Comment on: "Nucleon-nucleon scattering lengths in QCD sum rules,"

In a recent Physical Review Letter, Kondo and Morimatsu present a QCD sum rule calculation of nucleon-nucleon scattering lengths. They also relate the empirical scattering lengths to the nucleon mass shift in nuclear matter to cast doubt on the “linear density approximation.” In this Comment, we point out flaws in both parts of their analysis and draw very different conclusions.