FINITE SIZE, FERMION MASS AND NF SYSTEMATICS IN COMPUTER-SIMULATIONS OF QUANTUM ELECTRODYNAMICS

Non-compact Quantum Electrodynamics (QED) with zero or two species of fermions (Nf = 0.2) is simulated on a 104 lattice with high statistics. Three bare fermion masses (0.04, 0.03 and 0.02) are considered to study the chiral limit of the condensate 〈ψψ〉 by various extrapolation methods. 〈ψψ〉 is found to be sensitive to the extrapolation method in both cases, but the Nf = 0 and 2 systematics are very similar. The Nf = 2 theory is simulated by the hybrid algorithm while the Nf = 0 case is studied by generating independent gauge configurations populating momentum space with photons appropriately. These results are contrasted with Nf = 8 simulations which indicate that this theory is free. The systematics of the Nf = 4 theory in three dimensions and the SU(2) theory with Nf = 4 in four dimensions are also discussed and compared to the Nf = 0 and 2 simulations presented here. We discuss the progress in simulating QED with Nf = 2 on a dedicated array processor. © 1990.