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Constructive Cut Elimination in Geometric Logic

Authors Giulio Fellin , Sara Negri , Eugenio Orlandelli

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Author Details

Giulio Fellin
  • Department of Computer Science, University of Verona, Italy
  • Department of Mathematics, University of Trento, Italy
  • Department of Philosophy, History and Art Studies, University of Helsinki, Finland
Sara Negri
  • Department of Mathematics, University of Genoa, Italy
Eugenio Orlandelli
  • Department of Philosophy and Communication Studies, University of Bologna, Italy


We are very grateful to Peter Schuster for precious comments and helpful discussions on various points. We also thank the three anonymous referees for their detailed and insightful comments that helped improving the paper.

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Giulio Fellin, Sara Negri, and Eugenio Orlandelli. Constructive Cut Elimination in Geometric Logic. In 27th International Conference on Types for Proofs and Programs (TYPES 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 239, pp. 7:1-7:16, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2022)


A constructivisation of the cut-elimination proof for sequent calculi for classical and intuitionistic infinitary logic with geometric rules - given in earlier work by the second author - is presented. This is achieved through a procedure in which the non-constructive transfinite induction on the commutative sum of ordinals is replaced by two instances of Brouwer’s Bar Induction. Additionally, a proof of Barr’s Theorem for geometric theories that uses only constructively acceptable proof-theoretical tools is obtained.

Subject Classification

ACM Subject Classification
  • Theory of computation → Proof theory
  • Geometric theories
  • sequent calculi
  • axioms-as-rules
  • infinitary logic
  • constructive cut elimination


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