More on strongly coupled quenched QED

Abstract

We study the critical region of lattice QED4 in the quenched approximation. The issue of triviality is addressed by contrasting simulation results for $<\bar\psi\psi>$ and for the susceptibilities with the predictions of two critical scenarios -- powerlaw scaling, and triviality \`a la Nambu--Jona Lasinio. We discriminate among the two possibilities with reasonable accuracy and we confirm previous results for the critical point and exponents thanks to new analysis strategies and good quality data. The interplay of chiral symmetry breaking with the Goldstone mechanism is studied in detail, and some puzzling features of past results are clarified. Chiral symmetry restoration is observed in the spectrum: the candidate Goldstone boson decouples in the weak coupling phase, while the propagators of the chiral doublets become degenerate. We also present the first measurements of the full mesonic spectrum, relevant for the study of flavour/ rotational symmetry restoration. The systematic effects associated