Chiral NN interactions in nuclear matter

We consider an effective field theory of NN system in nuclear medium. The shallow bound states, which complicate the effective field theory analysis and lead to the large scattering length in the vacuum case do not exist in matter. We study whether the chiral expansion of the effective potential can be truncated in such situation. The cutoff regularization is used to render the solution of the Bethe-Goldstone equation finite. We show that the next-to-leading order terms in the chiral expansion of the effective NN potential can indeed be interpreted as corrections so that the truncation of the expansion is justified. However, it is pointed out that it is still useful to treat the problem nonperturbatively since it may allow the consideration of the nuclear systems with the density smaller that the normal nuclear matter one. The possible directions of constructing the chiral theory of NN interaction in medium are outlined.