Z<SUB>2</SUB> monopoles, vortices, and the deconfinement transition in mixed action SU(2) gauge theory

Adding separate chemical potentials &#955; and &#947; for Z2 monopoles and vortices, respectively, in the Villain form of the mixed fundamental-adjoint action for the SU(2) lattice gauge theory, we investigate their role in the interplay between the deconfinement and bulk phase transitions using Monte Carlo techniques. Setting &#955; to be nonzero, we find that the line of deconfinement transitions is shifted in the coupling plane but it behaves curiously also like the bulk transition line for large enough adjoint coupling, as for &#955;=0. In a narrow range of couplings, however, we find separate deconfinement and bulk phase transitions on the same lattice for nonzero and large &#955;, suggesting the two to be indeed coincident in the region where a first order deconfinement phase transition is seen. In the limit of large &#955; and &#947;, we obtain only lines of second order deconfinement phase transitions, as expected from universality