Improved Power Counting and Fermi Surface Renormalization *

  • Manfred Salmhofer
  • Published 1996


The naive perturbation expansion for many-fermion systems is infrared divergent. One can remove these divergences by introducing counterterms. To do this without changing the model, one has to solve an inversion equation. We call this procedure Fermi surface renormalization (FSR). Whether or not FSR is possible depends on the regularity properties of the fermion self{energy. When the Fermi surface is nonspherical, this regularity problem is rather nontrivial. Using improved power counting at all orders in perturbation theory, we have shown suucient diierentiability to solve the FSR equation for a class of models with a non-nested, non-spherical Fermi surface. I will rst motivate the problem and give a deenition of FSR, and then describe the combination of geometric and graphical facts that lead to the improved power counting bounds. These bounds also apply to the four{point function. They imply that only ladder diagrams can give singular contributions to the four{point function.

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Cite this paper

@inproceedings{Salmhofer1996ImprovedPC, title={Improved Power Counting and Fermi Surface Renormalization *}, author={Manfred Salmhofer}, year={1996} }