Cactus; Signless Laplacian spread; Upper bound
A cactus is a connected graph in which any two cycles have at most one vertex in common. The signless Laplacian spread of a graph is defined as the difference between the largest eigenvalue and the smallest eigenvalue of the associated signless Laplacian matrix. In this paper, all cacti of order n with signless Laplacian spread greater than or equal to n − 1/2 are determined.
Lin, Zhen and Guo, Shu-Guang.
"Ordering cacti with signless Laplacian spread",
Electronic Journal of Linear Algebra,
Volume 34, pp. 609-619.
DOI: https://doi.org/10.13001/1081-3810, 1537-9582.3797