An n × n ray pattern A is called a spectrally arbitrary ray pattern if the complex matrices in Q(A) give rise to all possible complex polynomials of degree n. In a paper of Mei, Gao, Shao, and Wang (2014) was proved that the minimum number of nonzeros in an n×n irreducible spectrally arbitrary ray pattern is 3n-1. In this paper, we introduce a new family of spectrally arbitrary ray patterns of order n with exactly 3n - 1 nonzeros., Yinzhen Mei, Yubin Gao, Yanling Shao, Peng Wang., and Obsahuje seznam literatury
A close relationship between the class of totally positive matrices and anti-Monge matrices is used for suggesting a new direction for investigating totally positive matrices. Some questions are posed and a partial answer in the case of Vandermonde-like matrices is given., Miroslav Fiedler., and Obsahuje seznam literatury
Let G be a group. If every nontrivial subgroup of G has a proper supplement, then G is called an aS-group. We study some properties of aS-groups. For instance, it is shown that a nilpotent group G is an aS-group if and only if G is a subdirect product of cyclic groups of prime orders. We prove that if G is an aS-group which satisfies the descending chain condition on subgroups, then G is finite. Among other results, we characterize all abelian groups for which every nontrivial quotient group is an aS-group. Finally, it is shown that if G is an aS-group and |G| ≠ pq, p, where p and q are primes, then G has a triple factorization., Reza Nikandish, Babak Miraftab., and Obsahuje seznam literatury
We show that there is a model structure in the sense of Quillen on an arbitrary Frobenius category F such that the homotopy category of this model structure is equivalent to the stable category F as triangulated categories. This seems to be well-accepted by experts but we were unable to find a complete proof for it in the literature. When F is a weakly idempotent complete (i.e., every split monomorphism is an inflation) Frobenius category, the model structure we constructed is an exact (closed) model structure in the sense of Gillespie (2011)., Zhi-Wei Li., and Seznam literatury
Let (G) and i(G) be the domination number and the independent domination number of G, respectively. Rad and Volkmann posted a conjecture that i(G)/ (G) 6 (G)/2 for any graph G, where (G) is its maximum degree (see N. J.Rad, L.Volkmann (2013)). In this work, we verify the conjecture for bipartite graphs. Several graph classes attaining the extremal bound and graphs containing odd cycles with the ratio larger than (G)/2 are provided as well., Shaohui Wang, Bing Wei., and Seznam literatury
According to the Oxford English Dictonary George Berkeley introduced the term a priori into English. His inspiration for this was, it seems, to be found partly in the writings of his immediate predecessors, particularly Pierre Bayle, and partly in his pedagogical work where he adjudicated disputations between his pupils. Some of his arguments against the existence of matter Berkeley tells us are a priori, others a posteriori. Even the a priori arguments are underpinned by prior semantic principles of an anti-abstractionist character, which are shown to be important particularly in the immaterialist philosophy of mathematics. Berkeley's courageously unorthodox, and generally unpublished, thoughts about mathematics thus grow from the same soil as his celebrated denial of matter., Marek Tomeček., and Obsahuje poznámky a bibliografii
Let \Omega \subset {{\Bbb C}^n} be a bounded, simply connected \mathbb{C} -convex domain. Let \alpha \in \mathbb{Z}_{+}^{n} and let f be a function on Ω which is separately {C^{2{\alpha _j} - 1}} -smooth with respect to zj (by which we mean jointly {C^{2{\alpha _j} - 1}} -smooth with respect to Rezj, Imzj). If f is α-analytic on Ω\f−1(0), then f is α-analytic on Ω. The result is well-known for the case a_{i}=1, 1\leqslant i\leqslant n even when f a priori is only known to be continuous., Abtin Daghighi, Frank Wikström., and Obsahuje seznam literatury
We obtain a sharp upper bound for the spectral radius of a nonnegative matrix. This result is used to present upper bounds for the adjacency spectral radius, the Laplacian spectral radius, the signless Laplacian spectral radius, the distance spectral radius, the distance Laplacian spectral radius, the distance signless Laplacian spectral radius of an undirected graph or a digraph. These results are new or generalize some known results., Lihua You, Yujie Shu, Xiao-Dong Zhang., and Obsahuje seznam literatury