New families of highly neighborly centrally symmetric spheres

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

  • Isabella Novik
  • Hailun Zheng

Jockusch [J. Combin. Theory Ser. A 72 (1995), pp. 318-321] constructed an infinite family of centrally symmetric (cs, for short) triangulations of 3-spheres that are cs-2-neighborly. Recently, Novik and Zheng [Adv. Math. 370 (2020), 16 pp.] extended Jockusch's construction: for all d and n > d, they constructed a cs triangulation of a d-sphere with 2n vertices, Δdn, that is cs-⌈d/2⌉-neighborly. Here, several new cs constructions, related to Δdn, are provided. It is shown that for all k > 2 and a sufficiently large n, there is another cs triangulation of a (2k − 1)-sphere with 2n vertices that is cs-k-neighborly, while for k = 2 there are Ω(2n) such pairwise non-isomorphic triangulations. It is also shown that for all k > 2 and a sufficiently large n, there are Ω(2n) pairwise non-isomorphic cs triangulations of a (2k − 1)-sphere with 2n vertices that are cs-(k − 1)-neighborly. The constructions are based on studying facets of Δdn, and, in particular, on some necessary and some sufficient conditions similar in spirit to Gale's evenness condition. Along the way, it is proved that Jockusch's spheres Δ3n are shellable and an affirmative answer to Murai-Nevo's question about 2-stacked shellable balls is given.

OriginalsprogEngelsk
TidsskriftTransactions of the American Mathematical Society
Vol/bind375
Udgave nummer6
Sider (fra-til)4445-4475
ISSN0002-9947
DOI
StatusUdgivet - 2022

Bibliografisk note

Funding Information:
Received by the editors May 13, 2020, and, in revised form, January 1, 2022. 2020 Mathematics Subject Classification. Primary 52B05, 52B15, 57Q15. The first author was partially supported by NSF grants DMS-1664865 and DMS-1953815, and by Robert R. & Elaine F. Phelps Professorship in Mathematics. The second author was partially supported by a postdoctoral fellowship from ERC grant 716424 -CASe.

Publisher Copyright:
© 2022 American Mathematical Society

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