15,343 research outputs found

    Improvement of surface water quality variables modelling that incorporates a hydro-meteorological factor: a state-space approach

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    In this work it is constructed a hydro-meteorological factor to improve the adjustment of statistical time series models, such as state space models, of water quality variables by observing hydrological series (recorded in time and space) in a River basin. The hydro-meteorological factor is incorporated as a covariate in multivariate state space models fitted to homogeneous groups of monitoring sites. Additionally, in the modelling process it is considered a latent variable that allows incorporating a structural component, such as seasonality, in a dynamic way

    Application of Change-Point Detection to a Structural Component of Water Quality Variables

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    In this study, methodologies were developed in statistical time series models, such as multivariate state-space models, to be applied to water quality variables in a river basin. In the modelling process it is considered a latent variable that allows incorporating a structural component, such as seasonality, in a dynamic way and a change-point detection method is applied to the structural component in order to identify possible changes in the water quality variables in consideration

    Using udometric network data to estimate an environmental covariate

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    Manyhydrologicalandecologicalstudiesrecognizetheimportanceofcharacterizingthetemporalandspatialvari- ability of precipitation. In this study, geostatistical methodologies were developed in order to estimate a hydro-meteorological factor by (re)building the space-time distribution of the precipitation associated to monthly averages in a certain hydrological river basin that will be used in the modelling of surface water quality. A hydro-meteorological factor is constructed for each water quality monitoring site (WQMS), based on the analysis of the space-time behaviour of the precipitation observed in an udometric network located in a Portuguese river basin

    NLO electroweak corrections in general scalar singlet models

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    If no new physics signals are found, in the coming years, at the Large Hadron Collider Run-2, an increase in precision of the Higgs couplings measurements will shift the dicussion to the effects of higher order corrections. In Beyond the Standard Model (BSM) theories this may become the only tool to probe new physics. Extensions of the Standard Model (SM) with several scalar singlets may address several of its problems, namely to explain dark matter, the matter-antimatter asymmetry, or to improve the stability of the SM up to the Planck scale. In this work we propose a general framework to calculate one loop-corrections in BSM models with an arbitrary number of scalar singlets. We then apply our method to a real and to a complex scalar singlet models. We assess the importance of the one-loop radiative corrections first by computing them for a tree level mixing sum constraint, and then for the main Higgs production process gg→Hgg \to H. We conclude that, for the currently allowed parameter space of these models, the corrections can be at most a few percent. Notably, a non-zero correction can survive when dark matter is present, in the SM-like limit of the Higgs couplings to other SM particles.Comment: 35 pages, 3 figure

    Globally simple Heffter arrays and orthogonal cyclic cycle decompositions

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    In this paper we introduce a particular class of Heffter arrays, called globally simple Heffter arrays, whose existence gives at once orthogonal cyclic cycle decompositions of the complete graph and of the cocktail party graph. In particular we provide explicit constructions of such decompositions for cycles of length k≤10k\leq 10. Furthermore, starting from our Heffter arrays we also obtain biembeddings of two kk-cycle decompositions on orientable surfaces.Comment: The present version also considers the problem of biembedding

    A problem on partial sums in abelian groups

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    In this paper we propose a conjecture concerning partial sums of an arbitrary finite subset of an abelian group, that naturally arises investigating simple Heffter systems. Then, we show its connection with related open problems and we present some results about the validity of these conjectures

    Charting Dark Matter interactions

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    The nature of Dark Matter (DM) is one of the most compelling problems in Fundamental Physics.It is a well established fact that the Standard Model (SM) of particle physics and General Relativity (GR) by themselves cannot explain astrophysical and cosmological data such as galactic rotation curves, the Cosmic Microwave Background (CMB) and the distribution of structures at large scales.These data indicate the existence of a new fluid, the DM, that is: 1) collisionless 2) cold 3) dominated by GR at large distances.Very few properties are known about the particles making up the DM.The two main ones are: i) the DM must interact weakly with SM particles, and ii) the DM must be stable on cosmological time scales.These two properties by themselves are too general to draw a clear picture of the Dark Sector (DS). In this Thesis we will try to assess some of its properties in light of current and future experiments.The most natural possibility is for the DM to interact with the weakest of the SM forces, the electroweak (EW) force. We completely characterize this kind of DM particles, called WIMPs.After computing their masses, set by EW annihilations, we study their phenomenology at future lepton colliders and at Direct Detection (DD) experiments. The lightest WIMPs are a perfect target for realistic future lepton colliders, while to probe the heaviest ones future Xenon DD experiments are needed.The second scenario we analyze is the case in which DM does not interact with any of the SM force mediators. In this case, the Effective Field Theory (EFT) approach is needed. We introduce a set of portal operators that have received little attention in the past. After describing a model-independent approach, we discuss bounds on the portals coming from high intensity experiments, like neutrino experiments at Fermilab (e.g. DUNE). These are competitive with respect to current constraints.The last possibility is the case in which even portals are absent. In this scenario, the clustering of both species during the Universe evolution can provide a window on the DM nature. We focus on models in which the DM has a long range self-interaction mediated by a light scalar.We study the evolution of inhomogeneities, and compare the predicted CMB anisotropies and galaxy power spectra with current and future data (like Euclid), setting strong bounds on the strength of the self-interaction.Finally we comment on how theoretical insights on DM stability can constrain DM model building

    Asymptotics of ground states for fractional H\'enon systems

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    We investigate the asymptotic behavior of positive ground states for H\'enon type systems involving a fractional Laplacian on a bounded domain, when the powers of the nonlinearity approach the Sobolev critical exponent.Comment: 18 page
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