Supercomputing the Effective Action

We describe a new method for large-scale computer simulation of the effective action in lattice field theories. As a first application, the scalar ${\phi }^4$ model with spontaneous symmetry breaking is studied, and the renormalization of physical parameters is calculated from the effective action. Mean-field scaling behavior with calculable logarithmic scaling corrections at the trivial Gaussian fixed point (vanishing renormalized coupling) is supported by our results. Applications to the electroweak theory are outlined and a bound on the Higgs-boson mass is estimated.