On the index of cactuses with n vertices

summary:Let $W_{n}=K_{1}\vee C_{n-1}$ be the wheel graph on $n$ vertices, and let $S(n,c,k)$ be the graph on $n$ vertices obtained by attaching $n-2c-2k-1$ pendant edges together with $k$ hanging paths of length two at vertex $v_{0}$, where $v_{0}$ is the unique common vertex of $c$ triangles. In this paper we show that $S(n,c,k)$ ($c\geq 1$, $k\geq 1$) and $W_{n}$ are determined by their signless Laplacian spectra, respectively. Moreover, we also prove that $S(n,c,k)$ and its complement graph are determined by their Laplacian spectra, respectively, for $c\geq 0$ and $k\geq 1$