the dimension $n\neq 4$.

Arithmetic Torelli maps for cubic surfaces and threefolds

It has long been known that to a complex cubic surface or threefold one can canonically associate a principally polarized abelian variety. We give a construction which works for cubics over an arithmetic base. This answers, away from the prime 2, an old question of Deligne and a recent question of Kudla and Rapoport. We further classify the Mumford-Tate groups of the abelian varieties which arise, and give additional arithmetic applications.

Homaloidal nets and ideals of fat points I

One considers plane Cremona maps with proper base points and the {\em base ideal} generated by the linear system of forms defining the map. The object of this work is the interweave between the algebraic properties of the base ideal and those of the ideal of these points fattened by the virtual multiplicities arising from the linear system. One reveals conditions which naturally regulate this association, with particular emphasis on the homological side. While most classical numerical inequalities concern the three highest virtual multiplicities, here one emphasizes also the role of one single…

随机的birational映射乘积：曲线预像的等分布

Random products of birational maps: Equidistribution of preimages of curves

本文研究了随机birational变换乘积对平面中曲线预像的等分布性质，基于Diller和Roeder最近的工作，探讨了Cremona群在所有平面模型的当前空间逆极限上的作用，并证明了随机有限支持行走的等分布性。

On maps taking lines to plane curves

We study cubic rational maps that take lines to plane curves. A complete description of such cubic rational maps concludes the classification of all planarizations, i.e., maps taking lines to plane curves.

On the hypersurface of Luroth quartics

The hypersurface of Luroth quartic curves inside the projective space of plane quartics has degree 54. We give a proof of this fact along the lines outlined in a paper by Morley, published in 1919. Another proof has been given by Le Potier and Tikhomirov in 2001, in the setting of moduli spaces of vector bundles on the projective plane. Morley's proof uses the description of plane quartics as branch curves of Geiser involutions and gives new geometrical interpretations of the 36 planes associated to the Cremona hexahedral representations of a nonsingular cubic surface.

三次超曲面上的代数环的柱映射

Cylinder maps of algebraic cycles on cubic hypersurfaces

本文证明含一次一维环的光滑三次超曲面的直线簇与超曲面的Chow群柱映射满射，并给出三次四维簇直线簇上积分Hodge猜想的新证明及积分Tate猜想的确认。

某些神秘周期映射的轨形方面

Orbifold Aspects of Certain Occult Period Maps

本文刻画了三次三维簇和四次簇的霍奇结构自同构群，并确定了小维数射影流形自同构群在循环覆盖霍奇结构上的作用，证实了Kudla和Rapoport的猜想。

Hilbert scheme of rational cubic curves via stable maps

The space of smooth rational cubic curves in projective space $\PP^r$ ($r\ge 3$) is a smooth quasi-projective variety, which gives us an open subset of the corresponding Hilbert scheme, the moduli space of stable maps, or the moduli space of stable sheaves. By taking its closure, we obtain three compactifications $\bH$, $\bM$, and $\bS$ respectively. In this paper, we compare these compactifications. First, we prove that $\bH$ is the blow-up of $\bS$ along a smooth subvariety which is the locus of stable sheaves which are planar (i.e. support is contained in a plane). Next we prove that $\bS$ …

三维空间中某些双有理映射的增长与可积性

Growth and integrability of some birational maps in dimension three

本文研究复射影三维空间中标准 Cremona 变换与置换其特殊点的射影变换复合所得映射，刻画其三类次数增长、周期性、可积性及不变量特征。

On birational maps from cubic threefolds

We characterise smooth curves in a smooth cubic threefold whose blow-ups produce a weak-Fano threefold. These are curves $C$ of genus $g$ and degree $d$, such that (i) $2(d-5) \le g$ and $d\le 6$; (ii) $C$ does not admit a 3-secant line in the cubic threefold. Among the list of ten possible such types $(g,d)$, two were previously left as open numerical possibilities, namely $(g,d) = (0,5)$ and $(2,6)$. Using the Sarkisov link associated with a curve of type $(2,6)$, we are able to produce the first example of a pseudo-automorphism with dynamical degree greater than $1$ on a smooth threefold wi…

Enumeration of rational plane curves tangent to a smooth cubic

We use twisted stable maps to compute the number of rational degree d plane curves having prescribed contacts to a smooth plane cubic.

Degree growth of birational maps of the plane

This article studies the sequence of iterative degrees of a birational map of the plane. This sequence is known either to be bounded or to have a linear, quadratic or exponential growth. The classification elements of infinite order with a bounded sequence of degrees is achieved, the case of elements of finite order being already known. The coefficients of the linear and quadratic growth are then described, and related to geometrical properties of the map. The dynamical number of base-points is also studied. Applications of our results are the description of embeddings of the Baumslag-Solitar …

Computing Moment Maps of Hypersurfaces using MAXIMA

We use Maxima to compute the moment matrices of hypersurfaces. After that, we compute the Hilbert-Mumford numerical criterion for plane cubics and plane quartics, and give the stability of these curves.

On occult period maps

We consider the "occult" period maps into ball quotients which exist for the moduli spaces of cubic surfaces, cubic threefolds, non-hyperelliptic curves of genus three and four. These were constructed in the work of Allcock/Carlson/Toledo, Looijenga/Swierstra, and Kondo. We interpret these maps as morphisms into moduli spaces of polarized abelian varieties of Picard type, and show that these morphisms, whose initial construction is transcendental, are defined over the natural field of definition of the spaces involved. This paper is extracted from section 15 of our paper arXiv:0912.3758, and d…