Reports de recerca
http://hdl.handle.net/2117/3919
Wed, 22 Nov 2017 16:58:23 GMT2017-11-22T16:58:23ZLocating domination in bipartite graphs and their complements
http://hdl.handle.net/2117/111067
Locating domination in bipartite graphs and their complements
Hernando Martín, María del Carmen; Mora Giné, Mercè; Pelayo Melero, Ignacio Manuel
A set S of vertices of a graph G is distinguishing if the sets of neighbors in S for every pair of vertices not in S are distinct. A locating-dominating set of G is a dominating distinguishing set. The location-domination number of G , ¿ ( G ), is the minimum cardinality of a locating-dominating set. In this work we study relationships between ¿ ( G ) and ¿ ( G ) for bipartite graphs. The main result is the characterization of all connected bipartite graphs G satisfying ¿ ( G ) = ¿ ( G ) + 1. To this aim, we define an edge-labeled graph G S associated with a distinguishing set S that turns out to be very helpful
Wed, 22 Nov 2017 12:08:39 GMThttp://hdl.handle.net/2117/1110672017-11-22T12:08:39ZHernando Martín, María del CarmenMora Giné, MercèPelayo Melero, Ignacio ManuelA set S of vertices of a graph G is distinguishing if the sets of neighbors in S for every pair of vertices not in S are distinct. A locating-dominating set of G is a dominating distinguishing set. The location-domination number of G , ¿ ( G ), is the minimum cardinality of a locating-dominating set. In this work we study relationships between ¿ ( G ) and ¿ ( G ) for bipartite graphs. The main result is the characterization of all connected bipartite graphs G satisfying ¿ ( G ) = ¿ ( G ) + 1. To this aim, we define an edge-labeled graph G S associated with a distinguishing set S that turns out to be very helpfulMetric-locating-dominating partitions in graphs
http://hdl.handle.net/2117/111061
Metric-locating-dominating partitions in graphs
Hernando Martín, María del Carmen; Mora Giné, Mercè; Pelayo Melero, Ignacio Manuel
A partition ¿ = { S 1 ,...,S k } of the vertex set of a connected graph G is a metric-locating partition of G if for every pair of vertices u,v belonging to the same part S i , d ( u,S j ) 6 = d ( v,S j ), for some other part S j . The partition dimension ß p ( G ) is the minimum cardinality of a metric- locating partition of G . A metric-locating partition ¿ is called metric-locating-dominanting if for every vertex v of G , d ( v,S j ) = 1, for some part S j of ¿. The partition metric-location-domination number ¿ p ( G ) is the minimum cardinality of a metric-locating-dominating partition of G . In this paper we show, among other results, that ß p ( G ) = ¿ p ( G ) = ß p ( G ) + 1. We also charac- terize all connected graphs of order n = 7 satisfying any of the following conditions: ¿ p ( G ) = n - 1, ¿ p ( G ) = n - 2 and ß p ( G ) = n - 2. Finally, we present some tight Nordhaus-Gaddum bounds for both the partition dimension ß ( G ) and the partition metric-location-domination number ¿ ( G ). Keywords: dominating partition, locating partition, location, domination, metric location
Wed, 22 Nov 2017 11:22:19 GMThttp://hdl.handle.net/2117/1110612017-11-22T11:22:19ZHernando Martín, María del CarmenMora Giné, MercèPelayo Melero, Ignacio ManuelA partition ¿ = { S 1 ,...,S k } of the vertex set of a connected graph G is a metric-locating partition of G if for every pair of vertices u,v belonging to the same part S i , d ( u,S j ) 6 = d ( v,S j ), for some other part S j . The partition dimension ß p ( G ) is the minimum cardinality of a metric- locating partition of G . A metric-locating partition ¿ is called metric-locating-dominanting if for every vertex v of G , d ( v,S j ) = 1, for some part S j of ¿. The partition metric-location-domination number ¿ p ( G ) is the minimum cardinality of a metric-locating-dominating partition of G . In this paper we show, among other results, that ß p ( G ) = ¿ p ( G ) = ß p ( G ) + 1. We also charac- terize all connected graphs of order n = 7 satisfying any of the following conditions: ¿ p ( G ) = n - 1, ¿ p ( G ) = n - 2 and ß p ( G ) = n - 2. Finally, we present some tight Nordhaus-Gaddum bounds for both the partition dimension ß ( G ) and the partition metric-location-domination number ¿ ( G ). Keywords: dominating partition, locating partition, location, domination, metric locationDominating 2- broadcast in graphs: complexity, bounds and extremal graphs
http://hdl.handle.net/2117/109101
Dominating 2- broadcast in graphs: complexity, bounds and extremal graphs
Hernando Martín, María del Carmen; Mora Giné, Mercè; Pelayo Melero, Ignacio Manuel; Cáceres, José; Puertas, M. Luz
Limited dominating broadcasts were proposed as a variant of dominating broadcasts, where the broadcast function is upper bounded. As a natural extension of domination, we consider dominating 2-broadcasts along with the associated parameter, the dominating 2-broadcast number. We prove that computing the dominating 2-broadcast number is a NP-complete problem, but can be achieved in linear time for trees. We also give an upper bound for this parameter, that is tight for graphs as large as desired
Wed, 25 Oct 2017 05:28:42 GMThttp://hdl.handle.net/2117/1091012017-10-25T05:28:42ZHernando Martín, María del CarmenMora Giné, MercèPelayo Melero, Ignacio ManuelCáceres, JoséPuertas, M. LuzLimited dominating broadcasts were proposed as a variant of dominating broadcasts, where the broadcast function is upper bounded. As a natural extension of domination, we consider dominating 2-broadcasts along with the associated parameter, the dominating 2-broadcast number. We prove that computing the dominating 2-broadcast number is a NP-complete problem, but can be achieved in linear time for trees. We also give an upper bound for this parameter, that is tight for graphs as large as desiredBifurcation of 2-periodic orbits from non-hyperbolic fixed points
http://hdl.handle.net/2117/106815
Bifurcation of 2-periodic orbits from non-hyperbolic fixed points
Cima Mollet, Anna; Gasull Embid, Armengol; Mañosa Fernández, Víctor
We introduce the concept of 2-cyclicity for families of one-dimensional maps with a non-hyperbolic fixed point by analogy to the cyclicity for families of planar vector fields with a weak focus. This new concept is useful in order to study the number of 2-periodic orbits that can bifurcate from the fixed point. As an application we study the 2-cyclicity of some natural families of polynomial maps.
Prepublicació
Tue, 25 Jul 2017 11:28:59 GMThttp://hdl.handle.net/2117/1068152017-07-25T11:28:59ZCima Mollet, AnnaGasull Embid, ArmengolMañosa Fernández, VíctorWe introduce the concept of 2-cyclicity for families of one-dimensional maps with a non-hyperbolic fixed point by analogy to the cyclicity for families of planar vector fields with a weak focus. This new concept is useful in order to study the number of 2-periodic orbits that can bifurcate from the fixed point. As an application we study the 2-cyclicity of some natural families of polynomial maps.Geometric quantization of semitoric systems and almost toric manifolds
http://hdl.handle.net/2117/106532
Geometric quantization of semitoric systems and almost toric manifolds
Miranda Galcerán, Eva; Presas, Francisco; Solha, Romero
Kostant gave a model for the real geometric quantization
associated to polarizations via the cohomology associated to the sheaf of
flat sections of a pre-quantum line bundle. This model is well-adapted
for real polarizations given by integrable systems and toric manifolds.
In the latter case, the cohomology can be computed counting integral
points inside the associated Delzant polytope. In this article we extend
Kostant’s geometric quantization to semitoric integrable systems and
almost toric manifolds. In these cases the dimension of the acting torus
is smaller than half of the dimension of the manifold. In particular, we
compute the cohomology groups associated to the geometric quantization
if the real polarization is the one associated to an integrable system
with focus-focus type singularities in dimension four. As application
we determine models for the geometric quantization of K3 surfaces, a
spin-spin system, the spherical pendulum, and a spin-oscillator system
under this scheme.
Mon, 17 Jul 2017 10:56:24 GMThttp://hdl.handle.net/2117/1065322017-07-17T10:56:24ZMiranda Galcerán, EvaPresas, FranciscoSolha, RomeroKostant gave a model for the real geometric quantization
associated to polarizations via the cohomology associated to the sheaf of
flat sections of a pre-quantum line bundle. This model is well-adapted
for real polarizations given by integrable systems and toric manifolds.
In the latter case, the cohomology can be computed counting integral
points inside the associated Delzant polytope. In this article we extend
Kostant’s geometric quantization to semitoric integrable systems and
almost toric manifolds. In these cases the dimension of the acting torus
is smaller than half of the dimension of the manifold. In particular, we
compute the cohomology groups associated to the geometric quantization
if the real polarization is the one associated to an integrable system
with focus-focus type singularities in dimension four. As application
we determine models for the geometric quantization of K3 surfaces, a
spin-spin system, the spherical pendulum, and a spin-oscillator system
under this scheme.An invitation to singular symplectic geometry
http://hdl.handle.net/2117/106301
An invitation to singular symplectic geometry
Miranda Galcerán, Eva; Delshams Valdés, Amadeu; Planas Bahí, Arnau; Oms, Cedric; Dempsey Bradell, Roisin Mary
In this paper we analyze in detail a collection of motivating examples to consider bm-
symplectic forms and folded-type symplectic structures. In particular, we provide models in
Celestial Mechanics for every bm-symplectic structure. At the end of the paper, we introduce
the odd-dimensional analogue to b-symplectic manifolds: b-contact manifolds.
Mon, 10 Jul 2017 09:18:33 GMThttp://hdl.handle.net/2117/1063012017-07-10T09:18:33ZMiranda Galcerán, EvaDelshams Valdés, AmadeuPlanas Bahí, ArnauOms, CedricDempsey Bradell, Roisin MaryIn this paper we analyze in detail a collection of motivating examples to consider bm-
symplectic forms and folded-type symplectic structures. In particular, we provide models in
Celestial Mechanics for every bm-symplectic structure. At the end of the paper, we introduce
the odd-dimensional analogue to b-symplectic manifolds: b-contact manifolds.From subKautz digraphs to cyclic Kautz digraphs
http://hdl.handle.net/2117/105173
From subKautz digraphs to cyclic Kautz digraphs
Dalfó Simó, Cristina
Kautz digraphs K(d,l) are a well-known family of dense digraphs, widely studied as a good model for interconnection networks. Closely related with these, the cyclic Kautz digraphs CK(d,l) were recently introduced by Böhmová, Huemer and the author, and some of its distance-related parameters were fixed. In this paper we propose a new approach to cyclic Kautz digraphs by introducing the family of subKautz digraphs sK(d,l), from where the cyclic Kautz digraphs can be obtained as line digraphs. This allows us to give exact formulas for the distance between any two vertices of both sK(d,l) and CK(d,l). Moreover, we compute the diameter and the semigirth of both families, also providing efficient routing algorithms to find the shortest path between any pair of vertices. Using these parameters, we also prove that sK(d,l) and CK(d,l) are maximally vertex-connected and super-edge-connected. Whereas K(d,l) are optimal with respect to the diameter, we show that sK(d,l) and CK(d,l) are optimal with respect to the mean distance, whose exact values are given for both families when l = 3. Finally, we provide a lower bound on the girth of CK(d,l) and sK(d,l)
Tue, 06 Jun 2017 12:12:17 GMThttp://hdl.handle.net/2117/1051732017-06-06T12:12:17ZDalfó Simó, CristinaKautz digraphs K(d,l) are a well-known family of dense digraphs, widely studied as a good model for interconnection networks. Closely related with these, the cyclic Kautz digraphs CK(d,l) were recently introduced by Böhmová, Huemer and the author, and some of its distance-related parameters were fixed. In this paper we propose a new approach to cyclic Kautz digraphs by introducing the family of subKautz digraphs sK(d,l), from where the cyclic Kautz digraphs can be obtained as line digraphs. This allows us to give exact formulas for the distance between any two vertices of both sK(d,l) and CK(d,l). Moreover, we compute the diameter and the semigirth of both families, also providing efficient routing algorithms to find the shortest path between any pair of vertices. Using these parameters, we also prove that sK(d,l) and CK(d,l) are maximally vertex-connected and super-edge-connected. Whereas K(d,l) are optimal with respect to the diameter, we show that sK(d,l) and CK(d,l) are optimal with respect to the mean distance, whose exact values are given for both families when l = 3. Finally, we provide a lower bound on the girth of CK(d,l) and sK(d,l)On quotient digraphs and voltage digraphs
http://hdl.handle.net/2117/105171
On quotient digraphs and voltage digraphs
Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Miller, Mirka; Ryan, Joe
In this note we present a general approach to construct large digraphs from small ones. These are called expanded digraphs, and, as particular cases, we show their close relationship between voltage digraphs and line digraphs, which are two known approaches to obtain dense digraphs. In the same context, we show the equivalence
between the vertex-splitting and partial line digraph techniques. Then, we give a sufficient condition for a lifted digraph of a base line digraph to be again a line digraph. Some of the results are illustrated with two well-known families of digraphs. Namely, De Bruijn and Kautz digraphs.
Tue, 06 Jun 2017 12:00:49 GMThttp://hdl.handle.net/2117/1051712017-06-06T12:00:49ZDalfó Simó, CristinaFiol Mora, Miquel ÀngelMiller, MirkaRyan, JoeIn this note we present a general approach to construct large digraphs from small ones. These are called expanded digraphs, and, as particular cases, we show their close relationship between voltage digraphs and line digraphs, which are two known approaches to obtain dense digraphs. In the same context, we show the equivalence
between the vertex-splitting and partial line digraph techniques. Then, we give a sufficient condition for a lifted digraph of a base line digraph to be again a line digraph. Some of the results are illustrated with two well-known families of digraphs. Namely, De Bruijn and Kautz digraphs.On alpha-roughly weighted games
http://hdl.handle.net/2117/103235
On alpha-roughly weighted games
Freixas Bosch, Josep; Kurz, Sascha
Very recently Gvozdeva, Hemaspaandra, and Slinko (2011) h
ave introduced three hierarchies for simple games in order to measure the distance of a given simple game to the class of weighted voting games or roughly weighted voting games. Their third class C aconsists of all simple games
permitting a weighted representation such that each winnin
g coalition has a weight of at least 1 and each losing coalition a weight of at most a. We continue their work and contribute some new results on the possible values of a for a given number of voters.
Mon, 03 Apr 2017 15:53:36 GMThttp://hdl.handle.net/2117/1032352017-04-03T15:53:36ZFreixas Bosch, JosepKurz, SaschaVery recently Gvozdeva, Hemaspaandra, and Slinko (2011) h
ave introduced three hierarchies for simple games in order to measure the distance of a given simple game to the class of weighted voting games or roughly weighted voting games. Their third class C aconsists of all simple games
permitting a weighted representation such that each winnin
g coalition has a weight of at least 1 and each losing coalition a weight of at most a. We continue their work and contribute some new results on the possible values of a for a given number of voters.The complexity of testing properties of simple games
http://hdl.handle.net/2117/103171
The complexity of testing properties of simple games
Freixas Bosch, Josep; Molinero Albareda, Xavier; Olsen, Martin; Serna Iglesias, María José
Simple games cover voting systems in which a single alternative, such as a bill or an amendment, is pitted against the status quo. A simple game or a yes-no voting system is a set of rules that specifies exactly which collections of ``yea'' votes yield passage of the issue at hand. A collection of ``yea'' voters forms a winning coalition.
We are interested on performing a complexity analysis of problems on such games depending on the game representation. We consider four natural explicit representations, winning, loosing, minimal winning, and maximal loosing. We first analyze the computational complexity of obtaining a particular representation of a simple game from a different one. We show that some cases this transformation can be done in polynomial time while the others require exponential time. The second question is classifying the complexity for testing whether a game is simple or weighted. We show that for the four types of representation both problem can be solved in polynomial time. Finally, we provide results on the complexity of testing whether a simple game or a weighted game is of a special type. In this way, we analyze strongness, properness, decisiveness and homogeneity, which are desirable properties to be fulfilled for a simple game.
Fri, 31 Mar 2017 15:48:07 GMThttp://hdl.handle.net/2117/1031712017-03-31T15:48:07ZFreixas Bosch, JosepMolinero Albareda, XavierOlsen, MartinSerna Iglesias, María JoséSimple games cover voting systems in which a single alternative, such as a bill or an amendment, is pitted against the status quo. A simple game or a yes-no voting system is a set of rules that specifies exactly which collections of ``yea'' votes yield passage of the issue at hand. A collection of ``yea'' voters forms a winning coalition.
We are interested on performing a complexity analysis of problems on such games depending on the game representation. We consider four natural explicit representations, winning, loosing, minimal winning, and maximal loosing. We first analyze the computational complexity of obtaining a particular representation of a simple game from a different one. We show that some cases this transformation can be done in polynomial time while the others require exponential time. The second question is classifying the complexity for testing whether a game is simple or weighted. We show that for the four types of representation both problem can be solved in polynomial time. Finally, we provide results on the complexity of testing whether a simple game or a weighted game is of a special type. In this way, we analyze strongness, properness, decisiveness and homogeneity, which are desirable properties to be fulfilled for a simple game.