1ST ORDER PHASE-TRANSITIONS IN SU(2) GAUGE-THEORIES WITH MANY FLAVORS OF STAGGERED FERMIONS

We present a hybrid Monte Carlo study of SU(2) lattice gauge theory coupled to 8 and 12 flavours of staggered fermions. The chiral and deconfinement phase transitions are coincident on 64 and 84 lattices. For Nf = 8 there are large finite size effects suggesting a temperature driven transition induced by the finite size of the system. With this assumption, aTc does not satisfy asymptotic scaling. For 12 flavours, asymptotic freedom is lost and we expect a bulk transition on a sufficiently large lattice; our numerical results for the critical point with Nf = 12 show large finite size effects. Evidence for the first order nature of the transitions derives from the observation of tunneling between metastable states. © 1990.