Rings and Gödel algebras

In this paper, we study those rings whose semiring of ideals can be given the structure of a Gödel algebra. Such rings are called Gödel rings. We investigate such structures both from an algebraic and a topological point of view. Our main result states that every Gödel ring R is a subdirect product of prime Gödel rings R _i , and the Gödel algebra Id(R) associated to R is subdirectly embeddable as an algebraic lattice into ${{\prod_{i}}Id(R_{i})}$ , where each Id(R _i ) is the algebraic lattice of ideals of R _i that can be equipped with the structure of a Gödel algebra. We see that the mapping associating to each Gödel ring its Gödel algebra of ideals is functorial from the category of Gödel rings with epimorphisms into the full subcategory of frames whose objects are Gödel algebras and whose morphisms are complete epimorphisms.     

On the classification of first order Gödel logics

We characterize the recursively enumerable first order Gödel logics with △ with respect to validity and non-satisfiability. The finitely valued and four infinitely valued Gödel logics with △ are recursively enumerable, not-satisfiability is recursively enumerable if validity is recursively enumerable. This is in contrast to first order Gödel logics without △, where validity is recursively enumerable for finitely valued and two infinitely valued Gödel logics, not-satisfiability is recursively enumerable if validity is recursively enumerable or 0 isolated in the truth value set.     

Geodesic connectedness in Gödel type space-times

In this paper we use a variational approach in order to prove the geodesic connectedness of some Gödel type space-times; moreover direct methods allow to prove the geodesic connectedness of the Gödel Universe. At last a result of geodesic completeness is given.     

Ordinally equivalent data: A measurement-theoretic look at formal concept analysis of fuzzy attributes

We show that if two fuzzy relations, representing data tables with graded attributes, are ordinally equivalent then their concept lattices with respect to the Gödel operations on chains are (almost) isomorphic and that the assumption of Gödel operations is essential. We argue that measurement-theoretic results like this one are important for pragmatic reasons in relational data modeling and outline issues for future research.     

On constructivity and the Rosser property: a closer look at some Gödelean proofs

The proofs of Kleene, Chaitin and Boolos for Gödel's First Incompleteness Theorem are studied from the perspectives of constructivity and the Rosser property. A proof of the incompleteness theorem has the Rosser property when the independence of the true but unprovable sentence can be shown by assuming only the (simple) consistency of the theory. It is known that Gödel's own proof for his incompleteness theorem does not have the Rosser property, and we show that neither do Kleene's or Boolos' proofs. However, we show that a variant of Chaitin's proof can have the Rosser property. The proofs of Gödel, Rosser and Kleene are constructive in the sense that they explicitly construct, by algorithmic ways, the independent sentence(s) from the theory. We show that the proofs of Chaitin and Boolos are not constructive, and they prove only the mere existence of the independent sentences.     

The metalogic of economic predictions,calculations and propositions

Indeterminacy is a matter of concern in the analysis of ideal forms and this paper shows that Gödel incompleteness and undecidability directly pertain to the analysis of theoretical economic systems - specifically, that certain solution concepts such as ‘predictions of characteristics of policy outcomes guided by a social welfare function’, ‘the existence of equilibrium’, ‘the existence of welfare optima’ are subject to Gödel undecidability. This consideration brings into question the convention of a finite decision unit or economic actor, and the paper considers more-appropriate (metatheoretic) assumption structures and the implications of specifying richer information structures in microeconomics and choice theory.     

A note on the principle of mathematical induction,intuition and consciousness in the light of ideas of Poincaré and Galois

In his argumentation for the non-computability of thought-processes (in general) Penrose is invoking Gödel’s theorem (see [R. Penrose, Shadows of the Mind – A search for the Missing Science of Consciousness, Oxford University Press, Oxford, 1994]). It is the aim with the following note to indicate that the same effect may be obtained in a simpler and possibly also more fundamental way. This does not necessarily mean that I fully believe in Penrose’s thesis – the question is still largely open – but I think that my note indicates that there are a lot of items that remains to be clarified before a satisfactory scientific consensus will be reached. There is a huge gap between the precision of strict scientific contexts and those where this kind of processes are going on. At the same time we will see that the same kind of ideas had been impinging themselves on mathematicians like Poincaré and Galois, like Penrose himself of a very intuitive kind. It is plausible that the solution of the enigma of the scientific character of processes referring back to themselves lies in deep properties of autonomous systems. The self-referential character of the interpretations in Gödel’s theorem is quite central. This will be the subject of a forthcoming paper.     

Monotone operators on Gödel logic

We consider an extension of Gödel logic by a unary operator that enables the addition of non-negative reals to truth-values. Although its propositional fragment has a simple proof system, first-order validity is Π ₂-hard. We explain the close connection to Scarpellini’s result on Π ₂-hardness of ?ukasiewicz’s logic.     

Hamiltonian dynamics of a spaceship in Alcubierre and Gödel metrics: Recursion operators and underlying master symmetries

Theoretical and Mathematical Physics - We study the Hamiltonian dynamics of a spaceship in the background of Alcubierre and Gödel metrics. We derive the Hamiltonian vector fields governing the...     

Study of cylindrically symmetric solutions in an $$f(R)$$ gravity background

Theoretical and Mathematical Physics - We investigate static cylindrically symmetric solutions of the Weyl and Gödel space–times in the framework of modified $$f(R)$$ gravity. With this...     

THEOREMS AD INFINITUM

Abstract

The theorems of a first order theory can be partially ordered according to their strength. As a Consequence of two famous theorems of Gödel. the order turns out to be dense. This consequence is either disastrous or amusing, according to your personal view of research in mathematics.     

A Routley–Meyer Semantics for Gödel 3-Valued Logic and Its Paraconsistent Counterpart

Routley–Meyer semantics (RM-semantics) is defined for Gödel 3-valued logic G3 and some logics related to it among which a paraconsistent one differing only from G3 in the interpretation of negation is to be remarked. The logics are defined in the Hilbert-style way and also by means of proof-theoretical and semantical consequence relations. The RM-semantics is defined upon the models for Routley and Meyer’s basic positive logic B₊, the weakest positive RM-semantics. In this way, it is to be expected that the models defined can be adapted to other related many-valued logics.     

The principle of duality in Euclidean and in absolute geometry

In Euclidean geometry and in absolute geometry fragments of the principle of duality hold. Bachmann (Aufbau der Geometrie aus dem Spiegelungsbegriff, 1973, §3.9) posed the problem to find a general theorem which describes the extent of an allowed dualization. It is the aim of this paper to solve this problem. To this end a first-order axiomatization of Euclidean (resp. absolute) geometry is provided which allows the application of Gödel’s Completeness Theorem for first-order logic and the solution of Bachmann’s problem.     

Finite-valued reductions of infinite-valued logics

In this paper we present a method to reduce the decision problem of several infinite-valued propositional logics to their finite-valued counterparts. We apply our method to ?ukasiewicz, Gödel and Product logics and to some of their combinations. As a byproduct we define sequent calculi for all these infinite-valued logics and we give an alternative proof that their tautology problems are in co-NP.     

Zermelo in the mirror of the Baer correspondence, 1930–1931

Around 1931 Zermelo had an extended correspondence with the young Reinhold Baer concerning the edition of Cantor's collected works. Some of the letters also deal with Skolem's paradox and Gödel's first incompleteness theorem. Whereas Zermelo's letters are lost, most of Baer's letters are contained in the Zermelo Nachlass. Besides giving insight into Zermelo's reaction to Skolem's and Gödel's results, the letters also demonstrate Baer's clear understanding of the behavior of models of set theory and of the relevance of Gödel's first incompleteness theorem.     

Register computations on ordinals

We generalize ordinary register machines on natural numbers to machines whose registers contain arbitrary ordinals. Ordinal register machines are able to compute a recursive bounded truth predicate on the ordinals. The class of sets of ordinals which can be read off the truth predicate satisfies a natural theory SO. SO is the theory of the sets of ordinals in a model of the Zermelo-Fraenkel axioms ZFC. This allows the following characterization of computable sets: a set of ordinals is ordinal register computable if and only if it is an element of Gödel’s constructible universe L.     

Infinitary first-order categorical logic

We present a unified categorical treatment of completeness theorems for several classical and intuitionistic infinitary logics with a proposed axiomatization. This provides new completeness theorems and subsumes previous ones by Gödel, Kripke, Beth, Karp and Joyal. As an application we prove, using large cardinals assumptions, the disjunction and existence properties for infinitary intuitionistic first-order logics.     

Gentzen’s consistency proof without heightlines

This paper gives a Gentzen-style proof of the consistency of Heyting arithmetic in an intuitionistic sequent calculus with explicit rules of weakening, contraction and cut. The reductions of the proof, which transform derivations of a contradiction into less complex derivations, are based on a method for direct cut-elimination without the use of multicut. This method treats contractions by tracing up from contracted cut formulas to the places in the derivation where each occurrence was first introduced. Thereby, Gentzen’s heightline argument, which introduces additional cuts on contracted compound cut formulas, is avoided. To show termination of the reduction procedure an ordinal assignment based on techniques of Howard for Gödel’s T is used.     

Normal forms for fuzzy logics: a proof-theoretic approach

A method is described for obtaining conjunctive normal forms for logics using Gentzen-style rules possessing a special kind of strong invertibility. This method is then applied to a number of prominent fuzzy logics using hypersequent rules adapted from calculi defined in the literature. In particular, a normal form with simple McNaughton functions as literals is generated for ?ukasiewicz logic, and normal forms with simple implicational formulas as literals are obtained for Gödel logic, Product logic, and Cancellative hoop logic.