Where the Nuclear Pions are
  Three recent experiments, which looked at pionic effects in nuclei have concluded that there are no excess pions. This puts into serious question the conventional meson-exchange picture of the nucleon-nucleon interaction. Based on arguments of partial restoration of chiral symmetry with density we propose a resolution to this problem. 
G.E. Brown, M. Buballa, Zi Bang Li and J. Wambach