Intuitionistic linear temporal logic (iLTL) has been studied extensively, especially in the last decade. It enjoys natural semantics over intuitionistic Kripke frames equipped with an order-preserving function representing the temporal dynamics, known as 'expanding models'. This leads to a logic that is known to be decidable but whose axiomatisation has long remained open. We propose an extension of iLTL with the co-implication connective of Hilbert–Brouwer logic and call it 'bi-intuitionistic linear temporal logic' (biLTL). We establish that this extension is still decidable for the class of expanding models. We moreover give a sound and complete Hilbert-style calculus for it, the first for any logic extending iLTL. As a corollary, the topological semantics for intuitionistic propositional logic cannot be extended to a topological semantics for Hilbert-Brouwer logic, which thus establishes co-implication as a distinctive feature of the Kripke semantics for bi-intuitionistic logic.

We investigate intuitionistic logics extended both with the co-implication connective of Hilbert-Brouwer logic and with diamond and box modalities. We use a Kripke semantics based on frames with two 'forth' confluence conditions on the modal relation with respect to the intuitionistic relation. We give sound and strongly complete axiomatisations for entailment on this class of frames, and give similar axiomatisations for the subclasses of frames satisfying any combination of reflexivity, transitivity, and seriality. We then prove that all of these logics are decidable, by proving that they have the finite frame property.

Abstract We introduce ill-founded sequent calculi for two intuitionistic linear-time temporal logics. Both logics are based on the language of intuitionistic propositional logic with ‘next’ and ‘until’ operators and are evaluated on dynamic Kripke models wherein the intuitionistic and temporal accessibility relations are assumed to satisfy one of two natural confluence properties: forward confluence in one case, and both forward and backward confluence in the other. The presented sequent calculi are cut-free and incorporate a simple form of formula nesting. Soundness of the calculi is shown by a standard argument and completeness via proof search.