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arXiv · 1512.03406

Quark Condensate from Renormalization Group Optimized Spectral Density

J. -L. Kneur·A. Neveu
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Abstract

Our renormalization group consistent variant of optimized perturbation, RGOPT, is used to calculate the nonperturbative QCD spectral density of the Dirac operator and the related chiral quark condensate $\langle \bar q q \rangle$, for $n_f=2$ and $n_f=3$ massless quarks. Sequences of approximations at two-, three-, and four-loop orders are very stable and give $\langle \bar q q \rangle^{1/3}_{n_f=2}(2\, {\rm GeV}) = -(0.833-0.845) \barΛ_2 $, and $ \langle \bar q q \rangle^{1/3}_{n_f=3}(2\, {\rm GeV}) = -(0.814-0.838) \barΛ_3 $ where the range is our estimated theoretical error and $\barΛ_{n_f}$ the basic QCD scale in the $\rm \bar{MS}$-scheme. We compare those results with other recent determinations (from lattice calculations and spectral sum rules).

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J. -L. Kneur, A. Neveu. 2015-12-10. Quark Condensate from Renormalization Group Optimized Spectral Density. https://arxiv.org/abs/1512.03406

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