LATQCD-CHIPT · Probing Chiral Perturbation Theory from realistic two-flavour Lattice QCD simulations
FP7 — People (Marie Curie Actions)
- Duration
- 2009-03-01 → 2010-08-31
- EU contribution
- €137,450
- Participants
- 1
- Scheme
- MC-IEF
Lines connect the coordinator with its partners.
Results in brief
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.
Data: CORDIS, © European Union
Project objective
Research objectives and content: we propose to apply recently developed non-perturbative techniques for the simulation of two-flavour QCD with sea quark masses at physical values in order to investigate the convergence properties of Chiral Perturbation Theory (ChiPT) in pi-pi scattering and other light-quark physics quantities. Our approach is based on the Wilson formulation of the fermionic QCD action and an original modification of the Domain Decomposition Hybrid Monte Carlo (DD-HMC) algorithm. Target observables are: pi-pi scattering lenghts, pion mass, pion decay constant, other channels of the light-hadron spectrum. As a result, we expect to find conclusive quantitative information concerning the convergence radius of the chiral expansion and to consequently improve the understanding of the sponaneous breaking of chiral symmetry. Methodology: the main obstacle to simulate light-quarks at physical masses is represented by instability and non-ergodicity phenomena in the HMC, related to the structure of the low-end of the Wilson-Dirac spectrum. We propose to adopt a modification of the algorithm where the low-modes are separated from the bulk of the modes and included in a reweighting factor. Training: the candidate would like to acquire and deepen technical skills and knowledge in the areas of : a) Chiral Perturbation Theory; b) phenomenology of the light hadron interactions; c) Monte Carlo simulations of lattice QCD; d) Parallel computing.
Original text from CORDIS.
Participants
- ORGANISATION EUROPEENNE POUR LA RECHERCHE NUCLEAIRE · GENEVE 23CoordinatorSwitzerland
Links
Data: CORDIS, © European Union