2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/151805Regularity of the deformation of the Fermi surface under short-range interactions is established to all orders in perturbation theory. The proofs are based on a new classification of all graphs that are not doubly overlapping. They turn out to be generalized RPA graphs. This provides a simple extension to all orders of the regularity theorem of the Fermi surface movement proven in [FST2]. Models in which the Fermi surface is not symmetric under the reflection p to -p are included.46 pages, plain TeX, ps figures If you have problems with the figures when TeXing, choose showfigsfalse at the beginning of the TeX file and request the figures from manfred@math.ethz.chStrongly Correlated ElectronsStatistical Mechanicstext