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In this work we show how by using a Padé type analytical continuation scheme, based on the Schlessinger point method, it is possible to find higher production thresholds in hadron physical problems. Recently, an extension of this numerical approach to the complex energy plane enabled the calculations of auto-ionization decay resonance poles in atomic and molecular systems. Here we use this so-called Resonances via Padé (RVP) method, to show its convergence beyond the singular point in hadron physical problems. In order to demonstrate the capabilities of the RVP method, two illustrations for the ability to identify singularities and branch points are given. In addition, two applications for hadron physical problems are given. In the first one, we identify the decay thresholds from a numerically calculated spectral function. In the second one, we use experimental data. First, we calculate the resonance pole of the f 0 ( 500 ) or σ meson using the S 0 partial wave amplitude for ππ scattering in very good agreement with the literature. Second, we use data on the cross section ratio R ( s ) for e + e − collisions and discuss the prediction of decay thresholds which proves to be difficult if the data is noisy. [ABSTRACT FROM AUTHOR]

We prove the conjecture of Sfetsos, Siampos and Thompson that suitable analytic continuations of the Poisson–Lie T-duals of the bi-Yang–Baxter sigma models coincide with the recently introduced generalized λ -models. We then generalize this result by showing that the analytic continuation of a generic σ -model of “universal WZW-type” introduced by Tseytlin in 1993 is nothing but the Poisson–Lie T-dual of a generic Poisson–Lie symmetric σ -model introduced by Klimčík and Ševera in 1995. [ABSTRACT FROM AUTHOR]

We present the crossover line between the quark gluon plasma and the hadron gas phases for small real chemical potentials. First we determine the effect of imaginary values of the chemical potential on the transition temperature using lattice QCD simulations. Then we use various formulas to perform an analytic continuation to real values of the baryo-chemical potential. Our data set maintains strangeness neutrality to match the conditions of heavy ion physics. The systematic errors are under control up to μ B ≈ 300 MeV . For the curvature of the transition line we find that there is an approximate agreement between values from three different observables: the chiral susceptibility, chiral condensate and strange quark susceptibility. The continuum extrapolation is based on N t = 10 , 12 and 16 lattices. By combining the analysis for these three observables we find, for the curvature, the value κ = 0.0149 ± 0.0021 . [ABSTRACT FROM AUTHOR]

Abstract: We study the light-front zero-mode contribution to the tensor form factors () for the exclusive rare decays using a covariant fermion field theory model in dimensions. While the zero-mode contribution in principle depends on the form of the vector meson vertex , the three tensor form factors are found to be free from the zero mode if the denominator D contains the term proportional to the light-front energy or the longitudinal momentum fraction factor of the struck quark with the power . Since the denominator D used in the light-front quark model (LFQM) has the power , the three tensor form factors () can be computed in LFQM safely without involving any complicate zero-mode contribution. The lack of zero-mode contribution benefits the phenomenology with LFQM. [Copyright &y& Elsevier]

Abstract: We present a method for calculating any (nested) harmonic sum to arbitrary accuracy for all complex values of the argument. The method utilizes the relation between harmonic sums and (derivatives of) Hurwitz zeta functions, which allows a harmonic sum to be calculated as an expansion valid for large values of its argument. A program for implementing this method is also provided. [Copyright &y& Elsevier]