J. Pech

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.

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.

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.

A high statistics lattice calculation of ƒB in the static limit on APE

We present a high statistics calculation of ƒB in the static limit. The results have been obtained by numerical simulation of quenched QCD, at β = 6.0 on a 183 × 32 lattice. We compare ƒB calculated by using the Wilson and the Clover quark actions. The decay constant is obtained by studying heavy-light correlation functions of different smeared operators, on a sample of 210 gauge field configurations. We find that cubic smearings of size Ls ⩽ 3 or Ls ⩾ 9 are bad projectors on the lightest pseudoscalar state. Combining the information coming from smearing Ls = 5 and Ls = 7, we have obtained ƒB = 370±40 MeV in the clover case and ƒB = 350±40±30 MeV in the Wilson case. Our results support a large value of the pseudoscalar decay constant in the static approximation.

The U(1)-Higgs model: critical behaviour in the confining-Higgs region

Abstract We study numerically the critical properties of the U(1)-Higgs lattice model, with fixed Higgs modulus, in the region of small gauge coupling where the Higgs and confining phases merge. We find evidence for a first-order transition line that ends in a second-order point. By means of a rotation in parameter space we introduce thermodynamic magnitudes and critical exponents in close resemblance with simple models that show analogous critical behaviour. The measured data allow us to fit the critical exponents finding values in agreement with the mean-field prediction. The location of the critical point and the slope of the first-order line are accurately measured.

A new computation of the correlation length near the deconfining transition in SU(3)

Abstract We compute the correlation length of an SU(3) gauge system in the neighbourhood of the deconfining phase transition by measuring loop-loop correlation functions. We find values that are linearly divergent with the lattice size at the critical point and fully compatible with our former estimates obtained by using a cold source method. Together with a precise determination of the location of the critical point these results make stronger the evidence for a large ξ at β close to β c .

APE quenched spectrum

Abstract We present the most recent APE result about hadronic mass spectrum in the quenched framework, using both Wilson and staggered fermions on a 24 3 × 32 lattice at β = 6.0. We also discuss the numerical determination of scattering lengths.

The Ape with a small mass

Abstract We discuss the most recent quenched hadron mass spectrum results from the Ape Collaboration. We discuss Wilson and staggered fermions, and we underline our efforts toward small quark masses, and the most serious problems we encountered.