The Experts below are selected from a list of 633 Experts worldwide ranked by ideXlab platform
David Greynat - One of the best experts on this subject based on the ideXlab platform.
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From OPE to chiral perturbation theory in holographic QCD
'EDP Sciences', 2016Co-Authors: Luigi Cappiello, Giancarlo D’ambrosio, David GreynatAbstract:The soft wall model in holographic QCD has Regge trajectories but wrong operator product expansion (OPE) for the two-point vectorial QCD Green Function. We modify the dilaton potential to comply with the OPE. We study also the axial two-point Function using the same modified dilaton field and an additional scalar field to address chiral symmetry breaking. OPE is recovered adding a boundary term and low energy chiral parameters, Fπ and L10, are well described analytically by the model in terms of Regge spacing and QCD condensates. The model nicely supports and extends previous theoretical analyses advocating Digamma Function to study QCD two-point Functions in different momentum regions
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Assuming Regge trajectories in holographic QCD: from OPE to chiral perturbation theory
The European Physical Journal C, 2015Co-Authors: Luigi Cappiello, Giancarlo D’ambrosio, David GreynatAbstract:The soft wall model in holographic QCD has Regge trajectories but wrong operator product expansion (OPE) for the two-point vectorial QCD Green Function. We modify the dilaton potential to comply with the OPE. We study also the axial two-point Function using the same modified dilaton field and an additional scalar field to address chiral symmetry breaking. OPE is recovered adding a boundary term and low energy chiral parameters, $$F_\pi $$ F π and $$L_{10}$$ L 10 , are well described analytically by the model in terms of Regge spacing and QCD condensates. The model nicely supports and extends previous theoretical analyses advocating Digamma Function to study QCD two-point Functions in different momentum regions.
Luigi Cappiello - One of the best experts on this subject based on the ideXlab platform.
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From OPE to chiral perturbation theory in holographic QCD
'EDP Sciences', 2016Co-Authors: Luigi Cappiello, Giancarlo D’ambrosio, David GreynatAbstract:The soft wall model in holographic QCD has Regge trajectories but wrong operator product expansion (OPE) for the two-point vectorial QCD Green Function. We modify the dilaton potential to comply with the OPE. We study also the axial two-point Function using the same modified dilaton field and an additional scalar field to address chiral symmetry breaking. OPE is recovered adding a boundary term and low energy chiral parameters, Fπ and L10, are well described analytically by the model in terms of Regge spacing and QCD condensates. The model nicely supports and extends previous theoretical analyses advocating Digamma Function to study QCD two-point Functions in different momentum regions
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Assuming Regge trajectories in holographic QCD: from OPE to chiral perturbation theory
The European Physical Journal C, 2015Co-Authors: Luigi Cappiello, Giancarlo D’ambrosio, David GreynatAbstract:The soft wall model in holographic QCD has Regge trajectories but wrong operator product expansion (OPE) for the two-point vectorial QCD Green Function. We modify the dilaton potential to comply with the OPE. We study also the axial two-point Function using the same modified dilaton field and an additional scalar field to address chiral symmetry breaking. OPE is recovered adding a boundary term and low energy chiral parameters, $$F_\pi $$ F π and $$L_{10}$$ L 10 , are well described analytically by the model in terms of Regge spacing and QCD condensates. The model nicely supports and extends previous theoretical analyses advocating Digamma Function to study QCD two-point Functions in different momentum regions.
Schubert C - One of the best experts on this subject based on the ideXlab platform.
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Two-loop self-dual Euler-Heisenberg Lagrangians; 1, Real part and helicity amplitudes
2002Co-Authors: Dunne G, Schubert CAbstract:We show that, for both scalar and spinor QED, the two-loop Euler-Heisenberg effective Lagrangian for a constant Euclidean self-dual background has an extremely simple closed-form expression in terms of the Digamma Function. Moreover, the scalar and spinor QED effective Lagrangians are very similar to one another. These results are dramatic simplifications compared to the results for other backgrounds. We apply them to a calculation of the low energy limits of the two-loop massive N-photon `all +' helicity amplitudes. The simplicity of our results can be related to the connection between self-duality, helicity and supersymmetry
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Closed-form two-loop Euler-Heisenberg Lagrangian in a self-dual background
2001Co-Authors: Dunne G, Schubert CAbstract:We show that the two-loop Euler-Heisenberg effective Lagrangian for scalar QED in a constant Euclidean self-dual background has a simple explicit closed form expression in terms of the Digamma Function. This result leads to a simple analysis of the weak- and strong-field expansions, the two-loop scalar QED beta Function, and the analytic continuation properties of the effective Lagrangian and its imaginary part
Schubert Christian - One of the best experts on this subject based on the ideXlab platform.
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Two-loop self-dual Euler-Heisenberg Lagrangians (I): Real part and helicity amplitudes
'IOP Publishing', 2002Co-Authors: Dunne Gerald, Schubert ChristianAbstract:We show that, for both scalar and spinor QED, the two-loop Euler-Heisenberg effective Lagrangian for a constant Euclidean self-dual background has an extremely simple closed-form expression in terms of the Digamma Function. Moreover, the scalar and spinor QED effective Lagrangians are very similar to one another. These results are dramatic simplifications compared to the results for other backgrounds. We apply them to a calculation of the low energy limits of the two-loop massive N-photon `all +' helicity amplitudes. The simplicity of our results can be related to the connection between self-duality, helicity and supersymmetry.Comment: 24 pp, no figure
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Closed-form two-loop Euler-Heisenberg Lagrangian in a self-dual background
'Elsevier BV', 2001Co-Authors: Dunne Gerald, Schubert ChristianAbstract:We show that the two-loop Euler-Heisenberg effective Lagrangian for scalar QED in a constant Euclidean self-dual background has a simple explicit closed form expression in terms of the Digamma Function. This result leads to a simple analysis of the weak- and strong-field expansions, the two-loop scalar QED beta Function, and the analytic continuation properties of the effective Lagrangian and its imaginary part.Comment: 8 pages, late
Qi Feng - One of the best experts on this subject based on the ideXlab platform.
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Partial solutions to several conjectures on completely monotonic degrees for remainders in asymptotic expansions of the Digamma Function
2021Co-Authors: Qi Feng, Mahmoud MansourAbstract:Motivated by several conjectures posed in the paper "F. Qi and A.-Q. Liu, Completely monotonic degrees for a difference between the logarithmic and psi Functions, J. Comput. Appl. Math., vol. 361, pp. 366--371 (2019); available online at https://doi.org/10.1016/j.cam.2019.05.001", the authors compute several completely monotonic degrees of the remainders in the asymptotic expansions of the logarithm of the gamma Function and in the asymptotic expansions of the logarithm of the Digamma Function.Comment: 11 page
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Completely monotonic degrees of remainders of asymptotic expansions of the Digamma Function: Completely monotonic degrees of remainders
HAL CCSD, 2019Co-Authors: Qi Feng, Mahmoud MansourAbstract:Motivated by several conjectures posed in the paper [F. Qi and A.-Q. Liu, Completely monotonic degrees for a difference between the logarithmic and psi Functions, J. Comput. Appl. Math. 361 (2019), 366--371; available online at https://doi.org/10.1016/j.cam.2019.05.001], the authors calculate some completely monotonic degrees of remainders of the asymptotic expansion of the logarithm of the gamma Function, compute some completely monotonic degrees of remainders of asymptotic expansions of the Digamma Function, and confirm some conjectures on completely monotonic degrees of remainders of the asymptotic expansion of the logarithm of the gamma Function and on completely monotonic degrees of remainders of asymptotic expansions of polygamma Functions
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Some inequalities for the trigamma Function in terms of the Digamma Function
'Elsevier BV', 2015Co-Authors: Qi Feng, Mortici CristinelAbstract:In the paper, the authors establish three kinds of double inequalities for the trigamma Function in terms of the exponential Function to powers of the Digamma Function. These newly established inequalities extend some known results. The method in the paper utilizes some facts from the asymptotic theory and is a natural way to solve problems for approximating some quantities for large values of the variable.Comment: 13 page
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Limit formulas for ratios of derivatives of the gamma and Digamma Functions at their singularities
'National Library of Serbia', 2012Co-Authors: Qi FengAbstract:In the paper the author simply presents the limit formulas for ratios of derivatives of the gamma Function and the Digamma Function at their singularities.Comment: 3 page
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Sharp inequalities for the psi Function and harmonic numbers
'Walter de Gruyter GmbH', 2009Co-Authors: Qi Feng, Guo Bai-niAbstract:In this paper, two sharp inequalities for bounding the psi Function $\psi$ and the harmonic numbers $H_n$ are established respectively, some results in [I. Muqattash and M. Yahdi, \textit{Infinite family of approximations of the Digamma Function}, Math. Comput. Modelling \textbf{43} (2006), 1329\nobreakdash--1336.] are improved, and some remarks are given.Comment: 6 pages, 2 figure