44,633 research outputs found

    Fitting the Quark and Lepton Masses in String Theories

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    The capability of string theories to reproduce at low energy the observed pattern of quark and lepton masses and mixing angles is examined, focusing the attention on orbifold constructions, where the magnitude of Yukawa couplings depends on the values of the deformation parameters which describe the size and shape of the compactified space. A systematic exploration shows that for Z3Z_3, Z4Z_4, Z6Z_6--I and possibly Z7Z_7 orbifolds a correct fit of the physical fermion masses is feasible. In this way the experimental masses, which are low--energy quantities, select a particular size and shape of the compactified space, which turns out to be very reasonable (in particular the modulus TT defining the former is T=O(1)T=O(1)). The rest of the ZNZ_N orbifolds are rather hopeless and should be discarded on the assumption of a minimal SU(3)Ă—SU(2)Ă—U(1)YSU(3)\times SU(2)\times U(1)_Y scenario. On the other hand, due to stringy selection rules, there is no possibility of fitting the Kobayashi--Maskawa parameters at the renormalizable level, although it is remarked that this job might well be done by non--renormalizable couplings.Comment: 19 page

    The Standard Model instability and the scale of new physics

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    We apply a general formalism for the improved effective potential with several mass scales to compute the scale M of new physics which is needed to stabilize the Standard Model potential in the presence of a light Higgs. We find, by imposing perturbativity of the new physics, that M can be as large as one order of magnitude higher than the instability scale of the Standard Model. This implies that, with the present lower bounds on the Higgs mass, the new physics could easily (but not necessarily) escape detection in the present and future accelerators.Comment: latex2e, 12 pages, 3 figure

    F-term inflation in Superstring Theories

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    A supersymmetric inflationary stage dominated by an FF-term has the problem that the flatness of the potential is spoiled by supergravity corrections, that is the slow-roll parameter η\eta gets contributions of order unity. We show that in FF-term inflationary models based on strings there is natural way of obtaining small values of η\eta. This happens in models of hybrid inflation based on orbifold constructions, in which a modulus TT field is responsible for the large value of the potential during inflation, and a second field ϕ\phi with appropriate modular weight is responsible for the roll-over. We illustrate the mechanism with a model in which the inflaton potential is provided by gaugino condensation, leading to succesful inflation.Comment: 9 pages, LaTe

    Discovering unbounded episodes in sequential data

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    One basic goal in the analysis of time-series data is to find frequent interesting episodes, i.e, collections of events occurring frequently together in the input sequence. Most widely-known work decide the interestingness of an episode from a fixed user-specified window width or interval, that bounds the subsequent sequential association rules. We present in this paper, a more intuitive definition that allows, in turn, interesting episodes to grow during the mining without any user-specified help. A convenient algorithm to efficiently discover the proposed unbounded episodes is also implemented. Experimental results confirm that our approach results useful and advantageous.Postprint (published version

    Statistical strategies for pruning all the uninteresting association rules

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    We propose a general framework to describe formally the problem of capturing the intensity of implication for association rules through statistical metrics. In this framework we present properties that influence the interestingness of a rule, analyze the conditions that lead a measure to perform a perfect prune at a time, and define a final proper order to sort the surviving rules. We will discuss why none of the currently employed measures can capture objective interestingness, and just the combination of some of them, in a multi-step fashion, can be reliable. In contrast, we propose a new simple modification of the Pearson coefficient that will meet all the necessary requirements. We statistically infer the convenient cut-off threshold for this new metric by empirically describing its distribution function through simulation. Final experiments serve to show the ability of our proposal.Postprint (published version

    SUSY and BSM in the face of LHC-14

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    In this talk I review the motivations for physics beyond the Standard Model at the TeV scale and the prospects for their detection in the second Run of LHC. Then I focus in the supersymmetric case, paying special attention to the formulation and implications of the Natural SUSY scenario.Comment: Contribution to the proceedings of the X SILAFAE, Medellin, Colombia, November 24-28 201

    Study of Minimal String Unification in Z8Z_8 Orbifold Models

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    We study the construction of the minimal supersymmetric standard model from the Z8Z_8 orbifold models. We use a target-space duality anomaly cancellation and a unification of gauge couplings as constraints. It is shown that some models obtained through a systematical search realize the unification of SU(3) and SU(2) coupling constants.Comment: 11 pages, KANAZAWA-93-08, LaTeX fil
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