sorry about the late reply.malawi_glenn said:What are your thoughts so far?
Is the solid black line a charged fermion, or are you dealing with scalar QED?
Insert that here on the forum. It supports latexElmo said:sorry about the late reply.
Yes this solid line is meant to be a charged fermion. This can be taken to mean a gluon loop on quarks for example or even a self energy diagram in HQET.
I have elaborated my question in the attached pdf file "Q" .
ah man sorry ,for whatever reason whenever I preview my latex typing in this chat box it never actually renders correctly. SO i use pdfmalawi_glenn said:Insert that here on the forum. It supports latex
Post the source code and I can read and fix it.Elmo said:ah man sorry ,for whatever reason whenever I preview my latex typing in this chat box it never actually renders correctly. SO i use pdf
oh thank you !malawi_glenn said:Post the source code and I can read and fix it.
Whatever you are using to compose your LaTeX is assuming you are writing a document and using LaTeX pagebreak, begin document, and end document codes. You're not writing a document in posts here. You won't be able to just cut and paste the LaTeX from whatever source you used to write the PDF; you'll have to then remove the LaTeX codes that are only valid in a document context, not here.Elmo said:for whatever reason whenever I preview my latex typing in this chat box it never actually renders correctly
I have now done this with post #7; it should render properly now.PeterDonis said:You won't be able to just cut and paste the LaTeX from whatever source you used to write the PDF; you'll have to then remove the LaTeX codes that are only valid in a document context, not here.
$$
\int_{0}^{1}dx(2m-x \displaystyle{\not}{p})\ln\left(\frac{x\Lambda^2}{(1-x)m^2+x\mu^2-x(1-x)p^2}\right)
$$
##
, not single dollar signs. That is the only LaTeX markup in the rest of post #7.What do you mean by this?Elmo said:Can they not be subtracted off from the diagram itself ?
I was under the impression that you add a soft leading order real emission diagram to the vertex correction diagram and the IR divergences in the soft real emission amplitude mod square and the vertex-real emission cross term ,they mutually cancel as in here :malawi_glenn said:What do you mean by this?
Have you studied Peskin & Schroeder chapter 6.5?
One add counter terms to the Lagrangian.Elmo said:Counterterm diagrams being added to loop diagrams is done to cancel UV divergences as far as I am aware.
ah thanks.vanhees71 said:The reason, why you don't add counterterms for IR divergences is that IR divergences are cured by resummations of soft-photon ladder diagrams, i.e., they occur, because you have to reorganize your perturbative calculation, because due to the denominators from the propagators involving massless particles you have infinitely many diagrams contributing to a given order of the coupling constant.
The physics behind this is that plane waves for charged particles are not the right asymptotic states if a massless gauge field as in electrodynamics is involved.