Space Translation: Sidney Coleman's Lectures Problem

[direct99]

Hi,

In Sidney Coleman's Lectures he talked about space translations such that

but when I expanded the exponentials

and

and used the commutation relation of p and x, I got ρ(x+a) instead of ρ(x-a)

Does anyone see where I may of went wrong?

 

[arkajad]

Which version of "Lectures" you have in mind? In the online version at

http://www.physics.emory.edu/students/tbrunson/PDF/QFT_Lecture_1.pdf

there is a plus sign (bottom pf p. 16).