Yaojun Chen

activity

20232026

collaborators

Showing 2026Show all

12 papers · 1 filter

math.RT2026

Derived Picard reconstruction for graded surfaces with stops

Wen Chang, Dongjian Wu

We study reconstruction of graded surfaces with stops $(S, M, η)$ from their mapping class groups and the derived Picard groups of their partially wrapped Fukaya categories. In genus…

math.CO2026

Degree-square Turán problem for two self-converse tournaments

Zhuoran Han, Yaojun Chen

For a fixed digraph $F$ , let $ex_{2}^{+} (n, F)$ be the maximum of $\sum_{v \in V (D)} d_{D}^{+} (v)^{2}$ over all $n$ -vertex $F$ -free digraphs. Ai et al. [arXiv:2606.03520, 2026] a…

math.CO2026

Ramsey multiplicity and extremal colorings for odd cycles

Ting Huang, Junying Lu, Jiabao Yang +1

The Ramsey number $r (H)$ of a graph $H$ is the minimum positive integer $N$ such that every red/blue edge-coloring of the complete graph $K_{N}$ on $N$ vertices contains a monochroma…

math.CO2026

Counterexamples to two conjectures on the diameter of clique-free graphs

Hangdi Chen, Yaojun Chen

Erdős et al. (JCT-B, 1989) conjectured that, for integers $r \geq 2$ and $δ \geq 2$ with $3 r - 1 ∣ δ$ , every connected $K_{2 r + 1}$ -free graph of order $n$ and minimum degree $δ$ has diam…

math.CO2026

New upper bound for the Ramsey number of odd cycles

Ting Huang, Jiabao Yang, Yaojun Chen

The \emph{ $k$ -color Ramsey number} $R_{k} (C_{2 ℓ + 1})$ is the least integer $n$ such that any $k$ -edge-coloring of a complete graph $K_{n}$ has a monochromatic odd cycle $C_{2 ℓ + 1}$ …

math.CO2026

Erdős--Ko--Rado theorems in $ℓ_{2}$ -norm for three finite spaces

Qian Bao, Yaojun Chen, Yanbo Zhang

Let $F$ be a $k$ -uniform hypergraph. The famous Erdős--Ko--Rado (1961) theorem determines the maximum size and extremal structure for $F$ being $t$ -intersecting…

math.CO2026

On monochromatic path covers conjecture of Erdős--Gyárfás

Hangdi Chen, Yaojun Chen

Erdős and Gyárfás conjectured in 1995 that, in every red--blue edge-coloring of a complete graph $K_{n}$ , the vertex set can be covered by at most $n$ monochromatic paths, all…

math.CO2026

A note on tree-cycle Ramsey numbers

Ting Huang, Yanbo Zhang, Yaojun Chen

Let $R (T_{n}, C_{m})$ denote the Ramsey number of a tree $T_{n}$ on $n$ vertices versus a cycle $C_{m}$ of length $m$ . Burr, Erdős, Faudree, Rousseau, and Schelp (1982) asked for the least…

math.CO2026

Two-block cycles and chromatic number of Hamiltonian digraphs

Ruilin Zheng, Junying Lu, Xiaolin Wang +1

Let $k$ and $ℓ$ be positive integers. The family $C (k, ℓ)$ consists of all digraphs obtained from two internally vertex-disjoint directed paths of lengths at least $k$ and $\e…

math.CO2026

On regular homogeneously traceable nonhamiltonian graphs

Hangdi Chen, Yaojun Chen

A graph is homogeneously traceable if each vertex is an endpoint of a Hamiltonian path. Chartrand, Gould, and Kapoor (1979) proved irregular homogeneously traceable nonhamiltonian…

math.CO2026

Odd covers for complete graphs and complete 3-graphs

Ting Huang, Jiabao Yang, Yaojun Chen

The Graham-Pollak theorem says that one needs at least $n - 1$ complete bipartite graphs to cover each edge of a complete graph $K_{n}$ on $n$ vertices exactly once. The odd cover…

math.CO2026

The Turán number of the triangular pyramid of 4-layers

Hangdi Chen, Yaojun Chen, Xiutao Zhu

The Turán number $e x (n, H)$ of a graph $H$ is the maximum number of edges in any $H$ -free graph on $n$ vertices. The triangular pyramid of $k$ -layers, denoted by $T P_{k}$ , is a genera…

Derived Picard reconstruction for graded surfaces with stops

Degree-square Turán problem for two self-converse tournaments

Ramsey multiplicity and extremal colorings for odd cycles

Counterexamples to two conjectures on the diameter of clique-free graphs

New upper bound for the Ramsey number of odd cycles

Erdős--Ko--Rado theorems in ℓ2​-norm for three finite spaces

On monochromatic path covers conjecture of Erdős--Gyárfás

A note on tree-cycle Ramsey numbers

Two-block cycles and chromatic number of Hamiltonian digraphs

On regular homogeneously traceable nonhamiltonian graphs

Odd covers for complete graphs and complete 3-graphs

The Turán number of the triangular pyramid of 4-layers

Erdős--Ko--Rado theorems in $ℓ_{2}$ -norm for three finite spaces