  Defects play a key role in the electronic structure of graphene layers flat
or curved. Topological defects in which an hexagon is replaced by an n-sided
polygon generate long range interactions that make them different from
vacancies or other potential defects. In this work we review previous models
for topological defects in graphene. A formalism is proposed to study the
electronic and transport properties of graphene sheets with corrugations as the
one recently synthesized. The formalism is based on coupling the Dirac equation
that models the low energy electronic excitations of clean flat graphene
samples to a curved space. A cosmic string analogy allows to treat an arbitrary
number of topological defects located at arbitrary positions on the graphene
plane. The usual defects that will always be present in any graphene sample as
pentagon-heptagon pairs and Stone-Wales defects are studied as an example. The
local density of states around the defects acquires characteristic modulations
that could be observed in scanning tunnel and transmission electron microscopy.
