Small partial Latin squares that embed in an infinite group but not into any finite group

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Abstract

Suppose that Y1, Y2, Y3 are finite sets and P ⊆ Y1 × Y2 × Y3.  We say that P embeds in a group G if there exist injective maps Φi :Yi → G for i = 1, 2, 3 such that Φ1(y1)Φ2(y2) = Φ3(y3) for each (y1,y2,y3) ∈ P. Hirsch and Jackson asked for the cardinality of the smallest P that embeds in some infinite group but not into any finite group.  We prove that the answer to their question is 12. Moreover, we show that there are 50 examples of cardinality 12, up to equivalence, and each of them embeds in the (infinite) Baumslag group G =〈a,b|b=[b,ba]〉. Our proof uses computations to answer questions about finitely presented groups which are known to be algorithmically undecidable in general.

Original languageEnglish
Pages (from-to)142-152
Number of pages11
JournalJournal of Symbolic Computation
Volume86
DOIs
Publication statusPublished - 2018

Keywords

  • Baumslag group
  • Finitely presented group
  • Group embedding
  • Partial Latin square

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