














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 spacetime
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
quarkgluon 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 quarkantiquark 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.
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, Jianbo 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, Landaugauge
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).
