Yan Yang

activity

20232026

collaborators

4 papers

math.CO2026

On derivatives and higher-order derivatives of chromatic polynomials

Bo Ning, Yan Yang

Let $ G $ be a graph of order $ n $ with maximum degree $Δ$ , and let $P (G, x)$ denote its chromatic polynomial. We investigate several properties of $P (G, x)$ related to its deri…

math.CO2026

On a conjecture concerning the property of chromatic polynomials with negative variables

Yan Yang

Let $G$ be a graph of order $n$ and $P (G, x)$ be the chromatic polynomial of $G$ . Dong, Ge, Gong, Ning, Ouyang, and Tay (J. Graph Theory 96(2021) 343) conjectured that $\frac{d^k}{d…

math.CO2024

Counterexamples to two conjectures on mean color numbers of graphs

Wushuang Zhai, Yan Yang

The mean color number of an $n$ -vertex graph $G$ , denoted by $μ (G)$ , is the average number of colors used in all proper $n$ -colorings of $G$ . For any graph $G$ and a vertex $w$ in…

math.CO2023

Some results on the maximal chromatic polynomials of $2$ -connected $k$ -chromatic graphs

Yan Yang

In 2015, Brown and Erey conjectured that every $2$ -connected graph $G$ on $n$ vertices with chromatic number $k \geq 4$ has at most $(x - 1)_{k - 1} ((x - 1)^{n - k + 1} + (- 1)^{n - k})$ p…

On derivatives and higher-order derivatives of chromatic polynomials

On a conjecture concerning the property of chromatic polynomials with negative variables

Counterexamples to two conjectures on mean color numbers of graphs

Some results on the maximal chromatic polynomials of 2-connected k-chromatic graphs

Some results on the maximal chromatic polynomials of $2$ -connected $k$ -chromatic graphs