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Antidirected hamiltonian paths in $k$-hypertournaments

Combinatorics 2024-06-25 v1

Abstract

A kk-hypertournament HH on nn vertices is a pair (V(H),A(H))(V(H),A(H)), where V(H)V(H) is a set of vertices and A(H)A(H) is a set of kk-tuples of vertices, called arcs, such that for any kk-subset SS of V(H)V(H), A(H)A(H) contains exactly one of the k!k! kk-tuples whose entries belong to SS. Clearly, a 2-hypertournament is a tournament. An antidirected path in HH is a sequence x1a1x2a2x3xt1at1xtx_1 a_1 x_2 a_2 x_3 \ldots x_{t-1} a_{t-1} x_t of distinct vertices x1,x2,,xtx_1, x_2, \ldots, x_t and distinct arcs a1,a2,,at1a_1, a_{2},\ldots, a_{t-1} such that for any i{2,3,,t1}i\in \{2,3,\ldots, t-1\}, either xi1x_{i-1} precedes xix_{i} in ai1a_{i-1} and xi+1x_{i+1} precedes xix_{i} in aia_{i}, or xix_{i} precedes xi1x_{i-1} in ai1a_{i-1} and xix_{i} precedes xi+1x_{i+1} in aia_{i}. An antidirected path that includes all vertices of HH is known as an antidirected hamiltonian path. In this paper, we prove that except for four hypertournaments, T3c,T5c,T7cT_3^{c}, T_5^{c}, T_7^{c} and H4H_{4}, every kk-hypertournament with nn vetices, where 2kn12\leq k\leq n-1, has an antidirected hamiltonian path, which extends Gr\"{u}nbaum's theorem on tournaments (except for three tournaments, T3c,T5cT_3^{c}, T_5^{c} and T7cT_7^{c}, every tournament has an antidirected hamiltonian path).

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Cite

@article{arxiv.2406.15851,
  title  = {Antidirected hamiltonian paths in $k$-hypertournaments},
  author = {Hong Yang and Changchang Dong and Jixiang Meng and Juan Liu},
  journal= {arXiv preprint arXiv:2406.15851},
  year   = {2024}
}

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11 pages