Uniform Lyndon interpolation for the pure logic of necessitation with a modal reduction principle

Fuente: arXiv
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Main Author: Sato, Yuta
Format: Preprint
Published: 2025
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author Sato, Yuta
author_facet Sato, Yuta
contents We prove the uniform Lyndon interpolation property (ULIP) of some extensions of the pure logic of necessitation $\mathbf{N}$. For any $m, n \in \mathbb{N}$, $\mathbf{N}^+\mathbf{A}_{m,n}$ is the logic obtained from $\mathbf{N}$ by adding a single axiom $\Box^n φ\to \Box^m φ$, $\Diamond$-free modal reduction principle, together with a rule $\frac{\neg \Box φ}{\neg \Box \Box φ}$, required to make the logic complete with respect to its Kripke-like semantics. We first introduce a sequent calculus $\mathbf{GN}^+\mathbf{A}_{m,n}$ for $\mathbf{N}^+\mathbf{A}_{m,n}$ and show that it enjoys cut elimination, proving Craig and Lyndon interpolation properties as a consequence. We then introduce a general method, called propositionalization, that enables one to reduce ULIP of a logic to some weaker logic. Lastly, we construct a propositionalization of $\mathbf{N}^+\mathbf{A}_{m,n}$ into classical propositional logic $\mathbf{Cl}$, proving ULIP as a corollary. We also prove ULIP of $\mathbf{NA}_{m,n} = \mathbf{N} + \Box^n φ\to \Box^m φ$ and $\mathbf{NRA}_{m,n} = \mathbf{N} + \Box^n φ\to \Box^m φ+ \frac{\neg φ}{\neg \Box φ}$ in the same manner.
format Preprint
id arxiv_https___arxiv_org_abs_2503_10176
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Uniform Lyndon interpolation for the pure logic of necessitation with a modal reduction principle
Sato, Yuta
Logic
03B45, 03C40, 03F05
We prove the uniform Lyndon interpolation property (ULIP) of some extensions of the pure logic of necessitation $\mathbf{N}$. For any $m, n \in \mathbb{N}$, $\mathbf{N}^+\mathbf{A}_{m,n}$ is the logic obtained from $\mathbf{N}$ by adding a single axiom $\Box^n φ\to \Box^m φ$, $\Diamond$-free modal reduction principle, together with a rule $\frac{\neg \Box φ}{\neg \Box \Box φ}$, required to make the logic complete with respect to its Kripke-like semantics. We first introduce a sequent calculus $\mathbf{GN}^+\mathbf{A}_{m,n}$ for $\mathbf{N}^+\mathbf{A}_{m,n}$ and show that it enjoys cut elimination, proving Craig and Lyndon interpolation properties as a consequence. We then introduce a general method, called propositionalization, that enables one to reduce ULIP of a logic to some weaker logic. Lastly, we construct a propositionalization of $\mathbf{N}^+\mathbf{A}_{m,n}$ into classical propositional logic $\mathbf{Cl}$, proving ULIP as a corollary. We also prove ULIP of $\mathbf{NA}_{m,n} = \mathbf{N} + \Box^n φ\to \Box^m φ$ and $\mathbf{NRA}_{m,n} = \mathbf{N} + \Box^n φ\to \Box^m φ+ \frac{\neg φ}{\neg \Box φ}$ in the same manner.
title Uniform Lyndon interpolation for the pure logic of necessitation with a modal reduction principle
topic Logic
03B45, 03C40, 03F05
url https://arxiv.org/abs/2503.10176