## Peskin and Schroeder Eqn 15.9 - infinitesimal comparator of non-Abelian gauge theory

Hi,

I am working through Chapter 15 of Peskin and Schroeder, and I was wondering how the form of the infinitesimal comparator $U(y,x)$ is deduced as stated in equation 15.9 (page 484), merely from the requirements that

(1) $[U(y,x)]^\dagger = U(x, y)$

(2) $U(y,x)$ is a pure phase, i.e. $U(y,x) = e^{i\phi(y,x)}$

How does one get $\epsilon/2$?