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We prove that a plactic monoid of any finite rank has decidable first order theory. This resolves other open decidability problems about the finite rank plactic monoids, such as the Diophantine problem and identity checking. This is achieved by interpreting a plactic monoid of arbitrary rank in Presburger arithmetic, which is known to have decidable first order theory. We also prove that the interpretation of the plactic monoids into Presburger Arithmetic is in fact a bi-interpretation, hence any two plactic monoids of finite rank are bi-interpretable with one another. The algorithm generating the interpretations is uniform, which answers positively the decidability of the Diophantine problem for the infinite rank plactic monoid. [ABSTRACT FROM AUTHOR]

This paper studies a combined system of intuitionistic and classical propositional logic from proof-theoretic viewpoints. Based on the semantic treatment of Humberstone (J Philos Log 8:171–196, 1979) and del Cerro and Herzig (Frontiers of combining systems: FroCoS, Springer, 1996), a sequent calculus G (C + J) is proposed. An approximate idea of obtaining G (C + J) is adding rules for classical implication on top of the intuitionistic multi-succedent sequent calculus by Maehara (Nagoya Math J 7:45–64, 1954). However, in the semantic treatment, some formulas do not satisfy heredity, which leads to the necessity of a restriction on the right rule for intuitionistic implication to keep the soundness of the calculus. The calculus G (C + J) enjoys cut elimination and Craig interpolation, whose detailed proofs are described in this paper. Cut elimination enables us to show the decidability of this combination both directly and syntactically. This paper also employs a canonical model argument to establish the strong completeness of Hilbert system C + J proposed by del Cerro and Herzig (Frontiers of combining systems: FroCoS, Springer, 1996). [ABSTRACT FROM AUTHOR]

We show that the finite sequentiality problem is decidable for finitely ambiguous max-plus tree automata. A max-plus tree automaton is a weighted tree automaton over the max-plus semiring. A max-plus tree automaton is called finitely ambiguous if the number of accepting runs on every tree is bounded by a global constant. The finite sequentiality problem asks whether for a given max-plus tree automaton, there exist finitely many deterministic max-plus tree automata whose pointwise maximum is equivalent to the given automaton. [ABSTRACT FROM AUTHOR]

We introduce the infix inclusion problem of two languages S and T that decides whether or not S is a subset of the set of all infixes of T. This problem is motivated by the need for identifying malicious computation patterns according to their semantics, which are often disguised with additional sub-patterns surrounding information. In other words, malicious patterns are embedded as an infix of the whole pattern. We examine the infix inclusion problem for the case where a source S and a target T are finite, regular or context-free languages. We prove that the problem is 1) co-NP-complete when one of the languages is finite, 2) PSPACE-complete when both S and T are regular, 3) EXPTIME-complete when S is context-free and T is regular, 4) undecidable when S is either regular or context-free and T is context-free and 5) undecidable when one of S and T is in a language class where the emptiness of its languages is undecidable, even if the other is finite. We, furthermore, explore the infix inclusion problem for visibly pushdown languages, a subclass of context-free languages. [ABSTRACT FROM AUTHOR]

We provide an alternative proof of the decidability of the equational theory of lattices. The proof presented here is quite short and elementary. [ABSTRACT FROM AUTHOR]

This paper is dedicated to studying the algorithmic properties of unars with an injective function. We prove that the theory of every such unar admits quantifier elimination if the language is extended by a countable set of predicate symbols. Necessary and sufficient conditions are established for the quantifier elimination to be effective, and a criterion for decidability of theories of such unars is formulated. Using this criterion, we build a unar such that its theory is decidable, but the theory of the unar of its subsets is undecidable. [ABSTRACT FROM AUTHOR]

This paper studies proof systems for the logics of super-strict implication ST 2 – ST 5 , which correspond to C.I. Lewis' systems S 2 – S 5 freed of paradoxes of strict implication. First, Hilbert-style axiomatic systems are introduced and shown to be sound and complete by simulating STn in Sn and backsimulating Sn in STn , respectively (for n = 2 , ... , 5 ). Next, G 3 -style labelled sequent calculi are investigated. It is shown that these calculi have the good structural properties that are distinctive of G 3 -style calculi, that they are sound and complete, and it is shown that the proof search for G 3. ST 2 is terminating and therefore the logic is decidable. [ABSTRACT FROM AUTHOR]

String assembling systems are biologically inspired mechanisms that generate strings from copies out of finite sets of assembly units. The underlying mechanism is based on piecewise assembly of a double-stranded sequence of symbols, where the upper and lower strand have to match. The generation is additionally controlled by the requirement that the first symbol of a unit has to be the same as the last symbol of the strand generated so far, as well as by the distinction of assembly units that may appear at the beginning, during, or at the end of the assembling process and by a length restriction on the units. We investigate the power of these model-inherent control mechanisms by considering variants where one or more of these mechanisms are relaxed. The generative capacities and the relative power of the variants are our main interest. In particular, we prove that the power gained in the different control mechanisms may yield strictly more powerful systems and incomparable capacities. Additionally, we generalize these systems to multi-stranded systems. We obtain a strong connection to one-way multi-head finite automata and show an infinite, dense, and strict strand hierarchy. Finally, we examine the closure properties of the different variants of string assembling systems. [ABSTRACT FROM AUTHOR]

We construct an example of a group G = Z 2 × G 0 for a finite abelian group G 0 , a subset E of G 0 , and two finite subsets F 1 , F 2 of G, such that it is undecidable in ZFC whether Z 2 × E can be tiled by translations of F 1 , F 2 . In particular, this implies that this tiling problem is aperiodic, in the sense that (in the standard universe of ZFC) there exist translational tilings of E by the tiles F 1 , F 2 , but no periodic tilings. Previously, such aperiodic or undecidable translational tilings were only constructed for sets of eleven or more tiles (mostly in Z 2 ). A similar construction also applies for G = Z d for sufficiently large d. If one allows the group G 0 to be non-abelian, a variant of the construction produces an undecidable translational tiling with only one tile F. The argument proceeds by first observing that a single tiling equation is able to encode an arbitrary system of tiling equations, which in turn can encode an arbitrary system of certain functional equations once one has two or more tiles. In particular, one can use two tiles to encode tiling problems for an arbitrary number of tiles. [ABSTRACT FROM AUTHOR]

The present paper studies formal properties of so-called modal information logics (MILs)—modal logics first proposed in (van Benthem 1996) as a way of using possible-worlds semantics to model a theory of information. They do so by extending the language of propositional logic with a binary modality defined in terms of being the supremum of two states. First proposed in 1996, MILs have been around for some time, yet not much is known: (van Benthem 2017, 2019) pose two central open problems, namely (1) axiomatizing the two basic MILs of suprema on preorders and posets, respectively, and (2) proving (un)decidability. The main results of the first part of this paper are solving these two problems: (1) by providing an axiomatization [with a completeness proof entailing the two logics to be the same], and (2) by proving decidability. In the proof of the latter, an emphasis is put on the method applied as a heuristic for proving decidability 'via completeness' for semantically introduced logics; the logics lack the FMP w.r.t. their classes of definition, but not w.r.t. a generalized class. These results are build upon to axiomatize and prove decidable the MILs attained by endowing the language with an 'informational implication'—in doing so a link is also made to the work of (Buszkowski 2021) on the Lambek Calculus. [ABSTRACT FROM AUTHOR]

In recent years, there has been a growing interest in truthmaker semantics as a framework for understanding a range of phenomena in philosophy and linguistics. Despite this interest, there has been limited study of the various logics that arise from the semantics. This paper aims to address this gap by exploring numerous ‘truthmaker logics’ and proving their compactness and decidability. This is in continuation with the inquiry of Fine and Jago (2019), who proved compactness and decidability for a particular kind of truthmaker logic. The key results going into this are (1) ‘standard translations’ into first-order logic; (2) a truthmaker analogue of the finite model property; and (3) a proof showing that truthmaker consequence on semilattices coincides with truthmaker consequence on complete lattices. Finally, the connection with modal logic is examined. Specifically, it is illustrated how endowing truthmaker semantics with classical negation results in modal information logics. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a variant of second-order propositional modal logic interpreted on general (or Henkin) frames, S O P M L H , and present a decidable fragment of this logic, S O P M L dec H , that preserves important expressive capabilities of S O P M L H . S O P M L dec H is defined as a modal loosely guarded fragment of S O P M L H . We demonstrate the expressive power of S O P M L dec H using examples in which modal operators obtain (a) the epistemic interpretation, (b) the dynamic interpretation. S O P M L dec H partially satisfies the principle of non-Fregean logic: two different atomic propositions with the same truth value can have different contents. In S O P M L dec H , we also define relating connectives and show that the weak Boethius' Thesis built using these connectives is a valid formula of S O P M L dec H . [ABSTRACT FROM AUTHOR]

Reasoning about equilibria in normal form games involves the study of players’ incentives to deviate unilaterally from any profile. In the case of large anonymous games, the pattern of reasoning is different. Payoffs are determined by strategy distributions rather than strategy profiles. In such a game each player would strategise based on expectations of what fraction of the population makes some choice, rather than respond to individual choices by other players. A player may not even know how many players there are in the game. Logicising such strategisation involves many challenges as the set of players is potentially unbounded. This suggests a logic of quantification over player variables and modalities for player deviation, but such a logic is easily seen to be undecidable. Instead, we propose a propositional modal logic using player types as names and implicit quantification over players. With modalities for player deviation and transitive closure, the logic can be used to specify game equilibrium and interesting patterns of reasoning in large games. We show that the logic is decidable and present a complete axiomatisation of the valid formulas. [ABSTRACT FROM AUTHOR]

In this paper we study colorings (or tilings) of the two-dimensional grid ℤ 2 . A coloring is said to be valid with respect to a set P of n × m rectangular patterns if all n × m sub-patterns of the coloring are in P. A coloring c is said to be of low complexity with respect to a rectangle if there exist m , n ∈ ℕ and a set P of n × m rectangular patterns such that c is valid with respect to P and |P|≤ nm. Open since it was stated in 1997, Nivat's conjecture states that such a coloring is necessarily periodic. If Nivat's conjecture is true, all valid colorings with respect to P such that |P|≤ mn must be periodic. We prove that there exists at least one periodic coloring among the valid ones. We use this result to investigate the tiling problem, also known as the domino problem, which is well known to be undecidable in its full generality. However, we show that it is decidable in the low-complexity setting. Then, we use our result to show that Nivat's conjecture holds for uniformly recurrent configurations. These results also extend to other convex shapes in place of the rectangle. After that, we prove that the nm bound is multiplicatively optimal for the decidability of the domino problem, as for all ε > 0 it is undecidable to determine if there exists a valid coloring for a given m , n ∈ ℕ and set of rectangular patterns P of size n × m such that |P|≤ (1 + ε)nm. We prove a slightly better bound in the case where m = n, as well as constructing aperiodic SFTs of pretty low complexity. This paper is an extended version of a paper published in STACS 2020 (Kari and Moutot 12). [ABSTRACT FROM AUTHOR]

We have provided a model-theoretic proof for the decidability of the additive structure of integers together with the function f mapping x to ⌊ φ x ⌋ where φ is the golden ratio. [ABSTRACT FROM AUTHOR]

This article presents results and open problems related to definability spaces (reducts) and sources of this field since the 19th century. Finiteness conditions and constraints are investigated, including the depth of quantifier alternation and the number of arguments. Results related to the description of lattices of definability spaces for numerical and other natural structures are described. Research methods include the study of automorphism groups of elementary extensions of the structures under consideration, application of the Svenonius theorem. [ABSTRACT FROM AUTHOR]

We propose a new topological semantics for evidence, evidence-based justifications, belief, and knowledge. Resting on the assumption that an agent’s rational belief is based on the available evidence, we try to unveil the concrete relationship between an agent’s evidence, belief, and knowledge via a rich formal framework afforded by topologically interpreted modal logics. We prove soundness, completeness, decidability, and the finite model property for the associated logics, and apply this setting to analyze key epistemological issues such as “no false lemma” Gettier examples, misleading defeaters, undefeated justification versus undefeated belief, as well as the defeasibility theories of knowledge. [ABSTRACT FROM AUTHOR]

Concrete domains have been introduced in the area of Description Logic to enable reference to concrete objects (such as numbers) and predefined predicates on these objects (such as numerical comparisons) when defining concepts. Unfortunately, in the presence of general concept inclusions (GCIs), which are supported by all modern DL systems, adding concrete domains may easily lead to undecidability. To regain decidability of the DL ALC in the presence of GCIs, quite strong restrictions, in sum called ω -admissibility, were imposed on the concrete domain. On the one hand, we generalize the notion of ω -admissibility from concrete domains with only binary predicates to concrete domains with predicates of arbitrary arity. On the other hand, we relate ω -admissibility to well-known notions from model theory. In particular, we show that finitely bounded homogeneous structures yield ω -admissible concrete domains. This allows us to show ω -admissibility of concrete domains using existing results from model theory. When integrating concrete domains into lightweight DLs of the EL family, achieving decidability is not enough. One wants reasoning in the resulting DL to be tractable. This can be achieved by using so-called p-admissible concrete domains and restricting the interaction between the DL and the concrete domain. We investigate p-admissibility from an algebraic point of view. Again, this yields strong algebraic tools for demonstrating p-admissibility. In particular, we obtain an expressive numerical p-admissible concrete domain based on the rational numbers. Although ω -admissibility and p-admissibility are orthogonal conditions that are almost exclusive, our algebraic characterizations of these two properties allow us to locate an infinite class of p-admissible concrete domains whose integration into ALC yields decidable DLs. [ABSTRACT FROM AUTHOR]

Despite being fairly powerful, finite non-deterministic matrices are unable to characterize some logics of formal inconsistency, such as those found between mbCcl and Cila . In order to overcome this limitation, we propose here restricted non-deterministic matrices (in short, RNmatrices), which are non-deterministic algebras together with a subset of the set of valuations. This allows us to characterize not only mbCcl and Cila (which is equivalent, up to language, to da Costa's logic C 1 ) but the whole hierarchy of da Costa's calculi C n . This produces a novel decision procedure for these logics. Moreover, we show that the RNmatrix semantics proposed here induces naturally a labelled tableau system for each C n , which constitutes another decision procedure for these logics. This new semantics allows us to conceive da Costa's hierarchy of C-systems as a family of (non deterministically) (n + 2) -valued logics, where n is the number of "inconsistently true" truth-values and 2 is the number of "classical" or "consistent" truth-values, for every C n . [ABSTRACT FROM AUTHOR]

Often philosophers, logicians, and mathematicians employ a notion of intended structure when talking about a branch of mathematics. In addition, we know that there are foundational mathematical theories that can find representatives for the objects of informal mathematics. In this paper, we examine how faithfully foundational theories can represent intended structures, and show that this question is closely linked to the decidability of the theory of the intended structure. We argue that this sheds light on the trade-off between expressive power and meta-theoretic properties when comparing first-order and second-order logic. [ABSTRACT FROM AUTHOR]

We consider the restricted interpolation property IPR in modal logics. Earlier, the decidability of IPR over the modal logic S4 was proved and a finite list was found that contains all logics that can possess IPR over S4. However, this list contains some undue logics. The present article gives examples of the logics. [ABSTRACT FROM AUTHOR]

We consider the decomposability problem, i.e., the problem to decide whether a logical theory is equivalent to a union of two (or several) components in signatures, which correspond to a partition of the signature of "modulo" a given shared subset of symbols. We introduce several tools for proving that the computational complexity of this problem coincides with the complexity of entailment. As an application of these tools we derive tight bounds for the complexity of decomposability of theories in signature fragments of first-order logic, i.e., those fragments, which are obtained by restricting signature. [ABSTRACT FROM AUTHOR]

This survey is intended to provide an overview of one of the oldest and most celebrated open problems in combinatorial algebra: the word problem for one-relation monoids. We provide a history of the problem starting in 1914, and give a detailed overview of the proofs of central results, especially those due to Adian and his student Oganesian. After showing how to reduce the problem to the left cancellative case, the second half of the survey focuses on various methods for solving partial cases in this family. We finish with some modern and very recent results pertaining to this problem, including a link to the Collatz conjecture. Along the way, we emphasise and address a number of incorrect and inaccurate statements that have appeared in the literature over the years. We also fill a gap in the proof of a theorem linking special inverse monoids to one-relation monoids, and slightly strengthen the statement of this theorem. [ABSTRACT FROM AUTHOR]

We consider some extensions of Johansson's minimal logic J. Hybrid logics extend the intersection of the intuitionistic logic Int and the negative logic Neg. We show that the perceptibility and recognizability of a hybrid logic are reduced to the analogous properties of its intuitionistic and negative counterparts. Also, the interpolation properties of a hybrid logic are reduced to those of its intuitionistic and negative counterparts. The restricted interpolation property IPR and the projective Beth property PBP are known to be equivalent in the well-composed logics. Here we give an easier proof of this fact for hybrid logics. [ABSTRACT FROM AUTHOR]

The main result is as follows: Fix an arbitrary prime . A -divisible torsion-free (discrete, countable) abelian group has a -presentation if, and only if, its connected Pontryagin–van Kampen Polish dual admits a computable complete metrization (in which we do not require the operations to be computable). We use this jump-inversion/duality theorem to transfer the results on the degree spectra of torsion-free abelian groups to the results about the degree spectra of Polish spaces up to homeomorphism. For instance, it follows that for every computable ordinal and each there is a connected compact Polish space having proper jump degree (up to homeomorphism). Also, for every computable ordinal of the form , where is zero or is a limit ordinal and , there is a connected Polish space having an -computable copy if and only if is - . In particular, there is a connected Polish space having exactly the - complete metrizations. The case when is an unexpected consequence of the main result of the author's M.Sc. Thesis written under the supervision of Sergey S. Goncharov. [ABSTRACT FROM AUTHOR]

In this paper, a finite-automata model of attribute-based access control policies is used. The correctness of a policy is defined as a variation of the reachability problem for an infinite transition system induced by the policy. The problem of correctness validation for a given policy is shown decidable for information systems with a bounded number of objects. [ABSTRACT FROM AUTHOR]

Consider the problem of planning collision-free motion of n objects movable through contact with a robot that can autonomously translate in the plane and that can move a maximum of m ≤ n objects simultaneously. This represents the abstract formulation of a general class of manipulation planning problems that are proven to be decidable in this paper. The tools used for proving decidability of this simplified manipulation planning problem are, in fact, general enough to handle the decidability problem for the wider class of systems characterized by a stratified configuration space. These include, e.g., problems of legged and multi-contact locomotion, bi-manual manipulation. In addition, the approach described does not restrict the dynamics of the manipulation system modeled. [ABSTRACT FROM AUTHOR]

We show the decidability of the finite sequentiality problem for unambiguous max-plus tree automata. A max-plus tree automaton is called unambiguous if there is at most one accepting run on every tree. The finite sequentiality problem asks whether for a given max-plus tree automaton, there exist finitely many deterministic max-plus tree automata whose pointwise maximum is equivalent to the given automaton. [ABSTRACT FROM AUTHOR]

We investigate the first-order theory of closed subspaces of complex Hilbert spaces in the signature (∨ , ⊥ , 0 , 1) , where ' ⊥ ' is the orthogonality relation. Our main result is that already its quasi-identities are undecidable: there is no algorithm to decide whether an implication between equations and orthogonality relations implies another equation. This is a corollary of a recent result of Slofstra in combinatorial group theory. It follows upon reinterpreting that result in terms of the hypergraph approach to quantum contextuality, for which it constitutes a proof of the inverse sandwich conjecture. It can also be interpreted as stating that a certain quantum satisfiability problem is undecidable. [ABSTRACT FROM AUTHOR]

We study first-order concatenation theory with bounded quantifiers. We give axiomatizations with interesting properties, and we prove some normal-form results. Finally, we prove a number of decidability and undecidability results. [ABSTRACT FROM AUTHOR]

Detectability is a basic property of dynamic systems: when it holds an observer can use the current and past values of the observed output signal produced by a system to reconstruct its current state. In this paper, we consider properties of this type in the framework of discrete-event systems modeled by labeled Petri nets and finite automata. We first study weak approximate detectability. This property implies that there exists an infinite observed output sequence of the system such that each prefix of the output sequence with length greater than a given value allows an observer to determine if the current state belongs to a given set. We prove that the problem of verifying this property is undecidable for labeled Petri nets, and PSPACE-complete for finite automata. We also consider one new concept called eventual strong detectability. The new property implies that for each possible infinite observed output sequence, there exists a value such that each prefix of the output sequence with length greater than that value allows reconstructing the current state. We prove that for labeled Petri nets, the problem of verifying eventual strong detectability is decidable and EXPSPACE-hard, where the decidability result holds under a mild promptness assumption. For finite automata, we give a polynomial-time verification algorithm for the property. In addition, we prove that strong detectability is strictly stronger than eventual strong detectability for labeled Petri nets and even for deterministic finite automata. [ABSTRACT FROM AUTHOR]

Proof-theoretic methods are developed for subsystems of Johansson's logic obtained by extending the positive fragment of intuitionistic logic with weak negations. These methods are exploited to establish properties of the logical systems. In particular, cut-free complete sequent calculi are introduced and used to provide a proof of the fact that the systems satisfy the Craig interpolation property. Alternative versions of the calculi are later obtained by means of an appropriate loop-checking history mechanism. Termination of the new calculi is proved, and used to conclude that the considered logical systems are PSPACE-complete. [ABSTRACT FROM AUTHOR]

We present a propositional and a first-order logic for reasoning about higher-order upper and lower probabilities. We provide sound and complete axiomatizations for the logics and we prove decidability in the propositional case. Furthermore, we show that the introduced logics generalize some existing probability logics. [ABSTRACT FROM AUTHOR]

We introduce FO-AR, an approximation-refinement approach for first-order theorem proving based on counterexample-guided abstraction refinement. A given first-order clause set N is transformed into an over-approximation N ′ in a decidable first-order fragment. That means if N ′ is satisfiable so is N. However, if N ′ is unsatisfiable, then the approximation provides a lifting terminology for the found refutation which is step-wise transformed into a proof of unsatisfiability for N. If this fails, the cause is analyzed to refine the original clause set such that the found refutation is ruled out for the future and the procedure repeats. The target fragment of the transformation is the monadic shallow linear fragment with straight dismatching constraints, which we prove to be decidable via ordered resolution with selection. We further discuss practical aspects of SPASS-AR, a first-order theorem prover implementing FO-AR. We focus in particularly on effective algorithms for lifting and refinement. [ABSTRACT FROM AUTHOR]

We prove that if an n-element algebra generates the variety V which is actively structurally complete, then the cardinality of the carrier of each subdirectly irreducible algebra in V is at most n (n + 1) · n 2 · n . As a consequence, with the use of known results, we show that there exist algorithms deciding whether a given finite algebra A generates the (actively) structurally complete variety V (A) in the cases when V (A) is congruence modular or V (A) is congruence meet-semidistributive or A is a semigroup. [ABSTRACT FROM AUTHOR]

The complexity of graph homomorphism problems has been the subject of intense study for some years. In this paper, we prove a decidable complexity dichotomy theorem for the partition function of directed graph homomorphisms. Our theorem applies to all non-negative weighted forms of the problem: given any fixed matrix A with non-negative algebraic entries, the partition function ZA(G) of directed graph homomorphisms from any directed graph G is either tractable in polynomial time or #P-hard, depending on the matrix A. The proof of the dichotomy theorem is combinatorial, but involves the definition of an infinite family of graph homomorphism problems. The proof of its decidability on the other hand is algebraic and based on properties of polynomials. [ABSTRACT FROM AUTHOR]

This paper presents a counterexample for the open conjecture whether innermost joinability of all critical pairs ensures confluence of innermost terminating term rewriting systems. We then show that innermost joinability of all normalized instances of the critical pairs is a necessary and sufficient condition. Using this condition, we give a decidable sufficient condition for confluence of innermost terminating systems. Finally, we enrich the condition by introducing the notion of left-stable rules. As a corollary, confluence of innermost terminating left-weakly-shallow TRSs is shown to be decidable. [ABSTRACT FROM AUTHOR]

The ordered structures of natural, integer, rational and real numbers are studied here. It is known that the theories of these numbers in the language of order are decidable and finitely axiomatizable. Also, their theories in the language of order and addition are decidable and infinitely axiomatizable. For the language of order and multiplication, it is known that the theories of N and Z are not decidable (and so not axiomatizable by any computably enumerable set of sentences). By Tarski's theorem, the multiplicative ordered structure of R is decidable also; here we prove this result directly and present an axiomatization. The structure of Q in the language of order and multiplication seems to be missing in the literature; here we show the decidability of its theory by the technique of quantifier elimination, and after presenting an infinite axiomatization for this structure, we prove that it is not finitely axiomatizable. [ABSTRACT FROM AUTHOR]

Lambek elegantly characterized part of natural language. As is well-known, his substructural logic L, and its non-associative version NL, handle basic function/argument composition well, but not scope taking and syntactic displacement—at least, not in their full generality. In previous work, I propose NL λ , which is NL supplemented with a single structural inference rule ("abstraction"). Abstraction closely resembles the traditional linguistic rule of quantifier raising, and characterizes both semantic scope taking and syntactic displacement. Due to the unconventional form of the abstraction inference, there has been some doubt that NL λ should count at a legitimate substructural logic. This paper argues that NL λ is perfectly well-behaved. In particular, it enjoys cut elimination and an interpolation result. In addition, perhaps surprisingly, it is decidable. Finally, I prove that it is sound and complete with respect to the usual class of relational frames. [ABSTRACT FROM AUTHOR]

We study term modal logics, where modalities can be indexed by variables that can be quantified over. We suggest that these logics are appropriate for reasoning about systems of unboundedly many reasoners and define a notion of bisimulation which preserves propositional fragment of term modal logics. Also we show that the propositional fragment is already undecidable but that its monodic fragment (formulas using only one free variable in the scope of a modality) is decidable, and expressive enough to include interesting assertions. [ABSTRACT FROM AUTHOR]

Parametric timed automata (PTAs) are a powerful formalism to reason, simulate and formally verify critical real-time systems. After 25 years of research on PTAs, it is now well understood that any non-trivial problem studied is undecidable for general PTAs. We provide here a survey of decision and computation problems for PTAs. On the one hand, bounding time, bounding the number of parameters or the domain of the parameters does not (in general) lead to any decidability. On the other hand, restricting the number of clocks, the use of clocks (compared or not with the parameters), and the use of parameters (e. g., used only as upper or lower bounds) leads to decidability of some problems. We also put emphasis on open problems. We also discuss formalisms close to parametric timed automata (such as parametric hybrid automata or parametric interrupt timed automata), and we study tools dedicated to PTAs and their extensions. [ABSTRACT FROM AUTHOR]

This paper shows that, for the Hertz-Gentzen Systems of 1933 (without Thinning), extended by a classical rule T1 (from the Stoics) and using certain axioms (also from the Stoics), all derivations are analytic: every cut formula occurs as a subformula in the cut's conclusion. Since the Stoic cut rules are instances of Gentzen's Cut rule of 1933, from this we infer the decidability of the propositional logic of the Stoics. We infer the correctness for this logic of a "relevance criterion" and of two "balance criteria", and hence (in contrast to one of Gentzen's 1933 results) that a particular derivable sequent has no derivation that is "normal" in the sense that the first premiss of each cut is cut-free. We also infer that Cut is not admissible in the Stoic system, based on the standard Stoic axioms, the T1 rule and the instances of Cut with just two antecedent formulae in the first premiss. [ABSTRACT FROM AUTHOR]