Browsing by Author "Garriga Valle, Ernest"

On the algebraic theory of pseudodistanceregulariry around a set
Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (Elsevier, 199909)
Article
Restricted access  publisher's policyLet C be a connected graph with vertex set V, adjacency matrix A, positive eigenvector and corresponding eigenvalue 0. A natural generalization of distanceregularity around a vertex subset C V , which makes sense ... 
On the local spectra of the subconstituents of a vertex set and completely pseudoregular codes
Cámara Vallejo, Marc; Fàbrega Canudas, José; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (20141030)
Article
Restricted access  publisher's policyIn this paper we study the relation between the local spectrum of a vertex set C and the local spectra of its subconstituents. In particular, it is shown that, when C is a completely regular code, such spectra are uniquely ... 
Some families of orthogonal polynomials of a discrete variable and their applications to graphs and codes
Fiol Mora, Miquel Àngel; Garriga Valle, Ernest; Fàbrega Canudas, José; Cámara Vallejo, Marc (200008)
Article
Open AccessWe present some related families of orthogonal polynomials of a discrete variable and survey some of their applications in the study of (distanceregular) graphs and (completely regular) codes. One of the main peculiarities ... 
The alternating and adjacency polynomials, and their relation with the spectra and diameters of graphs
Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (Elsevier Science Publishers B. V., 199810)
Article
Open AccessLet Γ be a graph on n vertices, adjacency matrix A, and distinct eigenvalues λ > λ_1 > λ_2 > · · · > λ_d. For every k = 0,1, . . . ,d −1, the kalternating polynomial P_k is defined to be the polynomial of degree k and norm  
The geometry of tcliques in kwalkregular graphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (200809)
Article
Open AccessA graph is walkregular if the number of cycles of length $\ell$ rooted at a given vertex is a constant through all the vertices. For a walkregular graph $G$ with $d+1$ different eigenvalues and spectrally maximum ... 
The geometry of tspreads in kwalkregular graphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (Wiley InterScience, 201008)
Article
Open AccessA graph is walkregular if the number of closed walks of length rooted at a given vertex is a constant through all the vertices for all . For a walkregular graph G with d+1 different eigenvalues and spectrally maximum ... 
When almost distance regularity attains distance regularity
Dalfó Simó, Cristina; Van Dam, Edwin; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2010)
Conference report
Restricted access  publisher's policy 
When almost distanceregularity attains distanceregularity
Dalfó Simó, Cristina; Van Dam, Edwin; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2010)
Conference report
Open AccessGenerally speaking, `almost distanceregular graphs' are graphs which share some, but not necessarily all, regularity properties that characterize distanceregular graphs. In this paper we rst propose four basic di erent ...