26,486 research outputs found

    Coupling of ttˉt\bar t and γγ\gamma\gamma with a strongly interacting Electroweak Symmetry Breaking Sector

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    We report the coupling of an external γγ\gamma\gamma or ttˉt\bar t state to a strongly interacting EWSBS satisfying unitarity. We exploit perturbation theory for those coupling of the external state, whereas the EWSBS is taken as strongly interacting. We use a modified version of the IAM unitarization procedure to model such a strongly interacting regime. The matrix elements VLVL→VLVLV_LV_L\to V_LV_L, VLVL↔hhV_LV_L\leftrightarrow hh, hh→hhhh\to hh, VLVL↔{γγ,ttˉ}V_LV_L\leftrightarrow\{\gamma\gamma,t\bar t\}, and hh↔{γγ,ttˉ}hh\leftrightarrow\{\gamma\gamma,t\bar t\} are all computed to NLO in perturbation theory with the Nonlinear Effective Field Theory of the EWSBS, within the Equivalence Theorem. This allows us to describe resonances of the electroweak sector that may be found at the LHC and their effect on other channels such as γγ\gamma\gamma or ttˉt\bar t where they may be discovered.Comment: 9 pages, 3 figures. Contributions to the Procs. of the XIIth Quark Confinement and the Hadron Spectrum, Thessaloniki, Greece, August 201

    Africa's changing agricultural development strategies: past and present paradigms as a guide to the future

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    In this paper, Christopher L. Delgado, of IFPRI's senior research staff, takes a critical look at the changing paradigms of agricultural development that have influenced agricultural policy in Africa since the colonial era. The review shows how current approaches to meeting Africa's agricultural challenges to the year 2020 developed. It concludes that Africans have had relatively little input into the intellectual bases of strategies affecting their rural areas, a situation that must be changed if future strategies are to be effective in dealing with Africa's problems of development.Agricultural policy Africa., Agricultural economics and policies, agricultural development,

    Network-wide assessment of 4D trajectory adjustments using an agent-based model

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    This paper presents results from the SESAR ER3 Domino project. It focuses on an ECAC-wide assessment of two 4D-adjustment mechanisms, implemented separately and conjointly. These reflect flight behaviour en-route and at-gate, optimising given (cost) objective functions. New metrics designed to capture network effects are used to analyse the results of a microscopic, agent based model. The results show that some implementations of the mechanisms allow the protection of the network from ‘domino’ effects. Airlines focusing on costs may trigger additional side-effects on passengers, displaying, in some instances, clear trade-offs between passenger- and flight-centric metrics

    A bilayer Double Semion Model with Symmetry-Enriched Topological Order

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    We construct a new model of two-dimensional quantum spin systems that combines intrinsic topo- logical orders and a global symmetry called flavour symmetry. It is referred as the bilayer Doubled Semion model (bDS) and is an instance of symmetry-enriched topological order. A honeycomb bi- layer lattice is introduced to combine a Double Semion Topolgical Order with a global spin-flavour symmetry to get the fractionalization of its quasiparticles. The bDS model exhibits non-trival braid- ing self-statistics of excitations and its dual model constitutes a Symmetry-Protected Topological Order with novel edge states. This dual model gives rise to a bilayer Non-Trivial Paramagnet that is invariant under the flavour symmetry and the well-known spin flip symmetry.Comment: revtex4 file, color figure

    European route choice determinants: Examining fuel and route charge trade-offs

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    Different charging zones are found within European airspace. This allows airlines to select different routes between origin and destination that have different lengths and en-route charges. There is a trade- off between the shortest available route and other routes that might have different charges. This paper analyses the routes submitted by airlines to be operated on a given day and compares the associated costs of operating those routes with the shortest available at the time, in terms of en-route charges and fuel consumption. The flights are characterised by different variables with the idea of identifying a behaviour or pattern based on the airline or flight characteristics. Results show that in some areas of the European airspace there might be an incentive to select a longer route, leading to both a lower charge and a lower total cost. However, more variables need to be considered and other techniques used, such as factor analysis, to be able to identify the behaviour within an airline category

    En-route speed reduction for the mangement of ATFM delays

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    In this paper a new concept aimed at better dealing with delays caused by regulations is presented. Inspired in future 4D trajectories, where a time constraint can be applied at each way-point, it is proposed to spread the total delay imposed by a regulation over the trajectory that goes from the departing airport to the regulated airspace. Given a nominal cruise speed, there exist a set of possible lower speeds that allow a longer flight (and then, a cumulative flight delay) with the same or less fuel consumption if compared with the nominal situation. In this way, the aircraft that has been delayed can consider to take-off on time and loose this time by flying slower and requiring the same or less fuel than initially planed. Besides the positive environmental impact, the airliner can bet that finally the regulation at the congested airspace may be not applied and being the departure on time, the delay can be absorbed more easily in flight with a minimal or null fuel consumption increase. Finally, this concept is applied to some example flights

    Machine learning to improve tactical flight decision making - The case of Pilot3

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    Review of approach and challenges of using machine learning techniques for air transport systems with focus on the usage of these techniques in Pilot3 project

    Low-coverage heteroepitaxial growth with interfacial mixing

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    We investigate the influence of intermixing on heteroepitaxial growth dynamics, using a two-dimensional point island model, expected to be a good approximation in the early stages of epitaxy. In this model, which we explore both analytically and numerically, every deposited B atom diffuses on the surface with diffusion constant DBD_{\rm B}, and can exchange with any A atom of the substrate at constant rate. There is no exchange back, and emerging atoms diffuse on the surface with diffusion constant DAD_{\rm A}. When any two diffusing atoms meet, they nucleate a point island. The islands neither diffuse nor break, and grow by capturing other diffusing atoms. The model leads to an island density governed by the diffusion of one of the species at low temperature, and by the diffusion of the other at high temperature. We show that these limit behaviors, as well as intermediate ones, all belong to the same universality class, described by a scaling law. We also show that the island-size distribution is self-similarly described by a dynamic scaling law in the limits where only one diffusion constant is relevant to the dynamics, and that this law is affected when both DAD_{\rm A} and DBD_{\rm B} play a role.Comment: 16 pages, 6 figure

    An empirical investigation of short and long-run agricultural wage formation in Ghana

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    This paper investigates empirically the factors that influence real agricultural wage rates in Ghana, based on 1957 to 1991 data. The Johansen cointegration framework is used to examine long-run relationships among agricultural and urban wage rates, the domestic terms of trade between agriculture and non-agriculture, urban unemployment, capital stock in agriculture and the size of the rural population. An error correction model is then used to investigate short-run dynamic relationships among the variables. The results show that: (1) there is only one stable equilibrium relationship among agricultural wage rates and their determinants in the long-run; (2) a 1 percent change in the domestic terms of trade between agriculture and non-agriculture leads to a 0.48 percent change in the real agricultural wage rate in the short-run and a 0.83 percent change in the long run; (3) the analysis suggests a one-time and one way upwards structural shift of 3.6 percent in real agricultural wages during the 1980s.Income Ghana. ,Agriculture Economic aspects Ghana. ,
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