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In the present paper, we study conic-line arrangements having nodes, tacnodes, and ordinary triple points as singularities. We provide combinatorial constraints on such arrangements and we give the complete classification of free…

Algebraic Geometry · Mathematics 2022-08-16 Alexandru Dimca , Piotr Pokora

We provide a classification result on nearly free arrangements of lines in the complex projective plane with nodes and triple points.

Algebraic Geometry · Mathematics 2022-02-01 Jakub Kabat

In this paper we study plus-one generated arrangements of conics and lines in the complex projective plane with simple singularities. We provide several degree-wise classification results that allow us to construct explicit examples of such…

Algebraic Geometry · Mathematics 2025-07-11 Anca Măcinic , Piotr Pokora

In the present note we study combinatorial and algebraic properties of cubic-line arrangements in the complex projective plane admitting nodes, ordinary triple and $A_{5}$ singular points. We deliver a Hirzebruch-type inequality for such…

Algebraic Geometry · Mathematics 2024-03-27 Przemysław Talar

The main purpose of the present paper is to provide a partial classification, performed with respect the weak-combinatorics, of free arrangements consisting of lines and one smooth conic with quasi-homogeneous ordinary singularities.

Algebraic Geometry · Mathematics 2025-12-19 Piotr Pokora

In this paper, we examine the combinatorial properties of conic arrangements in the complex projective plane that possess certain quasi-homogeneous singularities. First, we introduce a new tool that enables us to characterize the property…

Algebraic Geometry · Mathematics 2026-02-04 Artur Bromboszcz , Bartosz Jarosławski , Piotr Pokora

We study the geometry of $\mathcal{Q}$-conic arrangements in the complex projective plane. These are arrangements consisting of smooth conics and they admit certain quasi-homogeneous singularities. We show that such $\mathcal{Q}$-conic…

Algebraic Geometry · Mathematics 2023-04-24 Piotr Pokora

In the present note we provide a partial classification of nearly free conic-line arrangements in the complex plane having nodes, tacnodes, and ordinary triple points. In this setting, our theoretical bound tells us that the degree of such…

Algebraic Geometry · Mathematics 2022-07-05 Aleksandra Gałecka

The main goal of this note is to begin a systematic study on conic-line arrangements in the complex projective plane. We show a de Bruijn-Erd\H{o}s-type inequality and Hirzebruch-type inequality for a certain class of conic-line…

Algebraic Geometry · Mathematics 2022-04-13 Piotr Pokora , Tomasz Szemberg

In the present note we construct new families of free plane curves starting from a curve $C$ and adding high order inflectional tangent lines of $C$, lines joining the singularities of the curve $C$, or lines in the tangent cone of some…

Algebraic Geometry · Mathematics 2023-11-16 Alexandru Dimca , Giovanna Ilardi , Piotr Pokora , Gabriel Sticlaru

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 give two examples of plane curve arrangements of pencil type which are very close to line arrangements, though the action of the monodromy operator on the first cohomology group of the Milnor Fiber has eigenvalues of order 5 and 6,…

Algebraic Geometry · Mathematics 2016-06-16 Pauline Bailet

In this note we study curves (arrangements) in the complex projective plane which can be considered as generalizations of free curves. We construct families of arrangements which are nearly free and possess interesting geometric properties.…

Algebraic Geometry · Mathematics 2021-09-22 Grzegorz Malara , Piotr Pokora , Halszka Tutaj-Gasińska

We study the combinatorics of pseudoline arrangements in the real projective plane. Our focus lies on two classes of arrangements: simplicial arrangements and arrangements whose characteristic polynomials have only real roots. We derive…

Combinatorics · Mathematics 2019-02-08 David Geis

We give a geometric characterisation of plus-one generated projective line arrangements that are next-to-free. We present new succinct proofs, via associated line bundles, for some properties of plus-one generated projective line…

Algebraic Geometry · Mathematics 2026-03-25 Anca Macinic , Jean Vallès

In this paper we focus on various aspects of singular complex plane curves, mostly in the context of their homological properties and the associated combinatorial structures. We formulate some challenging open problems that can point to new…

Algebraic Geometry · Mathematics 2026-03-26 Michael Cuntz , Piotr Pokora

We describe the behaviour of a free reduced plane projective curve with respect to the deletion, respectively addition, of a smooth conic. These results apply in particular to conic-line arrangements. We present some obstructions to the…

Algebraic Geometry · Mathematics 2026-03-25 Anca Macinic

In the present note we focus on conic line arrangements in the plane with quasihomogeneous ordinary singularities from the perspective of weak Ziegler pairs. The foundations of this article come from an active area of research devoted to…

Algebraic Geometry · Mathematics 2024-03-26 Magdalena Lampa-Baczyńska , Daniel Wojcik

We define the type of a plane curve as the initial degree of the corresponding Bourbaki ideal. Then we show that this invariant behaves well with respect to the union of curves. Curves of type $0$ are precisely the free curves, while curves…

Algebraic Geometry · Mathematics 2025-11-17 Takuro Abe , Alexandru Dimca , Piotr Pokora

We study some natural operators acting on configurations of points and lines in the plane and remark that many interesting configurations are fixed points for these operators. We review ancient and recent results on line or point…

Algebraic Geometry · Mathematics 2024-11-05 Xavier Roulleau
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