Towards pp -> VVjj at NLO QCD: Bosonic contributions to triple vector boson production plus jet

In this work, some of the NLO QCD corrections for pp -> VVjj + X are presented. A program in Mathematica based on the structure of FeynCalc which automatically simplifies a set of amplitudes up to the hexagon level of rank 5 has been created for this purpose. We focus on two different topologies. The first involves all the virtual contributions needed for quadruple electroweak vector boson production, i.e. pp -> VVVV + X. In the second, the remaining "bosonic" corrections to electroweak triple vector boson production with an additional jet (pp -> VVV j + X) are computed. We show the factorization formula of the infrared divergences of the bosonic contributions for VVVV and VVVj production with V=(W,Z,gamma). Stability issues associated with the evaluation of the hexagons up to rank 5 are studied. The CPU time of the FORTRAN subroutines rounds the 2 milliseconds and seems to be competitive with other more sophisticated methods. Additionally, in Appendix A the master equations to obtain the tensor coefficients up to the hexagon level in the external momenta convention are presented including the ones needed for small Gram determinants.Comment: 48 pages,16 figure

Constituent quark model for baryons with strong quark-pair correlations and non-leptonic weak transitions of hyperon

We study the roles of quark-pair correlations for baryon properties, in particular on non-leptonic weak decay of hyperons. We construct the quark wave function of baryons by solving the three body problem explicitly with confinement force and the short range attraction for a pair of quarks with their total spin being 0. We show that the existence of the strong quark-quark correlations enhances the non-leptonic transition amplitudes which is consistent with the data, while the baryon masses and radii are kept to the experiment.Comment: 4 pages, 2 figures, talk presented at KEK-Tanashi International Symposium on Physics of Hadrons and Nuclei, Tokyo, Japan, 14-17 Dec. 199

Dominantnost jezika dvojezicnih govornika talijanskog I hrvatskog jezika

Because of the high variability in any bilingual population, it is of a great importance to control for language dominance in both research and language assessment. This control is crucial in research in order to form unified groups of participants according to language dominance. In the language assessment of bilingual children, determining language dominance should be a priority. Children exposed to two languages from an early age may acquire them at a slower rate when compared to their monolingual piers. While this lag is hardly noticeable in some children, for others it is significant. Without knowledge about the child\u2019s language skills in the other, non-assessed language, it is impossible to determine if the results of language assessment point to the dominance of one language over another or general language difficulties. In bilingual areas of Croatia, such as Rijeka and Istria, this can be quite a challenge. While language dominance has generally been measured using a large number of different methods, there is no universally accepted procedure. This research uses the results of the Italian and Croatian versions of the TROG test to determine language dominance. Participants were 56 preschool-aged children attending kindergartens with an Italian language programme in Rijeka and Istria. Participants were preselected by their kindergarten teachers as children that might be balanced bilinguals. Using the differences in results between both TROG tests, approximately 70% of children were placed in a balanced bilinguals group. No differences were shown between groups of participants from Rijeka and Istria

Dominantnost jezika dvojezicnih govornika talijanskog I hrvatskog jezika [Language dominance in bilingual speakers of Italian and Croatian language]

Because of the high variability in any bilingual population, it is of a great importance to control for language dominance in both research and language assessment. This control is crucial in research in order to form unified groups of participants according to language dominance. In the language assessment of bilingual children, determining language dominance should be a priority. Children exposed to two languages from an early age may acquire them at a slower rate when compared to their monolingual piers. While this lag is hardly noticeable in some children, for others it is significant. Without knowledge about the child\u2019s language skills in the other, non-assessed language, it is impossible to determine if the results of language assessment point to the dominance of one language over another or general language difficulties. In bilingual areas of Croatia, such as Rijeka and Istria, this can be quite a challenge. While language dominance has generally been measured using a large number of different methods, there is no universally accepted procedure. This research uses the results of the Italian and Croatian versions of the TROG test to determine language dominance. Participants were 56 preschool-aged children attending kindergartens with an Italian language programme in Rijeka and Istria. Participants were preselected by their kindergarten teachers as children that might be balanced bilinguals. Using the differences in results between both TROG tests, approximately 70% of children were placed in a balanced bilinguals group. No differences were shown between groups of participants from Rijeka and Istria

Hyperon Nonleptonic Weak Decays Revisited

We first review the current algebra - PCAC approach to nonleptonic octet baryon 14 weak decay B (\to) (B^{\prime})(\pi) amplitudes. The needed four parameters are independently determined by (\Omega \to \Xi \pi),(\Lambda K) and (\Xi ^{-}\to \Sigma ^{-}\gamma) weak decays in dispersion theory tree order. We also summarize the recent chiral perturbation theory (ChPT) version of the eight independent B (\to) (B^{\prime}\pi) weak (\Delta I) = 1/2 amplitudes containing considerably more than eight low-energy weak constants in one-loop order.Comment: 10 pages, RevTe

Learning about knowledge: A complex network approach

This article describes an approach to modeling knowledge acquisition in terms of walks along complex networks. Each subset of knowledge is represented as a node, and relations between such knowledge are expressed as edges. Two types of edges are considered, corresponding to free and conditional transitions. The latter case implies that a node can only be reached after visiting previously a set of nodes (the required conditions). The process of knowledge acquisition can then be simulated by considering the number of nodes visited as a single agent moves along the network, starting from its lowest layer. It is shown that hierarchical networks, i.e. networks composed of successive interconnected layers, arise naturally as a consequence of compositions of the prerequisite relationships between the nodes. In order to avoid deadlocks, i.e. unreachable nodes, the subnetwork in each layer is assumed to be a connected component. Several configurations of such hierarchical knowledge networks are simulated and the performance of the moving agent quantified in terms of the percentage of visited nodes after each movement. The Barab\'asi-Albert and random models are considered for the layer and interconnecting subnetworks. Although all subnetworks in each realization have the same number of nodes, several interconnectivities, defined by the average node degree of the interconnection networks, have been considered. Two visiting strategies are investigated: random choice among the existing edges and preferential choice to so far untracked edges. A series of interesting results are obtained, including the identification of a series of plateaux of knowledge stagnation in the case of the preferential movements strategy in presence of conditional edges.Comment: 18 pages, 19 figure

Message Transfer in a Communication Network

We study message transfer in a $2-d$ communication network of regular nodes and randomly distributed hubs. We study both single message transfer and multiple message transfer on the lattice. The average travel time for single messages travelling between source and target pairs of fixed separations shows $q-$exponential behaviour as a function of hub density with a characteristic power-law tail, indicating a rapid drop in the average travel time as a function of hub density. This power-law tail arises as a consequence of the log-normal distribution of travel times seen at high hub densities. When many messages travel on the lattice, a congestion-decongestion transition can be seen. The waiting times of messages in the congested phase show a Gaussian distribution, whereas the decongested phase shows a log-normal distribution. Thus, the congested or decongested behaviour is encrypted in the behaviour of the waiting time distributions.Comment: 7 Pages, 6 figure, to appear in the Proceeding of the conference Perspectives in Nonlinear Dynamics 2007, a special issue of the Journal Praman

Mirror matter admixtures and isospin breaking in the \Delta I=1/2 rule in \Omega^- two body non-leptonic decays

We discuss a description of \Omega^- two body non-leptonic decays based on possible, albeit tiny, admixtures of mirror matter in ordinary hadrons. The \Delta I=1/2 rule enhancement is obtained as a result of isospin symmetry and, more importantly, the rather large observed deviations from this rule result from small isospin breaking. This analysis lends support to the possibility that the enhancement phenomenon observed in low energy weak interactions may be systematically described by mirror matter admixtures in ordinary hadrons.Comment: Changed conten

Transport of multiple users in complex networks

We study the transport properties of model networks such as scale-free and Erd\H{o}s-R\'{e}nyi networks as well as a real network. We consider the conductance $G$ between two arbitrarily chosen nodes where each link has the same unit resistance. Our theoretical analysis for scale-free networks predicts a broad range of values of $G$, with a power-law tail distribution $\Phi_{\rm SF}(G)\sim G^{-g_G}$, where $g_G=2\lambda -1$, and $\lambda$ is the decay exponent for the scale-free network degree distribution. We confirm our predictions by large scale simulations. The power-law tail in $\Phi_{\rm SF}(G)$ leads to large values of $G$, thereby significantly improving the transport in scale-free networks, compared to Erd\H{o}s-R\'{e}nyi networks where the tail of the conductivity distribution decays exponentially. We develop a simple physical picture of the transport to account for the results. We study another model for transport, the \emph{max-flow} model, where conductance is defined as the number of link-independent paths between the two nodes, and find that a similar picture holds. The effects of distance on the value of conductance are considered for both models, and some differences emerge. We then extend our study to the case of multiple sources, where the transport is define between two \emph{groups} of nodes. We find a fundamental difference between the two forms of flow when considering the quality of the transport with respect to the number of sources, and find an optimal number of sources, or users, for the max-flow case. A qualitative (and partially quantitative) explanation is also given

Simple models of small world networks with directed links

We investigate the effect of directed short and long range connections in a simple model of small world network. Our model is such that we can determine many quantities of interest by an exact analytical method. We calculate the function $V(T)$, defined as the number of sites affected up to time $T$ when a naive spreading process starts in the network. As opposed to shortcuts, the presence of un-favorable bonds has a negative effect on this quantity. Hence the spreading process may not be able to affect all the network. We define and calculate a quantity named the average size of accessible world in our model. The interplay of shortcuts, and un-favorable bonds on the small world properties is studied.Comment: 15 pages, 9 figures, published versio