2020 Impact factor 4.590
Particles and Fields
Eur. Phys. J. C 17, 285-302
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

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 $\mu$, 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 $4^3\times8$ 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 $N\ge2$. 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