Using Monte Carlo methods, we conclude that there are no first-order phase transitions in SU(5) lattice gauge theory with a renormalization-group–improved action, the form of which has been proposed previously by a block-spin renormalization-group analysis. This is quite different from the situation with the standard one-plaquette action.

• Received 22 May 1985

DOI:https://doi.org/10.1103/PhysRevLett.55.273