Exact Dragging of Inertial Axes by Cosmic Energy-Currents on the Past   Light-Cone
  We prove exact rotational dragging of local inertial axes (= spin axes of gyroscopes) by arbitrary cosmic energy-currents on the past light-cone of the gyroscope for linear perturbations of Friedmann-Robertson-Walker cosmologies. Hence the principle formulated by Mach holds for arbitrary linear cosmological perturbations. 
Christoph Schmid
gr-qc