▎ 摘　　要

The electronic structure of graphene in the presence of either sevenfolds or eightfolds is studied using a gauge field-theory model. The graphene sheet with topological defects is considered as a negative cone surface with an infinite Gaussian curvature at the center. The density of electronic states is calculated for a single seven-and eightfold as well as for a pair of sevenfolds with different morphology. The density of states at the Fermi energy is found to be zero in all cases except two sevenfolds with translational factor M not equal 0.