Particle propagation on spacetime manifolds with static defects

We investigate the effects of small static defects in the spacetime manifold. The presence of the defects leads to a modification of the scalar field two-point function in Klein-Gordon theory. We calculate the energy-momentum tensor and discuss the possible mass generation for the scalar field in single and multiple defect spacetimes. We also extend these results to the photon field and show that, as a result of the interaction with the defects, the photon dispersion relations are modified.