Inflaton fluctuations in the presence of cosmological defects
  We study quantum fluctuations of a free massless scalar field during inflation in the presence of a point, line, or plane defect such as a black hole, cosmic string, or domain wall, using a perturbative expansion in powers of small defect parameters. We provide results for the scalar two-point correlation functions that show explicitly a small violation of translational invariance during inflation. 
Hing-Tong Cho, Kin-Wang Ng and I-Chin Wang
hep-th