Sep 9 – 13, 2019
Europe/Zurich timezone

Quark condensate and spectral density from renormalization group optimized perturbation

Sep 12, 2019, 5:30 PM
Chambre du Trésorier

Chambre du Trésorier


Jean-Loic Kneur (Univ. Montpellier)


Our renormalization group consistent version of optimized perturbation, RGOPT, had been 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 gave stable parameter-free determinations
$\langle\bar q q\rangle^{1/3}_{n_f=2}(2\, {\rm GeV}) = -(0.833-0.845) \bar\Lambda_2 $, and $ \langle\bar q q\rangle^{1/3}_{n_f=3}(2\, {\rm GeV}) = -(0.814-0.838) \bar\Lambda_3 $, where the range is our estimated theoretical error and $\bar\Lambda_{n_f}$ the basic QCD scale in the $\overline{MS}$-scheme.
We update our previous analysis up to 5-loop order of (RG optimized) perturbation, thanks to the recently available five-loop order QCD renormalization group functions, and compare our results with other recent determinations from lattice simulations or other approaches.

Primary authors

Jean-Loic Kneur (Univ. Montpellier) André Neveu (Lab. Charles Coulomb)

Presentation materials