Abstract
Let X be a d-dimensional simplicial complex with N faces of dimension d-1. Suppose that every (d-1)-face of X is contained in at least κ ≥ d + 2 faces of X, of dimension d. Extending the classical Moore bound for graphs, it is shown that X must contain a ball B of radius at most |"log κ-d N] whose d-dimensional homology Hd(B) is non-zero. The Ramanujan complexes constructed by Lubotzky, Samuels and Vishne are used to show that this upper bound on the radius of B cannot be improved by more than a multiplicative constant factor.
Original language | English |
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Pages (from-to) | 353-358 |
Number of pages | 6 |
Journal | Bulletin of the London Mathematical Society |
Volume | 39 |
Issue number | 3 |
DOIs | |
State | Published - Jun 2007 |