Abstract
A simplicial complex Δ is called flag if all minimal nonfaces of Δ have at most two elements. The following are proved: First, if Δ is a flag simplicial pseudomanifold of dimension d−1, then the graph of Δ (i) is (2d−2)-vertex-connected and (ii) has a subgraph which is a subdivision of the graph of the d-dimensional cross-polytope. Second, the h-vector of a flag simplicial homology sphere Δ of dimension d−1 is minimized when Δ is the boundary complex of the d-dimensional cross-polytope.
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Dedicated to Anders Björner on the occasion of his sixtieth birthday.
Supported by the 70/4/8755 ELKE Research Fund of the University of Athens.
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Athanasiadis, C.A. Some combinatorial properties of flag simplicial pseudomanifolds and spheres. Ark Mat 49, 17–29 (2011). https://doi.org/10.1007/s11512-009-0106-4
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DOI: https://doi.org/10.1007/s11512-009-0106-4