A characterization of the classical unital

We define Buekenhout unitals in derivable translation planes of dimension 2 over their kernel and provide a characterization of these unitals. We use this result to improve the characterization of classical unitals given by Lefèvre-Percsy [13] and Faina and Korchmáros [7].     

Schensted Algorithms for Dual Graded Graphs

This paper is a sequel to [3]. We keep the notation and terminology and extend the numbering of sections, propositions, and formulae of [3].The main result of this paper is a generalization of the Robinson-Schensted correspondence to the class of dual graded graphs introduced in [3], This class extends the class of Y-graphs, or differential posets [22], for which a generalized Schensted correspondence was constructed earlier in [2].The main construction leads to unified bijective proofs of various identities related to path counting, including those obtained in [3]. It is also applied to permutation enumeration, including rook placements on Ferrers boards and enumeration of involutions.As particular cases of the general construction, we re-derive the classical algorithm of Robinson, Schensted, and Knuth [19, 12], the Sagan-Stanley [18], Sagan-Worley [16, 29] and Haiman's [11] algorithms and the author's algorithm for the Young-Fibonacci graph [2]. Some new applications are suggested.The rim hook correspondence of Stanton and White [23] and Viennot's bijection [28] are also special cases of the general construction of this paper.In [5], the results of this paper and the previous paper [3] were presented in a form of extended abstract.     

Around Pelikán’s conjecture on very odd sequences

Very odd sequences were introduced in 1973 by Pelikán who conjectured that there were none of length 5. This conjecture was disproved first by MacWilliams and Odlyzko [17] in 1977 and then by two different sets of authors in 1992 [1], 1995 [9]. We give connections with duadic codes, cyclic difference sets, levels (Stufen) of cyclotomic fields, and derive some new asymptotic results on the length of very odd sequences and the number of such sequences of a given length.     

具有周期系数的左定Sturm-Liouville问题的特征值不等式

该文利用了左定问题与右定问题的联系,得到了具有周期系数的左定Sturm-Liouville问题在区间[a,a+kh]上的周期和半周期特征值的描述,阐明了周期特征值之间的不等式关系,并明确给出了区间[a,a+kh]上的周期、半周期特征值和区间[a,a+h]上特征值的一一对应关系.     

On the correspondence between arithmetic theories and propositional proof systems – a survey

The purpose of this paper is to survey the correspondence between bounded arithmetic and propositional proof systems. In addition, it also contains some new results which have appeared as an extended abstract in the proceedings of the conference TAMC 2008 [11]. Bounded arithmetic is closely related to propositional proof systems; this relation has found many fruitful applications. The aim of this paper is to explain and develop the general correspondence between propositional proof systems and arithmetic theories, as introduced by Krají?ek and Pudlák [46]. Instead of focusing on the relation between particular proof systems and theories, we favour a general axiomatic approach to this correspondence. In the course of the development we particularly highlight the role played by logical closure properties of propositional proof systems, thereby obtaining a characterization of extensions of EF in terms of a simple combination of these closure properties (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Alternative approaches to the absolute continuity of Jacobi matrices with monotonic weights

We present two approaches to the spectral studies for infinite Jacobi matrices with monotonic or near-to-monotonic weights. The first one is based on the subordination theory due to Khan and Pearson [17] combined with the detailed analysis of the transfer matrices for the solutions of the formal eigenequation. The second one uses an extension of the commutator approach developed by Putnam in [19]. Applying these methods we prove the absolute continuity for several classes of weights and diagonals. For some other cases we prove the emptiness of the point spectrum. The results are illustrated with examples and compared with the results of Dombrowski [7]-[13], Clark [2] and of Máté and Nevai [18]. We show that some of our results are stronger.The research of the first author has been supported by the KBN grant PB 2 P03A 002 13.     

Convergences,pretopologies and proximities induced by Cauchy and Riesz screens

We answer a question of Császár [12]: under which conditions a given pretopological closure or proximity can be induced by a Cauchy structure? We give a characterization for these closures and proximities using properties of convergences and nasses [14] induced by Cauchy structures. We prove also that the set of Cauchy screens inducing a given reciprocal convergence structure is a non empty interval of the set of Cauchy screens equipped with the usual inclusion order.     

3-Interval irreducible partially ordered sets

In this paper we discuss the characterization problem for posets of interval dimension at most 2. We compile the minimal list of forbidden posets for interval dimension 2. Members of this list are called 3-interval irreducible posets. The problem is related to a series of characterization problems which have been solved earlier. These are: The characterization of planar lattices, due to Kelly and Rival [5], the characterization of posets of dimension at most 2 (3-irreducible posets) which has been obtained independently by Trotter and Moore [8] and by Kelly [4] and the characterization of bipartite 3-interval irreducible posets due to Trotter [9].We show that every 3-interval irreducible poset is a reduced partial stack of some bipartite 3-interval irreducible poset. Moreover, we succeed in classifying the 3-interval irreducible partial stacks of most of the bipartite 3-interval irreducible posets. Our arguments depend on a transformationP B(P), such that IdimP=dimB(P). This transformation has been introduced in [2].Supported by the DFG under grant FE 340/2–1.     

The ε-algorithm for the identification of a transfer-function model: some applications

The aim of this paper is to apply an algorithm related to the rational approximation for the identification of the lag structure in a transfer-function model. In fact, we apply the -algorithm proposed by Berlinet [3–5] to determine the polynomial orders in univariate and multivariate ARMA models. Furthermore, it has been proposed by Berlinet [5], González and Cano [13, 14] and González et al. [15] for a transfer-function model with one input and multiple inputs, respectively.The main contribution in this paper concerns the study of the relative significance of the elements in the -algorithm table, in the same way as that given by Berlinet and Francq [7] for ARMA models, to confirm the pattern used to specify the model. Two examples will be considered, namely, the sales series M [8] and a simulated model [20].A comparison is also made between the results of the -algorithm and the corner method generally used in the econometric literature. Although the -algorithm requires a more advanced theory in Numerical Analysis, it can be applied in a more simple way than the corner method.     

Information radius

Summary This paper is an account of a new method of constructing measures of divergence between probability measures; the new divergence measures so constructed are called information radius measures. They are information-theoretic in character, and are based on the work of Rényi [8] and Csiszár [2, 3]. The divergence measure K ₁ can be used for the measurement of dissimilarity in numerical taxonomy, and its application to this field is discussed in Jardine and Sibson [5]; it was this application which originally motivated the study of information radius. Other forms of information radius are related to the variation distance, and the normal information radius discussed in § 3 is related to Mahalanobis D ² Statistic. This paper is in part intended to lay the mathematical foundations for [5], but because information radius appears to be of some general interest, the investigation of its properties is here carried further than is needed for the applications discussed in [5].Part of this work was carried out during the author's tenure of an S.R.C. Research Studentship.     

On the characterization of departure rules for discrete-time queueing networks with batch movements and its applications

This paper supplements and generalizes the results of sawa [11] in this special issue from the viewpoint of discrete-time networks of queues with batch arrivals and batch departures, due to Henderson and Taylor [7]. We first note that the D-rule of sawa [11] is equivalent to the specific form for the release rate function, introduced in [7]. Such forms have widely appeared in the literature, too. sawa [11] found that the D-rule can be characterized in terms of the reversed-time process of a certain vector-valued process. He obtained this characterization for a single node model. We generalize this result for networks of queues with batch arrivals and batch departures. This reveals why the specific form of the release rate function is common in the literature. Furthermore, the characterization is useful to consider traffic flows in a discrete-time queueing network.This research is partially supported by NEC C&C Laboratories.     

A generalization of the AZ identity

The identity discovered in [1] can be viewed as a sharpening of the LYM inequality ([3], [4], [5]). It was extended in [2] so that it covers also Bollobás' inequality [6]. Here we present a further generalization and demonstrate that it shares with its predecessors the usefullness for uniqueness proofs in extremal set theory.     

On some riesz bases

In this paper we consider three problems concerning systems of vector exponentials. In the first part we prove a conjecture of V. Komornik raised in [14] on the independence of the movement of a rectangular membrane in different points. It was independently proved by M. Horváth [9] and S. A. Avdonin (personal communication). The analogous problem for the circular membrane was partly solved in [3] — the complete solution is given in [10]. In the second part we fill in a gap in the theory of Blaschke-Potapov products developed in the paper [19] of Potapov. Namely we prove that the Blaschke-Potapov product is determined by its kernel sets up to a multiplicative constant matrix. In the third part of the present paper we give a multidimensional generalization of the notion of sine type function developed by Levin [16], [17] and by our generalization we prove the multidimensional variant of the Levin-Golovin basis theorem [16], [6].     

A general fibre theorem for moment problems and some applications

The fibre theorem [12] for the moment problem on closed semi-algebraic subsets of R ^d is generalized to finitely generated real unital algebras. As an application two new theorems on the rational multidimensional moment problem are proved. Another application is a characterization of moment functionals on the polynomial algebra R[x ₁,..., x _d ] in terms of extensions. Finally, the fibre theorem and the extension theorem are used to reprove basic results on the complex moment problem due to Stochel and Szafraniec [13] and Bisgaard [2].     

A Nash type solution for hemivariational inequality systems

In this paper, we prove an existence result for a general class of hemivariational inequality systems using the Ky Fan version of the KKM theorem Fan (1984) [10] or Tarafdar fixed points Tarafdar (1987) [11]. As application, we give an infinite-dimensional version for the existence result of Nash generalized derivative points introduced recently by Kristály (2010) [5]. We also give an application to a general hemivariational inequality system.     

Matrix differential equations and scalar polynomials satisfying higher order recursions

We show that any scalar differential operator with a family of polynomials as its common eigenfunctions leads canonically to a matrix differential operator with the same property. The construction of the corresponding family of matrix valued polynomials has been studied in [A. Durán, A generalization of Favard's theorem for polynomials satisfying a recurrence relation, J. Approx. Theory 74 (1993) 83-109; A. Durán, On orthogonal polynomials with respect to a positive definite matrix of measures, Canad. J. Math. 47 (1995) 88-112; A. Durán, W. van Assche, Orthogonal matrix polynomials and higher order recurrence relations, Linear Algebra Appl. 219 (1995) 261-280] but the existence of a differential operator having them as common eigenfunctions had not been considered. This correspondence goes only one way and most matrix valued situations do not arise in this fashion. We illustrate this general construction with a few examples. In the case of some families of scalar valued polynomials introduced in [F.A. Grünbaum, L. Haine, Bispectral Darboux transformations: An extension of the Krall polynomials, Int. Math. Res. Not. 8 (1997) 359-392] we take a first look at the algebra of all matrix differential operators that share these common eigenfunctions and uncover a number of phenomena that are new to the matrix valued case.     

Topological mesh for shell structures

Recently a new technique for the meshing of tension structures has been developed by Hernández-Montes et al. [E. Hernández Montes, R. Jurado-Piña, E. Bayo, Topological mapping for tension structures, J. Struct. Eng. ASCE 132 (6) (2006) 970–977]. This new procedure was based on topology and it was specially designed for tension structures. In this paper an extension of this technique to shell structures is developed. Topological meshing may constitute the first step in the common iterative process of discretization to facilitate the resolution of a partial differential equation.     

Lift-and-project cuts and perfect graphs

We analyze the application of lift-and-project to the clique relaxation of the stable set polytope. We characterize all the inequalities that can be generated through the application of the lift-and-project procedure, introduce the concept of 1-perfection and prove its equivalence to minimal imperfection. This characterization of inequalities and minimal imperfection leads to a generalization of the Perfect Graph Theorem of Lovász, as proved by Aguilera, Escalante and Nasini [1].Mathematics Subject Classification:05C17, 90C57     

An alternative characterization of the weighted Banzhaf value

We provide a new characterization of the weighted Banzhaf value derived from some postulates in a recent paper by Radzik, Nowak and Driessen [7]. Our approach owes much to the work by Lehrer [4] on the classical Banzhaf value based on the idea of amalgamation of pairs of players and an induction construction of the value. Compared with the approach in [7] we consider two new postulates: a weighted version of Lehrer’s “2-efficiency axiom” [4] and a generalized “null player out” property studied in terms of symmetric games by Derks and Haller [2]. Received: December 1997/final version: October 1999