Jianguo Qian

activity

20172022

collaborators

Showing 2018Show all

6 papers · 1 filter

math.CO2018

A generalization of Noel-Reed-Wu Theorem to signed graphs

Wei Wang, Jianguo Qian

Let $Σ$ be a signed graph where two edges joining the same pair of vertices with opposite signs are allowed. The zero-free chromatic number $χ^{*} (Σ)$ of $Σ$ is the minimum even inte…

math.CO2018

Alon-Tarsi number of signed planar graphs

Wei Wang, Jianguo Qian

Let $(G, σ)$ be any signed planar graph. We show that the Alon-Tarsi number of $(G, σ)$ is at most 5, generalizing a recent result of Zhu for unsigned case. In addition, if $(G, σ)$ i…

math.CO2018

Chromatic-choosability of hypergraphs with high chromatic number

Wei Wang, Jianguo Qian

It was conjectured by Ohba and confirmed recently by Noel et al. that, for any graph $G$ , if $∣ V (G) ∣ \leq 2 χ (G) + 1$ then $χ_{l} (G) = χ (G)$ . This indicates that the graphs with high chroma…

math.CO2018

Flow polynomials of a signed graph

Jianguo Qian

In contrast to ordinary graphs, the number of the nowhere-zero group-flows in a signed graph may vary with different groups, even if the groups have the same order. In fact, for a…

math.CO2018

Colorings v.s. list colorings of uniform hypergraphs

Wei Wang, Jianguo Qian, Zhidan Yan

Let $r$ be an integer with $r \geq 2$ and $G$ be a connected $r$ -uniform hypergraph with $m$ edges. By refining the broken cycle theorem for hypergraphs, we show that if $k>\frac{m-1…

math.CO2018

Inclusion-exclusion by ordering-free cancellation

Yin Chen, Jianguo Qian

Whitney's broken circuit theorem gives a graphical example to reduce the number of the terms in the sum of the inclusion-exclusion formula by a predicted cancellation. So far, the…