DOI 10.1007/s100520000477
Numerical study of dense adjoint matter in two color QCD
S. Hands1 - I. Montvay2,3 - S. Morrison1 - M. Oevers4 - L. Scorzato1 - J. Skullerud2
1 Department of Physics, University of Wales Swansea,
Singleton Park, Swansea SA2 8PP, UK
2 Theory Division, DESY, Notkestrasse 85, 22603 Hamburg,
Germany
3 Center for Computational Physics, University of Tsukuba,
1-1-1 Tennodai, Tsukuba-shi, Ibariki-ken 305-8577, Japan
4 Department of Physics and Astronomy, University of Glasgow,
Glasgow G12 8QQ, UK
Received: 20 June 2000 / Published online: 31 August 2000 - © Springer-Verlag 2000
Abstract
We identify the global symmetries of SU(2) lattice gauge theory
with N flavors of staggered fermion in the presence of a quark
chemical potential 
,
for fermions in both fundamental
and adjoint representations, and anticipate likely patterns of symmetry
breaking at both low and high densities. Results from numerical simulations
of the model with N=1 adjoint flavor on a
lattice
are presented, using both hybrid Monte Carlo
and Two-Step Multi-Boson algorithms. It is shown that the sign of the fermion
determinant starts to fluctuate once the model enters a phase
with non-zero baryon charge density. HMC simulations are not ergodic in
this regime, but TSMB simulations
retain ergodicity even in the dense phase, and in addition appear to
show superior decorrelation.
The HMC results for the equation of state and the pion mass
show good quantitative
agreement with the predictions of chiral perturbation theory, which should hold
only for 
.
The TSMB results incorporating
the sign of the determinant support a delayed onset transition,
consistent with the pattern of symmetry breaking expected for N=1.
Copyright Società Italiana di Fisica, Springer-Verlag 2000
