Mass Spectrum and Bounds on the Couplings in Yukawa Models With   Mirror-Fermions
  The $\rm SU(2)_L\otimes SU(2)_R$ symmetric Yukawa model with mirror-fermions in the limit where the mirror-fermion is decoupled is studied both analytically and numerically. The bare scalar self-coupling $\lambda$ is fixed at zero and infinity. The phase structure is explored and the relevant phase transition is found to be consistent with a second order one. The fermionic mass spectrum close to that transition is discussed and a first non-perturbative estimate of the influence of fermions on the upper and lower bounds on the renormalized scalar self-coupling is given. Numerical results are confronted with perturbative predictions. 
L. Lin, G. M\"unster, M. Plagge, I. Montvay, H. Wittig, C. Frick, T.   Trappenberg