1,726 research outputs found

    Integrated planning of water and land-use

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    The role of water in spatial planning has received increasing attention in recent years. It was, for example, one of the leading motives in the preparation of the latest National Spatial Planning Note for The Netherlands. For the preparation of such spatial plans, and to support the associated policy analysis, there is a need to fully identify and characterize the interactions between the water sector and spatial planning and establish the process for making consistent joint projections for the water sector and land-use. This should account for spatial claims from the water sector, balance those claims with claims from other sectors, and feed back spatial constraints and opportunities. Land-use markets and government policies (translated e.g. in spatial reservations) form an important input in this balance. Modeling is indispensable to keep track of spatial characteristics and trace changes. Most of the available modeling considers a layered structure with a layer for national/regional projections and a GIS based layer to keep track of land use changes. Basically such model makes a distribution (rule based) of the national projections into the GIS based spatial raster, followed by an impact assessment based on the changes in the raster. Those models are generally weak in representing the processes driving land use changes such as the housing and labor market and – the water sector. The challenge remains to set up a suitable module covering these spatial - and water sector development processes. Based on the experience of the authors with many water studies and the recent development of a space-transport modeling tool (integration of transport and land-use), a sketch will be made of the requirements for such module. The scope for such planning tool will be illustrated (with data for The Netherlands), addressing key aspects such as competition for space, costs, risk, and environmental impact.

    New Factorization Relations for Yang Mills Amplitudes

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    A double-cover extension of the scattering equation formalism of Cachazo, He and Yuan (CHY) leads us to conjecture covariant factorization formulas of n-particle scattering amplitudes in Yang-Mills theories. Evidence is given that these factorization relations are related to Berends-Giele recursions through repeated use of partial fraction identities involving linearized propagators.Comment: 7 pages, 3 figures, version to appear in PR

    Unusual identities for QCD at tree-level

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    We discuss a set of recently discovered quadratic relations between gauge theory amplitudes. Such relations give additional structural simplifications for amplitudes in QCD. Remarkably, their origin lie in an analogous set of relations that involve also gravitons. When certain gluon helicities are flipped we obtain relations that do not involve gravitons, but which refer only to QCD.Comment: Talk given at XIV Mexican School on Particles and Fields, Morelia, Nov. 201

    Manifesting Color-Kinematics Duality in the Scattering Equation Formalism

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    We prove that the scattering equation formalism for Yang-Mills amplitudes can be used to make manifest the theory's color-kinematics duality. This is achieved through a concrete reduction algorithm which renders this duality manifest term-by-term. The reduction follows from the recently derived set of identities for amplitudes expressed in the scattering equation formalism that are analogous to monodromy relations in string theory. A byproduct of our algorithm is a generalization of the identities among gravity and Yang-Mills amplitudes.Comment: 20 pages, 20 figure

    Impact of SDN Controllers Deployment on Network Availability

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    Software-defined networking (SDN) promises to improve the programmability and flexibility of networks, but it may bring also new challenges that need to be explored. The purpose of this technical report is to assess how the deployment of the SDN controllers affects the overall availability of SDN. For this, we have varied the number, homing and location of SDN controllers. A two-level modelling approach that is used to evaluate the availability of the studied scenarios. Our results show how network operators can use the approach to find the optimal cost implied by the connectivity of the SDN control platform by keeping high levels of availability.Comment: Department of Telematics, NTNU, Tech. Rep., March 201

    Scattering Equations and Feynman Diagrams

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    We show a direct matching between individual Feynman diagrams and integration measures in the scattering equation formalism of Cachazo, He and Yuan. The connection is most easily explained in terms of triangular graphs associated with planar Feynman diagrams in ϕ3\phi^3-theory. We also discuss the generalization to general scalar field theories with ϕp\phi^p interactions, corresponding to polygonal graphs involving vertices of order pp. Finally, we describe how the same graph-theoretic language can be used to provide the precise link between individual Feynman diagrams and string theory integrands.Comment: 18 pages, 57 figure

    Analytic Representations of Yang-Mills Amplitudes

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    Scattering amplitudes in Yang-Mills theory can be represented in the formalism of Cachazo, He and Yuan (CHY) as integrals over an auxiliary projective space---fully localized on the support of the scattering equations. Because solving the scattering equations is difficult and summing over the solutions algebraically complex, a method of directly integrating the terms that appear in this representation has long been sought. We solve this important open problem by first rewriting the terms in a manifestly Mobius-invariant form and then using monodromy relations (inspired by analogy to string theory) to decompose terms into those for which combinatorial rules of integration are known. The result is a systematic procedure to obtain analytic, covariant forms of Yang-Mills tree-amplitudes for any number of external legs and in any number of dimensions. As examples, we provide compact analytic expressions for amplitudes involving up to six gluons of arbitrary helicities.Comment: 29 pages, 43 figures; also included is a Mathematica notebook with explicit formulae. v2: citations added, and several (important) typos fixe
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