Abstract

Commutative properties in formal languages pose problems at the frontier of computer science, computational linguistics and computational group theory. A prominent problem of this kind is the position of the language On, the language that contains the same number of letters ai and a¯i with 1⩽i⩽n, in the known classes of formal languages. It has recently been shown that On is a Multiple Context-Free Language (MCFL). However the more precise conjecture of Nederhof that On is an MCFL of dimension n was left open. We prove this conjecture using tools from algebraic topology. On our way, we prove a variant of the necklace splitting theorem.

Original languageEnglish
Pages (from-to)41-52
Number of pages12
JournalJournal of Computer and System Sciences
Volume127
DOIs
Publication statusPublished - 1 Aug 2022

Keywords

  • Commutative Languages
  • Formal Languages
  • Multiple Context Free Languages
  • Necklace splitting theorem
  • Tucker Lemma
  • Word problem in groups

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