Using heavy-baryon chiral perturbation theory, we have calculated all the diagrams up to twoloop
order which contribute to the S-wave pion self-energy in symmetric nuclear matter. Some
subtleties related to the denition of pion elds are discussed. The...
Using heavy-baryon chiral perturbation theory, we have calculated all the diagrams up to twoloop
order which contribute to the S-wave pion self-energy in symmetric nuclear matter. Some
subtleties related to the denition of pion elds are discussed. The in-medium pion mass turns out
to increase by only 5 % at normal nuclear matter density, and this result is model independent.