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 \(QP_{n+1}\).
\(CP_{n+1}\) 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 \(QP_{n+1}\).
Reviewer: Victor V. Pambuccian (Glendale)
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 |
Keywords:
moduli space of planar polygons; discrete Morse theory; homology; permutohedron; poset of ordered partitionsReferences:
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