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A pseudoline is a homeomorphic image of the real line in the plane so that its complement is disconnected. An arrangement of pseudolines is a set of pseudolines in which every two cross exactly once. A drawing of a graph is pseudolinear if…

Combinatorics · Mathematics 2018-04-26 Alan Arroyo , Julien Bensmail , R. Bruce Richter

We use the differential algebra of polytopes to explain the known remarkable relation of the combinatorics of the associahedra and permutohedra with the universal compositional and multiplicative inversion formulas for the formal power…

Combinatorics · Mathematics 2025-02-11 V. M. Buchstaber , A. P. Veselov

Every n-edge colored n-regular graph G naturally gives rise to a simple abstract n-polytope, the colorful polytope of G, whose 1-skeleton is isomorphic to G. The paper describes colorful polytope versions of the associahedron and…

Combinatorics · Mathematics 2014-09-19 Gabriela Araujo-Pardo , Isabel Hubard , Deborah Oliveros , Egon Schulte

In this paper we give a combinatorial view on the adjunction theory of toric varieties. Inspired by classical adjunction theory of polarized algebraic varieties we define two convex-geometric notions: the Q-codegree and the nef value of a…

Combinatorics · Mathematics 2016-01-20 Sandra Di Rocco , Christian Haase , Benjamin Nill , Andreas Paffenholz

For all integers $4 \leq r \leq d$, we show that there exists a finite simple graph $G= G_{r,d}$ with toric ideal $I_G \subset R$ such that $R/I_G$ has (Castelnuovo-Mumford) regularity $r$ and $h$-polynomial of degree $d$. To achieve this…

Commutative Algebra · Mathematics 2020-03-17 Giuseppe Favacchio , Graham Keiper , Adam Van Tuyl

We define a simple orthogonal polyhedron to be a three-dimensional polyhedron with the topology of a sphere in which three mutually-perpendicular edges meet at each vertex. By analogy to Steinitz's theorem characterizing the graphs of…

Computational Geometry · Computer Science 2016-08-12 David Eppstein , Elena Mumford

This manuscript introduces a finite collection of generalized permutohedra associated to a simple graph. The first polytope of this collection is the graphical zonotope of the graph and the last is the graph-associahedron associated to it.…

Combinatorics · Mathematics 2022-09-27 Marko Pešović , Tanja Stojadinović

An algebraic domain is a closed topological subsurface of a real affine plane whose boundary consists of disjoint smooth connected components of real algebraic plane curves. We study the geometric shape of an algebraic domain by collapsing…

Geometric Topology · Mathematics 2023-06-09 Arnaud Bodin , Patrick Popescu-Pampu , Miruna-Stefana Sorea

We introduce fractional realizations of a graph degree sequence and a closely associated convex polytope. Simple graph realizations correspond to a subset of the vertices of this polytope. We describe properties of the polytope vertices and…

Combinatorics · Mathematics 2015-08-04 Michael D. Barrus

The tensor product $(G_1,G_2)$ of a graph $G_1$ and a pointed graph $G_2$ (containing one distinguished edge) is obtained by identifying each edge of $G_1$ with the distinguished edge of a separate copy of $G_2$, and then removing the…

Combinatorics · Mathematics 2014-06-10 Yuanan Diao , Gábor Hetyei

A pseudoline arrangement graph is a planar graph induced by an embedding of a (simple) pseudoline arrangement. We study the corresponding graph realization problem and properties of pseudoline arrangement graphs. In the first part, we give…

Combinatorics · Mathematics 2021-03-04 Sandip Das , Siddani Bhaskara Rao , Uma kant Sahoo

The associahedron is a polytope whose graph is the graph of flips on triangulations of a convex polygon. Pseudotriangulations and multitriangulations generalize triangulations in two different ways, which have been unified by Pilaud and…

Combinatorics · Mathematics 2013-10-29 Vincent Pilaud , Francisco Santos

For each poset $P$, we construct a polytope $A(P)$ called the $P$-associahedron. Similarly to the case of graph associahedra, the faces of $A(P)$ correspond to certain nested collections of subsets of $P$. The Stasheff associahedron is a…

Combinatorics · Mathematics 2023-11-09 Pavel Galashin

We introduce the concept of pseudocover, which is a counterpart of cover, for symmetric graphs. The only known example of pseudocovers of symmetric graphs so far was given by Praeger, Zhou and the first-named author a decade ago, which…

Combinatorics · Mathematics 2024-12-10 Cai Heng Li , Yan Zhou Zhu

Let $P$ be a set of $n \geq 5$ points in convex position in the plane. The path graph $G(P)$ of $P$ is an abstract graph whose vertices are non-crossing spanning paths of $P$, such that two paths are adjacent if one can be obtained from the…

Combinatorics · Mathematics 2018-01-03 Chaya Keller , Yael Stein

Let $G$ be a connected graph on $n$ vertices with adjacency matrix $A_G$. Associated to $G$ is a polynomial $d_G(x_1,\dots, x_n)$ of degree $n$ in $n$ variables, obtained as the determinant of the matrix $M_G(x_1,\dots,x_n)$, where…

Number Theory · Mathematics 2023-11-14 Dino Lorenzini

Associated to a finite graph $X$ is its quantum automorphism group $G$. The main problem is to compute the Poincar\'e series of $G$, meaning the series $f(z)=1+c_1z+c_2z^2+...$ whose coefficients are multiplicities of 1 into tensor powers…

Quantum Algebra · Mathematics 2007-05-23 Teodor Banica

A partial complement of the graph $G$ is a graph obtained from $G$ by complementing all the edges in one of its induced subgraphs. We study the following algorithmic question: for a given graph $G$ and graph class $\mathcal{G}$, is there a…

Computational Complexity · Computer Science 2020-06-11 Fedor V. Fomin , Petr A. Golovach , Torstein J. F. Strømme , Dimitrios M. Thilikos

We classify projective toric manifolds whose dual variety is not a hypersurface in the dual projective space. Under the standard dictionary between toric geometry and convex geometry, they correspond to certain convex Delzant integer…

Algebraic Geometry · Mathematics 2007-05-23 Sandra Di Rocco

We investigate a family of polytopes introduced by E.M.\ Feichtner, A.\ Postnikov and B.\ Sturmfels, which were named nestohedra. The vertices of these polytopes may intuitively be understood as constructions of hypergraphs. Limit cases in…

Combinatorics · Mathematics 2011-10-07 K. Dosen , Z. Petric