Physical Review D
First-order semiclassical perturbations to the Schwarzschild black hole geometry are studied within the black hole interior. The source of the perturbations is taken to be the vacuum stress-energy of quantized scalar, spinor, and vector fields, evaluated using analytic approximations developed by Page and others (for massless fields) and the DeWitt-Schwinger approximation (for massive fields). Viewing the interior as an anisotropic collapsing cosmology, we find that minimally or conformally coupled scalar fields, and spinor fields, decrease the anisotropy as the singularity is approached, while vector fields increase the anisotropy. In addition, we find that for massless fields of all spins, the massive conformally coupled scalar field, and massive vector fields, the metric perturbations initially strengthen the singularity, while for minimally coupled massive scalar and spinor fields the metric perturbations tend to initially slow the growth of curvature.
Hiscock, W. A., Larson, S. L., & Anderson, P. R. (1997). Semiclassical effects in black hole interiors. Physical Review D, 56(6), 3571.