Now showing items 1-20 of 21

    • A characterization of PFNP|| = PFNP[log] 

      Lozano Bojados, Antoni (1993-02)
      Research report
      Open Access
      Some implications of the fact PFNP∥ = PFNP[log] are known in terms of equalities between complexity classes of sets, but a characterization in the same terms is still unknown. Here we provide a characterization in terms ...
    • Antimagic labelings of caterpillars 

      Lozano Bojados, Antoni; Mora Giné, Mercè; Seara Ojea, Carlos (2019-04-15)
      Article
      Open Access
      A k-antimagic labeling of a graph G is an injection from E(G) to {1,2, ..., |E(G)|+k} such that all vertex sums are pairwise distinct, where the vertex sum at vertex u is the sum of the labels assigned to edges incident ...
    • Bounded queries to arbitrary sets 

      Lozano Bojados, Antoni (1991-09)
      Research report
      Open Access
      We prove that if P superA[k] = P superA[k+1] for some k and an arbitrary set A, then A is reducible to its complement under a relativized nondeterministic conjunctive reduction. This result shows the first known property ...
    • Caterpillars are antimagic 

      Lozano Bojados, Antoni; Mora Giné, Mercè; Seara Ojea, Carlos; Tey Carrera, Joaquín (2021-01-21)
      Article
      Open Access
      An antimagic labeling of a graph G is a bijection from the set of edges E(G) to {1,2,…,|E(G)|}, such that all vertex sums are pairwise distinct, where the vertex sum at vertex u is the sum of the labels assigned to the ...
    • Caterpillars have antimagic orientations 

      Lozano Bojados, Antoni (2018-01-01)
      Article
      Open Access
      An antimagic labeling of a directed graph D with m arcs is a bijection from the set of arcs of D to {1, . . . , m} such that all oriented vertex sums of vertices in D are pairwise distinct, where the oriented vertex sum ...
    • Complejidad de problemas sobre representaciones sucintas de grafos 

      Lozano Bojados, Antoni (1988-05)
      Research report
      Open Access
    • Distinguishing tournaments with small label classes 

      Lozano Bojados, Antoni (2019-07-30)
      Article
      Open Access
      A d-distinguishing vertex (arc) labeling of a digraph is a vertex (arc) labeling using d labels that is not preserved by any nontrivial automorphism. Let ρ(T) (ρ′(T)) be the minimum size of a label class in a 2-distinguishing ...
    • Els Límits de la computació : indecidibilitat i NP-completesa 

      Serna Iglesias, María José; Álvarez Faura, M. del Carme; Cases Muñoz, Rafel; Lozano Bojados, Antoni (Edicions UPC, 2001)
      Book
      Restricted access to the UPC academic community
      Aquest text presenta una introducció a les teories de la calculabilitat i la complexitat a l'abast d'un estudiant de primer cicle d'una enginyeria informàtica. A partir de la justificació de la necessitat d'un model formal ...
    • Fast calculation of entropy with Zhang's estimator 

      Lozano Bojados, Antoni; Casas Fernández, Bernardino; Bentz, Chris; Ferrer Cancho, Ramon (RAM - Verlag, 2016-12-01)
      Part of book or chapter of book
      Restricted access - publisher's policy
      Entropy is a fundamental property of a repertoire. Here, we present an efficient algorithm to estimate the entropy of types with the help of Zhang’s estimator. The algorithm takes advantage of the fact that the number of ...
    • Mining frequent closed rooted trees 

      Balcázar Navarro, José Luis; Bifet Figuerol, Albert Carles; Lozano Bojados, Antoni (2010-01)
      Article
      Open Access
      Many knowledge representation mechanisms are based on tree-like structures, thus symbolizing the fact that certain pieces of information are related in one sense or another. There exists a well-studied process of closure-based ...
    • On one query self-reducible sets 

      Lozano Bojados, Antoni; Ogiwara, Mitsunori (1991-01)
      Research report
      Open Access
      We study one word-decreasing self-reducible sets, which were introduced by Lozano and Torán. These are usual self-reducible sets with the peculiarity that the self-reducibility machine makes at most one query and this is ...
    • On the complexity of moving vertices in a graph 

      Lozano Bojados, Antoni; Raghavan, Vijay (1998-01)
      Research report
      Open Access
      We consider the problem of deciding whether a given graph G has an automorphism which moves at least k vertices (where k is a function of |V(G)|), a question originally posed by Lubiw (1981). Here we show that this ...
    • Relativized and positive separations of [delta sub 2 super p] and [fi sub 2 super p] 

      Lozano Bojados, Antoni; Torán Romero, Jacobo (1989)
      Research report
      Open Access
    • Self-reducible sets of small density 

      Lozano Bojados, Antoni; Torán Romero, Jacobo (1989-11)
      Research report
      Open Access
      We study the complexity of sets that are at the same time self-reducible and sparse or m-reducible to sparse sets. We show that sets of this kind are low for the complexity clases [delta sub 2 super p], [fi sub 2 super p], ...
    • Succinct circuit representations and leaf languages are basically the same concept 

      Borchert, Bernd; Lozano Bojados, Antoni (1996-01)
      Research report
      Open Access
      This paper connects two topics of Complexity Theory: The topic of succinct circuit representations initiated by Galperin and Wigderson, and the topic of leaf languages. A Boolean circuit c describes in a natural way the ...
    • Symmetry breaking in tournaments 

      Lozano Bojados, Antoni (2010)
      Research report
      Open Access
      We provide upper bounds for the determining number and the metric dimension of tournaments. A set of vertices S is a determining set for a tournament T if every nontrivial automorphism of T moves at least one vertex of S, ...
    • Symmetry breaking in tournaments 

      Lozano Bojados, Antoni (2013-03-24)
      Article
      Open Access
      We provide upper bounds for the determining number and the metric dimension of tournaments. A set of vertices S in V(T) is a determining set for a tournament T if every nontrivial automorphism of T moves at least one vertex ...
    • The Complexity of modular graph automorphism 

      Arvind, V.; Beigel, Richard; Lozano Bojados, Antoni (1998-12)
      Research report
      Open Access
      Motivated by the question of the relative complexities of the Graph Isomorphism and the Graph Automorphism problems, we define and study the modular graph automorphism problems. These are the decision problems mod_k-GA ...
    • Tile-packing tomography is NP-hard 

      Chrobak, Marek; Dürr, Christoph; Guíñez, Flavio; Lozano Bojados, Antoni; Kim Thang, Nguyen (2010)
      Conference report
      Restricted access - publisher's policy
      Discrete tomography deals with reconstructing finite spatial objects from their projections. The objects we study in this paper are called tilings or tile-packings, and they consist of a number of disjoint copies of a fixed ...
    • Trees whose even-degree vertices induce a path are antimagic 

      Lozano Bojados, Antoni; Mora Giné, Mercè; Seara Ojea, Carlos; Tey Carrera, Joaquín (2019-05-16)
      Research report
      Open Access
      An antimagic labeling of a connected graph G is a bijection from the set of edges E(G) to {1, 2, . . . , |E(G)|} such that all vertex sums are pairwise distinct, where the vertex sum at vertex v is the sum of the labels ...