Nucleon-nucleon interaction in nuclear matter

The effective two-body NN potential in nuclear matter due to the two-pion-exchange three-body force can be expressed such that it arises due to a change in the pion propagator pertaining to the one-pion-exchange potential. The pion propagator in nuclear matter is examined with the NN correlation taken into account. It is found that the modified propagator can be approximated by [(1-α)(q2+μ′2)]-1 where μ′=μ(1-α)-12, μ is the pion mass, and α is a positive constant which is roughly proportional to the nuclear matter density. For example, α≈0.3 for the normal density of nuclear matter. The modified one-pion-exchange potential in nuclear matter is then obtained by scaling the one-pion-exchange potential in vacuum. It is suggested that other parts of the NN potential, e.g., the two-pion-exchange part, are also modified by the same mechanism, and hence the NN interaction in nuclear matter could be strongly density dependent. NUCLEAR STRUCTURE Pion propagator in nuclear matter, many-body forces.