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We prove that under certain combinatorial conditions, the realization spaces of line arrangements on the complex projective plane are connected. We also give several examples of arrangements with eight, nine and ten lines which have…

Algebraic Geometry · Mathematics 2011-05-18 Shaheen Nazir , Masahiko Yoshinaga

In this article we address the length of perverse sheaves arising as direct images of rank one local systems on complements of hyperplane arrangements. In the case of a cone over an essential line arrangement with at most triple points, we…

Algebraic Topology · Mathematics 2019-09-10 Nero Budur , Yongqiang Liu

We treat threefolds with divisorial contractions whose exceptional divisors contract to compound Du Val points. We prove that general elements in their anticanonical systems around the exceptional divisors have at worst Du Val…

Algebraic Geometry · Mathematics 2007-05-23 Masayuki Kawakita

In this article we prove in main Theorem A that any infinity type real hyperplane arrangement $\mathcal{H}_n^m$ (Definition 2.11) with the associated normal system $\mathcal{N}$ (Definitions [2.2,2.4] can be represented isomorphically…

Combinatorics · Mathematics 2026-01-21 C. P. Anil Kumar

We compute the fundamental groups of the complements of the family of real conic-line arrangements with up to two conics which are tangent to each other at two points, with an arbitrary number of tangent lines to both conics. All the…

Geometric Topology · Mathematics 2007-09-17 Meirav Amram , David Garber , Mina Teicher

We investigate several hyperplane arrangements that can be viewed as deformations of Coxeter arrangements. In particular, we prove a conjecture of Linial and Stanley that the number of regions of the arrangement x_i - x_j = 1, 1 \leq i<j…

Combinatorics · Mathematics 2007-05-23 Alexander Postnikov , Richard P. Stanley

The SHGH conjecture proposes a solution to the question of how many conditions a general union of fat points imposes on the complete linear system of curves in $\mathbb P^2$ of fixed degree $d$, and it is known to be true in many cases. We…

Algebraic Geometry · Mathematics 2019-02-20 David Cook , Brian Harbourne , Juan Migliore , Uwe Nagel

We investigate point arrangements $v_i\in\mathbb R^d,i\in \{1,...,n \}$ with certain prescribed symmetries. The arrangement space of $v$ is the column span of the matrix in which the $v_i$ are the rows. We characterize properties of $v$ in…

Metric Geometry · Mathematics 2021-03-02 Martin Winter

A closed convex subset of a normed linear space is said to have the strong separation property if it can be strongly separated from every other disjoint closed and convex set by a closed hyperplane. In this paper we give some results on the…

Optimization and Control · Mathematics 2020-03-26 Phung Huynh The

Given a real finite hyperplane arrangement A and a point p not on any of the hyperplanes, we define an arrangement vo(A,p), called the *valid order arrangement*, whose regions correspond to the different orders in which a line through p can…

Combinatorics · Mathematics 2013-06-11 Richard P. Stanley

The fundamental group of the complement of a plane curve is a very important topological invariant. In particular, it is interesting to find out whether this group is determined by the combinatorics of the curve or not, and whether it is a…

Geometric Topology · Mathematics 2013-04-30 Michael Friedman , David Garber

A linear system of plane curves satisfying multiplicity conditions at points in general position is called special if the dimension is larger than the expected dimension. A (-1) curve is an irreducible curve with self intersection -1 and…

Algebraic Geometry · Mathematics 2007-05-23 James Seibert

We study linear series on a general curve of genus $g$, whose images are exceptional with regard to their secant planes. Working in the framework of an extension of Brill-Noether theory to pairs of linear series, we prove that a general…

Algebraic Geometry · Mathematics 2010-04-05 Ethan Cotterill

This article focuses on a combinatorial structure specific to triangulated plane graphs with quadrangular outer face and no separating triangle, which are called irreducible triangulations. The structure has been introduced by Xin He under…

Combinatorics · Mathematics 2008-02-07 Eric Fusy

Observing a linear superposition principle, a family of new minimal hypersurfaces in Euclidean space is found, as well as that linear combinations of generalized helicoids induce new algebraic minimal cones of arbitrarily high degree.

Differential Geometry · Mathematics 2016-06-30 Jens Hoppe

We study divergence and thickness for general Coxeter groups $W$. We first characterise linear divergence, and show that if $W$ has superlinear divergence then its divergence is at least quadratic. We then formulate a computable…

Group Theory · Mathematics 2026-04-16 Pallavi Dani , Yusra Naqvi , Ignat Soroko , Anne Thomas

We show that there are only finitely many combinatorial types of free real line arrangements with only double, triple and quadruple intersection points, and we enlist all admissible weak-combinatorics of them. Then we classify all real…

Algebraic Geometry · Mathematics 2025-10-01 Marek Janasz , Izabela Leśniak

We present a complete computational classification of the combinatorial types of hyperplane sections, or slices, of the regular cube up to dimension six. For each dimension, we determine the exact number of distinct combinatorial types.…

Combinatorics · Mathematics 2025-10-13 Marie-Charlotte Brandenburg , Chiara Meroni

Hetyei introduced in 2019 the homogenized Linial arrangement and showed that its regions are counted by the median Genocchi numbers. In the course of devising a different proof of Hetyei's result, Lazar and Wachs considered another…

Combinatorics · Mathematics 2025-10-16 Quan Yuan , Qi Fang , Shishuo Fu , Haijun Li

Let $\mathcal{A}$ be a real line arrangement and $\mathcal{D}(\mathcal{A})$ the module of $\mathcal{A}$-derivations view as the set of polynomial vector fields which possess $\mathcal{A}$ as an invariant set. We first characterize…

Dynamical Systems · Mathematics 2015-04-23 Benoît Guerville-Ballé , Juan Viu-Sos