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PreprintarXiv licencearXiv

Non-finite Axiomatizability and Undecidability of Cheq

  • Han Xiao
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Abstract

We prove that Cheq is not finitely axiomatizable, resolving a longstanding open problem in intermediate and modal logics. We further prove that the undecidability of Medvedev logic implies the undecidability of Cheq.

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Cite

BibTeXRIS
BibTeX
@misc{xiao2026nonfinite,
  title = {{Non-finite Axiomatizability and Undecidability of $\mathsfCheq$}},
  author = {Han Xiao},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.39577},
  eprint = {2609.39577},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.39577},
}
RIS
TY  - UNPB
TI  - Non-finite Axiomatizability and Undecidability of Cheq
AU  - Han Xiao
PY  - 2026
DA  - 2026/09/30
PB  - arXiv
DO  - 10.48550/arxiv.2609.39577
UR  - https://arxiv.org/abs/2609.39577
AB  - We prove that Cheq is not finitely axiomatizable, resolving a longstanding open problem in intermediate and modal logics. We further prove that the undecidability of Medvedev logic implies the undecidability of Cheq.
ER  -