What is meant by ``Renormalon"?

[arroy_0205]

Can anybody explain what is meant by ``Renormalon"? What is its significance?

[tiny-tim]

Hi arroy_0205! :wink:

If you mean renormalisation, see http://en.wikipedia.org/wiki/Renormalisation :smile:

[genneth]

No, the OP actually meant renormalon. As with many things, we name them way before we understand them --- it makes discussions easier to focus. As with all things theoretical HEP related, the first call of reference is in Peskin and Schroeder. That has a brief intro. Otherwise, it's best to rely on Google --- the first couple of results, including the review paper on Arxiv are good resources.

However, if the OP isn't a practising theoretical particle physicist, then I would advise simply forgetting about it. Like I said, it's a name for something we don't really know. It's a thing that pops up when playing the kind of hefty mathematical games that are necessary in HEP.

[arroy_0205]

Thanks, genneth. Regarding your comment about my identity, I am trying to understand qft and intend to become a theoretical particle physicist. I will look it up from peskin and schroeder.

[nrqed]

Thanks, genneth. Regarding your comment about my identity, I am trying to understand qft and intend to become a theoretical particle physicist. I will look it up from peskin and schroeder.

The following is a good introduction:

http://cdsweb.cern.ch/record/360469/files/9807443.pdf

See also

http://arxiv.org/PS_cache/hep-ph/pdf/0311/0311050v1.pdf

[blechman]

also the book "Heavy Quark Physics" by Manohar and Wise has a very nice section on it. It's also an excellent book for learning effective field theory in general. One step higher than Peskin-Schroeder.

[Haelfix]

There are two types of renormalons. Infrared and Ultraviolet.

Typically they are associated with various singularities in the Borel transform to improve the convergence of some divergent series.

In QCD, the singularities known as qcd renormalons are those that arise from terms in the Operator product expansion and act to obstruct us from resumming the series. The IR renormalon goes with specific N loop feynmann diagrams whose contribution grows factorially.

It gets pretty technical, not recommended for beginners!