Geometric Phases in Graphitic Cones
  In this article we use a geometric approach to study geometric phases in graphitic cones. The spinor that describes the low energy states near the Fermi energy acquires a phase when transported around the apex of the cone, as found by a holonomy transformation. This topological result can be viewed as an analogue of the Aharonov-Bohm effect. The topological analysis is extended to a system with $n$ cones, whose resulting configuration is described by an effective defect. 
Claudio Furtado, Fernando Moraes, A. M. de M. Carvalho