Regular bipartite multigraphs have many (but not too many) symmetries

Peter J. Cameron, Coen del Valle, Colva M. Roney-Dougal

Let $k$ and $l$ be integers, both at least 2. A $(k,l)$-bipartite graph is an $l$-regular bipartite multigraph with coloured bipartite sets of size $k$. Define $\chi (k,l)$ and $μ(k,l)…