CTCP
Centre for Theoretical Chemistry and Physics
at Massey University (Albany Campus), New Zealand





Quantum Chromodynamics

Hadronic physics remains a challenging area of fundamental science. Its fundamental theory, Quantum Chromodynamics, has aspects that are well tested, but in general the theory is difficult to treat exactly. The QCD group at Massey is interested in unravelling the low energy behaviour of QCD by nonperturbative methods, particularly Lattice QCD.

Dr. Patrick Bowman
Senior Lecturer in Physics
Massey University (Auckland)
INS Staff page

Lattice QCD

One way to handle Quantum Chromodynamics is to approximate space-time by a (four dimensional) grid: a lattice. Sample configurations - snapshots of the vacuum - are generated by montecarlo simulation. We then calculate interesting quantities using these sample backgrounds and take an ensemble average. Interesting quantities might be observables like the mass of a particle or its decay constant, or elements of the field theory such as the quark propagator or the quark-gluon vertex. Lattice QCD is, in principle, exact, but it is computationally intensive.

The figure below shows the mass function of the quark propagator integrated over all gluonic fluctuations including, in the case of the "unquenched" data, all quark-anti-quark pairs. The error bars represent the statistical uncertainty in calculating the functional integral a finite set of configurations from a finite set of configurations (around 250). The Hydra supercomputer at the University of Adelaide was just one of the machines used in this calculation.

Unquenched quark propagator in Landau gauge Hydra supercomputer
Hydra supercomputer,
SAPAC, Adelaide.
Unquenched quark propagator in Landau gauge
P.O. Bowman, U.M. Heller, D.B. Leinweber, M.B. Parappilly, A.G. Williams and J.B. Zhang
Phys. Rev. D71, 054507 (2005).

Selected Publications

  • P.O. Bowman, K. Langfeld, D.B. Leinweber, A. O' Cais, A. Sternbeck, L. von Smekal, A.G. Williams, Center vortices and the quark propagator in SU(2) gauge theory, Phys. Rev. D78, 054509, 2008.
  • H.H. Matevosyan, A.P. Szczepaniak, P.O. Bowman, A Numerical Approach to Coulomb Gauge QCD, Phys. Rev. D78, 014033, 2008.
  • P.O. Bowman, U.M. Heller, D.B. Leinweber, M.B. Parappilly, A. Sternbeck, L. von Smekal, A.G. Williams, Jian-bo Zhang, Scaling behavior and positivity violation of the gluon propagator in full QCD, Phys. Rev. D76, 094505, 2007.
  • P.O. Bowman, U.M. Heller, D.B. Leinweber, A.G. Williams and J.B. Zhang, Quark Propagator from LQCD and Its Physical Implications, Lecture Notes in Physics, Volume 663 (2005).
  • P.O. Bowman, U.M. Heller, D.B. Leinweber, M.B. Parappilly, A.G. Williams and J.B. Zhang, Unquenched quark propagator in Landau gauge, Phys. Rev. D71, 054507 (2005).
  • E. Ruiz Arriola, P.O. Bowman and W. Broniowski, Landau-gauge condensates from the quark propagator on the lattice, Phys. Rev. D70, 097505 (2004).
  • P.O. Bowman and A.P. Szczepaniak, Chromoelectric flux tubes, Phys. Rev. D70, 016002 (2004).
  • P.O. Bowman, U.M. Heller, D.B. Leinweber, M.B. Parappilly and A.G. Williams, Unquenched gluon propagator in Landau gauge, Phys. Rev. D70, 034509 (2004).
  • P.O. Bowman, U.M. Heller and A.G. Williams, Lattice quark propagator with staggered quarks in Landau and Laplacian gauges, Phys. Rev. D66, 014505 (2002).
  • F.D.R. Bonnet, P.O. Bowman, D.B. Leinweber, A.G. Williams and J.M. Zanotti, Infinite volume and continuum limits of the Landau gauge gluon propagator, Phys. Rev. D64, 034501 (2001).
Maintained by Peter Schwerdtfeger | Last updated: January, 2015 | Copyright 2014 | Massey University