# How can we solve IR divergences problem?

1. Jan 27, 2012

### ndung200790

The UV divergence problems are solved by Renormalization Procedure,but I do not understand how to solve IR divergence problems.
Thank you very much for your kind helping.

2. Jan 27, 2012

### Staff: Mentor

I am no expert in re-normalisation but my understanding is it is solved in the same way - by regularisation, imposing a cutoff, and then taking the limit:
http://www.hep.phys.soton.ac.uk/hepwww/staff/D.Ross/qft/aqft5.pdf [Broken]

Right now I am going a bit deeper into QFT than I have before and this is something I too am trying to grasp. The following paper really helped me a lot by exposing its mathematical underpinnings:
http://arxiv.org/pdf/hep-th/0212049.pdf

Thanks
Bill

Last edited by a moderator: May 5, 2017
3. Jan 27, 2012

### strangerep

If you're talking about QED, the usual textbook procedure is to sum the cross section over all possible configurations with soft photons in the final state. See, e.g., Peskin & Schroeder.

Another approach is to redefine the asymptotic electron states to include soft photon clouds.

BTW, which textbook(s) are you studying from?

4. Jan 27, 2012

### ndung200790

I am studying Peskin&Schroeder and I am confused with mass singularities in QCD(Parton evolution).

5. Jan 28, 2012

### ndung200790

In Peskin&Schroeder (&17.5 Parton Evolution)saying ''.....when quarks and gluons appear in initial state of parton subprocess,...mass singularities do not cancel''.Then I worry if there are any disasters because of the singularities?

6. Jan 28, 2012

### ndung200790

And are there any differences between the singularities because of p→0 when m=0 and the singularities because of p$^{2}$→m$^{2}$?