CAN THE COUPLINGS IN THE FERMION-HIGGS SECTOR OF THE STANDARD MODEL BE STRONG

We present results for the renormalized quartic self-coupling lambda(R) and the Yukawa coupling y(R) in a lattice fermion-Higgs model with two SU(2)L doublets, mostly for large values of the bare couplings. One-component (''reduced'') staggered fermions are used in a numerical simulation with the Hybrid Monte Carlo algorithm. The fermion and Higgs masses and the renormalized scalar field expectation value are computed on L(3)24 lattices where L ranges from 6 to 16. In the scaling region these quantities are found to have a 1/L2 dependence, which is used to determine their values in the infinite-volume limit. We then calculate the y(R) and lambda(R) from their tree-level definitions in terms of the masses and renormalized scalar field expectation value, extrapolated to infinite volume. The scalar field propagators can be described momenta up to the cut-off by one-fermion-loop renormalized perturbation theory and the results for lambda(R) and y(R) come out to be close to the tree-level unitarity bounds. There are no signs that are in contradiction with the triviality of the Yukawa and quartic self-coupling.