Simulating the vacuum properties of QCD with dynamical quarks

The vacuum properties of lattice QCD with staggered quarks are investigated by an efficient simulation method. I present data for the quark condensate with flavor number $N_f=0, ~ 1, ~ 2, ~ 3, ~ 4$ and many quark masses, including the vacuum energy in the chiral limit. Obvious sea quark effects are observed in some parameter space. I also describe a mechanism to understand this and a formula relating the chiral condensate and zero modes.Comment: 3 pages, Latex. Talk given at Lattice 97: 15th International Symposium on Lattice Field Theory, Edinburgh, Scotland, 22-26 Jul 1997, to appear in Nucl. Phys. B(Proc. Suppl.

Hamiltonian lattice quantum chromodynamics at finite density with Wilson fermions

Quantum chromodynamics (QCD) at sufficiently high density is expected to undergo a chiral phase transition. Understanding such a transition is of particular importance for neutron star or quark star physics. In Lagrangian SU(3) lattice gauge theory, the standard approach breaks down at large chemical potential $\mu$, due to the complex action problem. The Hamiltonian formulation of lattice QCD doesn't encounter such a problem. In a previous work, we developed a Hamiltonian approach at finite chemical potential $\mu$ and obtained reasonable results in the strong coupling regime. In this paper, we extend the previous work to Wilson fermions. We study the chiral behavior and calculate the vacuum energy, chiral condensate and quark number density, as well as the masses of light hadrons. There is a first order chiral phase transition at zero temperature.Comment: 23 pages. Version accepted for publication in Physical Review

Chiral transition in a strongly coupled fermion-gauge-scalar model

We report the recent results from the computer simulations of a fermion-gauge-scalar model with dynamical chiral-symmetry breaking and chiral transition induced by the scalar field. This model might be considered to be a possible alternative to the Higgs mechanism of mass generation. A new scheme is developed for detecting the chiral transition. Our results show with higher precision than the earlier works that the chiral transition line joins the Higgs phase transition line, separating the Higgs and Nambu (chiral-symmetry breaking) phases. The end point of the Higgs transition with divergent correlation lengths is therefore suitable for an investigation of the continuum limit.Comment: 3 pages, 3 eps figs, encoded with uufiles (Contribution to Lattice 94