18-24 June 2017
Palacio de Congresos
Europe/Madrid timezone
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Seminarios 1+2
Vacuum Structure and Confinement

Instanton dominance over $\alpha_s$ at low momenta from lattice QCD simulations at $N_f=0$, $N_f=2+1$ and $N_f=2+1+1$.


  • Dr. Feliciano DE SOTO

Primary authors



We report on an instanton-based analysis of gluon Green functions in the Landau gauge for low momenta; in particular we used lattice results for $\alpha_s$ in the symmetric momentum subtraction scheme (${\rm MOM}$) for large-volume lattice simulations. We have exploited quenched gauge field configurations, $N_f=0$, with both Wilson and tree-level Symanzik improved actions, and unquenched ones with $N_f=2+1$ and $N_f=2+1+1$ dynamical flavors (domain wall and twisted-mass fermions respectively). We show that the dominance of instanton correlations on the low-momenta gluon Green functions can be applied to the determination of phenomenological parameters of the instanton liquid and, eventually, to a determination of the lattice spacing for the purely gauge sector of the theory.

We furthermore apply Wilson Flow technique to remove short-distance fluctuations. Wilson Flow gets rid of the QCD scale, $\Lambda_{\rm QCD}$, and reveals that the instanton prediction extents to large momenta. For those gauge field configurations free of quantum fluctuations, the direct study of topological charge density shows the appearance of large-scale lumps that can be identified as instantons, giving access to a direct study of instanton density and size distribution that is compatible with the ones extracted from the analysis of the Green functions.

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Vacuum Structure and Confinement