9,757 research outputs found

    Geometrical and spectral study of beta-skeleton graphs

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    We perform an extensive numerical analysis of beta-skeleton graphs, a particular type of proximity graphs. In beta-skeleton graph (BSG) two vertices are connected if a proximity rule, that depends of the parameter beta is an element of (0, infinity), is satisfied. Moreover, for beta > 1 there exist two different proximity rules, leading to lune-based and circle-based BSGs. First, by computing the average degree of large ensembles of BSGs we detect differences, which increase with the increase of beta, between lune-based and circle-based BSGs. Then, within a random matrix theory (RMT) approach, we explore spectral and eigenvector properties of random BSGs by the use of the nearest-neighbor energy-level spacing distribution and the entropic eigenvector localization length, respectively. The RMT analysis allows us to conclude that a localization transition occurs at beta = 1

    Possible new resonance from WLWLW_L W_L-hhhh interchannel coupling

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    We propose and theoretically study a possible new resonance caused by strong coupling between the Higgs-Higgs and the W_L W_L (Z_L Z_L) scattering channels, without regard to the intensity of the elastic interaction in either channel at low energy (that could be weak as in the Standard Model). We expose this channel-coupling resonance from unitarity and dispersion relations encoded in the Inverse Amplitude Method, applied to the Electroweak Chiral Lagrangian with a scalar Higgs.Comment: 4 pages, 7 figure

    Unitarity, analyticity, dispersion relations and resonances in strongly interacting WLWLW_L W_L, ZLZLZ_L Z_L and hhhh scattering

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    If the Electroweak Symmetry Breaking Sector turns out to be strongly interacting, the actively investigated effective theory for longitudinal gauge bosons plus Higgs can be efficiently extended to cover the regime of saturation of unitarity (where the perturbative expansion breaks down). This is achieved by dispersion relations, whose subtraction constants and left cut contribution can be approximately obtained in different ways giving rise to different unitarization procedures. We illustrate the ideas with the Inverse Amplitude Method, one version of the N/D method and another improved version of the K-matrix. In the three cases we get partial waves which are unitary, analytical with the proper left and right cuts and in some cases poles in the second Riemann sheet that can be understood as dynamically generated resonances. In addition they reproduce at Next to Leading Order (NLO) the perturbative expansion for the five partial waves not vanishing (up to J=2) and they are renormalization scale (μ\mu) independent. Also the unitarization formalisms are extended to the coupled channel case. Then we apply the results to the elastic scattering amplitude for the longitudinal components of the gauge bosons V=W,ZV=W, Z at high energy. We also compute hh→hhh h \rightarrow h h and the inelastic process VV→hhVV\rightarrow h h which are coupled to the elastic VVVV channel for custodial isospin I=0I=0. We numerically compare the three methods for various values of the low-energy couplings and explain the reasons for the differences found in the I=J=1I=J=1 partial wave. Then we study the resonances appearing in the different elastic and coupled channels in terms of the effective Lagrangian parameters.Comment: 45 pages, 28 figure

    One-loop WLWLW_L W_L and ZLZLZ_L Z_L scattering from the Electroweak Chiral Lagrangian with a light Higgs-like scalar

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    By including the recently discovered Higgs-like scalar φ\varphi in the Electroweak Chiral Lagrangian, and using the Equivalence Theorem, we carry out the complete one-loop computation of the elastic scattering amplitude for the longitudinal components of the gauge bosons V=W,ZV=W, Z at high energy. We also compute φφ→φφ\varphi\varphi \rightarrow \varphi\varphi and the inelastic process VV→φφVV\rightarrow \varphi\varphi, and identify the counterterms needed to cancel the divergences, namely the well known a4a_4 and a5a_5 chiral parameters plus three additional ones only superficially treated in the literature because of their dimension 8. Finally we compute all the partial waves and discuss the limitations of the one-loop computation due to only approximate unitarity.Comment: 28 pages, 19 plots, 9 Feynman-diagram sets This version revised and accepted in JHE

    Distributional versions of Littlewood's Tauberian theorem

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    We provide several general versions of Littlewood's Tauberian theorem. These versions are applicable to Laplace transforms of Schwartz distributions. We apply these Tauberian results to deduce a number of Tauberian theorems for power series where Ces\`{a}ro summability follows from Abel summability. We also use our general results to give a new simple proof of the classical Littlewood one-sided Tauberian theorem for power series.Comment: 15 page
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