# Why we do not consider the divergence due to mass-shell in QED?

1. Jan 30, 2012

### ndung200790

Why we do not consider the divergences in loops in QED when p$^{2}$→m$^{2}$ but only consider the soft photon when k$^{2}$→0(IR divergence) and UV divergence?
Thank you very much in advance.

2. Jan 30, 2012

### tom.stoer

p²-m² is always regulated via the "iε-Term" and is evaluated via the Cauchy contour integral

3. Jan 30, 2012

### ndung200790

Why we have not the same consideration when m=0?

4. Jan 30, 2012

### ndung200790

Sorry,Now I have understood.Applying Cauchy's theorem when m=0(so k$^{2}$→0)
we have divergence(IR divergence)