Robust flux error estimation of an unfitted Nitsche method for   high-contrast interface problems
  We prove an optimal error estimate for the flux variable for a stabilized unfitted Nitsche finite element method applied to an elliptic interface problem with discontinuous constant coefficients. Our result shows explicitly that this error estimate is totally independent of the diffusion coefficients 
Erik Burman, Johnny Guzman, Manuel A. Sanchez and Marcus Sarkis
math.NA