H. Broersma

activity

20072025

most citedOn a conjecture of Nikiforov involving a spectral radius condition for a graph to contain all trees

5 citations · 15 across the 15 of their papers we have counts for

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12 papers · 1 filter

math.CO2025

Path Extendable Tournaments

Zan-Bo Zhang, Weihua He, Hajo Broersma +1

A digraph $D$ is called \emph{path extendable} if for every nonhamiltonian (directed) path $P$ in $D$ , there exists another path $P^{'}$ with the same initial and terminal verti…

math.CO2024

Closures and heavy pairs for hamiltonicity

Wangyi Shang, Hajo Broersma, Shenggui Zhang +1

We say that a graph $G$ on $n$ vertices is ${H, F}$ - $o$ -heavy if every induced subgraph of $G$ isomorphic to $H$ or $F$ contains two nonadjacent vertices with degree sum at least…

math.CO2024

Connected Turán numbers for Berge paths in hypergraphs

Lin-Peng Zhang, Hajo Broersma, Ervin Győri +2

Let $F$ be a family of $r$ -uniform hypergraphs. Denote by $\ex^{\mathrm{conn}}_r(n,\mathcal{F})$ the maximum number of hyperedges in an $n$ -vertex connected $r$ -uniform h…

math.CO2024

A note on generalized crowns in linear r-graphs

Lin-Peng Zhang, Hajo Broersma, Ligong Wang

An $r$ -graph $H$ is a hypergraph consisting of a nonempty set of vertices $V$ and a collection of $r$ -element subsets of $V$ we refer to as the edges of $H$ . An $r$ -graph $H$ is ca…

math.CO2023

Turán numbers of general hypergraph star forests

Lin-Peng Zhang, Hajo Broersma, Ligong Wang

Let $F$ be a family of $r$ -uniform hypergraphs, and let $H$ be an $r$ -uniform hypergraph. Then $H$ is called $F$ -free if it does not contain any member of $\mat…

math.CO2023

Sharp bounds for Laplacian spectral moments of digraphs with a fixed dichromatic number

Xiuwen Yang, Hajo Broersma, Ligong Wang

The $k$ -th Laplacian spectral moment of a digraph $G$ is defined as $\sum_{i = 1}^{n} λ_{i}^{k}$ , where $λ_{i}$ are the eigenvalues of the Laplacian matrix of $G$ and $k$ is a nonnegative in…

math.CO2021★ 5 cited

On a conjecture of Nikiforov involving a spectral radius condition for a graph to contain all trees

Xiangxiang Liu, Hajo Broersma, Ligong Wang

We partly confirm a Brualdi-Solheid-Turán type conjecture due to Nikiforov, which is a spectral radius analogue of the well-known Erdős-Sós Conjecture that any tree of order $t$ is…

math.CO2021

Growth rates of the bipartite Erdős-Gyárfás function

Xihe Li, Hajo Broersma, Ligong Wang

Given two graphs $G, H$ and a positive integer $q$ , an $(H, q)$ -coloring of $G$ is an edge-coloring of $G$ such that every copy of $H$ in $G$ receives at least $q$ distinct colors.…

math.CO2021★ 4 cited

Spectral radius conditions for the existence of all subtrees of diameter at most four

Xiangxiang Liu, Hajo Broersma, Ligong Wang

Let $μ (G)$ denote the spectral radius of a graph $G$ . We partly confirm a conjecture due to Nikiforov, which is a spectral radius analogue of the well-known Erdős-Sós Conjecture th…

math.CO2020★ 1 cited

The Erdős-Gyárfás function with respect to Gallai-colorings

Xihe Li, Hajo Broersma, Ligong Wang

For fixed $p$ and $q$ , an edge-coloring of the complete graph $K_{n}$ is said to be a $(p, q)$ -coloring if every $K_{p}$ receives at least $q$ distinct colors. The function $f(n, p, q)…

math.CO2020

Extremal problems and results related to Gallai-colorings

Xihe Li, Hajo Broersma, Ligong Wang

A Gallai-coloring (Gallai- $k$ -coloring) is an edge-coloring (with colors from ${1, 2, \dots, k}$ ) of a complete graph without rainbow triangles. Given a graph $H$ and a positive…

math.CO2017★ 3 cited

Vertex-disjoint properly edge-colored cycles in edge-colored complete graphs

Ruonan Li, Hajo Broersma, Shenggui Zhang

It is conjectured that every edge-colored complete graph $G$ on $n$ vertices satisfying $Δ^{m o n} (G) \leq n - 3 k + 1$ contains $k$ vertex-disjoint properly edge-colored cycles. We confir…