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In this paper, we study the cylindricity of $\Bbbk$-forms of singular del Pezzo surfaces obtained by blowing up weighted projective planes $\mathbb{P}(1,1,m)$ over an arbitrary field $\Bbbk$ of characteristic zero. As an application, we…

Algebraic Geometry · Mathematics 2026-03-31 In-Kyun Kim , Dae-Won Lee , Masatomo Sawahara

Let $\pi: X \to Y$ be a morphism of projective varieties and suppose that $\alpha$ is a pseudo-effective numerical cycle class satisfying $\pi_*\alpha = 0$. A conjecture of Debarre, Jiang, and Voisin predicts that $\alpha$ is a limit of…

Algebraic Geometry · Mathematics 2017-05-17 Mihai Fulger , Brian Lehmann

Contents: Rational functions with given monodromy on generic curves (I. Bouw & S. Wewers); Can deformation rings of group representations not be local complete intersections? (T. Chinburg); Lifting an automorphism group to finite…

Algebraic Geometry · Mathematics 2007-05-23 I. Bouw , T. Chinburg , G. Cornelissen , C. Gasbarri , D. Glass , C. Lehr , M. Matignon , F. Oort , R. Pries , S. Wewers

This article investigates the torsion homology behaviour in towers of Oeljeklaus-Toma (OT) manifolds. This adapts an idea of Silver and Williams from knot theory to OT-manifolds and extends it to higher degree homology groups. In the case…

Differential Geometry · Mathematics 2025-10-10 Dung Phuong Phan , Tuan Anh Bui , Alexander D. Rahm

In this paper, we prove that for any smooth hypersurface $Y$ of degree $d$ in $\mathbb{P}^{n+1}_k$, the cyclic $d$-fold cover $\widetilde{Y} \to \mathbb{P}^{n+1}_k$ branched along $Y$ completely characterizes $Y$ up to projective…

Algebraic Geometry · Mathematics 2025-10-28 Zhiyuan Li , Zhichao Tang

In this article we show that all cyclic branched covers of a Seifert link have left-orderable fundamental groups, and therefore admit co-oriented taut foliations and are not $L$-spaces, if and only if it is not an $ADE$ link up to…

Geometric Topology · Mathematics 2024-02-27 Steven Boyer , Cameron McA. Gordon , Ying Hu

In this paper we develop methods to extend the minimal hypersurface approach to positive scalar curvature problems to all dimensions. This includes a proof of the positive mass theorem in all dimensions without a spin assumption. It also…

Differential Geometry · Mathematics 2017-04-20 Richard Schoen , Shing-Tung Yau

We present the construction of canonical lifts of $\ell$-adic cycle classes of sections of $p$-adic projective anabelian curves to the cohomology of arbitrary proper, regular, flat models. This answers a question of Esnault and Wittenberg.

Algebraic Geometry · Mathematics 2017-06-07 Johannes Schmidt

According to a result of Kocinac and Scheepers, the Hurewicz covering property is equivalent to a somewhat simpler selection property: For each sequence of large open covers of the space one can choose finitely many elements from each cover…

General Topology · Mathematics 2010-11-02 Boaz Tsaban

We derive a closed-form expression for all genus 1 Hurwitz numbers, and give a simple new graph-theoretic interpretation of Hurwitz numbers in genus 0 and 1. (Hurwitz numbers essentially count irreducible genus g covers of the sphere, with…

Combinatorics · Mathematics 2007-05-23 Ravi Vakil

The descent method is one of the approaches to study the Brauer--Manin obstruction to the local--global principle and to weak approximation on varieties over number fields, by reducing the problem to ``descent varieties''. In recent lecture…

Algebraic Geometry · Mathematics 2026-01-21 Nguyen Manh Linh

Finite covers are a technique for building new structures from simpler ones. The original motivation to study finite covers is in the Ladder theorem of Zilber which describes how totally categorical structures are built from strictly…

Logic · Mathematics 2007-06-13 Elisabetta Pastori

In the context of a tower of (strongly Birkhoff) Galois structures in the sense of categorical Galois theory, we show that the concept of a higher covering admits a characterisation which is at the same time absolute (with respect to the…

Category Theory · Mathematics 2023-07-26 Fara Renaud , Tim Van der Linden

Let k be a number field, p$\ge$2 a prime and S a set of tame or wild finite places of k. We call K/k a totally S-ramified cyclic p-tower if Gal(K/k)=Z/p^NZ and if S non-empty is totally ramified. Using analogues of Chevalley's formula…

Number Theory · Mathematics 2022-08-05 Georges Gras

In this article, we aim to largely complete the program of proving the Tate conjecture for surfaces of geometric genus one, by introducing techniques to analyze those surfaces whose "natural models" are singular. As an application, we show…

Algebraic Geometry · Mathematics 2025-06-12 Haoyang Guo , Ziquan Yang

Recently a simple proof of the generalizations of Hawking's black hole topology theorem and its application to topological black holes for higher dimensional ($n\geq 4$) spacetimes was given \cite{rnew}. By applying the associated new line…

General Relativity and Quantum Cosmology · Physics 2010-06-29 István Rácz

We show that any compact surface of genus zero in Euclidean 3-space that satisfies a quasiconformal inequality between its principal curvatures is a round sphere. This solves an old open problem by H. Hopf, and gives a spherical version of…

Differential Geometry · Mathematics 2021-03-24 Jose A. Galvez , Pablo Mira , Marcos P. Tassi

We prove that any compact surface with constant positive curvature and conical singularities can be decomposed into irreducible components of standard shape, glued along geodesic arcs connecting conical singularities. This is a spherical…

Geometric Topology · Mathematics 2022-01-05 Guillaume Tahar

I consider the class of surfaces $X$ over algebraically closed fields with numerical invariants given in the title. In characteristic zero, this class contains fake projective planes which were introduced by David Mumford. I prove that in…

Algebraic Geometry · Mathematics 2025-08-19 Kirti Joshi

Let $k$ be a field of arbitrary characteristic. Let $S$ be a singular surface defined over $k$ with multiple rational curve singularities and suppose that the Chow group of zero cycles of its normalisation $\tilde{S}$ is finite dimensional.…

Algebraic Geometry · Mathematics 2007-05-23 G V Ravindra