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arxiv: 2601.08432 · v2 · submitted 2026-01-13 · 💻 cs.LO

Forcing and Interpolation in first-order hybrid Logic with rigid symbols

Pith reviewed 2026-05-16 14:52 UTC · model grok-4.3

classification 💻 cs.LO
keywords Craig interpolationfirst-order hybrid logicforcing techniquemany-sorted logicrigid symbolssignature square
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The pith

A forcing technique that adds constants while preserving consistency proves Craig interpolation for many-sorted first-order hybrid logic.

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

The paper establishes an analogue of the Craig Interpolation Property for many-sorted first-order hybrid logic with rigid symbols. It introduces a forcing technique that adds new constants to the signature dynamically. This addition preserves consistency even when models have empty domains. The technique leads to general criteria sufficient for signature squares to satisfy the interpolation property. Readers interested in logical foundations for computer science would value this because interpolation supports modular proofs and reasoning.

Core claim

We establish an analogue of Craig Interpolation Property for a many-sorted variant of first-order hybrid logic. We develop a forcing technique that dynamically adds new constants to the underlying signature in a way that preserves consistency, even in the presence of models with possibly empty domains. Using this forcing method, we derive general criteria that are sufficient for a signature square to satisfy Craig interpolation property.

What carries the argument

The forcing technique that dynamically adds new constants to the signature preserving consistency in models possibly with empty domains.

If this is right

  • Craig interpolation holds for the many-sorted first-order hybrid logic when the signature square meets the derived criteria.
  • The method works for logics that include rigid symbols.
  • Consistency holds during forcing even for models with empty domains.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The forcing method could extend to other hybrid or modal logics with similar signature structures.
  • It may support the construction of interpolation-based decision procedures for verification problems.
  • Further links to model-theoretic transfer properties in first-order settings remain open for investigation.

Load-bearing premise

The forcing technique dynamically adds new constants to the underlying signature in a way that preserves consistency, even in the presence of models with possibly empty domains.

What would settle it

A specific signature square that meets the general criteria derived from the forcing method yet fails Craig interpolation for some pair of formulas would show the criteria are insufficient.

read the original abstract

In this paper, we establish an analogue of Craig Interpolation Property for a many-sorted variant of first-order hybrid logic. We develop a forcing technique that dynamically adds new constants to the underlying signature in a way that preserves consistency, even in the presence of models with possibly empty domains. Using this forcing method, we derive general criteria that are sufficient for a signature square to satisfy Craig 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

1 major / 1 minor

Summary. The paper claims to establish an analogue of the Craig Interpolation Property for a many-sorted variant of first-order hybrid logic with rigid symbols. It develops a forcing technique that dynamically adds new constants to the underlying signature while preserving consistency even in the presence of models with possibly empty domains, and uses this method to derive general criteria sufficient for a signature square to satisfy the CIP.

Significance. If the forcing construction is rigorously shown to preserve consistency without post-hoc restrictions on empty domains, the result would be a solid technical contribution to the model theory of hybrid logics. It provides a new device for deriving interpolation criteria in the presence of rigid symbols and many-sorted structures, potentially applicable to related modal and hybrid systems. The explicit treatment of signature squares and consistency preservation is a strength when the details hold.

major comments (1)
  1. [Forcing lemma and proof of the general CIP criterion] Forcing lemma and proof of the general CIP criterion: the central construction extends the signature by fresh constants while claiming to preserve consistency even for models with possibly empty domains. In semantics permitting empty domains, a constant symbol must be interpreted by a domain element, so adjoining any constant renders an empty-domain model inconsistent. The manuscript must demonstrate either that the forcing step never requires populating a previously empty domain or that the interpolant can be recovered without the added constants in the empty case; no such case distinction is stated in the general criterion for signature squares. This point is load-bearing for the abstract's claim.
minor comments (1)
  1. The abstract states the method clearly, but the full text would benefit from an explicit preliminary section recalling the semantics of rigid symbols and the precise definition of empty-domain models to aid readability.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading of the manuscript and for identifying this important technical point concerning the interaction between the forcing construction and empty domains. We agree that the current presentation would benefit from greater explicitness on this matter to fully support the claims in the abstract and the general criterion. We address the comment below and will revise the manuscript accordingly.

read point-by-point responses
  1. Referee: Forcing lemma and proof of the general CIP criterion: the central construction extends the signature by fresh constants while claiming to preserve consistency even for models with possibly empty domains. In semantics permitting empty domains, a constant symbol must be interpreted by a domain element, so adjoining any constant renders an empty-domain model inconsistent. The manuscript must demonstrate either that the forcing step never requires populating a previously empty domain or that the interpolant can be recovered without the added constants in the empty case; no such case distinction is stated in the general criterion for signature squares. This point is load-bearing for the abstract's claim.

    Authors: We acknowledge that the referee's observation is correct and that the manuscript does not currently contain an explicit case distinction for empty domains within the statement of the general CIP criterion. In the revised version we will add the following clause to the general criterion: if every model of the relevant theories has an empty domain, then the interpolant is recovered directly from the base logic without applying the forcing step (hence without adjoining constants). In all other cases the forcing construction proceeds only on non-empty domains, preserving consistency by the existing lemma. This case distinction will be inserted both in the statement of the criterion and in the proof of the forcing lemma, together with a short verification that the empty-domain case is vacuously consistent with the signature square. We believe these additions fully address the concern while leaving the core technical results unchanged. revision: yes

Circularity Check

0 steps flagged

No circularity in forcing-based derivation of CIP criteria

full rationale

The paper introduces a forcing technique that dynamically extends signatures by fresh constants while preserving consistency, including for models with possibly empty domains, then applies it to obtain sufficient conditions on signature squares for the Craig interpolation property in many-sorted first-order hybrid logic. No load-bearing step reduces by construction to its own inputs: the forcing construction is presented as an independent technical device whose consistency preservation is asserted directly from the semantics rather than derived from the target interpolation result, and no self-citation, fitted parameter, or ansatz is invoked to close the derivation. The central claims therefore remain self-contained against the external semantics of hybrid logic.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The paper relies on standard background axioms of first-order hybrid logic and the many-sorted signature framework with rigid symbols; the forcing construction is the primary new device. No free parameters or invented entities are mentioned in the abstract.

axioms (2)
  • standard math Standard axioms and semantics of first-order hybrid logic
    The logic variant is defined as an extension of known hybrid logic.
  • domain assumption Many-sorted signatures allowing rigid symbols and possibly empty domains
    Explicitly stated as part of the variant considered.

pith-pipeline@v0.9.0 · 5350 in / 1101 out tokens · 29507 ms · 2026-05-16T14:52:07.375045+00:00 · methodology

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Reference graph

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