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We examine homogeneous metrics on spheres and determine which ones have positive sectional curvature. The answer is subtle and surprisingly difficult to prove. In some cases we also determine their pinching constants. This completes the…

Differential Geometry · Mathematics 2009-09-29 Luigi Verdiani , Wolfgang Ziller

In a 2013 paper, Gromov proves that if smooth Riemannian metrics $g_i$ converge to a smooth Riemannian metric $g$ uniformly, and $g_i$ have scalar curvature uniformly bounded below, then $g$ shares the same scalar curvature lower bound. In…

Differential Geometry · Mathematics 2018-10-04 Haggai Nuchi

In this paper, we introduce and develop the circle embedding method. This method hinges essentially on a combinatorial-geometric structure which we choose to call circles of partition. We provide applications in the context of problems that…

General Mathematics · Mathematics 2026-04-21 Theophilus Agama , Berndt Gensel

Let $X$ be a compact Riemann surface of genus $g$ and let $x \in X$. We derive the classical presentation of $\pi_1(X,x)$ (i.e the one given by $2g$ generators $a_1,b_1, \dots, a_g,b_g$ and the relation $\prod_{i=1}^g[a_i,b_i] = 1$) from…

Algebraic Topology · Mathematics 2025-02-28 Meirav Amram , Michael Chitayat , Yaacov Kopeliovich

In this article we consider compact Riemann surfaces that are uniquely determined by the property of possessing a group of automorphisms of a prescribed order, strengthening uniqueness results proved by Nakagawa. More precisely, we deal…

Algebraic Geometry · Mathematics 2025-02-03 Sebastián Reyes-Carocca , Pietro Speziali

The natural automorphism group of a translation surface is its group of translations. For finite translation surfaces of genus g > 1 the order of this group is naturally bounded in terms of g due to a Riemann-Hurwitz formula argument. In…

Geometric Topology · Mathematics 2013-12-02 Jan-Christoph Schlage-Puchta , Gabriela Weitze-Schmithuesen

We study the K\"ahler geometry of the classical Hurwitz space $\mathcal{H}^{n,b}$ of simple branched coverings of the Riemann sphere $\mathbb{P}^1$ by compact hyperbolic Riemann surfaces. A generalized Weil-Petersson metric on the Hurwitz…

Complex Variables · Mathematics 2016-12-08 Philipp Naumann

It is one of the wonderful ``coincidences'' of the theory of finite groups that the simple group G of order 25920 arises as both a symplectic group in characteristic 3 and a unitary group in characteristic 2. These two realizations of G…

Algebraic Geometry · Mathematics 2007-05-23 Noam D. Elkies

In this paper, I shall demonstrate that sufficiently high-dimensional closed positively-curved Riemannian manifolds are either diffeomorphic to a spherical space form, or isometric to a locally compact rank one symmetric space. This…

Metric Geometry · Mathematics 2016-08-05 Yashar Memarian

We prove the refined Loughran--Smeets conjecture of Loughran--Rome--Sofos for a wide class of varieties arising as products of conic bundles. One interesting feature of our varieties is that the subordinate Brauer group may be arbitrarily…

Number Theory · Mathematics 2025-05-01 Stephanie Chan , Peter Koymans , Nick Rome

We show that every degree $d$ meromorphic function on a smooth connected projective curve $C\subset \mathbb P^2$ of degree $d>4$ is isomorphic to a linear projection from a point $p\in \mathbb {P}^2 \setminus C$ to $\mathbb P^1$. We then…

Algebraic Geometry · Mathematics 2019-03-28 Jared Ongaro

In this work we establish a necessary and sufficient condition for a genus $0$ entire function $f(z)$ has only positive zeros by applying Hausdorff moment problem and Mergelyan's theorem, the obtained criterion is very much reminiscent of…

Classical Analysis and ODEs · Mathematics 2016-02-23 Ruiming Zhang

The Borel-Weil-Bott theorem can be used to decompose the cohomology of twisted sheaves of holomorphic forms on the complex Grassmannian into irreducible representations of the general linear group. By analyzing this decomposition, we…

Combinatorics · Mathematics 2026-05-11 Fern Gossow , Andrew Huchala

We consider the sub-Riemannian $3$-sphere $(\mathbb{S}^3,g_h)$ obtained by restriction of the Riemannian metric of constant curvature $1$ to the planar distribution orthogonal to the vertical Hopf vector field. It is known that…

Differential Geometry · Mathematics 2021-06-11 Ana Hurtado , César Rosales

The Maroni stratification on the Hurwitz space of degree $d$ covers of genus $g$ has a stratum that is a divisor only if $d-1$ divides $g$. Here we construct a stratification on the Hurwitz space that is analogous to the Maroni…

Algebraic Geometry · Mathematics 2015-10-27 Gerard van der Geer , Alexis Kouvidakis

In this work we study an inverse problem for the minimal surface equation on a Riemannian manifold $(\mathbb{R}^{n},g)$ where the metric is of the form $g(x)=c(x)(\hat{g}\oplus e)$. Here $\hat{g}$ is a simple Riemannian metric on…

Analysis of PDEs · Mathematics 2023-09-20 Janne Nurminen

The Euclidean cone metrics coming from q-differentials on a closed surface of genus g > 1 define an equivalence relation on homotopy classes of closed curves declaring two to be equivalent if they have the equal length in every such metric.…

Geometric Topology · Mathematics 2014-11-26 Anja Bankovic

We partly extend the localisation technique from convex geometry to the multiple constraints setting. For a given $1$-Lipschitz map $u\colon\mathbb{R}^n\to\mathbb{R}^m$, $m\leq n$, we define and prove the existence of a partition of…

Metric Geometry · Mathematics 2021-08-17 Krzysztof J. Ciosmak

We show that $b$-Hurwitz numbers with a rational weight are obtained by taking an explicit limit of a Whittaker vector for the $\mathcal{W}$-algebra of type $A$. Our result is a vast generalization of several previous results that treated…

Algebraic Geometry · Mathematics 2026-04-16 Nitin K. Chidambaram , Maciej Dołęga , Kento Osuga

We consider the Laguerre partition function, and derive explicit generating functions for connected correlators with arbitrary integer powers of traces in terms of products of Hahn polynomials. It was recently proven that correlators have a…

Mathematical Physics · Physics 2021-08-27 Massimo Gisonni , Tamara Grava , Giulio Ruzza