On the Definition of the Partition Function in Quantum Regge Calculus

We argue that the definition of the partition function used recently to demonstrate the failure of Regge calculus is wrong. In fact, in the one-dimensional case, we show that there is a more natural definition, with which one can reproduce the correct results.Comment: 9 pages, LaTe

A New Method for Simulating QCD at Finite Density

We propose a new method for simulating QCD at finite density, where interesting phases such as the color superconductivity phase is conjectured to appear. The method is based on a general factorization property of distribution functions of observables, and it is therefore applicable to any system with a complex action. The so-called overlap problem is completely eliminated by the use of constrained simulations. We test this method in a Random Matrix Theory for finite density QCD, where we are able to reproduce the exact results for the quark number density. The achieved system size is large enough to extract the thermodynamic limit. Our results provide a clear understanding of how the expected first order phase transition is induced by the imaginary part of the action. We also discuss the noncommutativity of the zero chemical potential limit and the thermodynamic limit, which is relevant to recent Monte Carlo studies at small chemical potential.Comment: 12 pages, 6 figures, Invited talk at International Symposium on Color Confinement and Hadrons in Quantum Chromodynamics (Confinement 2003), Tokyo, Japan, 21-24 July 200

On Existence of Nontrivial Fixed Points in Large NN Gauge Theory in More than Four Dimensions

Inspired by a possible relation between large $N$ gauge theory and string theory, we search for nontrivial fixed points in large $N$ gauge theory in more than four dimensions. We study large $N$ gauge theory through Monte Carlo simulation of the twisted Eguchi-Kawai model in six dimensions as well as in four dimensions. The phase diagram of the system with the two coupling constants which correspond to the standard plaquette action and the adjoint term has been explored.Comment: 10 pages, latex, 6 figure

Factorization Method for Simulating QCD at Finite Density

We propose a new method for simulating QCD at finite density. The method is based on a general factorization property of distribution functions of observables, and it is therefore applicable to any system with a complex action. The so-called overlap problem is completely eliminated by the use of constrained simulations. We test this method in a Random Matrix Theory for finite density QCD, where we are able to reproduce the exact results for the quark number density.Comment: 7 pages, 1 figure, Talk given at 2002 International Workshop on Strong Coupling Gauge Theories and Effective Field Theories (SCGT 02), Nagoya, Japan, 10-13 Dec 200

Exactly Solvable Matrix Models for the Dynamical Generation of Space-Time in Superstring Theory

We present a class of solvable SO(D) symmetric matrix models with D bosonic matrices coupled to chiral fermions. The SO(D) symmetry is spontaneously broken due to the phase of the fermion integral. This demonstrates the conjectured mechanism for the dynamical generation of four-dimensional space-time in the IIB matrix model, which was proposed as a nonperturbative definition of type IIB superstring theory in ten dimensions.Comment: REVTeX, 4 pages, no figure