Hi all, I have two questions regarding chapter 27 and 28 in Srednicki's book. On page 163 he states: But this would mean that [tex]|<k|\phi |0>|^2 = R[/tex] I can not see why this is? I would expect that the result is R^2 because there is a factor of k^2 + m^2 in the LRZ formula... My second question: On p.170 Srednicki states that bare parameters must be independent of [tex]\mu[/tex]. Because if we "were smart enough, we would be able to compute the exact scattering amplitudes in terms of them". Why is this? After all bare parameters have no physical meaning at all (at least as far as I understand this), so why can't they be dependent on [tex]\mu[/tex]? How would you calculate an exact amplitude just with arbitrary, unphysical bare parameters? Hope anyone can help me and thanks for reading!