• Media type: Text; E-Article; Electronic Conference Proceeding
  • Title: Herbrand-Confluence for Cut Elimination in Classical First Order Logic
  • Contributor: Hetzl, Stefan [Author]; Straßburger, Lutz [Author]
  • imprint: Schloss Dagstuhl – Leibniz-Zentrum für Informatik, 2012
  • Language: English
  • DOI: https://doi.org/10.4230/LIPIcs.CSL.2012.320
  • Keywords: first-order logic ; semantics of proofs ; tree languages ; term rewriting ; proof theory
  • Origination:
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  • Description: We consider cut-elimination in the sequent calculus for classical first-order logic. It is well known that this system, in its most general form, is neither confluent nor strongly normalizing. In this work we take a coarser (and mathematically more realistic) look at cut-free proofs. We analyze which witnesses they choose for which quantifiers, or in other words: we only consider the Herbrand-disjunction of a cut-free proof. Our main theorem is a confluence result for a natural class of proofs: all (possibly infinitely many) normal forms of the non-erasing reduction lead to the same Herbrand-disjunction.
  • Access State: Open Access