Symmetries and Ambiguities in the linear sigma model with light quarks
  We investigate the role of undetermined finite contributions generated by radiative corrections in a $SU(2)\times SU(2)$ linear sigma model with quarks. Although some of such terms can be absorbed in the renormalization procedure, one such contribution is left in the expression for the pion decay constant. This arbitrariness is eliminated by chiral symmetry. 
E. W. Dias (1), Brigitte Hiller (2), A. L. Mota (3), M. C. Nemes   (2,4), M. Sampaio (1), A. A. Osipov (4) ((1)Universidade ...