arXiv subjects

Yan Cao

Publications and source records attributed to Yan Cao.

61 records · Page 4Linked to original sources

arXiv2017

Average degrees of edge-chromatic critical graphs

Given a graph $G$, denote by $Δ$, $\bar{d}$ and $χ^\prime$ the maximum degree, the average degree and the chromatic index of $G$, respectively. A simple graph $G$ is called {\it edge-$Δ$-critical} if $χ^\prime(G)=Δ+1$ and $χ^\prime(H)\leΔ$ for every proper subgraph $H$ of $G$. Vizing in 1968 conjectured that if $G$ is edge-$Δ$-critical, then $\bar{d}\geq Δ-1+ \frac{3}{n}$. We show that $$ \begin{displaystyle} \avd \ge \begin{cases} 0.69241\D-0.15658 \quad\,\: \mbox{ if } Δ\geq 66, 0.69392\D-0.20642\quad\;\,\mbox{ if } Δ=65, \mbox{ and } 0.68706\D+0.19815\quad\! \quad\mbox{if } 56\leq Δ\leq64. \end{cases} \end{displaystyle} $$ This result improves the best known bound $\frac{2}{3}(Δ+2)$ obtained by Woodall in 2007 for $Δ\geq 56$. Additionally, Woodall constructed an infinite family of graphs showing his result cannot be improved by well-known Vizing's Adjacency Lemma and other known edge-coloring techniques. To over come the barrier, we follow the recently developed recoloring technique of Tashkinov trees to expand Vizing fans technique to a larger class of trees.

math.CO↗

arXiv2016

On the structure of graded Leibniz triple systems

We study the structure of a Leibniz triple system $\mathcal{E}$ graded by an arbitrary abelian group $G$ which is considered of arbitrary dimension and over an arbitrary base field $\mathbb{K}$. We show that $\mathcal{E}$ is of the form $\mathcal{E}=U+\sum_{[j]\in \sum^{1}/\sim} I_{[j]}$ with $U$ a linear subspace of the 1-homogeneous component $\mathcal{E}_{1}$ and any ideal $I_{[j]}$ of $\mathcal{E}$, satisfying $\{I_{[j]},\mathcal{E},I_{[k]}\} =\{I_{[j]},I_{[k]},\mathcal{E}\}=\{\mathcal{E},I_{[j]},I_{[k]}\}=0$ if $[j]\neq [k]$, where the relation $\sim$ in $\sum^{1}=\{g \in G \setminus \{1\} : L_{g}\neq 0\}$, defined by $g \sim h$ if and only if $g$ is connected to $h$.

math.RA↗

arXiv2015

On split regular Hom-Lie color algebras

We introduce the class of split regular Hom-Lie color algebras as the natural generalization of split Lie color algebras. By developing techniques of connections of roots for this kind of algebras, we show that such a split regular Hom-Lie color algebra $L$ is of the form $L = U + \sum\limits_{[j] \in Λ/\sim}I_{[j]}$ with $U$ a subspace of the abelian graded subalgebra $H$ and any $I_{[j]}$, a well described ideal of $L$, satisfying $[I_{[j]}, I_{[k]}] = 0$ if $[j]\neq [k]$. Under certain conditions, in the case of $L$ being of maximal length, the simplicity of the algebra is characterized.

math.RA↗

arXiv2015

On split Regular Hom-Leibniz algebras

We introduce the class of split regular Hom-Leibniz algebras as the natural generalization of split Leibniz algebras and split regular Hom-Lie algebras. By developing techniques of connections of roots for this kind of algebras, we show that such a split regular Hom-Leibniz algebra $L$ is of the form $L = U + \sum\limits_{[j] \in Λ/\sim}I_{[j]}$ with $U$ a subspace of the abelian subalgebra $H$ and any $I_{[j]}$, a well described ideal of $L$, satisfying $[I_{[j]}, I_{[k]}] = 0$ if $[j]\neq [k]$. Under certain conditions, in the case of $L$ being of maximal length, the simplicity of the algebra is characterized.

math.RA↗

arXiv2014

On split Leibniz triple systems

In order to study the structure of arbitrary split Leibniz triple systems, we introduce the class of split Leibniz triple systems as the natural extension of the class of split Lie triple systems and split Leibniz algebras. By developing techniques of connections of roots for this kind of triple systems, we show that any of such Leibniz triple systems $T$ with a symmetric root system is of the form $T=U+\sum_{[j]\in Λ^{1}/\sim} I_{[j]}$ with $U$ a subspace of $T_{0}$ and any $I_{[j]}$ a well described ideal of $T$, satisfying $\{I_{[j]},T,I_{[k]}\} =\{I_{[j]},I_{[k]},T\}=\{T,I_{[j]},I_{[k]}\}=0$ if $[j]\neq [k]$.

math.RA↗

arXiv2014

On the structures of split Leibniz triple systems

We study the structures of arbitrary split Leibniz triple systems. By developing techniques of connections of roots for this kind of triple systems, under certain conditions, in the case of $T$ being of maximal length, the simplicity of the Leibniz triple systems is characterized.

math.RA↗

arXiv2014

On the structures of split $δ$ Jordan-Lie algebras

We study the structures of arbitrary split $δ$ Jordan-Lie algebras with symmetric root systems. We show that any of such algebras $L$ is of the form $L = U + \sum\limits_{[j] \in Λ/\sim}I_{[j]}$ with $U$ a subspace of $H$ and any $I_{[j]}$, a well described ideal of $L$, satisfying $[I_{[j]}, I_{[k]}] = 0$ if $[j]\neq [k]$. Under certain conditions, the simplicity of $L$ is characterized and it is shown that $L$ is the direct sum of the family of its minimal ideals, each one being a simple split $δ$ Jordan-Lie algebra with a symmetric root system and having all its nonzero roots connected.

math.RA↗