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

maverick280857

Hi,

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

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

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

How does one get [itex]\epsilon/2[/itex]?

Thanks in advance!