In-medium modification of the isovector pion-nucleon amplitude
  We study the in-medium modification of the isovector pi N amplitude using a non-linear representation of the sigma model but keeping the scalar degree of freedom. We check that our result does not depend on the representation. We discuss the connection with other approaches based on chiral perturbation theory. 
G. Chanfray, M. Ericson, M. Oertel