A rank inequality for finite geometric lattices
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Let L be a finite geometric lattice of dimension n, and let w(k) denote the number of elements in L of rank k. Two theorems about the numbers w(k) are proved: first, w(k)≥w(1) for k=2,3,…,n−1. Second, w(k)=w(1) if and only if k=n−1 and L is modular. Several corollaries concerning the “matching” of points and dual points are derived from these results.
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