Final Report Summary - LATQCD-CHIPT (Probing Chiral Perturbation Theory from realistic two-flavour Lattice QCD simulations)
Numerical simulations of QCD (the quantum field theory of the strong interactions) provide a unique tool to compute the properties of the light hadrons from first principles. Such simulations are in principle exact but may, in practice, be compromised by systematic effects such as the lack of ergodicity of the underlying Markov process.
Ergodicity problems are in fact caused by the emergence of disconnected sectors in field space, labelled by an integer-valued 'topological charge'. In this project an attempt was made to understand the nature of the transition region between the sectors. Furthermore, a new simulation algorithm was studied, which was expected to overcome the lack of ergodicity of the established algorithms.
As a by-product, the so-called topologicial susceptibility (a measure of the width of the distribution of the topological charge) was accurately computed and its universality in the continuum limit was confirmed. Moreover, the value of the susceptibility in the limit is found to be about of the right size to explain the large difference of the masses of the charged pion and the eta' meson.
Ergodicity problems are in fact caused by the emergence of disconnected sectors in field space, labelled by an integer-valued 'topological charge'. In this project an attempt was made to understand the nature of the transition region between the sectors. Furthermore, a new simulation algorithm was studied, which was expected to overcome the lack of ergodicity of the established algorithms.
As a by-product, the so-called topologicial susceptibility (a measure of the width of the distribution of the topological charge) was accurately computed and its universality in the continuum limit was confirmed. Moreover, the value of the susceptibility in the limit is found to be about of the right size to explain the large difference of the masses of the charged pion and the eta' meson.