Ab initio nonperturbative calculation of physical observables in light-front dynamics: Application to the Yukawa model

We present a coherent and operational strategy to calculate in a nonperturbative way, physical observables in light-front dynamics. This strategy is based on the decomposition of the state vector of any compound system in Fock components, and on the covariant formulation of light-front dynamics, together with the so-called Fock sector dependent renormalization scheme. We apply our approach to the calculation of the electromagnetic form factors of a fermion in the Yukawa model, in the nontrivial three-body Fock space truncation, for rather large values of the coupling constant. We find that once the renormalization conditions are properly taken into account, the form factors do not depend-within our numerical accuracy-on the regularization scale when the latter is much larger than the physical masses. We then extend the Fock space by including antifermion degrees of freedom.