Chiral physics in lattice QCD

Full text: Numerical simulations in lattice gauge theory have proven to be an efficient tool to study non-perturbative features of quantum chromodynamics (QCD), the underlying theory of the strong nuclear force. These simulations are restricted to using quark masses that are much heavier than those in nature. Commonly implemented is the quenched approximation, whereby dynamical sea quarks are excluded from the simulation The use of heavy quarks simulated on the lattice necessitates a method for the extrapolation of results to compare with the real world. By incorporating features of chiral symmetry one can reliably extract physical quantities from current lattice simulations. In the case of the quenched approximation, the properties of chiral symmetry are altered and correspondingly one requires a modified extrapolation for such simulations. Through the study of the chiral loops which play an important role at light quark mass, and therefore the extrapolation, one can identify the primary differences of baryon spectroscopy in quenched and physical simulations. The source of the pion cloud behaves very similar in both simulations, enabling one to compare physical properties from unphysical simulations