Extended Curry‐Howard terms for second‐order logic

In order to allow the use of axioms in a second‐order system of extracting programs from proofs, we define constant terms, a form of Curry‐Howard terms, whose types are intended to correspond to those axioms. We also define new reduction rules for these new terms so that all consequences of the axioms can be represented. We finally show that the extended Curry‐Howard terms are strongly normalizable.     

On the axioms of planes in quaternionic geometry

Summary The axioms of planes in Riemannian geometry and Kaehlerian geometry have been largely studied. In this paper we study axioms for three kinds of planes in Quaternionic geometry: the axiom of quaternionic 4-planes, the axiom of half-quaternionic planes and the axiom of totally real planes. We also give a characterization of quaternionspaceforms in terms of the constancy of the totally real sectional curvatures.     

Unary Semigroups with an Associate Subgroup

A subgroup H of a regular semigroup S is said to be an associate subgroup of S if for every s ∈ S, there is a unique associate of s in H. An idempotent z of S is said to be medial if czc = c, for every c product of idempotents of S. Blyth and Martins established a structure theorem for semigroups with an associate subgroup whose identity is a medial idempotent, in terms of an idempotent generated semigroup, a group and a single homomorphism. Here, we construct a system of axioms which characterize these semigroups in terms of a unary operation satisfying those axioms. As a generalization of this class of semigroups, we characterize regular semigroups S having a subgroup which is a transversal of a congruence on S.     

Subcategories of Filter Tower Spaces

The concept of a convergence tower space, or equivalently, a convergence approach space is formulated here in the context of a Cauchy setting in order to include a completion theory. Subcategories of filter tower spaces are defined in terms of axioms involving a general t-norm, T, in order to include a broad range of spaces. A T-regular sequence for a filter tower space is defined and, moreover, it is shown that the category of T-regular objects is a bireflective subcategory of all filter tower spaces. A completion theory for subcategories of filter tower spaces is given.     

Automated discovery of single axioms for ortholattices

We present short single axioms for ortholattices, orthomodular lattices, and modular ortholattices, all in terms of the Sheffer stroke. The ortholattice axiom is the shortest possible. We also give multiequation bases in terms of the Sheffer stroke and in terms of join, meet, and complementation. Proofs are omitted but are available in an associated technical report and on the Web. We used computers extensively to find candidates, reject candidates, and search for proofs that candidates are single axioms.Received February 26, 2004; accepted in final form September 14, 2004.     

Multivariate measures of concordance

In 1984 Scarsini introduced a set of axioms for measures of concordance of ordered pairs of continuous random variables. We exhibit an extension of these axioms to ordered n-tuples of continuous random variables, n ≥ 2. We derive simple properties of such measures, give examples, and discuss the relation of the extended axioms to multivariate measures of concordance previously discussed in the literature.     

A prominence theory of context‐sensitive choice behavior

A simple theory of context‐sensitive choice behavior is proposed which focuses on the role of perceived prominence among alternatives. The fundamental hypothesis is that the similarity (or lack of similarity) among alternatives determines their relative prominence, and that, other things being equal, more prominent alternatives have a better chance of being chosen. This prominence theory of choice is formalized in terms of two testable axioms, which are shown to characterize a wide class of prominence choice models. In addition, a number of refinements and extensions of the basic theory are explored which incorporate a richer variety of perceived‐prominence behavior.     

Projective planes over rings of stable rank 2

This paper gives an axiomatic characterization of projective planes over rings of stable rank 2. These rings, which are known from algebraic K-theory, beautifully reflect simple geometric properties. The basic relations in the plane are incidence and the neighbor relation. The axioms consist of a number of axioms expressing elementary relations between points and lines such as, e. g., the existence of a unique line joining any two non-neighboring points, and a couple of axioms ensuring the existence of transvections and dilatations.     

Equivalence of axioms for bankruptcy problems

The bankruptcy problem is concerned with how to divide the net worth of the bankrupt firm among its creditors. In this paper, we investigate the logical relations between various axioms in the context of bankruptcy. Those axioms are: population-and-resource monotonicity, consistency, converse consistency, agreement, and separability. In most axiomatic models, they are not directly related. However, we show that they are equivalent on the class of bankruptcy problems under minor additional requirements. Received: April 1998/Revised version: January 1999     

An axiomatization of the Banzhaf value for cooperative games on antimatroids

Cooperative games on antimatroids are cooperative games in which coalition formation is restricted by a combinatorial structure which generalizes permission structures. These games group several well-known families of games which have important applications in economics and politics. The current paper establishes axioms that determine the restricted Banzhaf value for cooperative games on antimatroids. The set of given axioms generalizes the axiomatizations given for the Banzhaf permission values. We also give an axomatization of the restricted Banzhaf value for the smaller class of poset antimatroids. Finally, we apply the above results to auction situations.     

Monotonicity and Consistency in Matching Markets

Objective: To obtain axiomatic characterizations of the core of one-to-one and one-to-many matching markets. Methods: The axioms recently applied to characterize the core of assignment games were adapted to the models of this paper. Results: The core of one-to-one matching markets is characterized by two different lists of axioms. The first one consists of weak unanimity, population monotonicity, and Maskin monotonicity. The second consists of weak unanimity, population monotonicity, and consistency. If we allow for weak preferences, the core is characterized by weak unanimity, population monotonicity, Maskin monotonicity, and consistency. For one-to-many matchings, the same lists as for the case of strict preferences characterize the core. Conclusions: The cores of the discrete matching markets are characterized by axioms that almost overlap with the axioms characterizing the core of the continuous matching markets. This provides an axiomatic explanation for the observations in the literature that almost parallel properties are obtained for the core of the two models. We observe that Maskin monotonicity is closely related to consistency in matching marketsThis research is financially supported by Waseda University Grant for Special Research Projects #2000A−887, 21COE-GLOPE, and Grant-in-Aid for Scientific Research #15530125, JSPS. This paper was presented at the 7th. International Meeting of the Society for Social Choice and Welfare held in Osaka, Japan. The comments of the participants are gratefully acknowledged. The author thanks Professors William Thomson, Eiichi Miyagawa and anonymous referees for their valuable comments and suggestions. Any remaining errors are independent     

A new approach to chordal graphs

By a chordal graph is meant a graph with no induced cycle of length ⩾ 4. By a ternary system is meant an ordered pair (W, T), where W is a finite nonempty set, and T ⊆ W × W × W. Ternary systems satisfying certain axioms (A1)–(A5) are studied in this paper; note that these axioms can be formulated in a language of the first-order logic. For every finite nonempty set W, a bijective mapping from the set of all connected chordal graphs G with V(G) = W onto the set of all ternary systems (W, T) satisfying the axioms (A1)–(A5) is found in this paper.     

Axiomatizing subcategories of Abelian categories

We investigate how to characterize subcategories of abelian categories in terms of intrinsic axioms. In particular, we find axioms which characterize generating cogenerating functorially finite subcategories, precluster tilting subcategories, and cluster tilting subcategories of abelian categories. As a consequence we prove that any d-abelian category is equivalent to a d-cluster tilting subcategory of an abelian category, without any assumption on the categories being projectively generated.     

Set-valued nonlinear analogues of the shapley value

One of Shapley's classic axioms deals with the addition of the games. We consider the family of axiom systems depending on various operations over the set of cooperative games. The existence and the uniqueness of the correspondinga priori set-valued solutions are studied. The family of solutions (satisfying the proposed system of axioms) contains, as particular cases, the Shapley value and the -core. The modification of the proposed system of axioms is studied, prekernel being the maximal solution satisfying this modification.We would like to thank two anonymous referees for helpful comments.     

The complexity of plane hyperbolic incidence geometry is ∀∃∀∃

We show that plane hyperbolic geometry, expressed in terms of points and the ternary relation of collinearity alone, cannot be expressed by means of axioms of complexity at most ???, but that there is an axiom system, all of whose axioms are ???? sentences. This remains true for Klingenberg's generalized hyperbolic planes, with arbitrary ordered fields as coordinate fields. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Metric Axiomatics of Euclidean Space @forename = A. A.

A version of axioms of Euclidean space based on a single initial notion, namely on the notion of distance, is considered. The notions of straight line and plane are introduced in terms of distance. Thus, Euclidean space is regarded as a metric space with metric satisfying the corresponding axioms. Bibliography: 3 titles.     

Zur Abhängigkeit von Anordnungsaxiomen

A halfordered or ordered plane can be described in terms of a betweenness function a on each of its lines, which fulfills some different axioms. In this paper we will discuss which of these axioms are equivalent to each other.

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Herrn Professor Dr. Helmut Karzel zum 60. Geburtstag     

Eine axiomatische Herleitung der 2-dimensionalen Lorentztransformation

Zusammenfassung Die 2-dimensionale Lorentztransformation wird aus sechs (z. T. bekannten) Axiomenstreng abgeleitet.Im Gegensatz zu den meisten Darstellungen wird die Linearität der Transformation nicht vorausgesetzt, sondern aus den Axiomen L4 (Invarianz der Kongruenz) und L5 (Stetigkeit der Transformation) gefolgert.

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The 2-dimensional Lorentz transformation isstrictly deduced from six (partially known) axioms.In contrast to most expositions the linearity of the transformation is not anticipated but is inferred from the axioms L4 (invariance of the congruence) and L5 (continuity of the transformation).

     

On Partially Ordered Semigroups and an Abstract Set-Difference

In this paper we prove the independence of a system of five axioms (S1)–(S5), which was proposed in the book of Pallaschke and Urbański (Pairs of Compact Convex Sets, vol. 548, Kluwer Academic Publishers, Dordrecht, 2002) for partially ordered commutative semigroups. These five axioms (S1)–(S5) are stated in the introduction below. A partially ordered commutative semigroup satisfying these axioms is called a F-semigroup. By the use of a further axiom (S6) we define an abstract difference for the elements of a F-semigroup and prove some basic properties. The most interesting example of a F-semigroup are the nonempty compact convex sets of a topological vector space endowed with the Minkowski sum as operation and the inclusion as partial order. In Section 4 we apply the abstract difference to the problem of minimality of convex fractions. Dedicated to Boris Mordukhovich in honour of his 60th birthday.