Phase transitions in SU(2) gauge theory with many flavours of staggered fermions

We present a Hybrid Monte Carlo study of SU(2) lattice gauge theory with 8 and 12 flavours of staggered fermions. The chiral and deconfinement phase transitions coincide on 64 and 84 lattices. For Nf = 8 there are large finite size effects suggesting that these are temperature driven transitions induced by the finite size of the system. With this assumption, aTc does not satisfy asymptotic scaling. For Nf = 12, the finite size effects are still large even though we expect a bulk transition for this non-asymptotically-free theory. Some evidence for the first order nature of the transitions comes from the observation of tunnelling between metastable states. (orig.)