Anna S. Lladó
Polytechnic University of Catalonia
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Featured researches published by Anna S. Lladó.
IEEE Transactions on Computers | 1992
Miguel Angel Fiol; Anna S. Lladó
The following problem arises in the design of some interconnection networks for distributed systems. Namely, to construct digraphs with given maximum out-degree, reduced diameter, easy routing, good connectivity, and good expandability. To this end, a method based on the concept of partial line digraph is presented. This proposal, which turns out to be a generalization of the so-called line digraph technique, allows digraphs that satisfy all the above-mentioned requirements to be obtained. In particular, it is shown that the partial line digraphs of Kautz digraphs solve the (d, N) digraph problem, i.e. to minimize the diameter D in a digraph of maximum out-degree d and number of vertices N, for any N in the range d/sup D-1/+d/sup D-2/+. . .+1 >
Graphs and Combinatorics | 1991
Yahya Ould Hamidoune; Anna S. Lladó; Oriol Serra
A digraphX is said to be Vosperian if any fragment has cardinality either 1 or|V(X)| − d+(X) − 1.A digraph is said to be superconnected if every minimum cutset is the set of vertices adjacent from or to some vertex.In this paper we characterize Vosperian and superconnected Abelian Cayley directed graphs. Our main tool is a difficult theorem of J.H. Kemperman from Additive Group Theory.In particular we characterize Vosperian and superconnected loops network (also called circulants).
Combinatorica | 1998
Yahya Ould Hamidoune; Anna S. Lladó; Oriol Serra
G be a nonabelian torsion-free group. Let C be a finite generating subset of G such that . We prove that, for all subsets B of G with , we have .In particular, a finite subset X with cardinality satisfies the inequality if and only if there are elements , such that the following two conditions hold:(i) .(ii) where .
Discrete Applied Mathematics | 1992
Yahya Ould Hamidoune; Anna S. Lladó; Oriol Serra
Abstract An ordered generating set of a group is hierarchical when the group generated by the first k generators is a proper subgroup of the group generated by the first k + 1 for each k . Hierarchical Cayley graphs were introduced by Akers and Krishnamurthy in [1] and other related papers as an interesting model to build symmetrical networks. In this paper we study the connectivity of hierarchical Cayley digraphs, and we show that they have maximum connectivity except in a special case. An example of this exceptional case is given. The result generalizes similar statements of Godsil [3], Akers [1] and Hamidoune [5].
Journal of Graph Theory | 2005
Anna S. Lladó; Susana-Clara López
We study the Häggkvist conjecture which states that, for each tree T with n edges, there is an edge-partition of the complete bipartite graph Kn;n into n isomorphic copies of T . We use the concept of bigraceful labelings, introduced in [7], which give rise to cyclic decompositions of Kn;n. When a tree T of size n is not known to be bigraceful it is shown, using similar techniques to the ones by Kézdy and Snevily [5], that T decomposes K2hn;2hn for some h dr=4e, where r is the radius of T . Moreover, if the base tree of T is bigraceful or if there is a vertex v in T such that jViðvÞj
SIAM Journal on Discrete Mathematics | 2000
Yahya Ould Hamidoune; Anna S. Lladó; Oriol Serra; Ralph Tindell
We shall define the
Combinatorica | 2003
W. Gao; O. Hamidoune; Anna S. Lladó; Oriol Serra
k
Combinatorics, Probability & Computing | 2000
Yahya Ould Hamidoune; Anna S. Lladó; Oriol Serra
-isoperimetric connectivity
Journal of Graph Theory | 2011
Yahya Ould Hamidoune; Anna S. Lladó; Susana-Clara López
\lambda _k
Theory of Computing Systems \/ Mathematical Systems Theory | 1999
Yahya Ould Hamidoune; Anna S. Lladó; Oriol Serra
of a regular graph