Masashi Mizutani

Numerical study of gauge fixing ambiguity

After reviewing how Gribov copies are found in lattice gauge theories, we propose a stochastic gauge fixing for the standard compact lattice gauge theories. Gauge fixed fields remain within the Gribov region in the algorithm.

Stochastic Gauge Fixing for Compact Lattice Gauge Theories

Abstract We propose an extension of Zwanzigers stochastic gauge fixing to compact lattice gauge theories. We study numerically photon and gluon propagators on the lattice using the stochastic gauge fixing implimented in the Langevin simulation. We find that the photon correlation function are not distorted by Gribov copies and behave as massless gauge propagators with renormalized gauge parameter in the Coulomb region. Preliminary analysis suggests that the gluon propagators are not simple massless ones.

Stochastic quantization of bottomless systems based on a kerneled Langevin equation

Abstract We propose a new method for quantizing systems with bottomless action functionals. Our method is based on the kerneled Langevin equation of the stochastic quantization method. We prove that our kerneled Langevin equation describes a stochastic process with a thermal equilibrium state. The proof makes the relation between our method and the conventional path-integral quantization clear. We check numerically in a simple model that dynamical evolution leads to the desired equilibrium state. We also calculate convergent nonperturbative expectation values that are consistent with the perturbative results in the case of a small coupling constant. We also confirm that our method gives the same perturbative results as the conventional path-integral quantization method. Finally, to augment understanding, we discuss a ( d + 1)-dimensional path-integral representation of our method.

QCD on a highly parallel vector computer

We report the first QCD calculations on a parallel vector computer, NWT, which has the peak performance of 236 GFLOPS and 35 GByte memory. After discussing its architecture, our parallel programming strategy, and QCD code performance, we present gluon propagators on a 48 3 × 64 lattice at β = 6.8, which shows the large deviation from the behavior of free massless gauge particles.

Derivation of a Langevin equation for the inflation field by means of a time-coarse-graining procedure

Abstract The stochastic approach in the new inflationary universe model is re-examined. First, a Langevin equation for a stochastic process of the Ornstein-Uhlenbeck-non-Markov-type is obtained from the equation of motion for the inflation field. Then, by a time-coarse-graining procedure, we derive a Langevin equation for a stochastic process of the Wiener-Markov-type. The time-coarse-graining procedure gives a new Wiener-Markov-type Langevin equation.