共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
A discrete function f defined on Zn is said to be logconcave if for , , . A more restrictive notion is strong unimodality. Following Barndorff-Nielsen [O. Barndorff-Nielsen, Unimodality and exponential families, Commun. Statist. 1 (1973) 189-216] a discrete function is called strongly unimodal if there exists a convex function such that if . In this paper sufficient conditions that ensure the strong unimodality of a multivariate discrete distribution, are given. Examples of strongly unimodal multivariate discrete distributions are presented. 相似文献
3.
4.
5.
6.
Adrian Kosowski 《Discrete Applied Mathematics》2009,157(2):321-329
Motivated by wavelength-assignment problems for all-to-all traffic in optical networks, we study graph parameters related to sets of paths connecting all pairs of vertices. We consider sets of both undirected and directed paths, under minimisation criteria known as edge congestion and wavelength count; this gives rise to four parameters of a graph G: its edge forwarding index π(G), arc forwarding index , undirected optical index , and directed optical index .In the paper we address two long-standing open problems: whether the equality holds for all graphs, and whether indices π(G) and are hard to compute. For the first problem, we give an example of a family of planar graphs {Gk} such that . For the second problem, we show that determining either π(G) or is NP-hard. 相似文献
7.
Jin-Hui Fang 《Discrete Applied Mathematics》2008,156(15):2950-2958
It is conjectured by Erd?s, Graham and Spencer that if 1≤a1≤a2≤?≤as are integers with , then this sum can be decomposed into n parts so that all partial sums are ≤1. This is not true for as shown by a1=?=an−2=1, . In 1997 Sandor proved that Erd?s-Graham-Spencer conjecture is true for . Recently, Chen proved that the conjecture is true for . In this paper, we prove that Erd?s-Graham-Spencer conjecture is true for . 相似文献
8.
9.
Two classes of edge domination in graphs 总被引:2,自引:0,他引:2
Baogen Xu 《Discrete Applied Mathematics》2006,154(10):1541-1546
Let (, resp.) be the number of (local) signed edge domination of a graph G [B. Xu, On signed edge domination numbers of graphs, Discrete Math. 239 (2001) 179-189]. In this paper, we prove mainly that and hold for any graph G of order n(n?4), and pose several open problems and conjectures. 相似文献
10.
11.
Given that r and s are natural numbers and and are independent random variables where q,p∈(0,1), we prove that the likelihood ratio of the convolution Z=X+Y is decreasing, increasing, or constant when q<p, q>p or q=p, respectively. 相似文献
12.
Alex V. Kontorovich 《Journal of Number Theory》2006,117(1):1-13
For every positive integer n, the quantum integer [n]q is the polynomial [n]q=1+q+q2+?+qn-1. A quadratic addition rule for quantum integers consists of sequences of polynomials , , and such that for all m and n. This paper gives a complete classification of quadratic addition rules, and also considers sequences of polynomials that satisfy the associated functional equation . 相似文献
13.
14.
Let be the anticipating smooth semimartingale and be its generalized local time. In this paper, we give some estimates about the quasi sure property of Xt and its quadratic variation process t〈X〉. We also study the fractional smoothness of and prove that the quadratic variation process of can be constructed as the quasi sure limit of the form , where is a sequence of subdivisions of [a,b], , i=0,1,…,n2. 相似文献
15.
16.
17.
18.
19.
20.
For a given structure D (digraph, multidigraph, or pseudodigraph) and an integer r large enough, a smallest inducing r-regularization of D is constructed. This regularization is an r-regular superstructure of the smallest possible order with bounded arc multiplicity, and containing D as an induced substructure. The sharp upper bound on the number, ρ, of necessary new vertices among such superstructures for n-vertex general digraphs D is determined, ρ being called the inducing regulation number of D. For being the maximum among semi-degrees in D, simple n-vertex digraphs D with largest possible ρ are characterized if either or (where the case is not a trivial subcase of ). 相似文献