arXiv subjects

Jin-Xing Cai

Publications and source records attributed to Jin-Xing Cai.

5 recordsLinked to original sources

arXiv2024

On regular surfaces of general type with numerically trivial automorphism group of order $4$

Let $S$ be a regular minimal surface of general type over the field of complex numbers, and $\mathrm{Aut}_\mathbb{Q}(S)$ the subgroup of automorphisms acting trivially on $H^*(S,\mathbb{Q})$. It has been known since twenty years that $|\mathrm{Aut}_\mathbb{Q}(S)|\leq 4$ if the invariants of $S$ are sufficiently large. Under the assumption that $K_S$ is ample, we characterize the surfaces achieving the equality, showing that they are isogenous to a product of two curves, of unmixed type, and that the group $\mathrm{Aut}_\mathbb{Q}(S)$ is isomorphic to $(\mathbb{Z}/2\mathbb{Z})^2$. Moreover, unbounded families of surfaces with $\mathrm{Aut}_\mathbb{Q}(S)\cong(\mathbb{Z}/2\mathbb{Z})^2$ are provided.

math.AG↗

arXiv2017

Automorphisms of surfaces of general type with q=1 acting trivially in cohomology

Let S be a complex minimal surface of general type with irregularity q(S)=1 and Aut_0(S) the subgroup of automorphisms acting trivially on the cohomology ring with rational coefficients. In this paper we show that |Aut_0(S)|<=4, and if the equality holds then $S$ is a surface isogenous to a product of unmixed type. Moreover, examples of surfaces with |Aut_0(S)|=4 and all possible values of the geometric genus are provided.

math.AG↗

arXiv2012

Automorphisms of surfaces of general type with q>=2 acting trivially in cohomology

A compact complex manifold X is said to be rationally cohomologically rigidified if its automorphism group Aut(X) acts faithfully on the cohomology ring H*(X,Q). In this note, we prove that, surfaces of general type with irregularity q>2 are rationally cohomologically rigidified, and so are minimal surfaces S with q=2 unless K^2=8X. This answers a question of Fabrizio Catanese in part. As examples we give a complete classification of surfaces isogenous to a product with q=2 that are not rationally cohomologically rigidified. These surfaces turn out however to be rigidified.

math.AG↗

arXiv2003

Irregular manifolds with a canonical linear system, composite with a pencil

Let X be a complex projective n-dimensional manifold of general type, whose canonical system is composite with a pencil. If the Albanese map is generically finite, but not surjective, or if the irregularity is strictly larger than n and the image of X in its Albanese variety of Kodaira dimension one, then the geometric genus of a general fibre of the canonical map is one and the latter factors through the Albanese map. The last part of this result holds true for any threefold with irregularity 5 or larger.

math.AG↗

arXiv1995

Abelian automorphism groups of threefolds of general type

This thesis is devoted to the study of abelian automorphism groups of surfaces and $3$-folds of general type over complex number field $\Bbb C$. We obtain a linear bound in $K^3$ for abelian automorphism groups of $3$-folds of general type whose canonical divisor $K$ is numerically effective, and we improve on Xiao's results on abelian automorphism groups of minimal smooth projective surfaces of general type. More precisely, the main results in this thesis are the following. {\bf Theorem 3.0.} Let $X$ be a smooth 3-fold of general type over the complex number field, $K$ the canonical divisor of $X$. Let $G$ be an abelian group of automorphisms of $X$. Suppose $K$ is nef. Then there exists a universal constant coefficient $c$ such that $\# G \le c K^3$.

alg-geom↗