E. Ghorbani

collaborators

2 papers

math.CO2007

Choice Number and Energy of Graphs

Saieed Akbari, Ebrahim Ghorbani

The energy of a graph G, denoted by E(G), is defined as the sum of the absolute values of all eigenvalues of G. It is proved that E(G)>= 2(n-χ(\bar{G}))>= 2(ch(G)-1) for every grap…

math.CO2007

Inclusion Matrices and Chains

E. Ghorbani, G. B. Khosrovshahi, Ch. Maysoori +1

Given integers $t$ , $k$ , and $v$ such that $0 \leq t \leq k \leq v$ , let $W_{t k} (v)$ be the inclusion matrix of $t$ -subsets vs. $k$ -subsets of a $v$ -set. We modify slightly the concep…