Zhang Yi-Cheng

The connection between local operators on the lattice and in the continuum and its relation to meson decay constants

Abstract We have computed, at first order in perturbation theory, the relation between lattice and continuum local operators used in Monte Carlo simulations to evaluate the meson decay constants. These corrections, although with the correct sign, are too small to compensate the discrepancy between existing lattice calculations and experimental values.

On the masses of the glueballs in pure SU(2) lattice gauge theory

Abstract Using a Monte Carlo method to measure the correlation functions of different quantities, the mass spectrum of the glue-ball is investigated for an SU(2) gauge model in an 8 4 lattice.

One loop corrections to extended operators on the lattice

Abstract We have computed at first order in perturbation theory the general expressions to establish the relation between lattice one site extended fermion operators (used in recent Monte Carlo simulations) and the corresponding operators in the continuum.

Large-distance correlation functions for an SU(2) lattice gauge theory

Abstract Solving the Langevin equation, describing the approach to equilibrium of two gauge systems at different temperature, numerically, we are able to measure plaquette-plaquette correlation functions at distances 0, 1, 2, 3, 4 on an 8 4 lattice. We estimate the glueball mass to be (2.72 ± 0.20)√ σ .

A modified Eguchi-Kawai model

Abstract A modified version of the Eguchi-Kawai model is proposed. We show that this modified model is equivalent to U(N) gauge theory in the infinite volume when N → ∞. The argument is based on investigations both in the continuum and on a lattice. We show that our modified model does not suffer from the notorious spontaneous symmetry breaking.

Staggered fermions and rotation-gauge invariance

Abstract We study the rotational invariance of the staggered fermions on the lattice by considering them as spin-zero fields in a quenched gauge field background. The non-integer spin fermionic fields are reconstructed. Bilinear operators (i.e. meson fields) in terms of the quark fields on a cube are classified according to the representations of the discrete rotational group.

Some negative results for avoiding lattice fermionic doubling

Abstract We show that it is impossible to solve the lattice fermion doubling problem via random fields in the perturbative framework.

On the single point field theories

Abstract A systematic approach to reduce the dynamical degrees of freedom is presented. Certain field theory models with non-trivial large-N limit defined in the infinite volume are shown to be reduced to theories defined at a single point in space-time when N → ∞.

Quenched lattice gauge models

Abstract We show that lattice gauge models can be studied in the complex coupling plane with couplings randomly distributed, it annealed version is the usual mixed action. We propose the quenched models and argue that they approach the continuum limit in a smoother way by avoiding first order phase transitions.

A simple random lattice ensemble and effective actions

Abstract We propose to get effective lattice actions by summing over an ensemble of random lattices. An example of such ensembles is given, in particular we argue that effective actions so obtained exclude free fields on a lattice.