Generation of Source Terms in General Relativity by differential   structures
  In this paper the relation between the choice of a differential structure and a smooth connection in the tangential bundle is discussed. For the case of an exotic $S^7$ one obtains corrections to the curvature after the change of the differential structure, which can not be neglected by a gauge transformation. In the more interesting case of four dimensions we obtain a correction of the connection constructed by intersections of embedded surfaces. This correction produce a source term in the equation of the general relativity theory which can be interpreted as the energy-momentum tensor of a embedded surface. 
T. Asselmeyer