共查询到20条相似文献,搜索用时 41 毫秒
1.
The skew energy of a digraph D is defined as the sum of the singular values of its skew adjacency matrix . In this paper, we first interpret the entries of the power of the skew adjacency matrix of a digraph in terms of the number of its walks and then focus on the question posed by Adiga et al. [C. Adiga, R. Balakrishnan, Wasin So, The skew energy of a graph, Linear Algebra Appl. 432 (2010) 1825–1835] of determining all -regular connected digraphs with optimum skew energy. 相似文献
2.
3.
Jussi Behrndt Seppo Hassi Henk De Snoo Rudi Wietsma 《Linear algebra and its applications》2012,436(5):935-953
The basic objects in this paper are monotonically nondecreasing matrix functions defined on some open interval of and their limit values and at the endpoints a and b which are, in general, selfadjoint relations in . Certain space decompositions induced by the matrix function are made explicit by means of the limit values and . They are a consequence of operator inequalities involving these limit values and the notion of strictness (or definiteness) of monotonically nondecreasing matrix functions. This treatment provides a geometric approach to the square-integrability of solutions of definite canonical systems of differential equations. 相似文献
4.
Let and be the adjacency matrix and the degree matrix of a graph , respectively. The matrix is called the signless Laplacian matrix of . The spectrum of the matrix is called the Q-spectrum of . A graph is said to be determined by its Q-spectrum if there is no other non-isomorphic graph with the same Q-spectrum. In this paper, we prove that all starlike trees whose maximum degree exceed are determined by their Q-spectra. 相似文献
5.
Let D be a commutative domain with field of fractions K, let A be a torsion-free D-algebra, and let B be the extension of A to a K-algebra. The set of integer-valued polynomials on A is , and the intersection of with is , which is a commutative subring of . The set may or may not be a ring, but it always has the structure of a left -module.A D-algebra A which is free as a D-module and of finite rank is called -decomposable if a D-module basis for A is also an -module basis for ; in other words, if can be generated by and A. A classification of such algebras has been given when D is a Dedekind domain with finite residue rings. In the present article, we modify the definition of -decomposable so that it can be applied to D-algebras that are not necessarily free by defining A to be -decomposable when is isomorphic to . We then provide multiple characterizations of such algebras in the case where D is a discrete valuation ring or a Dedekind domain with finite residue rings. In particular, if D is the ring of integers of a number field K, we show that an -decomposable algebra A must be a maximal D-order in a separable K-algebra B, whose simple components have as center the same finite unramified Galois extension F of K and are unramified at each finite place of F. Finally, when both D and A are rings of integers in number fields, we prove that -decomposable algebras correspond to unramified Galois extensions of K. 相似文献
6.
Let V be a 6-dimensional vector space over a field , let f be a nondegenerate alternating bilinear form on V and let denote the symplectic group associated with . The group has a natural action on the third exterior power of V and this action defines five families of nonzero trivectors of V. Four of these families are orbits for any choice of the field . The orbits of the fifth family are in one-to-one correspondence with the quadratic extensions of that are contained in a fixed algebraic closure of . In this paper, we divide the orbits corresponding to the separable quadratic extensions into suborbits for the action of on . 相似文献
7.
Let V be an n-dimensional vector space over the finite field consisting of q elements and let be the Grassmann graph formed by k-dimensional subspaces of V, . Denote by the restriction of to the set of all non-degenerate linear codes. We show that for any two codes the distance in coincides with the distance in only in the case when , i.e. if n is sufficiently large then for some pairs of codes the distances in the graphs and are distinct. We describe one class of such pairs. 相似文献
8.
Let be a digraph with vertex set and be the adjacency matrix of . The largest eigenvalue of , denoted by , is called the spectral radius of the digraph . In this paper, we establish some sharp upper or lower bounds for digraphs with some given graph parameters, such as clique number, girth, and vertex connectivity, and characterize the corresponding extremal graphs. In addition, we give the exact value of the spectral radii of those digraphs. 相似文献
9.
10.
11.
Let G be a complex linear algebraic group, its Lie algebra and a nilpotent element. Vust's Theorem says that in case of , the algebra , where is the stabilizer of e under the adjoint action, is generated by the image of the natural action of d-th symmetric group and the linear maps . In this paper, we give an analogue of Vust's Theorem for and when the nilpotent elements e satisfy that is normal. As an application, we study the higher Schur–Weyl duality in the sense of [4] for types B, C and D, which establishes a relationship between W-algebras and degenerate affine braid algebras. 相似文献
12.
13.
14.
15.
16.
Gangyong Lee Jae Keol Park S. Tariq Rizvi Cosmin S. Roman 《Journal of Pure and Applied Algebra》2018,222(9):2427-2455
Let V be a module with . V is called a quasi-Baer module if for each ideal J of S, for some . On the other hand, V is called a Rickart module if for each , for some . For a module N, the quasi-Baer module hull (resp., the Rickart module hull ) of N, if it exists, is the smallest quasi-Baer (resp., Rickart) overmodule, in a fixed injective hull of N. In this paper, we initiate the study of quasi-Baer and Rickart module hulls. When a ring R is semiprime and ideal intrinsic over its center, it is shown that every finitely generated projective R-module has a quasi-Baer hull. Let R be a Dedekind domain with F its field of fractions and let be any set of R-submodules of . For an R-module with , we show that has a quasi-Baer module hull if and only if is semisimple. This quasi-Baer hull is explicitly described. An example such that has no Rickart module hull is constructed. If N is a module over a Dedekind domain for which is projective and , where is the torsion submodule of N, we show that the quasi-Baer hull of N exists if and only if is semisimple. We prove that the Rickart module hull also exists for such modules N. Furthermore, we provide explicit constructions of and and show that in this situation these two hulls coincide. Among applications, it is shown that if N is a finitely generated module over a Dedekind domain, then N is quasi-Baer if and only if N is Rickart if and only if N is Baer if and only if N is semisimple or torsion-free. For a direct sum of finitely generated modules, where R is a Dedekind domain, we show that N is quasi-Baer if and only if N is Rickart if and only if N is semisimple or torsion-free. Examples exhibiting differences between the notions of a Baer hull, a quasi-Baer hull, and a Rickart hull of a module are presented. Various explicit examples illustrating our results are constructed. 相似文献
17.
18.
Let be a digraph with n vertices and m arcs without loops and multiarcs. The spectral radius of G is the largest eigenvalue of its adjacency matrix. In this paper, the following sharp bounds on have been obtained.where G is strongly connected and is the average 2-outdegree of vertex . Moreover, each equality holds if and only if G is average 2-outdegree regular or average 2-outdegree semiregular. 相似文献
19.
20.
Bruce Olberding 《Journal of Pure and Applied Algebra》2018,222(8):2267-2287
Let F be a field. For each nonempty subset X of the Zariski–Riemann space of valuation rings of F, let and , where denotes the maximal ideal of V. We examine connections between topological features of X and the algebraic structure of the ring . We show that if and is a completely integrally closed local ring that is not a valuation ring of F, then there is a space Y of valuation rings of F that is perfect in the patch topology such that . If any countable subset of points is removed from Y, then the resulting set remains a representation of . Additionally, if F is a countable field, the set Y can be chosen homeomorphic to the Cantor set. We apply these results to study properties of the ring with specific focus on topological conditions that guarantee is a Prüfer domain, a feature that is reflected in the Zariski–Riemann space when viewed as a locally ringed space. We also classify the rings where X has finitely many patch limit points, thus giving a topological generalization of the class of Krull domains, one that includes interesting Prüfer domains. To illustrate the latter, we show how an intersection of valuation rings arising naturally in the study of local quadratic transformations of a regular local ring can be described using these techniques. 相似文献