A counter-example in the partition calculus for an uncountable ordinal

The main theorem of the paper is a counter-example in the partition calculus introduced by P. Erdös and R. Rado: Ifκ is a regular cardinal and α=?(α,3)², then α ? (α,3)². The proof is combinatorial. Other counter-examples are produced from this one through the pinning relation which was introduced by E. Specker.     

On Shapiro's results in quasidifferential calculus

Several necessary minimum conditions for quasidifferentiable programming problems are discussed. Some statements of Shapiro (1986) are shown to be incorrect.     

On consistency relations for polynomial splines on a uniform partition

In this paper we present linear dependence relations connecting spline values, derivative values and integral values of the spline. These relations are useful when spline interpolants or histospline projections of a function are considered.This work was supported in part by the Ministère de l'Éducation du Québec and by the Department of the National Defence of Canada.     

More results in polychromatic Ramsey theory

We study polychromatic Ramsey theory with a focus on colourings of [ω ₂]². We show that in the absence of GCH there is a wide range of possibilities. In particular each of the following is consistent relative to the consistency of ZFC: (1) 2 ^ω = ω ₂ and \(\omega _2 \to ^{poly} (\alpha )_{\aleph _0 - bdd}^2 \) for every α <ω ₂; (2) 2 ^ω = ω ₂ and \(\omega _2 \nrightarrow ^{poly} (\omega _1 )_{2 - bdd}^2 \).     

Some results on surface measures in calculus of variations

We study some relations between the concepts of perimeter, Hausdorff measure, and Minkowsky content, when R ^N is endowed with a convex Finsler metric depending in a continuous way on the position. We show some connections with the theory of -convergence and with the anisotropic motion of a smooth hypersurface by mean curvature.This work was partially supported by NSF Grant DMS-9008999, and by MURST (Progetto Nazionale «Equazioni di Evoluzione e Applicazioni Fisico-Matematiche» and «Analisi Numerica e Matematica Computazionale») and CNR (IAN and Contracts 92.00833.01, 93.00564.01) of Italy.     

New results on optimizing rooted triplets consistency

A set of phylogenetic trees with overlapping leaf sets is consistent if it can be merged without conflicts into a supertree. In this paper, we study the polynomial-time approximability of two related optimization problems called the maximum rooted triplets consistency problem (MaxRTC) and the minimum rooted triplets inconsistency problem (MinRTI) in which the input is a set R of rooted triplets, and where the objectives are to find a largest cardinality subset of R which is consistent and a smallest cardinality subset of R whose removal from R results in a consistent set, respectively. We first show that a simple modification to Wu’s Best-Pair-Merge-First heuristic Wu (2004) [38] results in a bottom-up-based 3-approximation algorithm for MaxRTC. We then demonstrate how any approximation algorithm for MinRTI could be used to approximate MaxRTC, and thus obtain the first polynomial-time approximation algorithm for MaxRTC with approximation ratio less than 3. Next, we prove that for a set of rooted triplets generated under a uniform random model, the maximum fraction of triplets which can be consistent with any phylogenetic tree is approximately one third. We then provide a deterministic construction of a triplet set having a similar property which is subsequently used to prove that both MaxRTC and MinRTI are -hard even if restricted to minimally dense instances. Finally, we prove that unless , MinRTI cannot be approximated within a ratio of c⋅lnn for some constant c>0 in polynomial time, where n denotes the cardinality of the leaf label set of R.     

Two consistency results concerning thin-tall Boolean algebras

In this paper we show that the following is relatively consistent withZFC +CH: There is no superatomic Boolean algebra of height ₂+1 and width, and there is no superatomic Boolean algebraA with for 0<<₁ and Presented by J. Mycielski.     

New results on finite polarized partition relations

Let c = c(m,n,j,k) be the largest integer such that every matrix with m rows and n columns whose entries belong to a set of cardinal c has a constant submatrix with j rows and k columns. Some results in the case j = 2 are given.     

Approximation results for the weighted partition problem

We present several new standard and differential approximation results for the P₄-partition problem using the Hassin and Rubinstein algorithm [Information Processing Letters 63 (1997) 63–67]. Those results concern both minimization and maximization versions of the problem. However, the main point of this paper lies in the establishment of the robustness of this algorithm, in the sense that it provides good quality solutions for a variety of versions of the problem, under both standard and differential approximation ratios.     

More results on overlapping squares

Three recent papers (Fan et al., 2006; Simpson, 2007; Kopylova and Smyth, 2012) [5], [11], [8] have considered in complementary ways the combinatorial consequences of assuming that three squares overlap in a string. In this paper we provide a unifying framework for these results: we show that in 12 of 14 subcases that arise the postulated occurrence of three neighboring squares forces a breakdown into highly periodic behavior, thus essentially trivial and easily recognizable. In particular, we provide a proof of Subcase 4 for the first time, and we simplify and refine the previously established results for Subcases 11–14.     

More results on congruent modules

W.R. Scott characterized the infinite abelian groups G for which H≅G for every subgroup H of G of the same cardinality as G [W.R. Scott, On infinite groups, Pacific J. Math. 5 (1955) 589-598]. In [G. Oman, On infinite modules M over a Dedekind domain for which N≅M for every submodule N of cardinality |M|, Rocky Mount. J. Math. 39 (1) (2009) 259-270], the author extends Scott’s result to infinite modules over a Dedekind domain, calling such modules congruent, and in a subsequent paper [G. Oman, On modules M for which N≅M for every submodule N of size |M|, J. Commutative Algebra (in press)] the author obtains results on congruent modules over more general classes of rings. In this paper, we continue our study.     

New results in subdifferential calculus with applications to convex optimization

Chain and addition rules of subdifferential calculus are revisited in the paper and new proofs, providing local necessary and sufficient conditions for their validity, are presented. A new product rule pertaining to the composition of a convex functional and a Young function is also established and applied to obtain a proof of Kuhn-Tucker conditions in convex optimization under minimal assumptions on the data. Applications to plasticity theory are briefly outlined in the concluding remarks.The financial support of the Italian Ministry for University and Scientific and Technological Research is gratefully acknowledged.     

The calculus of partition sequences, changing cofinalities, and a question of Woodin

We study in this paper polarized infinite exponent partition relations. We apply our results to constructing a model for the theory ``ZFDC is the only regular, uncountable cardinal .' This gives a partial answer to a question of Woodin.

     

More Lowenheim-Skolem results for admissible sets

It is shown that ifA is a countable, admissible set and ø ∈{ie53-1}, then under certain conditions, ø has a model inA. In general, however, ifT is a consistent theory of {ie53-2}, Σ-definable onA, then there is an admissible setB?A, with the same ordinals asA, containing a model ofT.     

The use of partition polynomial series in Laplace inversion of composite functions with applications in fractional calculus

This paper presents an analytical method towards Laplace transform inversion of composite functions with the aid of Bell polynomial series. The presented results are used to derive the exact solution of fractional distributed order relaxation processes as well as time‐domain impulse response of fractional distributed order operators in new series forms. Evaluation of the obtained series expansions through computer simulations is also given. The results are then used to present novel series expansions for some special functions, including the one‐parameter Mittag‐Leffler function. It is shown that truncating these series expansions when combined with using potential partition polynomials provides efficient approximations for these functions. At the end, the results are shown to be also useful in studying asymptotical behavior of partial Bell polynomials. Numerical simulations as well as analytical examples are provided to verify the results of this paper.     

偶一致超图划分问题的若干结果

划分问题因其在多个领域的重要应用一直是图论的研究热点.利用张量的特征值研究超图的划分与奇划分,并结合边割的界给出最大奇割、平均最小割、等周数等超图拓扑指标的界.当k取2时,这些结果与对应的图谱理论中的经典结论一致,因此可视为这些结论在超图的推广.     

More results on Schur complements in Euclidean Jordan algebras

In a recent article Gowda and Sznajder (Linear Algebra Appl 432:1553–1559, 2010) studied the concept of Schur complement in Euclidean Jordan algebras and described Schur determinantal and Haynsworth inertia formulas. In this article, we establish some more results on the Schur complement. Specifically, we prove, in the setting of Euclidean Jordan algebras, an analogue of the Crabtree-Haynsworth quotient formula and show that any Schur complement of a strictly diagonally dominant element is strictly diagonally dominant. We also introduce the concept of Schur product of a real symmetric matrix and an element of a Euclidean Jordan algebra when its Peirce decomposition with respect to a Jordan frame is given. An Oppenheim type inequality is proved in this setting.     

Differential and integral calculus III through WebCT: analysis of results

In this paper a Calculus course for students of Engineering in the virtual environment is discussed. This course used WebCT course management software only, without traditional lessons. A feedback survey obtained by questionnaires and data concerning the progress of students are presented and analysed. Conclusions point out the need for further research into the use of the virtual universe within the teaching/learning process and the necessity of re-examining the work normally done in the classroom.     

关于正则图存在平衡划分的一些结果

一个图G的划分V(G)=V1∪V2,如果满足下列条件:(1)||V1|-|V2||≤1;(2)任给u ∈V(G),当u ∈V1时,满足dG[V1](u)-dG[V2∪{u}](u)≤1;当u ∈V2时,满足dG[V2](u)-dG[V1∪{u}](u)≤1.则称V(G)=V1 ∪ V2为G的一个平衡划分.Bollobas与Scott猜想任一图都存在平衡划分.文中证明了k-正则图存在平衡划分.其中k ∈{3,n-1,n-2,n-3,n-4).对于k=3或n-4的一个特殊情形,还给出了寻找k-正则图平衡划分的算法.