Monopoles and specific heat in SU(2) lattice gauge theory with a mixed action

Using Monte Carlo simulations, the density of Z(2) monopoles and the value of the specific heat have been measured in SU(2) lattice gauge theory with an action mixture of the fundamental and adjoint representations. A sharp peak in the specific heat has been observed along points lying on a straight line which stretches from the end-point of the first-order transition line. There has also been detected an abrupt decrease of the monopole density on this line. All these results show a strong correlation between the singular behaviour in the cross-over region of the Wilson action and the phase transition structure of the mixed fundamental-adjoint SU(2) theory. © 1987.