Tricritical point in compact U(1) lattice gauge theory with dynamical fermions

Abstract

The compact U(1) lattice gauge theory with dynamical fermions of mass m=0.1 and 0.05 with the gauge action ${\mathrm{\epsilon }}_{\mathit{P}}$(Βcos${\mathrm{\Theta }}_{\mathit{P}}$+ γcos2${\mathrm{\theta }}_{\mathit{P}}$) is studied numerically along phase-transition lines in the β,γ plane. On a $8^4$ lattice, discontinuities appearing in the internal energy and in the chiral order parameter 〈ψ¯ψ〉 at γ=0 are shown to vanish as γ decreases to negative values, indicating a existence of tricritical points. These results are compared with high-statistics data of the internal energy in the pure gauge theory on a ${16}^4$ lattice.