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On the topology of bi-cyclopermutohedra. (English) Zbl 1517.51010

G. Yu. Panina [Proc. Steklov Inst. Math. 288, No. 1, 132–144 (2015; Zbl 1322.51013)] has introduced an \((n-2)\)-dimensional regular CW complex whose \(k\)-cells are labeled by cyclically ordered partitions of \(\{1, 2, \ldots, n + 1\}]\) into \((n + 1-k)\) non-empty parts, where \((n + 1-k) > 2\) – the boundary relations in the complex corresponding to the orientation preserving refinement of partitions – called a cyclopermutohedron and denoted by \(CP_{n+1}\). Using discrete Morse theory, I. Nekrasov et al. [Eur. J. Math. 2 , no. 3, 835–852 (2016; Zbl 1361.51015)] showed that the homology groups \(H_i(CP_{n+1})\) are torsion free for all \(i\geq 0\) and computed their Betti numbers.
\(CP_{n+1}\) admits a free \({\mathbb Z}_2\) action; the quotient space \(CP_{n+1}/{\mathbb Z}_2\) is called a bi-cyclopermutohedron and denoted by \(QP_{n+1}\). The aim of this paper is to compute the \({\mathbb Z}_2\)- and the \({\mathbb Z}\)-homology groups of \(QP_{n+1}\).

MSC:

51M20 Polyhedra and polytopes; regular figures, division of spaces
52C25 Rigidity and flexibility of structures (aspects of discrete geometry)
57R70 Critical points and critical submanifolds in differential topology
06A11 Algebraic aspects of posets
05B99 Designs and configurations

References:

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