2-point 2-loop graph with arbitrary self-energy insertions

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In some cases, an important example being at finite temperature, extreme infrared, collinear, or light-cone behaviour may cause the usual loop expansion to break down. For some of these cases higher order ladder graphs can become important. In an earlier paper it was shown that, given a particular relation between a vertex and a self-energy function, the resummation of the ladder graphs simplifies significantly when other types of graphs are included in a consistent effective...

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A brief overview of some recent publications related to the evaluation of two-loop Feynman diagrams is given. (Talk given at the International Symposium on Radiative Corrections CRAD96, Cracow, Poland, 1--5 August 1996)

The author has consulted with us to withdraw this version from arXiv, and we both reach a consensus agreement. So we would like withdraw this paper from arXiv. For the detail of this paper and following update, one can refer to arXiv:1802.09942, which is uploaded by the author himself.

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Lecture notes given at the summer school ``Applications of random matrices to physics", Les Houches, June 2004.

This paper has been withdrawn by the authors. It has been superseded by hep-th/0309154

This paper has been withdrawn by the author.