Browsing by Author "Torán Romero, Jacobo"
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A combinatorial technique for separating counting complexity classes
Torán Romero, Jacobo (1988)
External research report
Open AccessWe introduce a new combinatorial technique to obtain relativized separations of certain complexity classes related to the idea of counting, like PP, G (exact counting), and ¿P (parity). To demonstrate its usefulness we ... 
Classes of bounded nondeterminism
Díaz Cort, Josep; Torán Romero, Jacobo (1988)
External research report
Open AccessWe study certain language classes located between P and N P that are defined by polynomial time machines with a bounded amount of nondeterminism. We observe that these classes have complete problems and find a characterization ... 
Computing functions with parallel queries to NP
Jenner Núñez, Birgit; Torán Romero, Jacobo (199303)
External research report
Open AccessThe class "Theta_2^p" of languages polynomial time truthtable reducible to sets in NP has a wide range of different characterizations. We survey some of them studying the classes obtained when the characterizations are ... 
Kolmogorov complexity of #P functions
Green, Frederic; Torán Romero, Jacobo (199101)
External research report
Open AccessAre the outputs of #P functions "random"? We way phrase this question more precisely: are there #P functions whose outputs cannot in general be compressed into a string of small length, and recovered quickly from that ... 
On the expected depth of boolean circuits
Díaz Cort, Josep; Serna Iglesias, María José; Spirakis, Paul George; Torán Romero, Jacobo (199402)
External research report
Open AccessIn this paper we analyze the expected depth of a circuit randomly generated from a uniform model. We show that the expected depth of such circuits is polylogarithmic in the number of gates. This result allows us to place ... 
Parallel approximation schemes for problems on planar graphs
Díaz Cort, Josep; Serna Iglesias, María José; Torán Romero, Jacobo (199303)
External research report
Open AccessThis paper describes a technique to obtain NC approximation schemes for the Maximum Independent Set in planar graphs and related optimization problems. 
Relativized and positive separations of [delta sub 2 super p] and [fi sub 2 super p]
Lozano Bojados, Antoni; Torán Romero, Jacobo (1989)
External research report
Open Access 
Selfreducible sets of small density
Lozano Bojados, Antoni; Torán Romero, Jacobo (198911)
External research report
Open AccessWe study the complexity of sets that are at the same time selfreducible and sparse or mreducible 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], ... 
Structural properties of the counting hierarchies
Torán Romero, Jacobo (1988)
External research report
Open AccessWe study three different hierarchies related to the notion of counting: the polynomial time counting hierarchy, the hierarchy of counting functions, and the logarithmic time counting hierarchy. We investigate the connections ... 
The MINSUMCUT problem
Díaz Cort, Josep; Gibbons, Alan M.; Paterson, Michael Stewart; Torán Romero, Jacobo (199101)
External research report
Open AccessIn this paper we first present a sequential linear algorithm for an linear arrangement problem on trees, the MINSUMCUT, and then a 0(log n) time parallel algorithm for the MINSUMCUT on trees, which uses n [super 2]/(log ... 
Turing machines with few accepting computations
Torán Romero, Jacobo; Köbler, Johannes (1988)
External research report
Open AccessIn this paper we study complexity classes defined by pathrestricted nondeterministic machines. We prove that for every language L in the class Few a polynomial time nondeterministic machine can be constructed which has ...