# Mandl & Shaw page 359

1. Aug 3, 2013

### Vic Sandler

1. The problem statement, all variables and given/known data
In the second edition of Mandl & Shaw QFT, on page 359, in the unnumbered eqn below eqn (15.117) it says:
$$N^{\mu\nu}(q - kz, k) = q^{\mu}q^{\nu} - k^{\mu}k^{\nu}z(1 -z) + \cdots$$

2. Relevant equations
eqn (15.116) on page 358 has a typo in it, but should say:
$$N^{\mu\nu}(p, k) = (p + k)^{\mu}k^{\nu}$$

The first unnumbered eqn at the top of page 359 says:
$$q = p + kz$$

3. The attempt at a solution
I don't see how this can possibly be since eqn (15.116) says N is linear in p and the unnumbered eqn at the top of page 359 says q is linear in p. So how can N be quadratic in q?