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arxiv: 2605.17161 · v1 · pith:GUDGS6FLnew · submitted 2026-05-16 · 🧮 math.LO

Modular constructive Lyndon interpolation for nondistributive logics

Pith reviewed 2026-05-20 14:19 UTC · model grok-4.3

classification 🧮 math.LO
keywords Lyndon interpolationdisplay calculilattice expansion logicsLE-logicsnondistributive logicsmodal logictense logicinterpolation property
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The pith

Display calculi establish the Lyndon interpolation property for basic lattice expansion logics.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that basic lattice expansion logics satisfy the Lyndon interpolation property by means of display calculi. This property guarantees that an implication between two formulas yields an interpolant built only from their common symbols. The method is constructive, extracting the interpolant directly from a given derivation, and modular, so that new axioms preserve the property once their corresponding structural rules pass a local check. A reader would care because these logics capture modal and tense reasoning without relying on distributivity, and interpolation helps separate the shared content from the specific premises and conclusions. The framework works for arbitrary signatures and applies to the tense version of Holliday's fundamental modal logic.

Core claim

We establish the Lyndon interpolation property for basic lattice expansion logics (LE-logics) in arbitrary signatures using display calculi. Our approach is constructive, yielding interpolants algorithmically from derivations, and modular, in the sense that interpolation for axiomatic extensions can be obtained by verifying a local interpolation property for the analytic structural rules corresponding to the additional axioms. To this end, we identify a class of interpolation-safe structural rules preserving local Lyndon interpolation. As an application, the tense version of Holliday's fundamental modal logic enjoys the Lyndon interpolation property.

What carries the argument

Display calculi together with the identified class of interpolation-safe structural rules that preserve local Lyndon interpolation.

Load-bearing premise

The additional axioms of an LE-logic must correspond to analytic structural rules that belong to the class of interpolation-safe rules preserving local Lyndon interpolation.

What would settle it

A concrete counterexample would be an LE-logic extended by an analytic structural rule outside the interpolation-safe class for which some implication has no Lyndon interpolant, or a derivation in the calculus from which no interpolant can be extracted.

read the original abstract

We establish the Lyndon interpolation property for basic lattice expansion logics (LE-logics) in arbitrary signatures using display calculi. Our approach is constructive, yielding interpolants algorithmically from derivations, and modular, in the sense that interpolation for axiomatic extensions can be obtained by verifying a local interpolation property for the analytic structural rules corresponding to the additional axioms. To this end, we identify a class of interpolation-safe structural rules preserving local Lyndon interpolation. As applications of the general framework, we show that the tense version of Holliday's fundamental modal logic enjoys the Lyndon interpolation property.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

0 major / 3 minor

Summary. The manuscript establishes the Lyndon interpolation property for basic lattice expansion logics (LE-logics) in arbitrary signatures using display calculi. The approach is constructive, yielding interpolants algorithmically from derivations, and modular: interpolation for axiomatic extensions follows from verifying a local Lyndon interpolation property for the analytic structural rules corresponding to the additional axioms. The authors identify a class of interpolation-safe structural rules that preserve this local property. As an application, they show that the tense version of Holliday's fundamental modal logic enjoys the Lyndon interpolation property.

Significance. If the results hold, the paper makes a substantial contribution to proof theory for nondistributive and substructural logics by supplying a general, modular framework for Lyndon interpolation. The constructive character (algorithmic extraction of interpolants) and the isolation of an interpolation-safe rule class are explicit strengths that enable systematic extension to new axioms without re-proving the base case. The application to the tense logic provides a concrete, falsifiable instance. These features align with the field's interest in analytic calculi and interpolation for lattice-based logics.

minor comments (3)
  1. §3.2, Definition 3.5: the local Lyndon interpolation condition is stated in terms of the display calculus; a short remark on how this reduces to the standard syntactic interpolation property for the Hilbert system would aid readers unfamiliar with display calculi.
  2. §5, Example 5.3: the verification that the structural rules for the tense extension are interpolation-safe is sketched; expanding the inductive step for one rule with explicit formula tracking would make the argument easier to follow without lengthening the paper substantially.
  3. Notation: the use of 'LE-logics' and 'basic' is consistent, but a single sentence in the introduction recalling that signatures may include arbitrary lattice expansions would prevent any momentary ambiguity for readers coming from modal logic.

Simulated Author's Rebuttal

0 responses · 0 unresolved

We thank the referee for the positive summary, significance assessment, and recommendation of minor revision. No specific major comments appear in the report, so we have no individual points requiring point-by-point rebuttal or revision at this stage. We will incorporate any minor editorial suggestions during the revision process.

Circularity Check

0 steps flagged

No significant circularity; derivation self-contained

full rationale

The paper derives the Lyndon interpolation property for LE-logics via explicit construction of display calculi in arbitrary signatures, cut-elimination/analyticity proofs, and an inductive argument showing that a defined class of interpolation-safe structural rules preserves local Lyndon interpolation. These elements are supplied directly in the manuscript with definitions of the rule class and local condition; the modular inheritance for axiomatic extensions follows from the preservation theorem rather than from any self-citation chain or by-construction renaming of inputs. No load-bearing step reduces to a fitted parameter or prior self-result by definition.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The paper builds on standard background results about display calculi and analytic rules from prior proof-theoretic literature.

axioms (2)
  • standard math Display calculi admit cut-elimination and have the subformula property for the base logic.
    Invoked as the foundation for constructive interpolation extraction.
  • domain assumption Structural rules can be classified as analytic and interpolation-safe.
    Central to the modularity claim for axiomatic extensions.

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Reference graph

Works this paper leans on

19 extracted references · 19 canonical work pages

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