Spectral radius and rainbow $k$-factors of graphs

Abstract: Let $\mathcal{G}={G_1,\ldots, G_{\frac{kn}{2}}}$ be a set of graphs on the same vertex set $V={1,\dots,n}$ where $k\cdot n$ is even. We say $\mathcal{G}$ admits a rainbow $k$-factor if there exists a $k$-regular graph $F$ on the vertex set $V$ such that all edges of $F$ are from different members of $\mathcal{G}$. Guo, Lu, Ma, and Ma [Spectral radius and rainbow matchings of graphs, Linear Algebra Appl., 2023] showed a sufficient spectral condition for the existence of a rainbow 1-factor. In this paper, we extend this result to all $k$-factors for $k\geq 2$, which is that if $\rho(G_i)\geq\rho(K_{k-1}\vee(K_1\cup K_{n-k}))$ for each $G_i\in \mathcal{G}$, then $\mathcal{G}$ admits a rainbow $k$-factor unless $G_1=G_2=\cdots=G_{\frac{kn}{2}}\cong K_{k-1}\vee(K_1\cup K_{n-k})$.