Assuming the existence of suitable large cardinals, we show it is consistent that the Provability logic $\mathbf{GL}$ is complete with respect to the filter sequence of normal measures. This result answers a question of Andreas Blass from 1990 and a related question of Beklemishev and Joosten.
In this paper, we study the provability logic of intuitionistic theories of arithmetic that prove their own completeness. We prove a completeness theorem for theories equipped with two provability predicates $\Box$ and $\triangle$ that prove the schemes $A\to\triangle A$ and $\Box\triangle S\to\Box S$ for $S\inΣ_1$. Using this theorem, we determine the logic of fast provability for a number of intuitionistic theories. Furthermore, we reprove a theorem previously obtained by M. Ardeshir and S. Mojtaba Mojtahedi determining the $Σ_1$-provability logic of Heyting Arithmetic.
We prove a topological completeness theorem for the modal logic GLP containing operators $\langleλ\rangle$ for $λ\in$ Ord intended to capture progressively stronger notions of consistency in mathematical theories. We show that, given a scattered space $X$ of large-enough rank, any sentence $ϕ$ consistent with GLP can be satisfied in a polytopological space based on the finitely many Icard topologies over $X$ that correspond to the finitely many modalities appearing in $ϕ$.
Strong Completeness of Provability Logic for Uncountable Languages
School of Mathematics, Institute for Research in Fundamental Sciences (IPM)(基础科学研究所数学学院);Institut für diskrete Mathematik und Geometrie, TU Wien(维也纳工业大学离散数学与几何研究所)
Provability logic GLP is well-known to be incomplete w.r.t. Kripke semantics. A natural topological semantics of GLP interprets modalities as derivative operators of a polytopological space. Such spaces satisfying all the axioms of GLP are called GLP-spaces. We develop some constructions to build nontrivial GLP-spaces and show that GLP is complete w.r.t. the class of all GLP-spaces.
In 1933, Gödel considered two modal approaches to describing provability. One captured formal provability and resulted in the logic GL and Solovay's Completeness Theorem. The other was based on the modal logic S4 and led to Artemov's Logic of Proofs LP. In this paper, we study introduced by the author logic GLA, which is a fusion of GL and LP in the union of their languages. GLA is supplied with a Kripke-style semantics and the corresponding completeness theorem. Soundness and completeness of GLA with respect to the arithmetical provability semantics is established.
By Solovay's celebrated completeness result on formal provability we know that the provability logic $\mathrm GL$ describes exactly all provable structural properties for any sound and strong enough arithmetical theory with a decidable axiomatisation. Japaridze generalised this result by considering a polymodal version $\mathrm GLP$ of $\mathrm GL$ with modalities $[n]$ for each natural number $n$ referring to ever increasing notions of provability. Modern treatments of $\mathrm GLP$ tend to interpret the $[n]$ provability notion as "provable in a base theory $T$ together with all true $Π^0_n$…
The branch of provability logic investigates the provability-based behavior of the mathematical theories. In a more precise way, it studies the relation between a mathematical theory $T$ and a modal logic $L$ via the provability interpretation which interprets the modality as the provability predicate of $T$. In this paper we will extend this relation to investigate the provability-based behavior of a hierarchy of theories. More precisely, using the modal language with infinitely many modalities, $\{\Box_n\}_{n=0}^{\infty}$, we will define the hierarchical counterparts of some of the classical…
In this paper we consider transfinite provability logics where for each ordinal in some recursive well-order we have a corresponding modal provability operator. The modality [xi] will be interpreted as "provable in ACA_0 together with at most xi nested applications of the omega rule". We show how to formalize this in in second order number theory. Next we prove both soundness and completeness under this interpretation. We conclude by showing how one can lower the base theory ACA_0 to theories below RCA_0.
Let $\mathcal{PL}({\sf T},{\sf T}')$ and $\mathcal{PL}_{Σ_1}({\sf T},{\sf T}')$ respectively indicates the provability logic and $Σ_1$-provability logic of ${\sf T}$ relative in ${\sf T}'$. In this paper we characterize the following relative provability logics: $\mathcal{PL}_{Σ_1}({\sf HA},\mathbb{N})$, $\mathcal{PL}_{Σ_1}({\sf HA},{\sf PA})$, $\mathcal{PL}_{Σ_1}({\sf HA}^*,\mathbb{N})$, $\mathcal{PL}_{Σ_1}({\sf HA}^*,{\sf PA})$, $\mathcal{PL}({\sf PA},{\sf HA})$, $\mathcal{PL}_{Σ_1}({\sf PA},{\sf HA})$, $\mathcal{PL}({\sf PA}^*,{\sf HA})$, $\mathcal{PL}_{Σ_1}({\sf PA}^*,{\sf HA})$, $\mathcal…
Provability logics are modal or polymodal systems designed for modeling the behavior of Gödel's provability predicate in arithmetical theories and its natural extensions. If Λis any ordinal, the Gödel-Löb calculus GLP(Λ) contains one modality [λ] for each λ<Λ, representing provability predicates of increasing strength. GLP(Λ) has no Kripke models, but Beklemishev and Gabelaia recently proved that GLP(ω) is complete for its class of topological models. In this paper we generalize Beklemishev and Gabelaia's result to GLP(Λ) for arbitrary Λ. We also introduce provability ambiances, which are topo…
Abashidze and Blass independently proved that the modal logic $\sf{GL}$ is complete for its topological interpretation over any ordinal greater than or equal to $ω^ω$ equipped with the interval topology. Icard later introduced a family of topologies $\mathcal I_λ$ for $λ< ω$, with the purpose of providing semantics for Japaridze's polymodal logic $\sf{GLP}$ $_ω$. Icard's construction was later extended by Joosten and the second author to arbitrary ordinals $λ\geq ω$. We further generalize Icard topologies in this article. Given a scattered space $\mathfrak X = (X, τ)$ and an ordinal $λ$, we de…
In this paper we present a new proof of Solovay's theorem on arithmetical completeness of Gödel-Löb provability logic GL. Originally, completeness of GL with respect to interpretation of $\Box$ as provability in PA was proved by R. Solovay in 1976. The key part of Solovay's proof was his construction of an arithmetical evaluation for a given modal formula that made the formula unprovable PA if it were unprovable in GL. The arithmetical sentences for the evaluations were constructed using certain arithmetical fixed points. The method developed by Solovay have been used for establishing similar …
In 1994 Jech gave a model theoretic proof of Gödel's second incompleteness theorem for Zermelo-Fraenkel set theory in the following form: ZF does not prove that ZF has a model. Kotlarski showed that Jech's proof can be adapted to Peano Arithmetic with the role of models being taken by complete consistent extensions. In this note we take another step in the direction of replacing proof-theoretic by model-theoretic arguments. We show, without passing through the arithmetized completeness theorem, that the existence of a model of PA of complexity $Σ^0_2$ is independent of PA, where a model is ide…
This paper presents the logic QRC$_1$, which is a strictly positive fragment of quantified modal logic. The intended reading of the diamond modality is that of consistency of a formal theory. Predicate symbols are interpreted as parametrized axiomatizations. We prove arithmetical soundness of the logic QRC$_1$ with respect to this arithmetical interpretation. Quantified provability logic is known to be undecidable. However, the undecidability proof cannot be performed in our signature and arithmetical reading. We conjecture the logic QRC$_1$ to be arithmetically complete. This paper takes the …
Considering classical first-order logic with equality, we give a "fully syntactic" construction of the (weak) syntactic category $\text{Syn}(T)$ associated to a consistent theory $T$; we show it is a consistent coherent category; and we show that a morphism of coherent categories $\text{Syn}(T)\to \bf{Set}$ gives rise to a model $\mathcal{M}$ of $T$ in the usual sense. We then invoke Deligne's theorem on small consistent coherent categories.