Renormalisation constants in QED

[blackie1008]

Hi,

I have been deriving the renormalisation constants in QED as part of my project. I have been using Peskin and Schroeder. I am a bit confused with a couple of things and was wondering if anyone could please help!

Firstly, why do we chose not to absorb the Z_3 constant in the electron charge but rather the photon wavefunction?

Secondly, why, when we have used the Ward identity to prove Z_1=Z_2 do we then include them separately in the electron charge renormalisation when they just cancel?

(This is around about p330-331 in Peskin and Schroeder)

 

[A. Neumaier]

Hi,

I have been deriving the renormalisation constants in QED as part of my project. I have been using Peskin and Schroeder. I am a bit confused with a couple of things and was wondering if anyone could please help!

Firstly, why do we chose not to absorb the Z_3 constant in the electron charge but rather the photon wavefunction?

Secondly, why, when we have used the Ward identity to prove Z_1=Z_2 do we then include them separately in the electron charge renormalisation when they just cancel?

(This is around about p330-331 in Peskin and Schroeder)

One can absorb terms only in terms of the same form, and one needs all these terms.