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hep-th2003
On the Four-Color-Map Theorem
A. Petermann
Coloring planar Feynman diagrams in spinor quantum electrodynamics, is a non trivial model soluble without computer. Four colors are necessary and sufficient.
hep-th1993
On a class of finite sigma-models and string vacua; a supersymmetric extension
A. Petermann
Following a suggestion made by Tseytlin, we investigate the case when one replaces the transverse part of the bosonic action by an supersymmetric sigma-model with a symmetric…