IR finite graviton propagators in de Sitter spacetime
  Graviton propagator diverges in certain gauges in de Sitter spacetime. We address this problem in this work by generalizing the infinitesimal BRST transformations in de Sitter spacetime to finite field-dependent BRST (FFBRST) transformations. These FFBRST transformations are symmetry of the classical action, but do not leave path integral measure invariant for the graviton theory in de Sitter spacetime. Due to the non-trivial Jacobian of such finite transformation the path integral measure changes and hence FFBRST transformation is capable of relating theories in two different gauges. We explicitly construct FFBRST transformation which relates theory with diverging graviton two-point function to theory with infrared (IR) finite graviton. The FFBRST transformation thus establishes that divergence in graviton two-point function may be only a gauge artifact. 
Mir Faizal, Sudhaker Upadhyay and Bhabani Prasad Mandal
hep-th gr-qc math-ph math.MP