Portuguese Lattice QCD Collaboration - Confinement Scenarios, Exotic Potentials, Algorithms for Dynamical Fermions, Effective Theories


This project gathers the portuguese community working with strong interactions and whose work relies on lattice QCD either as the basic numeric simulation tool or as using the results from the lattice QCD simulations to model the non-perturbative regime of the strong interaction. The team has already expertise on the research topics included in the project, namely confinement scenarios related with pure glue correlation functions and large N-limit of SU(N) gauge theories, exotic static potentials, algorithms for dynamical fermions and the use and build of effective models to describe the low energy QCD regime. Indeed, the various sub-projects are a natural continuation of the team work. We aim to address the problem of gluon confinement in the Landau gauge using the lattice formulation of QCD. We will focus on confinement criteria, related with the infrared behaviour of the gluon and ghost propagators and, in particular, with its zero momentum values. Our main goal is to be able to provide a reliable extrapolation of the gluon and ghost propagators to the infinite volume and, hopefully, check the validity of the gluon confinement criteria. In a different perspective, we also aim to study the confining properties of pure SU(N) gauge theories in the large-N limit. It is widely believed that the large-N limit of SU(N) gauge theories can be understood as a zeroth-order approximation, around which the finite-N theories can be systematically approached by a perturbative expansion in powers of 1/N. We plan to continue exploring the phase structure of Eguchi-Kawai-type models. Our aim is to give a closest to complete characterisation of possible phases. The interest in hybrid three-body gluon-quark-antiquark and exotic three gluon systems is increasing in anticipation to the future experiments BESIII, GLUEX and PANDA dedicated to study the mass range of the charmonium, with a focus in its plausible hybrid excitations. The knownledge of the static potential would at least provide one of the components of the dynamical potential and can help understanding the QCD confinement mechanics. In this project we aim to take a step further in the computation of both the static hybrid and exotic systems. Lattice simulations including dynamical fermions allow precise measurements of many relevant quantities for the particle experimental community. Currently almost all large-scale computations use some variant of the Hybrid Monte Carlo (HMC) algorithm. Any improvement to HMC is welcome, as we could decrease the computational effort. In this project we intend to improve the molecular dynamics (MD) part of the HMC method, by studying the integrators used in HMC in terms of Shadow Hamiltonians and Poisson brackets. We also intend to study force gradient integrators, and implement these techniques in the principal computer codes used for lattice QCD computations (Chroma and CPS). Another goal is to use lattice calculations and effective field theory techniques to investigate the behavior of strongly interacting matter. We intend to investigate signatures of the phase transition associated to restoration of symmetries, through the study of several thermodynamic quantities and meson properties, namely, their masses and decays, in the SU(3) Polyakov-loop extended Nambu-Jona-Lasinio model. These properties are a very interesting tool to investigate the restoration of chiral and axial symmetries at finite temperature and density. We aim as well at combining the lattice methods and effective quark models, namely a non-local NJL-type model, to investigate the chiral symmetry restoration at finite temperature (T) from a different point of view.

Status: Running

Starting date: 1/Jan/2010

End date: 31/Dec/2012

Financing: 50000 Euros

Financing entity: FCT

Project ID: PTDC/FIS/100968/2008

Person*month: 0

Group person*month: 0