Encontrados 19 documentos, a visualizar página 1 de 2
Face counting on an Acyclic Birkhoff polytope
Costa, Liliana; Fonseca, C. M. da; Martins, Enide Andradehttp://www.sciencedirect.com/science/article/B6V0R-4V5GD2H-1/2/5a4ab2f05e5a55a500bf0fc93554003a
Fibonacci numbers, alternating parity sequences and faces of the tridiagonal Bi...
Fonseca, C. M. da; Sá, E. Marques deWe determine the number of alternating parity sequences that are subsequences of an increasing m-tuple of integers. For this and other related counting problems we find formulas that are combinations of Fibonacci numbers. These results are applied to determine, among other things, the number of vertices of any face of the polytope of tridiagonal doubly stochastic matrices. ; http://www.sciencedirect.com/scie...
The diameter of the acyclic Birkhoff polytope
Costa, Liliana; Fonseca, C. M. da; Martins, Enide AndradeIn this work we give an interpretation of vertices and edges of the acyclic Birkhoff polytope, , where T is a tree with n vertices, in terms of graph theory. We generalize a recent result relatively to the diameter of the graph . ; http://www.sciencedirect.com/science/article/B6V0R-4R70RHM-1/1/4f38cb080e47b5fa8e0d6c36588d41a8
On the multiplicities of eigenvalues of a Hermitian matrix whose graph is a tree
Fonseca, C. M. daAbstract A different approach is given to recent results due mainly to R. C. Johnson and A. Leal Duarte on the multiplicities of eigenvalues of a Hermitian matrix whose graph is a tree. The techniques developed are based on some results of matching polynomials and used a work by O. L. Heilmann and E. H. Lieb on an apparently unrelated topic. ; http://dx.doi.org/10.1007/s10231-007-0044-3
The inverse eigenvalue problem for Hermitian matrices whose graphs are cycles
Fernandes, Rosário; Fonseca, C. M. daIn 1979, Ferguson characterized the periodic Jacobi matrices with given eigenvalues and showed how to use the Lanzcos Algorithm to construct each such matrix. This article provides general characterizations and constructions for the complex analogue of periodic Jacobi matrices. As a consequence of the main procedure, we prove that the multiplicity of an eigenvalue of a periodic Jacobi matrix is at most 2. ; ...
One size resolvability of graphs
Kwancharone, S.; Saenpholphat, V.; Fonseca, C. M. daFor an ordered set W = w1,w2, · · · ,wk of vertices in a connected graph G and a vertex v of G, the code of v with respect to W is the k-vector CW(v) = (d(v,w1), d(v,w2), · · · , d(v,wk)). The set W is a one size resolving set for G if (1) the size of subgraph hWi induced by W is one and (2) distinct vertices of G have distinct code with respect to W. The minimum cardinality of a one size resolving set in graph...
On the eigenvalues of some tridiagonal matrices
Fonseca, C. M. daA solution is given for a problem on eigenvalues of some symmetric tridiagonal matrices suggested by William Trench. The method presented can be generalizable to other problems. ; http://www.sciencedirect.com/science/article/B6TYH-4J9N0SV-1/1/f15fb954c01649af39599f88edf73d60
On (0,1)-matrices with prescribed row and column sum vectors
Fonseca, C. M. da; Mamede, RicardoGiven partitions R and S with the same weight, the Robinson-Schensted- Knuth correspondence establishes a bijection between the class A(R, S) of (0, 1)- matrices with row sum R and column sum S and pairs (P,Q) of Young tableaux of conjugate shapes and , with S 4 4 R. An algorithm for constructing a matrix in A(R, S) whose insertion tableaux has a prescribed shape with S 4 4 R, is provided. We generaliz some...
The cardinality of endomorphisms of some oriented paths: an algorithm
Arworn, Sr.; Fonseca, C. M. da; Saenpholphat, V.An endomorphism of a (oriented) graph is a mapping on the vertex set preserving (arcs) edges. In this paper we provide an algorithm to determine the cardinalities of endomorphism monoids of some ( nite) directed paths, based on results on simple paths. ; Chiang Mai University; CMUC - Centro de Matemática da Universidade de Coimbra; Srinakharinwirot University; Thailand Research Fund and Commission on Higher ...
An algorithm for the inertia sets of tree sign patterns
Fonseca, C. M. da; Mamede, RicardoA matrix whose entries are +, ¡ or 0 is said a sign pattern. The inertia set of an n-by-n symmetric sign pattern A is the set of inertias of all real symmetric matrices with the same sign pattern as A. We present an algorithm to compute the inertia set of any symmetric tree (or acyclic) sign pattern. The procedure generalizes some recent results. Some examples are provided. ; Centro de Matemática da Universi...
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