Abstract
In his 2008 thesis [16] , Tateno claimed a counterexample to the Bonato–Tardif conjecture regarding the number of equimorphy classes of trees. In this paper we revisit Tateno’s unpublished ideas to provide a rigorous exposition, constructing locally finite trees having an arbitrary finite number of equimorphy classes; an adaptation provides partial orders with a similar conclusion. At the same time these examples also disprove conjectures by Thomassé and Tyomkyn.
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Abdi, D.: Siblings of binary relations: the case of direct sums of chains, NE-free posets and trees. Ph.D. Thesis, University of Calgary (2022)
Bonato, A., Tardif, C.: Mutually embeddable graphs and the tree alternative conjecture. J. Combin. Theory Ser. B 96(6), 874–880 (2006)
Bonato, A., Bruhn, H., Diestel, R., Sprüssel, P.: Twins of rayless graphs. J. Combin. Theory Ser. B 101(1), 60–65 (2011)
Braunfeld, S., Laskowski, C.: Counting siblings in universal theories. J. Symb. Log. 87 (2022), no. 3, 1130–1155
Diestel, R.: Graph Theory. Graduate Texts in Mathematics, 4th edn., vol. 173, p. xviii+437. Springer, Heidelberg (2010)
Hahn, G., Pouzet, M., Woodrow, R.: Siblings of countable cographs. arXiv preprint arXiv:2004.12457v1 (2020)
Halin, R.: Fixed configurations in graphs with small number of disjoint rays. In: Bodendiek, R. (ed.) Contemporary Methods in Graph Theory, pp. 639–649. Bibliographisches Inst, Mannheim (1990)
Halin, R.: Automorphisms and endomorphisms of infinite locally finite graphs. Abh. Math. Sem. Univer. Hamburg 39, 251–283 (1973)
Halin, R.: The structure of rayless graphs. Abh. Math. Sem. Univer. Hamburg 68, 225–253 (1998)
Hamann, M.: Self-embeddings of trees. Discrete Math. 342(12), 111586 (2019)
Imrich, W.: Subgroup theorems and graphs. In: Combinatorial Mathematics, V (Proc. 5th Austral. Conf., Roy. Melbourne Inst. Tech., Melbourne, 1976). Lecture Notes in Math., vol. 622, pp. 1–27. Springer, Berlin (1977)
Laflamme, C., Pouzet, M., Woodrow, R.: Equimorphy—the case of chains, archive for mathematical logic. Arch. Math. Logic 56(7–8), 811–829 (2017)
Laflamme, C., Pouzet, M., Sauer, N.: Invariant subsets of scattered trees and the tree alternative property of Bonato and Tardif. Abh. Math. Semin. Univer. Hambg. 87(2), 369–408 (2017)
Laflamme, C., Pouzet, M., Sauer, N., Woodrow, R.: Siblings of an \(\mathfrak{N}_0\)–categorical relational structure. Contrib. Discrete Math.16(2021), no.2, 90–127
Polat, N., Sabidussi, G.: Fixed elements of infinite trees. Graphs and combinatorics (Lyon, 1987; Montreal, PQ, 1988). Discrete Math. 130(1–3), 97–102 (1994)
Tateno, A.: Problems in finite and infinite combinatorics. Ph.D Thesis, Oxford University (2008)
Thomassé, S.: Conjectures on countable relations, circulating manuscript, 17p. 2000, and personal communication (2012)
Tits, J.: Sur le groupe des automorphismes d’un arbre. In: Essays on topology and related topics, pp. 188–211. Springer, New-York (1970)
Tyomkyn, M.: A proof of the rooted tree alternative conjecture. Discrete Math. 309, 5963–5967 (2009)
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Communicated by Nathan Bowler.
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Kalow, D.A., Laflamme, C., Tateno, A. et al. An example of Tateno disproving conjectures of Bonato–Tardif, Thomasse, and Tyomkyn. Abh. Math. Semin. Univ. Hambg. 93, 99–131 (2023). https://doi.org/10.1007/s12188-023-00270-0
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DOI: https://doi.org/10.1007/s12188-023-00270-0