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We realize the logarithm of the third smallest known Salem number as the topological entropy of a K3 surface automorphism with a Siegel disk and a pointwisely fixed curve at the same time. We also show the logarithm of the Lehmer number,…

Algebraic Geometry · Mathematics 2009-05-15 Keiji Oguiso

We construct examples of hyperKahler manifolds of Picard number two with automorphisms of positive entropy via derived automorphisms of K3 surfaces of Picard number one. Our hyperKahler manifolds are constructed as moduli spaces of…

Algebraic Geometry · Mathematics 2016-08-22 Genki Ouchi

We derive a characterization of the complex projective K3 surfaces which have automorphisms of positive entropy in term of their N\'eron-Severi lattices. Along the way, we classify the projective K3 surfaces of zero entropy with infinite…

Algebraic Geometry · Mathematics 2022-11-15 Xun Yu

We classify all the K3 surfaces which are minimal models of the quotient of the product of two curves $C_1\times C_2$ by the diagonal action of either the group $\Z/p\Z$ or the group $\Z/2p\Z$. These K3 surfaces admit a non-symplectic…

Algebraic Geometry · Mathematics 2013-03-08 Alice Garbagnati , Matteo Penegini

Given $X$ a K3 surface admitting a symplectic automorphism $\tau$ of order 4, we describe the isometry $\tau^*$ on $H^2(X,\mathbb Z)$. Having called $\tilde Z$ and $\tilde Y$ respectively the minimal resolutions of the quotient surfaces…

Algebraic Geometry · Mathematics 2022-08-04 Benedetta Piroddi

We give an alternative proof of a result of Cantat and Dupont, showing that any automorphism of a K3 surface with measure of maximal entropy in the Lebesgue class must be a Kummer example. Our method exploits the existence of Ricci-flat…

Dynamical Systems · Mathematics 2021-11-09 Simion Filip , Valentino Tosatti

Derived equivalences of twisted K3 surfaces induce twisted Hodge isometries between them; that is, isomorphisms of their cohomologies which respect certain natural lattice structures and Hodge structures. We prove a criterion for when a…

Algebraic Geometry · Mathematics 2019-06-05 Emanuel Reinecke

We derive explicit equations for the Oguiso-Yu automorphism of minimum topological entropy on a complex Enriques surface. The approach is computer aided and makes use of elliptic fibrations.

Algebraic Geometry · Mathematics 2025-04-08 Simon Brandhorst , Matthias Zach

We give a complete classification of finite subgroups of automorphisms of K3 surfaces up to deformation. The classification is in terms of Hodge theoretic data associated to certain conjugacy classes of finite subgroups of the orthogonal…

Algebraic Geometry · Mathematics 2023-03-27 Simon Brandhorst , Tommy Hofmann

We prove gap theorems for entropy norms on automorphism groups of K3 surfaces, Enriques surfaces, and irreducible holomorphic symplectic manifolds. We also study the achirality of automorphisms of K3 surfaces and Enriques surfaces in terms…

Algebraic Geometry · Mathematics 2026-04-17 Kohei Kikuta , Yuta Takada , Taiki Takatsu

This article describes an example of a real projective K3 surface admitting a real automorphism $f$ satisfying $h_{top}(f, X(\mathbb{C})) < 2 h_{top}(f, X(\mathbb{R}))$. The example presented is a $(2,2,2)$-surface in $\mathbb{P}^1 \times…

Dynamical Systems · Mathematics 2025-06-05 Ethan Cohen

In this article we give a strategy to decide whether the logarithm of a given Salem number is realized as entropy of an automorphism of a supersingular K3 surface in positive characteristic. As test case it is proved that $\log \lambda_d$,…

Algebraic Geometry · Mathematics 2020-10-09 Simon Brandhorst , Víctor González-Alonso

Let X be a complex algebraic K3 surface or a supersingular K3 surface in odd characteristic. We present an algorithm by which, under certain assumptions on X, we can calculate a finite set of generators of the image of the natural…

Algebraic Geometry · Mathematics 2015-02-10 Ichiro Shimada

We consider K3 surfaces of Picard rank 14 which admit a purely nonsymplectic automorphism of order 16. The automorphism acts on the second cohomology group with integer coefficients and we compute the invariant sublattice for the action. We…

Algebraic Geometry · Mathematics 2021-03-04 Paola Comparin , Nathan Priddis , Alessandra Sarti

Using the theory of holes of the Leech lattice and Borcherds method for the computation of the automorphism group of a K3 surface, we give an effective bound for the set of isomorphism classes of projective models of fixed degree for…

Algebraic Geometry · Mathematics 2016-07-11 Ichiro Shimada

Consider an arbitrary automorphism of an Enriques surface with its lift to the covering K3 surface. We prove a bound of the order of the lift acting on the anti-invariant cohomology sublattice of the Enriques involution. We use it to obtain…

Algebraic Geometry · Mathematics 2018-12-11 Yuya Matsumoto , Hisanori Ohashi , Sławomir Rams

We prove that there is a projective K3 surface admitting a (fixed point) free automorphism of positive entropy and that no smooth compact K\"ahler surface other than projective K3 surfaces and their blow up admits such an automorphism.

Algebraic Geometry · Mathematics 2012-07-02 Keiji Oguiso

A complex compact surface which carries an automorphism of positive topological entropy has been proved by Cantat to be either a torus, a K3 surface, an Enriques surface or a rational surface. Automorphisms of rational surfaces are quite…

Algebraic Geometry · Mathematics 2015-09-02 Julie Déserti , Julien Grivaux

A complex compact surface which carries an automorphism of positive topological entropy has been proved by Cantat to be a torus, a K3 surface, an Enriques surface or a non-minimal rational surface. We deal with results obtained in this last…

Algebraic Geometry · Mathematics 2015-03-17 Julie Déserti

Using elliptic structures, we show that any supersingular K3 surface of Artin invariant $1$ in characteristic $p \not= 5$, $7$, $13$ has an automorphism the entropy of which is the natural logarithm of a Salem number of degree $22$.

Algebraic Geometry · Mathematics 2014-11-18 Hélène Esnault , Keiji Oguiso , Xun Yu
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