  Recently, Muralidhar et al. proposed a novel multi-access system model where
each user is connected to multiple caches in a manner that follows the
well-known combinatorial topology of combination networks. For such
multi-access topology, the same authors proposed an achievable scheme, which
stands out for the unprecedented coding gains even with very modest cache
resources. In this paper, we identify the fundamental limits of such
multi-access setting with exceptional potential, providing an
information-theoretic converse which establishes, together with the inner bound
by Muralidhar et al., the exact optimal performance under uncoded prefetching.
