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We classify del Pezzo surfaces with Du Val singularities that have infinite automorphism groups, and describe the connected components of their automorphisms groups.

Algebraic Geometry · Mathematics 2020-10-02 Ivan Cheltsov , Yuri Prokhorov

It is known that an automorphism group of a K3 surface with Picard number two is either infinite cyclic group or infinite dihedral group if it is infinite. In this paper, we study the generators of an automorphism group. We use the…

Algebraic Geometry · Mathematics 2022-10-25 Kwangwoo Lee

This paper proves two results on the field of rationality $\Q(\pi)$ for an automorphic representation $\pi$, which is the subfield of $\C$ fixed under the subgroup of $\Aut(\C)$ stabilizing the isomorphism class of the finite part of $\pi$.…

Number Theory · Mathematics 2019-02-20 Sug Woo Shin , Nicolas Templier

In this paper we prove criteria for a nonnormal toric variety to be flexible, to be rigid and to be almost rigid. For rigid and almost rigid toric varieties we describe the automorphism group explicitly.

Algebraic Geometry · Mathematics 2020-12-08 Ilya Boldyrev , Sergey Gaifullin

We classify finite groups acting by birational transformations of a non-trivial Severi--Brauer surface over a field of characteristc zero that are not conjugate to subgroups of the automorphism group. Also, we show that the automorphism…

Algebraic Geometry · Mathematics 2020-07-02 Constantin Shramov

We give more details to our examples in [9] of K3 surfaces over C such that they have infinite automorphism group but it preserves some elliptic pencil of the K3

Algebraic Geometry · Mathematics 2020-06-09 Viacheslav V. Nikulin

The purpose of this article is to study Lipschitz CR mappings from an $h$-extendible (or semi-regular) hypersurface in $\mbb C^n$. Under various assumptions on the target hypersurface, it is shown that such mappings must be smooth. A…

Complex Variables · Mathematics 2011-02-15 G. P. Balakumar , Kaushal Verma

We classify all possible automorphism groups of smooth cubic surfaces over an algebraically closed field of arbitrary characteristic. As an intermediate step we also classify automorphism groups of quartic del Pezzo surfaces. We show that…

Algebraic Geometry · Mathematics 2018-10-15 Igor Dolgachev , Alexander Duncan

We consider hypersurfaces of finite type in a direct product space ${\mathbb R}^2 \times {\mathbb R}^2$, which are analogues to real hypersurfaces of finite type in ${\mathbb C}^2$. We shall consider separately the cases where such…

Complex Variables · Mathematics 2016-11-24 Alessandro Ottazzi , Gerd Schmalz

We study the infinitesimal rigidity of equivariant minimal maps from the universal cover of a smooth oriented surface (possibly non-compact) into a Riemannian symmetric space, focusing on representations arising from cyclic harmonic…

Differential Geometry · Mathematics 2026-05-12 Qiongling Li , Junming Zhang

Let $X$ be an arbitrary complex surface and $D \subset X$ a domain that has a non compact group of holomorphic automorphisms. A characterization of those domains $D$ that admit a smooth real analytic, finite type boundary orbit accumulation…

Complex Variables · Mathematics 2011-10-19 Kaushal Verma

One of the consequences of residual finiteness of triangle groups is that for any given hyperbolic triple $(\ell,m,n)$ there exist infinitely many regular hypermaps of type $(\ell,m,n)$ on compact orientable surfaces. The same conclusion…

Group Theory · Mathematics 2025-08-15 Gareth A. Jones , Martin Mačaj , Jozef Širáň

We define and study analogs of curve graphs for infinite type surfaces. Our definitions use the geometry of a fixed surface and vertices of our graphs are infinite multicurves which are bounded in both a geometric and a topological sense.…

Geometric Topology · Mathematics 2014-10-14 Ariadna Fossas , Hugo Parlier

We explicitly determine the structure equations of 5-dimensional Levi 2-nondegenerate CR hypersurfaces, using our recently constructed canonical Cartan connection for this class of CR manifolds. We also give an outline of the basic…

Differential Geometry · Mathematics 2016-03-31 Costantino Medori , Andrea Spiro

In this paper, we prove the infinite dimensionality of some local and global cohomology groups on abstract Cauchy-Riemann manifolds.

Complex Variables · Mathematics 2018-07-25 Judith Brinkschulte , C. Denson Hill , Mauro Nacinovich

A local description of the non-flat infinitesimally bendable Euclidean hypersurfaces was recently given by Dajczer and Vlachos \cite{DaVl}. From their classification, it follows that there is an abundance of infinitesimally bendable…

Differential Geometry · Mathematics 2017-06-30 Miguel Ibieta Jimenez

In this paper, we discuss germs of smooth hypersurface in $\mathbb C^n$. We show that if a point on the boundary has infinite D'Angelo type, then there exists a formal complex curve in the hypersurface through that point.

Complex Variables · Mathematics 2009-11-13 John Erik Fornaess , Lina Lee , Yuan Zhang

We consider plane curves isomorphic to C*. We prove that with one exception the branches at infinity can be separated by an automorphism of C^2. We also give a bound for selfintersection number of the resolution curve.

Algebraic Geometry · Mathematics 2012-02-22 Mariusz Koras , Peter Russell

We prove the infinitesimal rigidity of some geometrically infinite hyperbolic 4- and 5-manifolds. These examples arise as infinite cyclic coverings of finite-volume hyperbolic manifolds obtained by colouring right-angled polytopes, already…

Geometric Topology · Mathematics 2023-01-19 Ludovico Battista

We investigate the action of the automorphism group of a closed Riemann surface on its set of theta characteristics (or spin structures). We give criteria for when an automorphism fixes all spin structures, or when it fixes just one. The…

Geometric Topology · Mathematics 2007-05-23 Sadok Kallel , Denis Sjerve