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Abstract

We construct for each nn an Eulerian partially ordered set TnT_n of rank n+1n+1 whose cece-index provides a non-commutative generalization of the nnth Tchebyshev polynomial. We show that the order complex of each TnT_n is shellable, homeomorphic to a sphere, and that its face numbers minimize the expression max|x| £ 1 |åj=0n (fj-1/fn-1)·2-j·(x-1)j|\max_{|x|\leq 1} |\sum_{j=0}^n (f_{j-1}/f_{n-1})\cdot 2^{-j}\cdot (x-1)^j| among the ff-vectors of all (n-1)(n-1)-dimensional simplicial complexes. The duals of the posets constructed have a recursive structure similar to face lattices of simplices or cubes, offering the study of a new special class of Eulerian partially ordered sets to test the validity of Stanleyrsquos conjecture on the non-negativity of the cdcd-index of all Gorenstein*^* posets.

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