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A common approach is present concerning the problem of Dirichlet, both for bounded 3D domains and their (unbounded) complements, regarding the fractional (3D) Poisson equation.

数学物理 · 物理学 2022-12-13 Toshko Boev , Georgi Georgiev

An $({\cal I},{\cal F}_d)$-partition of a graph is a partition of the vertices of the graph into two sets $I$ and $F$, such that $I$ is an independent set and $F$ induces a forest of maximum degree at most $d$. We show that for all $M<3$…

离散数学 · 计算机科学 2016-06-15 François Dross , Mickael Montassier , Alexandre Pinlou

A fundamental theorem of Wilson states that, for every graph $F$, every sufficiently large $F$-divisible clique has an $F$-decomposition. Here a graph $G$ is $F$-divisible if $e(F)$ divides $e(G)$ and the greatest common divisor of the…

组合数学 · 数学 2018-09-05 Ben Barber , Daniela Kühn , Allan Lo , Deryk Osthus

Temporal graphs provide a useful model for many real-world networks. Unfortunately the majority of algorithmic problems we might consider on such graphs are intractable. There has been recent progress in defining structural parameters which…

离散数学 · 计算机科学 2024-11-20 Jessica Enright , Samuel D. Hand , Laura Larios-Jones , Kitty Meeks

In this paper, we first prove that when the associated graph of a polynomial set is chordal, a particular triangular set computed by a general algorithm in top-down style for computing the triangular decomposition of this polynomial set has…

符号计算 · 计算机科学 2018-11-28 Chenqi Mou , Yang Bai , Jiahua Lai

A digraph is $3$-dicritical if it cannot be vertex-partitioned into two sets inducing acyclic digraphs, but each of its proper subdigraphs can. We give a human-readable proof that the number of 3-dicritical semi-complete digraphs is finite.…

组合数学 · 数学 2024-02-22 Frédéric Havet , Florian Hörsch , Lucas Picasarri-Arrieta

We solve three enumerative problems concerning families of planar maps. More precisely, we establish algebraic equations for the generating function of non-separable triangulations in which all vertices have degree at least d, for a certain…

组合数学 · 数学 2009-06-18 Olivier Bernardi

The iterative absorption method has recently led to major progress in the area of (hyper-)graph decompositions. Amongst other results, a new proof of the Existence conjecture for combinatorial designs, and some generalizations, was…

组合数学 · 数学 2020-03-02 Ben Barber , Stefan Glock , Daniela Kühn , Allan Lo , Richard Montgomery , Deryk Osthus

We explicitly describe the possible pairs of triangle and square densities for r-regular finite simple graphs. We also prove that every r-regular unimodular random graph can be approximated by r-regular finite graphs with respect to these…

组合数学 · 数学 2011-11-28 Viktor Harangi

For a family $\mathcal{F}$ of graphs, let $ex(n,\mathcal{F})$ denote the maximum number of edges in an $n$-vertex graph which contains none of the members of $\mathcal{F}$ as a subgraph. A longstanding problem in extremal graph theory asks…

组合数学 · 数学 2022-12-06 Jie Ma , Tianchi Yang

It is well known that a graph with $m$ edges can be made triangle-free by removing (slightly less than) $m/2$ edges. On the other hand, there are many classes of graphs which are hard to make triangle-free in the sense that it is necessary…

组合数学 · 数学 2010-09-03 Raphael Yuster

This paper develops an algorithm that identifies and decomposes a median graph of a triangulation of a 2-dimensional (2D) oriented bordered surface and in addition restores all corresponding triangulation whenever they exist. The algorithm…

组合数学 · 数学 2010-07-13 Weiwen Gu

A $K_4$-decomposition of a graph is a partition of its edges into $K_4$s. A fractional $K_4$-decomposition is an assignment of a nonnegative weight to each $K_4$ in a graph such that the sum of the weights of the $K_4$s containing any given…

组合数学 · 数学 2025-10-10 Menglong Zhang , Gennian Ge

The problem of finding necessary and sufficient conditions to decompose a complete tripartite graph $K_{r,s,t}$ into 5-cycles was first considered by E.S. Mahmoodian and Maryam Mirzakhani (1995). They stated some necessary conditions and…

组合数学 · 数学 2019-07-16 M. Abdolmaleki , S. Gh. Ilchi , E. S. Mahmoodian , MA. Shabani

We consider the problem of minimizing the number of triangles in a graph of given order and size and describe the asymptotic structure of extremal graphs. This is achieved by characterizing the set of flag algebra homomorphisms that…

组合数学 · 数学 2016-05-11 Oleg Pikhurko , Alexander Razborov

How much cutting is needed to simplify the topology of a surface? We provide bounds for several instances of this question, for the minimum length of topologically non-trivial closed curves, pants decompositions, and cut graphs with a given…

组合数学 · 数学 2015-04-08 Éric Colin de Verdière , Alfredo Hubard , Arnaud de Mesmay

The density matrix of a graph is the combinatorial laplacian matrix of a graph normalized to have unit trace. In this paper we generalize the entanglement properties of mixed density matrices from combinatorial laplacian matrices of graphs…

量子物理 · 物理学 2011-04-20 Zhen Wang , Zhixi Wang

Paul Erd\H{o}s suggested the following problem: Determine or estimate the number of maximal triangle-free graphs on $n$ vertices. Here we show that the number of maximal triangle-free graphs is at most $2^{n^2/8+o(n^2)}$, which matches the…

组合数学 · 数学 2014-09-30 József Balogh , Šárka Petříčková

We introduce series-triangular graph embeddings and show how to partition point sets with them. This result is then used to improve the upper bound on the number of Steiner points needed to obtain compatible triangulations of point sets.…

计算几何 · 计算机科学 2007-05-23 Jeff Danciger , Satyan L. Devadoss , Don Sheehy

We study the set of all decompositions (clusterings) of a graph through its characterization as a set of lifted multicuts. This leads us to practically relevant insights related to the definition of a class of decompositions by must-join…

离散数学 · 计算机科学 2017-06-09 Andrea Horňáková , Jan-Hendrik Lange , Bjoern Andres