Mollifiers for games in normal form and the Harsanyi-Selten valuation function

The concepts of disruption and mollifiers ofCharnes/Rousseau/Seiford [1978] for games in characteristic function form are here extended to games in normal form. We show for a large class of games that theHarsanyi-Selten [1959] modification ofvon Neumann /Morgenstern's [1953] construction of a characteristic function for games in normal form, to take better account of “disruption” or “threat” possibilities, yields a constant mollifier. In general, it can be non-superadditive when the von Neumann-Morgenstern function is superadditive, and it also fails to take account of coalitional sizes. Our extended “homomollifier” concept does, and always yields a superadditive constant sum characteristic function.     

A “planar” representation for generalized transition kernels

In [9], Mauldin, Preiss and von Weizsäcker have given a theorem representing transition kernels (atomless and between standard Borel spaces) by a planar model. Here, motivated by measure-theoretic as well as probabilistic considerations, we generalize by allowing the parametrizing spaceX to be arbitrary, with an arbitrary σ-field of “Borel” subsets, and allowing the corresponding measures to have atoms. (We also, for convenience rather than generality, allow arbitrary finite measures rather than probability ones.) The transition kernel is replaced by a substantially equivalent one fromX toX ×I that is “sectioned”, hence completely orthogonal. This is shown to be isomorphic to a model in which the image space consists of 3 specifically defined subsets ofX × ?: an ordinate set (in which vertical sections have Lebesgue measure), an “atomic” set contained inX × (??), and a “singular” set with null sections. The method incidentally produces and exploits a “reverse” transition kernel fromX toX ×I. Some further extensions are briefly discussed; in particular, allowing “uniformly σ-finite” measures (in the “standard” case) leads to a generalization that includes the planar representation theorem of Rokhlin [10] and the author [5]; cf. also [7, 2].     

Generalized impartial games

A complete mathematical theory of NIM type games have been developed byBouton [1902],Sprague [1935/36] andGrundy [1939]. The NIM type games are a special class of combinatorial games, called the impartial games. “Impartial” means that, at any stage, the set of legal moves is independent of whose turn it is to move. The outcome of an impartial game is that the first player either wins or loses. The results ofBouton, Sprague andGrundy are now generalized to a wider class of games which allow tie-positions. This wider class of games are defined on digraphs. It is proved that the games defined on a given digraph are all impartial games (without tie-positions) iff the birthday function (also called the terminal distance function) exists on this digraph.     

A complete analysis of Black-White Hackendot

RecentlyÚlehla [1980] gave a complete analysis of an impartial two-person combinatorial game called Hackendot which was invented by von Neumann. In this note we consider a partizan (or unimpartial) variation of Hackendot. Úlehla's analysis uses the Sprague-Grundy theory for disjunctive sums of impartial games. Our analysis employs Conway's theory for disjunctive sums of partizan games, two certain “biased” ways of “adding” dyadic rationals, and the usual addition of numbers.     

Zur Stabilität diskreter Teilspektren singulärer Differentialoperatoren zweiter Ordnung gegenüber Störungen der Koeffizienten und der Definitionsgebiete

The stability ofL ²-eigenvalues and associated eigenspaces of singular second order differential operators of Schrödinger-type is shown for asymptotic perturbations of the coefficients and the domain of definition. The perturbations involved are more general than those studied in [3] and [5], because we do not postulate the convergence of the coefficients “from above” or of the domains “from inside” or “from outside”. Moreover, the domain of definition is allowed to be perturbed in its interior. The underlying abstract perturbation theory was established in a previous paper [9].     

On the uniqueness of the Shapley value

L.S. Shapley [1953] showed that there is a unique value defined on the classD of all superadditive cooperative games in characteristic function form (over a finite player setN) which satisfies certain intuitively plausible axioms. Moreover, he raised the question whether an axiomatic foundation could be obtained for a value (not necessarily theShapley value) in the context of the subclassC (respectivelyC′, C″) of simple (respectively simple monotonic, simple superadditive) gamesalone. This paper shows that it is possible to do this. Theorem I gives a new simple proof ofShapley's theorem for the classG ofall games (not necessarily superadditive) overN. The proof contains a procedure for showing that the axioms also uniquely specify theShapley value when they are restricted to certain subclasses ofG, e.g.,C. In addition it provides insight intoShapley's theorem forD itself. Restricted toC′ orC″, Shapley's axioms donot specify a unique value. However it is shown in theorem II that, with a reasonable variant of one of his axioms, a unique value is obtained and, fortunately, it is just theShapley value again.     

Reduction of Silverman-like games to games on bounded sets

A two person zero sum game is regarded as Silverman-like if the strategy sets are sets of real numbers bounded below, the payoff function is bounded, the maximum payoff is achieved whenever the second player's numbery exceeds the first player's numberx by “too much”, and the minimum is achieved wheneverx exceedsy by “too much”. Explicit upper bounds are obtained for pure strategies to be included in an optimal mixed strategy in such games. In particular, if the strategy sets are discrete, the games may be reduced to games on specified finite sets.     

Normal dilatation of triangular matrices

LetR be a (real or complex) triangular matrix of ordern, say, an upper triangular matrix. Is it true that there exists a normaln×n matrixA whose upper triangle coincides with the upper triangle ofR? The answer to this question is “yes” and is obvious in the following cases: (1)R is real; (2)R is a complex matrix with a real or a pure imaginary main diagonal, and moreover, all the diagonal entries ofR belong to a straight line. The answer is also in the affirmative (although it is not so obvious) for any matrixR of order 2. However, even forn=3 this problem remains unsolved. In this paper it is shown that the answer is in the affirmative also for 3×3 matrices.     

What is a complex matroid?

Following an “ansatz” of Björner and Ziegler [BZ], we give an axiomatic development of finite sign vector systems that we callcomplex matroids. This includes, as special cases, the sign vector systems that encode complex arrangements according to [BZ], and the complexified oriented matroids, whose complements were considered by Gel'fand and Rybnikov [GeR]. Our framework makes it possible to study complex hyperplane arrangements as entirely combinatorial objects. By comparing complex matroids with 2-matroids, which model the more general 2-arrangements introduced by Goresky and MacPherson [GoM], the essential combinatorial meaning of a “complex structure” can be isolated. Our development features a topological representation theorem for 2-matroids and complex matroids, and the computation of the cohomology of the complement of a 2-arrangement, including its multiplicative structure in the complex case. Duality is established in the cases of complexified oriented matroids, and for realizable complex matroids. Complexified oriented matroids are shown to be matroids with coefficients in the sense of Dress and Wenzel [D1], [DW1], but this fails in general.     

Informational structure for differential games

A positional approach for the definition of information structure in differential games is considered. A generalization ofKuhn's theorem [1953] concerning pure strategy equivalence for finite positional games is proved.     

Semisimple games,enactment power and generalized power indices

By allowing for individual abstention, the classC of simplen-person games is extended to the class ofsemisimple gamesS. Using this extension, any given index of individual power onC gives rise to a measure of individual power onS in the form of a vector function with 2 ⁿ ?1 components. After developing an axiomatic characterization of Coleman's notion of collective power, thisenactment power is combined with any index of individual power to provide a general nonnormalized meausre of individual power. Using these results, enactment and individual power in different games can be meaningfully compared. In the presence of abstention, various “paradoxes” associated with power indices lose some of the impact.     

On thek-stability ofm-quota games

We consider thek-stability ofm-quota games ofn players. We prove that anm-quota game (N, v), which satisfies the conditionv(S)=0 for allS, ¦S¦ ≤m ?1, is (m ?1)-stable if and only if there is no weak player. Further, some relationships between ak-stable pair and anm-quota are shown. Some ofLuce's results [1955] on Shapley quota games are generalized tom-quota games.     

Intersection properties in geometry

In dealing with geometries and diagrams we often need some axioms on the intersections of shadows. Here are the most usual ones: the Intersection Property (see (IP) in [3]), conditions (Int) and (Int′) of [8], and the Linearity Condition (see (GL) in [3]). An example due to Brower shows that the Linearity Condition (GL) is weaker than the Intersection Property (IP). In this paper we point out some conditions which have to be added to (GL) in order to get (IP), and we describe some of the relations between these conditions and each of the four ‘intersection’ properties given above. We summarize most of these connections in the appendix to this paper. The main open question is: ‘Which are the “right” axioms for “good” geometries?’     

A positive answer to the basis problem

lcub;x _n rcub; with lcub;x _n ,x* _n rcub; biorthogonal is a “uniformly minimal basis with quasifixed brackets and permutations” of a Banach spaceX if lcub;x _n rcub; andx* _n rcub; are both bounded. Moreover, there is an increasing sequence lcub;q _m rcub; of positive integers such that, for eachx′ ofX, settingq′(0)=0, $$x' = \sum\limits_{m = 0}^\infty { \sum\limits_{n = q'(m) + 1}^{q'(m + 1)} {x_{\pi '(n)}^ * (x')x_{\pi '(n)} ,} } $$ , where, for eachm≥1,q(m)+1≤q′(m)≤q(m+1) while $$\left\{ {\pi '(n)} \right\}_{n = q(m) + 1}^{q(m + 1)} is a permutation of \left\{ n \right\}_{n = q(m) + 1}^{q(m + 1)} .$$ . Then, for each subspaceY of a separable Banach spaceX, there exists a uniformly minimal basis with quasi-fixed brackets and permutations ofY, which can be extended to a uniformly minimal basis with quasi-fixed brackets and permutations ofX.     

POWERSET OPERATOR BASED FOUNDATION FORPOINT-SET LATTICE-THEORETIC (POSLAT) FUZZY SET THEORIES and TOPOLOGIES

Abstract

This paper sets forth in detail point-set lattice-theoretic or poslat foundations of all mathematical and fuzzy set disciplines in which the operations of taking the image and pre-image of (fuzzy) subsets play a fundamental role; such disciplines include algebra, measure and probability theory, and topology. In particular, those aspects of fuzzy sets, hinging around (crisp) powersets of fuzzy subsets and around powerset operators between such powersets lifted from ordinary functions between the underlying base sets, are examined and characterized using point-set and lattice-theoretic methods. The basic goal is to uniquely derive the powerset operators and not simply stipulate them, and in doing this we explicitly distinguish between the “fixed-basis” case (where the underlying lattice of membership values is fixed for the sets in question) and the “variable-basis” case (where the underlying lattice of membership values is allowed to change). Applications to fuzzy sets/logic include: development and justification/characterization of the Zadeh Extension Principle [36], with applications for fuzzy topology and measure theory; characterizations of ground category isomorphisms; rigorous foundation for fuzzy topology in the poslat sense; and characterization of those fuzzy associative memories in the sense of Kosko [18] which are powerset operators. Some results appeared without proof in [31], some with partial proofs in [32], and some in the fixed-basis case in Johnstone [13] and Manes [22].     

On the choice of parameters in MAOR type splitting methods for the linear complementarity problem

In the present work we consider the iterative solution of the Linear Complementarity Problem (LCP), with a nonsingular H ₊ coefficient matrix A, by using all modulus-based matrix splitting iterative methods that have been around for the last couple of years. A deeper analysis shows that the iterative solution of the LCP by the modified Accelerated Overrelaxation (MAOR) iterative method is the “best”, in a sense made precise in the text, among all those that have been proposed so far regarding the following three issues: i) The positive diagonal matrix-parameter Ω ≥ diag(A) involved in the method is Ω = diag(A), ii) The known convergence intervals for the two AOR parameters, α and β, are the widest possible, and iii) The “best” possible MAOR iterative method is the modified Gauss-Seidel one.     

Multi-input multi-output fuzzy systems and the Inverse Problem

For the Inverse Problem: “given a fuzzy relation R ⊂ U × V and a fuzzy subset B ⊂ V, find all A ⊂ U such that A ° R = B”, an analytical solution has already been given. This solution is applicable to one-input one-output fuzzy systems. It is shown that it is also applicable to multi-input multi-output fuzzy systems.     

A note on a generalization of the nucleolus to games without sidepayments

We present a generalization of the nucleolus to games without sidepayments. By allowing the interpersonal utility comparison such that payoffs are determined proportionally to given weights, we define an excess of a coalition as a number depending on this vector of weights. The existence and the inclusion in nonempty cores are proved, but the uniqueness is not preserved. It is also remarked that the excess defined here is not the same as that ofKalai [1975]