Year: 2021
Type: article
Abstract: Nonzero topological charge is prohibited in the chiral limit of continuum gauge-fermion systems because any unpaired instanton would create a zero mode of the Dirac operator. On the lattice, however, the geometric ${Q}_{\mathrm{geom}}=⟨F\stackrel{\texttildelow{}}{F}⟩/32{\ensuremath{\pi}}^{2}$ definition of the topological charge does not necessarily vanish in the chiral limit even when the gauge fields are smoothed for example with gradient flow. Small vacuum fluctuations (dislocations) not seen by the fermions may be promoted to instantonlike objects by the gradient flow. We demonstrate that these artifacts of the flow cause the gradient flow renormalized gauge coupling to increase and appear to run faster. In step-scaling studies such strong coupling artifacts contribute a term that might not follow perturbative scaling. The usual $a/L\ensuremath{\rightarrow}0$ continuum limit extrapolations can hence lead to incorrect results. In this paper we investigate these topological lattice artifacts in the massless SU(3) 10-flavor system with domain wall fermions and the massless 8-flavor system with staggered fermions. For both systems we observe that in the range of strong coupling Symanzik gradient flow exhibits more lattice artifacts compared to Wilson gradient flow. We demonstrate how this artifact impacts the determination of the renormalized gauge coupling and the step-scaling $\ensuremath{\beta}$ function.
Authors: Anna Hasenfratz, Oliver Witzel
Institution: University of Colorado Boulder
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Funders: National Science Foundation, U.S. Department of Energy, Colorado State University, National Energy Research Scientific Computing Center, Deutsche Forschungsgemeinschaft, Munich Institute for Astro- and Particle Physics, Office of Science, University of Colorado Boulder, Mainz Institute for Theoretical Physics, Johannes Gutenberg University Mainz, Fermilab, Thomas Jefferson National Accelerator Facility
Awards: G122673668, G1286236842, G1394709509, G1414775356, G1677143136, G1816284028, G1863003419, G1897041155, ELEMENTARY PARTICLE PHYSICS AND HIGH ENERGY PHENOMENA, G2451073032, G2586609609, G2796167598, G3083819904, G3226045097, G332579857, G365575497, G3685081974, XSEDE 2.0: Integrating, Enabling and Enhancing National Cyberinfrastructure with Expanding Community Involvement, G4066435496, G419881185, MRI Collaborative Consortium: Acquisition of a Shared Supercomputer by the Rocky Mountain Advanced Computing Consortium, G42916606, G4382344593, EXC 2094: ORIGINS: Vom Ursprung des Universums bis zu den ersten Bausteinen des Lebens, G4501827968, G4958434179, G498139845, G5076365615, MRI Collaborative Consortium: Acquisition of a Shared Supercomputer by the Rocky Mountain Advanced Computing Consortium, G5296923526, G5590740066, G5607711389, G5608225264, G6806689448, ELEMENTARY PARTICLE PHYSICS AND HIGH ENERGY PHENOMENA, G805243471, G8929392486, G950203606, G969889393
OpenAlex ID: W3014230042