S. Cabasino

Glueball masses and string tension in lattice QCD

We study glueball masses in lattice QCD. We present the first numerical determination of the mass of the lowest spin 2 state in the scaling region, and find that it is close to the lowest spin 0 state. We present very precise results for the string tension and for the spin 0 state, obtained by analyzing a large set of operators. We find that finite size effects are significant.

Lbe Simulations Of Rayleigh-Bénard Convection On The Ape100 Parallel Processor

In this paper we describe an implementation of the Lattice Boltzmann Equation method for fluid-dynamics simulations on the APE100 parallel computer. We have performed a simulation of a two-dimensional Rayleigh-Benard convection cell. We have tested the theory proposed by Shraiman and Siggia for the scaling of the Nusselt number vs. Rayleigh number.

A HARDWARE IMPLEMENTATION OF THE APE100 ARCHITECTURE

APE100 processors are based on a simple Single Instruction Multiple Data architecture optimized for the simulation of Lattice Field Theories or other complex physical systems. This paper describes the hardware implementation of the first APE100 machine.

GLUEBALL MASSES AND THE LOOP LOOP CORRELATION-FUNCTIONS

Abstract We analyse the pure gauge lattice QCD by measuring loop-loop correlation functions on a 12 3 ×32 lattice at β =5.9. We select a set of operators given by the smearing procedure. We obtain a good estimate of the mass of the 0 ++ state and for the string tension, and upper bounds for the masses of the 2 ++ and the 1 +− states.

THE APE-100 COMPUTER: (I) THE ARCHITECTURE

We describe APE-100, a SIMD, modular parallel processor architecture for large scale scientific computation. The largest configuration that will be implemented in the present design will deliver a peak speed of 100 Gflops. This performance is, for instance, required for high precision computations in Quantum Chromo Dynamics, for which APE-100 is very well suited.

The Software Of The Ape100 Processor

We describe the software environment available for the APE100 parallel processor. We discuss the parallel programming language that we have defined for APE100 and its optimizing compiler. We then describe the operating system that allows to control APE100 from a host computer.

The hadronic mass spectrum in quenched lattice QCD: Results at β = 5.7 and β = 6.0

Abstract We study the hadronic mass spectrum in quenched lattice QCD. We present the results of numerical simulations done at β = 5.7 and β = 6.0. B and A1 meson masses get much closer to the physical values at β = 6.0, and so do the baryonic splittings. The mass ratio m p m p in the chiral limit tends to be from 10 to 20% higher than the experimental value. We estimate the nucleon σ term from the proton mass slope.

The deconfining phase transition in lattice gauge SU(3)

Abstract By using a source method and improved measuring techniques, we study the decay of the Polyakov loop in SU(3) lattice gauge theory at finite temperature. Our aim is to measure the correlation length of the system in the neighbourhood of the critical point. We work with lattices of size up to 162×64×4. We found that the maximum correlation length is only bounded by the spatial dimension of the lattice. This result is the one expected in a second order phase transition and appears to be incompatible with the presence of the strong first order transition claimed in the literature.

β=6.0 quenched Wilson fermions

Abstract We discuss the Ape Collaboration recent results for the Wilson fermions hadronic mass spectrum at β =6.0 on a 24 3 × 32 lattice. Some of the main new points are the results for the nucleon σ term and the estimates for excited states.

Scaling in lattice QCD: Glueball masses and string tension

Abstract We study the scaling behaviour of lattice quantum chromodynamics by comparing the β dependence of the string tension and the 0 ++ glueball mass. We use a source method at β =5.7, β =5.9 and β =6.1, on lattices from 9 3 · 24 to 16 3 · 32. Assuming a string tension of about (420 MeV) 2 , the lattice spacing ranges from 0.16 to 0.08 fm. In order to separate finite volume from scaling violation effects we have compared data from lattices having approximately the same overall physical size at the different values of β. We find deviations from scaling to be very small.