Topological susceptibility with the asqtad action

Understand

Chiral perturbation theory predicts that in quantum chromodynamics (QCD), light dynamical quarks suppress the gauge-field topological susceptibility of the vacuum.

• The degree of suppression depends on quark multiplicity and masses.
• It provides a strong consistency test for fermion formulations in lattice QCD.
• Such tests are especially important for staggered fermion formulations that lack a full chiral symmetry and use the "fourth-root" procedure to achieve the desired number of sea quarks.