Spectral radius of simplicial complexes without holes

Abstract: The Tur\'an problem for hypergraphs and its spectral version is a central and challenging topic in extremal combinatorics. In this paper, we view hypergraphs from the perspective of simplicial complexes, and investigate the spectral version of Tur\'an problem for simplicial complexes. We characterize the simplicial complex that maximizes the signless Laplacian spectral radius among all hole-free simplicial complexes, and establish an upper bound on the spectral radius for simplicial complexes with a prescribed Betti number. As an application, we derive bounds on Tur\'an numbers for both hypergraphs and simplicial complexes via the connection between the spectral radius and the face numbers.