Wednesday, February 11, 2015

quantum field theory - Relation between Noether's charge and the generator of a U(1) symmetry


Consider a U(1) symmetry of a complex scalar field realized as ϕϕ=eiQθϕ.

where Q is the generator of the symmetry. The conserved Noether's charge (in D-spatial dimensions) corresponding to this symmetry is given by QN=j0(x,t)dDx=iQdDx[(0ϕ)ϕ(0ϕ)ϕ].
So it turns out that QNQ but not equal to Q itself.


But in A. Zee's book QFT in a Nutshell, page 198, the Noether charge corresponding to a symmetry U(θ)=eiQθ

is written as QN=j0(x,t)dDx=Q
But as I've shown QNQ. So is it a mistake there? Or am I missing something?




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