Λ MS ¯ n f = 2 $$ {\varLambda}_{\overline{\mathrm{MS}}}^{\left({n}_f=2\right)} $$ from a momentum space analysis of the quark-antiquark static potential

Karbstein, Felix; Peters, Antje; Wagner, Marc

doi:10.1007/jhep09(2014)114

Cited by 22 publications

(11 citation statements)

References 69 publications

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“…Other analyses aiming at extracting Λ MS from the static energy with less than three flavors include Refs. [25,32,33,[37][38][39][40]. In particular, let us mention that the n f = 2 analysis of Ref.…”

Section: Discussion and Comparison With Other Workmentioning

confidence: 99%

Determination ofαsfrom the QCD static energy: An update

et al. 2014

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We present an update of our determination of the strong coupling αs from the quantum chromodynamics static energy. This updated analysis includes new lattice data, at smaller lattice spacings and reaching shorter distances, the use of better suited perturbative expressions to compare with data in a wider distance range, and a comprehensive and detailed estimate of the error sources that contribute to the uncertainty of the final result. Our updated value for αs at the Z-mass scale, MZ , is αs(MZ ) = 0.1166 +0.0012 −0.0008 , which supersedes our previous result.

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Section: Discussion and Comparison With Other Workmentioning

confidence: 99%

Determination ofαsfrom the QCD static energy: An update

et al. 2014

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“…In principle it is beyond purely perturbative reach, as it cannot be 'perturbatively connected' to the more precisely knownΛ 3 value [44]. Our own estimate [22] ofΛ 2 from the pion decay constant gaveΛ 2 ≃ 360 +42 −30 MeV, while some recent lattice determinations areΛ 2 ≃ 330 ± 45 (staggered Wilson fermions [46]) andΛ 2 ≃ 331 ± 21 (quark static potential method [47]). (Incidentally the latter most precise present lattice determination tended to increase the central value ofΛ 2 by ∼ 15 GeV with respect to former similar determinations [48]).…”

Section: Evolution To Higher Energy and Phenomenological Comparisonmentioning

confidence: 98%

Chiral condensate from renormalization group optimized perturbation

Kneur

Neveu

2015

Phys. Rev. D

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Our recently developed variant of variationnally optimized perturbation (OPT), in particular consistently incorporating renormalization group properties (RGOPT), is adapted to the calculation of the QCD spectral density of the Dirac operator and the related chiral quark condensate qq in the chiral limit, for n f = 2 and n f = 3 massless quarks. The results of successive sequences of approximations at two-, three-, and four-loop orders of this modified perturbation, exhibit a remarkable stability. We obtain qq 1/3 n f =2 (2 GeV) = −(0.833 − 0.845)Λ2, and qq 1/3 n f =3 (2 GeV) = −(0.814 − 0.838)Λ3 where the range spanned by the first and second numbers (respectively fourand three-loop order results) defines our theoretical error, andΛn f is the basic QCD scale in the M S-scheme. We obtain a moderate suppression of the chiral condensate when going from n f = 2 to n f = 3. We compare these results with some other recent determinations from other nonperturbative methods (mainly lattice and spectral sum rules).

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“…This raises the question of a suitable running coupling as there is no unique definition of α s beyond two-loop. A quasi-particle picture suggests that an appropriate choice of α s can be deduced from a heavy quark potential [28,29]. An analytic expression for a coupling that generates a linearly rising static quark potential at large distances is given by [30] α s,HQ (z) = 1 β 0…”

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Transport Coefficients in Yang-Mills Theory and QCD

et al. 2015

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We calculate the shear viscosity over entropy density ratio η/s in Yang-Mills theory from the Kubo formula using an exact diagrammatic representation in terms of full propagators and vertices using gluon spectral functions as external input. We provide an analytic fit formula for the temperature dependence of η/s over the whole temperature range from a glueball resonance gas at low temperatures, to a high-temperature regime consistent with perturbative results. Subsequently we provide a first estimate for η/s in QCD.PACS numbers: 12.38. Aw, 11.10.Wx , 11.15.Tk Introduction -The experimental heavy-ion programs at RHIC [1,2] and at the LHC [3] explore the physics of the quark-gluon plasma (QGP). It turns out that the dynamics of the hot plasma created in heavy-ion collisions is well-described by hydrodynamics. Therefore, the determination of transport coefficients in the QGP is of great interest. One aspect is that the inference of the initial state physics requires a precise description of the hydrodynamical evolution, which in turn depends on transport coefficients as microscopic input, [4]. In particular, the viscosity over entropy ratio η/s governs the efficiency of the conversion of the initial spatial anisotropy into a momentum anisotropy of the final state.For the determination of η/s and its temperature dependence in the quark-gluon plasma, theoretical approaches face several challenges.The temperature regimes below and above the critical temperature T c are characterised by different degrees of freedom, and for temperatures T 2T c non-perturbative effects become important. Of particular interest is the vicinity of T c , where the minimum for η/s is expected [5,6]. A universal lower bound for η/s of 1/4π was conjectured in [7] using the AdS/CFT correspondence. Indeed, measurements of the elliptic flow v 2 indicate a value for η/s which is of the order of this lower bound [8]. The bound has been tested theoretically with several methods for the QGP [9-15], but also for other potentially perfect liquids, such as ultracold atoms [16][17][18].The Kubo formulae relate η to the energy-momentum tensor (EMT) [19]. Spectral functions are real-time quantities and cannot be obtained directly from Euclidean correlation functions. However, the direct calculation of real-time correlation functions represents a notoriously difficult problem in non-perturbative approaches to quantum field theory. Even though first computations in this direction have been performed e.g. in [20,21], we shall utilise Euclidean correlation functions within a numerical analytic continuation.In this work we study the shear viscosity over entropy ratio η/s in pure SU (3) Landau gauge Yang-Mills (YM) theory within the approach set-up in [9]. In the present

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Λ MS ¯ n f = 2 $$ {\varLambda}_{\overline{\mathrm{MS}}}^{\left({n}_f=2\right)} $$ from a momentum space analysis of the quark-antiquark static potential

Cited by 22 publications

References 69 publications

Determination ofαsfrom the QCD static energy: An update

Determination ofαsfrom the QCD static energy: An update

Chiral condensate from renormalization group optimized perturbation

Transport Coefficients in Yang-Mills Theory and QCD

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