Shuo-Hong Guo

QCD AT FINITE DENSITY

At sufficiently high temperature and density, quantum chromodynamics (QCD) predicts phase transition from the hadronic phase to the quark-gluon plasma phase. Lattice QCD is the most useful tool to investigate this critical phenomenon, which status is briefly reviewed. The usual problem in the Lagrangian formulation at finite density is either an incorrect continuum limit or its complex action and a premature onset of the transition as the chemical potential is raised. We show how the difficulties are overcome in our Hamiltonian approach.

Variational estimates of chiral order parameter in 1+1 dimensional lattice QCD

We discuss analytically the vacuum structure and chiral-symmetry breaking in 1+1 dimensional lattice QCD with naive and Wilson fermions, using a unitary transformation and the variational method developed recently. As an example, the chiral order parameter is evaluated systematically for any coupling constant and fermion mass by including the multilink-terms in the transformation. The expected scaling behavior is observed. Our results are consistent with the continuum predictions.

Method for extracting the glueball wave function

Abstract We describe a nonperturbative method for calculating the QCD vacuum and glueball wave functions, based on an eigenvalue equation approach to Hamiltonian lattice gauge theory. Therefore, one can obtain more physical information than the conventional simulation methods. For simplicity, we take the 2+1 dimensional U(1) model as an example. The generalization of this method to 3+1 dimensional QCD is straightforward.

COUPLED CLUSTER EXPANSIONS FOR (2 + 1) DIMENSIONAL U(1) LATTICE GAUGE THEORY WITH IMPROVED HAMILTONIAN

Using coupled cluster method, we calculate the vacuum wave function and the mass gaps of (2 + 1)-dimensional U(1) lattice gauge theory with improved Hamiltonian up to the seventh order. The results are compared with those from the unimproved Hamiltonian.

Truncated eigenvalue equation and long wavelength behavior of lattice gauge theory

We review our new method, which might be the most direct and efficient way for approaching the continuum physics from Hamiltonian lattice gauge theory. It consists of solving the eigenvalue equation with a truncation scheme preserving the continuum limit. The efficiency has been confirmed by the observations of the scaling behaviors for the long wavelength vacuum wave functions and mass gaps in (2+1)-dimensional models and (1+1)-dimensional σ model even at very low truncation orders. Most of these results show rapid convergence to the available Monte Carlo data, ensuring the reliability of our method.